Systems for performing image-guided spinal procedures

Abstract

Systems, methods and devices are disclosed that facilitate navigated surgical procedures involving multiple tissue structures that can undergo intraprocedural changes in relative alignment. Glyphs are secured relative to, and associated with, respective tissue structures, and the poses of the glyphs are intraoperatively tracked via one or more imaging cameras. The intraoperative glyph pose is employed as proxy for the intraoperative pose of each associated tissue structure. Registration transformations obtained based on surface registration between surface data charactering an exposed surface of each tissue structure and segmented surface data obtained from volumetric image data is employed, along with a pre-determined association between glyph pose and tissue structure pose, to generate navigation images for navigating medical instruments tracked by an optical tracking system. Various examples of glyph structures are disclosed that facilitate attachment of a glyph in a stable pose relative to a given tissue structure.

Description

SYSTEMSAND METHODS FOR PERFORMING IMAGE-GUIDED SPINAL PROCEDURESCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims to the benefit of U.S. Provisional Patent Application No.63 / 779,755, titled “SYSTEMSAND METHODS FOR PERFORMING IMAGE-GUIDED SPINAL PROCEDURES”, filed March 28, 2025, the entire contents of which is incorporated herein by reference.BACKGROUND

[0002] This disclosure relates generally to surgical navigation systems.

[0003] The vertebral column is composed of a series of articulated overlapping segments. The function of the vertebral column is to support a person while standing, balance the individual in the presence of gravity, and enable locomotion and other useful movements. Deformities of the spine include conditions such as idiopathic adolescent scoliosis, congenital scoliosis, post-traumatic deformities, and other adult spinal deformities including post-infective kyphosis.

[0004] Spinal deformity correction surgery utilizes devices (primarily screws and rods) to fixate levels of the vertebrae in a corrected or compensating position to restore normal posture. Surgical navigation can be used to aid the positioning of screws and other implants within the vertebrae but provides relatively little feedback on the intraoperative orientation of the vertebrae.

[0005] Traditionally, intraoperative computed tomography (CT) and / or fluoroscopy can be used to assess the orientation of the vertebrae, but these systems are expensive, require the use of large amounts of ionizing radiation, and are cumbersome to use.SUMMARY

[0006] Systems, methods and devices are disclosed that facilitate navigated surgical procedures involving multiple tissue structures that can undergo intraprocedural changes in relative alignment. Glyphs are secured relative to, and associated with, respective tissue structures, and the poses of the glyphs are intraoperatively tracked via one or more imaging cameras. The intraoperative glyph pose is employed as proxy for the intraoperative pose of each associated tissue structure. Registration transformations obtained based on surface registration between surface data charactering an exposed surface of each tissue structure and segmented surface data obtained from volumetric image data is employed, along with a pre-determined association between glyph pose and tissue structure pose, to generate navigation images for navigating medical instruments tracked by an optical tracking system.Various examples of glyph structures are disclosed that facilitate attachment of a glyph in a stable pose relative to a given tissue structure.

[0007] A further understanding of the functional and advantageous aspects of the disclosure can be realized by reference to the following detailed description and drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments are described with reference to the accompanying drawings. In the drawings, like reference numbers can indicate identical or functionally similar elements.

[0009] FIGS. 1 A and 1 B show example systems for performing surgical navigation of a spinal procedure based on intraoperatively acquired vertebral surface data.

[0010] FIGS. 2A and 2B show example optical tracking support structures, with FIG. 2B showing an example optical tracking support structure with additional geometrical features for surface detection.

[0011] FIG. 2C is a flow chart illustrating an example workflow for performing surgical navigation using a tracking reference structure.

[0012] FIG. 3 shows example system for performing surgical navigation of a spinal procedure based on intraoperatively tracking of glyph poses.

[0013] FIG. 4A illustrates an example unitary marker base providing a glyph integrated with a marker base into a single component, along with an attachment structure.

[0014] FIG. 4B illustrates an example composite marker base providing a glyph fixedly or removably integrated with a marker base, along with an attachment structure.

[0015] FIG. 5A illustrates an example glyph including a QR code and a marker base removably associated with an attachment structure. A representative target site (spinous process) is also illustrated in this example.

[0016] FIG. 5B illustrates an example of an attachment structure as a bone clamp.

[0017] FIC. 5C illustrates an example of a tool including a removably interconnected clamp.

[0018] FIG. 5D provides an example of a marker base and attachment structure in situ associated with a spinous process.

[0019] FIG. 5E provides an example of a marker base including a visible glyph and an elongated attachment structure associated with a representative bone structure. FIG. 5E is similar to FIG. 5D, but FIG. 5E illustrates a screw / threaded elongated attachment component rather than a clamp.

[0020] FIG. 5F provides an alternative example of a marker base including a glyph and elongated attachment structure, and further provides a shallow bone screw (not shown) and a spiked tripod base for stabilization.

[0021] FIG. 5G provides another alternative example of a marker base with associated glyph and attachment structure, engaged with a representative bone structure.

[0022] FIG. 5H provides a detail illustration in cross-section of the FIG. 5G example.

[0023] FIG. 5I provides an example of a marker base with a visible glyph and an elongated attachment structure interfacing with an example tulip.

[0024] FIG. 6A provides an example of a marker base with integrated glyph associated with an example tower component.

[0025] FIG. 6B illustrates an example tower based reducer to lock polyaxial motion of the screw and also illustrates an example of an associated tile location.

[0026] FIG. 7A provides a pair of marker base examples with example associated glyphs and attachment structures.

[0027] FIG. 7B provides an example attachment structure removably connected to a screw shank.

[0028] FIG. 8 illustrates an example alternative marker base with a visible glyph and elongated attachment structure with a rod clamp at the attachment portion with the spinal fixation rod.

[0029] FIG. 9A provides an example of a screw shank to apply downward pressure on a lock washer with an integrated glyph mount.

[0030] FIG. 9B illustrates an example screw shank feature interfaced with a clamp.

[0031] FIGS. 9C, 9D and 9E provide example tulip attachment structures and their respective association with examples of marker bases and screws.

[0032] FIG. 10 is a flow chart illustrating an example method of surgical navigation employing the tracking of glyph poses.

[0033] FIG. 11 illustrates the spatial relationships and transformations between a vertebral level, a glyph secured relative to the vertebral level, and a tracked medical instrument.

[0034] FIG. 12A shows an example workflow for the detection of glyphs from stereographic images.

[0035] FIG. 12B illustrates the workflow shown in FIG. 12A in the context of example glyphs.

[0036] FIGS. 13A and 13B show examples of glyphs.

[0037] FIG. 13C schematically illustrates the use of surface detection in the determination of the pose of a glyph.

[0038] FIG. 14A, 14B, 14C and 14D show example screens of an example surgical navigation user interface in which volumetric image data and alignment planes associated glyph-tracked vertebral levels is shown in a common frame of reference with tracked medicalinstruments. FIGS. 14A and 14B show glyph association steps, and FIGS. 14C and 14D show example displays generated during intraoperative navigation.

[0039] FIG. 15 shows an alternative example system for performing surgical navigation of a spinal procedure based on intraoperatively tracking of glyph poses.

[0040] FIG. 16 shows an alternative example system for performing surgical navigation of a spinal procedure based on intraoperatively tracking glyph poses, where an optical tracking reference structure is employed to facilitate the generation of intraoperative guidance images.

[0041] FIG. 17 is a flow chart illustrating an example method of surgical navigation employing the intermittent tracking of glyph poses.

[0042] FIG. 18A is a flow chart illustrating an alternative example method of surgical navigation employing the intermittent tracking of glyph poses.

[0043] FIG. 18B is a flow chart illustrating an alternative example method of surgical navigation employing the tracking of glyph poses.

[0044] FIGS. 19A and 19B illustrate the spatial relationships and transformations between a vertebral level, a glyph secured relative to the vertebral level, the optical tracking reference structure, and a tracked medical instrument.

[0045] FIGS. 19C schematically illustrates the determination of changes in alignment among different vertebral levels.

[0046] FIGS. 20A, 20B, 20C and 20D show examples of user interface screens employed for alignment parameter planning.

[0047] FIGS. 21 A, 21 B and 21 C show examples of user interface screens employed for level definition.

[0048] FIG. 22 shows an example of user interface screen employed for alignment parameter calculation.

[0049] FIGS. 23A, 23B and 23C show examples of user interface screens employed for segmentation of volumetric image data on a per-level basis.

[0050] FIG. 24A, 24B, 24C, 24D, 24E, 24F and 24G show examples of user interface screens employed for surface-based registration.

[0051] FIGS. 25A and 25B show examples of user interface screens employed for the association of glyphs with respective vertebral levels.

[0052] FIGS. 26A, 26B, 26C and 26D show examples of user interface screens for glyph-pose-based navigation and intraoperative tracking of vertebral alignment.

[0053] FIG. 27 shows an example spine with scoliosis.

[0054] FIG. 28 schematically illustrates various alignment parameters, showing: a) pelvic incidence measurement, b) L1 pelvic angle measurement (pelvic angle can be calculated with a similar approach for any reference vertebra), c) sagittal plane Cobb anglemeasurement between two vertebrae, d) coronal plane Cobb angle between two vertebrae, and e) distance measurement between the centroids of a pair of vertebrae.

[0055] FIG. 29 illustrates various coordinate systems with reference in volumetric image data, showing: a) a global coordinate system b) a regional coordinate system, and c) a local coordinate system.DETAILED DESCRIPTION

[0056] Various embodiments and aspects of the disclosure will be described with reference to details discussed below. The following description and drawings are illustrative of the disclosure and are not to be construed as limiting the disclosure. Numerous specific details are described to provide a thorough understanding of various embodiments of the present disclosure. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of embodiments of the present disclosure.

[0057] As used herein, the terms “comprises” and “comprising” are to be construed as being inclusive and open ended, and not exclusive. Specifically, when used in the specification and claims, the terms “comprises” and “comprising” and variations thereof mean the specified features, steps or components are included. These terms are not to be interpreted to exclude the presence of other features, steps or components.

[0058] As used herein, the term “exemplary” means “serving as an example, instance, or illustration,” and should not be construed as preferred or advantageous over other configurations disclosed herein.

[0059] As used herein, the terms “about” and “approximately” are meant to cover variations that can exist in the upper and lower limits of the ranges of values, such as variations in properties, parameters, and dimensions. Unless otherwise specified, the terms “about” and “approximately” mean plus or minus 25 percent or less.

[0060] It is to be understood that unless otherwise specified, any specified range or group is as a shorthand way of referring to each and every member of a range or group individually, as well as each and every possible sub-range or sub-group encompassed therein and similarly with respect to any sub-ranges or sub-groups therein. Unless otherwise specified, the present disclosure relates to and explicitly incorporates each and every specific member and combination of sub-ranges or sub-groups.

[0061] As used herein, the term "on the order of, when used in conjunction with a quantity or parameter, refers to a range spanning approximately one tenth to ten times the stated quantity or parameter.

[0062] Unless defined otherwise, all technical and scientific terms used herein are intended to have the same meaning as commonly understood to one of ordinary skill in theart. Unless otherwise indicated, such as through context, as used herein, the following terms are intended to have the following meanings:

[0063] As used herein, the term “pose” refers to a 6 degree-of-freedom (DOF) pose (3D position and orientation), unless otherwise stated.

[0064] As used herein, the term “surface detection subsystem” refers to a system or subsystem that detects the topography of a three-dimensional surface (e.g. acquires a set of surface data describing the surface topography). Non-limiting examples of surface detection modalities include structured light illumination, laser range finding, and photogrammetry.

[0065] As used herein, the term “optical tracking subsystem” refers to a system or subsystem that operates with visible or infrared light, and which includes stereo cameras to detect the positions of passive optical tracking markers (e.g. reflective spheres) and / or active optical tracking markers (e.g. light emitting diodes (LEDs)). The optical tracking markers can be affixed or otherwise connected to a flexible or rigid handheld implement, patient, subject, instrument, tool, or other component of a surgical system or surgical field, and which are detectable by the optical tracking subsystem for use in determining the pose.

[0066] As used herein, the term "calibration transformation" refers to a transformation that relates the coordinate system (frame of reference) of a surface detection subsystem to the coordinate system (frame of reference) of tracking subsystem, such as an optical tracking subsystem.

[0067] As used herein, the term “intraoperative” refers to events associated with a medical procedure, including events occurring during a therapeutic portion of a medical procedure, events relating to the preparation of a patient prior to a therapeutic portion of a medical procedure, and also events related to assessment of an outcome of a medical procedure following the completion of a therapeutic portion of a medical procedure.

[0068] For the purpose of contextualizing the structure and operation of the systems, devices, and methods disclosed herein, headings are provided. The headings provided herein are for convenience only and do not interpret the scope or meaning of the claimed present technology. Embodiments under any one heading can be used in conjunction with embodiments under any other heading.Intraoperative Surface-Based Navigation of Spinal Procedures

[0069] Surgical navigation systems, developed for use in spinal surgical procedures, leverage surface detection to generate navigation images that show, in real time, the 6 DOF pose of surgical tools relative to pre-operative volumetric images. Such systems employ surface detection modalities such as structured light to intraoperatively acquire surface data characterizing the exposed vertebrae, and to perform intraoperative surface-to-surface registration between the intraoperatively acquired surface data and pre-operative surfacedata (obtained by segmenting pre-operative volumetric data). When a surface detection subsystem is integrated with an optical tracking subsystem that can track the pose of surgical tools, and when a calibration coordinate transformation is obtainable between the surface detection subsystem and the optical tracking subsystem, the resulting integrated system enables the display of intraoperative guidance images that show the pose of tracked surgical tools relative to the volumetric image data, and facilitates the determination of an intraoperative orientation of the vertebrae (and thus intraoperative orientation of the spine) based on intraoperative surface detection.

[0070] FIG. 1 A shows an illustration of an example of an integrated surgical guidance system fortracking the intraoperative position of a medical instrument relative to patient anatomy during a spinal surgery. Patient 5 is shown in the prone (face down) position, with vertebrae exposed. The example system includes a surface detection subsystem 10 capable of detecting surface topography, and an optical tracking subsystem 20 capable of tracking the pose medical instruments 40. As shown in the figure, the surface detection subsystem 10 and the optical tracking subsystem 20 can be rigidly connected, for example, secured to a common frame 15.

[0071] The optical tracking subsystem 20 enables the detection of the pose of an object based on detection of the position of a cluster of spatially distributed optical tracking markers. Each tracked object that is tracked or trackable by the optical tracking subsystem 20, such as the surgical instrument 40 shown in FIG. 1 A, is fitted with a set of optical tracking markers (e.g. passive reflective spheres 45) that are each fixed relative to the object in a pre-defined and spatially distributed configuration. To determine the 6-DOF pose (3D position + orientation) of the object, at least three markers must be used to track each object. When a given object is tracked, the optical tracking subsystem 20 identifies the markers within the field of view of the stereo camera pair, compares the observed positions of each detected optical tracking marker to a pre-defined spatial template stored in the system, identifies the object by comparing on the observed positions of the markers to predefined marker data associating different marker spatial configurations with different tracked objects, and employs geometric transformations to calculate the pose of the object within the coordinate system the camera pair. In general, the cluster of optical tracking markers affixed to a given object should be evenly distributed in space to ensure robust tracking from multiple angles, and the spacing should avoid near collinear configurations for tracking stability.

[0072] As noted above, the surface detection subsystem 10 is capable of acquiring intraoperative surface data characterizing the surface of the exposed vertebrae. One example of a surface detection subsystem 10 is a structured light imaging subsystem. A structured light imaging subsystem includes at least one illumination (e.g. projection) deviceand at least one camera. The illumination device(s) projects temporally and / or spatially modulated light onto the surface to be imaged, while the camera(s) capture images of the illuminated surface. This active illumination enables robust and efficient identification of pixel correspondences between calibrated camera-projector (a projector can be thought of as an inverse camera) or calibrated camera-camera system. The correspondence (disparity) data can then be transformed into real-space coordinate data in the coordinate system of the calibrated camera(s) and / or projector(s) by geometrical triangulation.

[0073] During a surgical procedure, the surface detection subsystem 10 is positioned such that 3D surface of the surgical site (e.g. the bony surfaces of the exposed vertebrae) is acquired. The created virtual representation of the 3D surface is then registered to volumetric image data (such as, but not limited to, computed tomography (CT) image data, magnetic resonance imaging (MRI) image data, positron emission tomography (PET) image data), using, for example, methods described in International Patent Application No.PCT / CA2011 / 050257, titled “SYSTEM AND METHODS FOR INTRAOPERATIVE GUIDANCE FEEDBACK”. The volumetric image data can be pre-operatively acquired but is not necessarily pre-operatively acquired. For example, in some applications, the volumetric image data can also be intra-operatively acquired.

[0074] In general, the surface detection subsystem 10 can be any suitable system for detecting, measuring, imaging, or otherwise determining the surface topography of one or more objects (such as, but not limited to, a region of an exposed vertebrae of a patient 5) using optical radiation. Non-limiting examples of suitable optical devices include laser range finders, photogrammetry systems, and structured light imaging systems, which project surface topography detection light onto a region of interest and detect surface topography light that is scattered or reflected from the region of interest. The detected optical signals can be used to generate surface topography datasets consisting of point clouds or meshes. Other example modalities of surface detection subsystems include using sound waves for determining surface topography, such as ultrasonography.

[0075] In order to combine the surgical tool pose information obtained from the optical tracking subsystem 20 (obtained in the frame of reference and coordinate system of the optical tracking subsystem 20) with the surface-registered volumetric image data (transformed, via coordinate transformation into the frame of reference and coordinate system of the surface detection subsystem 10) to facilitate surgical navigation, a calibration transformation is employed that relates the coordinate system of the optical tracking subsystem to that of the surface detection subsystem. If the relative pose of the optical tracking subsystem 20 and the surface detection subsystem 10 is maintained, this calibration can be performed by obtaining the position of at least 3 points from a calibration object that is detectable via both subsystems (e.g. a calibration object, device or structure that includesboth optical tracking markers detectable by the optical tracking subsystem and reference surface features detectable by the surface detection subsystem), and aligning these points to obtain the calibration transformation, as described in International Patent Application No.PCT / CA2011 / 050257. In example embodiments in which the optical tracking subsystem 20 is rigidly fixed relative to the surface detection subsystem 10, for example, via rigid frame 15 as shown in FIG. 1A, an initial (e.g. “factory”) calibration transformation can be determined, and the initial calibration transformation can be optionally updated, e.g. refined prior to and / or during a given surgical procedure, via use of a calibration object as described above.

[0076] After calibration, the calibration transformation between the coordinate system of the optical tracking subsystem and the surface detection subsystem is known. Registering the surface datasets and volumetric image data is therefore equivalent to identifying the position and orientation of the volumetric image data in the coordinate system of the optical tracking subsystem. As a result, any medical instrument 40, which is afterwards tracked with the tracking subsystem, can be presented to the surgeon as an overlay of the surgical instrument 40 on the registered volumetric image data on a display or other visualization devices.

[0077] To compensate for patient and / or system motion, an optical tracking reference structure can be employed, where the optical tracking reference structure is removably attached to the patient anatomy (e.g. to a skeletal feature of the patient). FIG. 1A shows an example optical tracking reference structure 50 having a cluster of optical tracking markers 55 fixed thereto or thereon. After having acquired an intraoperative surface dataset, the pose of the optical tracking reference structure 50 can be tracked using the optical tracking subsystem, and changes in the pose of the optical tracking reference structure 50, caused by relative motion between the system and the patient, can be employed to adapt the pose of the volumetric image data, such that the pose of the volumetric image data remains correct and facilitates accurate navigation of tracked surgical tools, without the need for continuous acquisition of surface data.

[0078] Non-limiting examples of optical tracking reference structures are disclosed in International Patent Application No. PCT / CA2015 / 050939, titled “OPTICAL TRACKING REFERENCE STRUCTURE AND SURFACE REGISTRATION METHODS EMPLOYING THE SAME FOR PERFORMING NAVIGATED SURGICAL PROCEDURES”, filed on September 23, 2015, which is incorporated herein by reference in its entirety. For example, FIG. 2A shows an example implementation of an optical tracking reference structure 200 which is based on a bone clamp design. The example device employs forceps (which can be referred to as a pair of forceps) including two members 205 that define longitudinal axis 201 and pivot around a pin 210, such that jaws 215 with spikes are rotated to grip the spinousprocess. As shown in the figure, a locking mechanism is operably connected to the forceps, with the example locking mechanism including a series of interlocking teeth 220 that cooperate with two handles 225 on the other end of the members 205 to allow the surgeon to tighten and to lock optical tracking reference structure 200 in place.

[0079] As can be seen in FIG. 2A, the example optical tracking reference structure 200 includes an optical tracking marker attachment 230 that supports, near its distal end, passive optical tracking (fiducial) markers 240, and where a proximal end of marker attachment 230 is mechanically coupled (e.g. attached, connected, or integrally formed) to the forceps at a location that is remote from the location of clamping jaws 215, in order to allow the optical tracking subsystem to track the position of the optical tracking reference structure. In the illustrated example, the optical tracking marker attachment 230 is mechanically coupled to the portion of the forceps that includes the interlocking teeth 220, but it will be understood that marker attachment 230 can be mechanically coupled to other portions of the forceps, such as to one of the handles, or to one of longitudinal members 205.

[0080] FIG. 2C is a flow chart that illustrates an example method in which an optical tracking marker structure is employed to facilitate intraoperative surgical guidance in the presence of changes in the position and orientation of the patient relative to the tracking subsystem and surface detection subsystems. In the present non-limiting example, at the beginning of a navigated posterior approach spine surgery, the patient is placed in a prone (face-down) configuration on the operating table (as in FIG. 1A) and anesthesia is administered. The surgeon approaches the spine of the patient from the back and exposes the bony surface of the vertebrae of interest by retracting soft tissue components.

[0081] Preparing the patient, the navigated portion of the surgery begins, which is illustrated in the example flow chart shown in FIG. 2C that is based on a level-by-level clinical workflow, with each level being separately navigated using the optical tracking marker structure, as described below. In step 300, the optical tracking reference structure is securely attached to a first selected vertebral level to be navigated. In step 305, the surface detection subsystem (such as a structured light system) acquires a surface scan of the vertebrae, and the optical tracking subsystem is employed to record the position of the optical tracking reference structure using triangulation of the detected positions of the optical tracking markers. In step 310, surface registration is performed between the acquired intraoperative surface data (e.g. surface data characterizing the visible lamina and / or spinous process regions), and pre-operative surface data, segmented from the volumetric image data (which can be segmented to only include surface data corresponding to the selected vertebral level), optionally using registration support information (e.g. a set of locations, identified by a user, within the coordinate systems of both the volumetric image data and the intraoperatively acquired surface data to determine an initial correspondence,and / or a known orientation of the optical tracking marker support structure relative to vertebrae and selected vertebral level) that can be employed to facilitate an initial alignment of the surfaces prior to surface registration. The surface data can be segmented from the volumetric image data according to a wide variety of methods. One example method involves the selection of a bone threshold and generating an isosurface using the marching cubes algorithm from the volumetric image data. Another example method involves the construction of an isocontour from each 2D slice of a volumetric image data based on a bone threshold, and stitching the slices together into a 3D surface. Any suitable surface registration method can be employed to perform registration between surfaces, when performing methods according to the example embodiments disclosed herein. One example registration method is the iterative closest point algorithm, in which the distance between points from different surfaces are minimized.

[0082] As shown at step 315, once the registration is complete, the system can present an overlaid image of any optically tracked medical instrument (that has optical tracking markers trackable by the optical tracking subsystem), such that the tracked medical instrument is shown relative to the registered volumetric image data for navigation of a portion of the surgical procedure pertaining to the selected vertebral level (such as, for example, the insertion of pedicle screws within the vertebra corresponding to the selected vertebral level). The optical tracking reference structure allows the surgical guidance system to detect, and compensate for, movement (due to respiration, patient movement, or system movement) of the vertebrae relative to the system during the navigation, without requiring acquisition and registration of additional surface data to the volumetric image data.

[0083] In step 320, the surgeon removes the optical tracking reference structure from the selected vertebral level and optionally restarts the process on the next vertebral level as per the surgical plan, and the method of shown in FIG. 2C is repeated. Notably, each time a new vertebral level is to be navigated, the optical tracking reference structure is moved to the new level and new intraoperative surface data is acquired characterizing the exposed surface of the current vertebral level.

[0084] The tracking of a medical instrument and display of navigation images showing the pose of the tracked medical instrument relative to volumetric image data, as shown in step 315 of FIG. 2C, relies on the accuracy of the calibration transformation between the optical tracking subsystem and the surface detection subsystem. As noted above, this calibration transformation can be determined prior to surgical procedure (e.g. as a “factory” calibration transformation) and the initial calibration transformation can be optionally updated, e.g. refined prior to and / or during a given surgical procedure, via use of a calibration object. The validity of the calibration transformation can be compromised if the relative position between the optical tracking subsystem and surface detection subsystemchanged (which can occur even when such systems are supported on a rigid frame), for instance, due to physical impact and / or thermal drift, and it can be beneficial to validate and / or re-acquire the calibration transformation during the surgical procedure.Use of Optical Tracking Reference Structure for Validating or Acquiring Calibration Transformation

[0085] In some example implementations, known surface features of the optical tracking reference structure can be employed to determine a calibration transformation, such that the optical tracking reference structure can be employed to perform both (i) optical-tracking-based compensation for changes in relative position and orientation between the patient anatomy and the system in between surface registration steps, and (ii) validation and / or updating of the calibration transformation. This can be achieved when the optical tracking reference structure includes (i) optical tracking markers that enable a determination of pose of the calibration reference structure, via the optical tracking subsystem, in the coordinate system (frame of reference) of the optical tracking subsystem and (ii) surface features that enable a determination of pose of the optical tracking reference structure, via the surface detection subsystem, in the coordinate system (frame of reference) of the surface detection subsystem.

[0086] In order to determine or update the calibration transformation, both surface and optical tracking data are acquired, with the acquired surface data including at least a portion of the optical tracking reference structure, where the portion that is included has sufficient surface topography (i.e. includes a sufficient number of reference surface structures or surface features) to enable the determination of the pose of the optical tracking reference structure via surface imaging and processing. This is generally easily facilitated in the example case of a spinal surgical procedure because the optical tracking reference structure is typically directly attached to or near the vertebra of interest. The segmented calibration reference structure from the acquired surface is registered to reference surface data characterizing the known surface of the optical tracking reference structure (for example, a 3D-model of one or more geometrical features of the calibration reference structure), and combined with the pose as currently measured by the optical tracking subsystem, which yields an updated calibration transformation.

[0087] For example, with regard to FIG. 2A, the known geometry (surfaces) of the optical tracking markers 240, and / or one or more known geometrical features of the optical tracking marker attachment 230, and / or the one or more known geometrical features of the forceps, can be employed to determine the intraoperative pose of the optical tracking reference structure. FIGS. 1B and 2B show an example embodiment in which the optical tracking reference structure includes one or more additional reference surface features (52in FIG. 1B, and 250 / 260 in FIG. 2B) that enable a determination of pose of the optical tracking reference structure, via the surface detection subsystem, in the coordinate system (frame of reference) of the surface detection subsystem. As noted in International Patent Application No. PCT / CA2015 / 050939, such additional reference surface features can provide additional non-symmetric surfaces useful for the registration process. First, additional reference surface features can enable the registration to be unique, whereas simple planar or spherical structures which have high degrees of symmetry can lead to registration ambiguity. Second, they can reduce the probability of overexposure by the surface detection subsystem and / or ambient lighting conditions on all characteristic structures simultaneously. Furthermore, surface properties (roughness / reflectivity) of characteristic structures can also be tuned in order to optimize surface image acquisition based on surface detection subsystem specification and ambient environmental condition in which surface detection subsystem is meant to be used.

[0088] This use of the optical tracking reference structure to validate and / or re-acquire a new calibration transformation can be performed at any time before or during a surgical procedure, such as each time surface registration is performed, and optionally each time the calibration reference structure is attached to a new skeletal feature of a patient. For example, in the case of a spinal surgical procedure, the method can be performed or repeated when the tracking marker support structure (or an additional tracking marker support structure) is attached to a new vertebral level.

[0089] As noted above, an optical tracking reference structure can be used to compensate for global intraoperative changes in the position and orientation of the spine. However, changes in local positions and orientations of the vertebral levels are not compensated by the optical tracking reference structure if the optical tracking reference structure is fixed at one vertebral level and other vertebral levels are subsequently navigated. Such changes can occur, for example, due to a spinal intervention, such as the use of screws and rods to correct for a spinal deformity or pathology. Accordingly, when navigation of multiple vertebral levels is required, a single registration transform (between one or multiple vertebral levels from the intraoperative surface data and preoperative volumetric data) will not necessarily be accurate across multiple vertebral levels. For example, inaccuracies can even exist for spinal levels immediately adjacent to the selected vertebral level on which the optical tracking reference structure is secured.

[0090] Accordingly, the accuracy of a single registration transform, when applied to multiple spinal levels, degrades when there are discrepancies between the local intraoperative vertebral orientation and the local preoperative vertebral orientation, and the inaccuracy typically worsens as the number of vertebral levels are increased. For example, Uehara et al. have shown that pedicle screw perforation rates are influenced by distancefrom the tracked reference frame in multi4evel registration using a CT-based navigation system in the setting of scoliosis [Uehara M1, Takahashi J2, Ikegami S1, Kuraishi S1, Shimizu M1 , Futatsugi T1 , Oba H1, Kato H1, Spine J. 2016 Oct 21. pii: S1529-9430(16)31034-8. doi: 10.1016 / j.spinee.2016.10.019],

[0091] This inaccuracy can be avoided using the aforementioned serial workflow shown in FIG. 2C (and repeated for subsequent levels), in which registration is independently performed for each relevant vertebral level during the medical procedure (moving the reference to each subsequent level for each registration). For example, when a spinal procedure involving multiple vertebral levels is to be performed, surface-based registration can be performed, on a per-level basis, separately and sequentially during the medical procedure, with only a single per-level registration transform employed at a time. As described above, and illustrated in FIG. 2C, if the surgical procedure begins with a first vertebral level, a single-level registration transform can be initially obtained and employed for the first vertebral level, and this first registration transform can then be employed to generate navigation images. Later, when the surgical procedure involves the second vertebral level, re-registration is performed to provide a new surface-based registration transform for the second vertebral level, and this second registration transform is employed to generate navigation images. This sequential process of registration results in a registration modality in which only a single registration transform is available and utilized at any given time during navigation of the surgical procedure.Single Level vs. Multilevel Registration when Navigating Spinal Procedures via Intraoperative Surface Detection

[0092] The preceding example workflow for performing intraoperative-surface-based navigation of spinal surgical procedures involves the use of an optical tracking reference structure to facilitate (i) optical-tracking-based compensation for changes in relative position and orientation between the patient anatomy and the system in between surface registration steps, and, optionally, (ii) validation and / or updating of the calibration transformation linking coordinate systems of the optical tracking subsystem and the surface detection subsystem. As described above, the optical tracking reference structure is removed and reattached to different vertebral levels as the spinal surgical procedure progresses and the different vertebral levels are navigated and operated upon.

[0093] Since registration is performed for a single selected spinal level of interest, resulting in a single registration transform between the pre-operative surface data and intraoperative surface data associated with a single selected spinal level. As a consequence of this local registration that is specific to a single selected spinal level, navigation accuracycan be maintained at the selected spinal level, because the selected spinal level consists of a single rigid body (e.g. a solid vertebrae).

[0094] This approach, however, is disadvantageous in that only a single spinal level is registered at any given time during the medical procedure, and navigation is therefore only accurate in a local region associated with a given spinal level. Moreover, this practice requires that registration be performed multiple times during the medical procedure, with a new registration being performed each time a new spinal level is encountered during the surgical plan. This need for multiple re-registration steps can disrupt clinical workflow and lead to increased expense due to the time delays involved in each registration step.

[0095] As described in International Patent Application No. PCT / CA2018 / 050757, titled “SYSTEMS AND METHODS FOR PERFORMING INTRAOPERATIVE SURFACE-BASED REGISTRATION AND NAVIGATION”, filed on June 21, 2018, which is incorporated herein by reference in its entirety, this problem can be mitigated by independently registering and tracking multiple intraoperatively exposed vertebral levels having independent positional and orientational degrees of freedom, via surface detection of the exposed multi-level vertebral surface, thereby enabling intraoperative surgical guidance in the presence of both global motion and local relative motion of the different vertebral levels. Such an approach, in which per-level registration transforms that each respectively correspond to a different vertebral level, are repeatedly and intraoperatively updated during the medical procedure, enables the determination of an updated “ground truth” of the per-level position and orientation (pose), without needing to perform the serial, single-level method described above with reference to FIG. 2C.

[0096] The segmented surface data can be obtained from the volumetric image data on a per-level basis, such that the segmented surface data corresponds to plurality of segmented surface datasets, each corresponding to a pre-selected vertebral level that is expected to be exposed intraoperatively during the surgical procedure. Each registration can be initially performed as an initial registration based on correspondence, at each respective surface region, between per-region volumetric fiducial points and respective per-region intraoperative fiducial points. The per-region intraoperative fiducial points associated with a given surface region can be provided via manual input (e.g. as input received from a user or operator), or automatically generated. After generating respective initial registrations for each surface region, a surface-to-surface registration can then be performed for each region, between the segmented surface data and the intraoperative surface data, thereby obtaining level-specific registration transforms. The registration transforms respectively map, for each level, the segmented surface in the pre-operative volumetric frame of reference to the intraoperative surface data.

[0097] During the surgical procedure, a determination or estimation of the position and / orientation of the vertebra (spine) can be obtained by performing intraoperative surface acquisition and performing multi-level registration of the intraoperative surface data with the multi-level surface data segmented from the volumetric image data. The orientation can be quantified according to one or more alignment parameters, examples of which are provided and described in detail in the Examples below. Various example methods of performing such per-level registration, and generating and displaying visualizations and / or measures of intraoperative vertebral orientation, are described in International Patent Application No. PCT / CA2017 / 050806, titled “SYSTEMS AND METHODS FOR DETERMINING INTRAOPERATIVE SPINAL ORIENTATION”, filed on July 4, 2017, which is incorporated herein by reference in its entirety.Challenges Associated with Intraoperative Assessment of Vertebral Alignment during when Navigating Spinal Procedures via Intraoperative Surface Detection

[0098] As described above, the vertebral (spinal) orientation (alignment), as determined intraoperatively during or after a spinal procedure involving an exposed portion of the vertebrae, can be determined by performing registration between segmented surface data (obtained from volumetric image data) and detected surface data, with surface registration being performed on a per-level basis. The resulting per-level registration transforms can be employed to generate measures, and / or a visualization, associated with the pose of the vertebrae, where the measures and / or visualization may, in some example embodiments, pertain to the change in the vertebral orientation relative to another vertebral orientation, such as, for example, the planned vertebral orientation, the vertebral orientation in the volumetric image data, and / or an intraoperative vertebral orientation corresponding to a previous time or phase during the surgical procedure.

[0099] Unfortunately, the present inventors have found that the intraoperative assessment of vertebral orientation (alignment) based intraoperative acquired surface data can be hindered or compromised by factors including, but not limited to, the obstruction of the surgical field due to the presence of blood and tissue and changes in (e.g. removal of) the structure of the vertebral levels caused by the surgical intervention. Such factors can preclude the ability to intraoperatively acquire surface data that achieves sufficiently accurate surface registration with the surface data segmented from the volumetric image data (e.g. failing to satisfy a pre-determined registration quality criterion or criteria, such as, for example, a registration error pertaining to the mean distance between points of the registered surfaces, or the standard deviation of the distances between points of the registered surfaces). The failure to achieve sufficiently accurate surface registration can result, for example, from the occlusion of the vertebral surface by tissue and / or blood, whichprevents the acquisition of intraoperative surface data that characterizes the underlying vertebral surface, but which would have resulted in sufficiently accurate surface registration if not occluded. The failure to achieve sufficiently accurate surface registration can result, additionally or alternatively, from surgical modifications to the surface of the exposed vertebra, causing a spatial mismatch between the intraoperatively acquired surface data and the surface data segmented from the volumetric image data that results in insufficient or surface inaccurate registration.Indirect Intraoperative Tracking of Vertebral Pose via Glyphs with Per-Level Association

[0100] As described in various example embodiments of the present disclosure, this problem can be addressed by alternative workflow in which a set of glyphs are secured relative to and respectively associated with vertebral levels, such that each glyph corresponds to a given vertebral level, and where the intraoperative pose of each glyph, as determined via computer vision, is employed to intraoperatively determine the position and orientation of each glyph-tracked vertebral level, without requiring the subsequent intraoperative surface detection of the underlying vertebral surface. Provided that each glyph is rigidly secured to a respective vertebral level such that intraoperative changes in the position and orientation of vertebrae is mirrored by changes in the pose of the corresponding glyph, intraoperative tracking of the pose of each glyph can be employed as a surrogate or proxy for the determination of the intraoperative position and orientation (pose) of each vertebral level.

[0101] In this manner, even when the surface of the underlying vertebral level is modified, via the surgical procedure, such that the intraoperatively detected surfaced data characterizing the modified surface would no longer be suitable for or capable of surface based registration with the associated segmented surface data from the volumetric image data, or the acquisition of intraoperative surface data characterizing the surface of the vertebral level is prevented due to occlusion via blood, tissue or other debris, the intraoperative pose of the vertebral level can still be inferred based on (i) a previously established relationship between the pose of the glyph and the position and orientation of the vertebral level, and (ii) maintaining the pose of the glyph relative to the vertebral level, such that the previously established relationship remains valid. Moreover, the use of glyphs for intraoperative per-vertebral-level tracking, as opposed to the use of optical tracking marker assemblies, provides a compact and uncluttered surgical field. Indeed, unlike the case of an optical tracking assembly, which requires a cluster of physically separate and spatially distributed optical tracking markers that occupies a large volume of space, a glyph can be provided as a single marker that occupies far less space within the surgical field thanan optical tracking marker assembly, enabling the surgical procedure to proceed unhindered even when several exposed vertebral levels have respective per-level glyphs attached thereto.

[0102] A “glyph”, as used herein, refers to a distinguishable symbol, mark, character, pattern, or image, defined on and / or forming at least one surface of an object, for facilitating identification of the object and a determination of three-dimensional position and orientation (pose) of the object by a computer vision system (such as a monocular camera or a stereo camera pair). A glyph can further be a multi-surface and / or multi-angle component to facilitate line-of-sight optical recognition by a computer vision system. Non-limiting examples of glyphs include letters, numerals, punctuation marks, icons, single- or multi-dimensional barcodes, QR codes, and other machine-readable or computer-recognizable features. A glyph can be formed through various means, including, but not limited to, printing, engraving, embossing, marking, etching, inlaid or embedded materials, incorporation of multilayer optical structures, or spatial variations in one or more material properties (for example, spatial variations in diffuse and / or specular reflectivity, conferred, for example, by spatial variations, surface finish, roughness, microstructure or nanostructure). A glyph can further comprise mono-chromatic or multi-chromatic print colors, or any combination thereof. A glyph can be passive, but can additionally or alternatively include optically active / emissive features such as, for example, light emitting diodes or optically scattering features configured to scatter light from a light source fixed relative to the glyph.

[0103] A glyph can be defined through various means, including but not limited to printing (e.g. silkscreen printing), lamination, engraving, embossing, marking, anodization, etching, inlaid or embedded materials, incorporation of multilayer optical structures, or spatial variations in one or more material properties (for example, spatial variations in diffuse and / or specular reflectivity, conferred, for example, by spatial variations in surface finish, roughness, microstructure or nanostructure). A glyph can be passive but can additionally or alternatively include optically active / emissive features such as, for example, light emitting diodes or optically scattering features configured to scatter light from a light source fixed relative to the glyph. A glyph can be formed on a surface of a material such as, but not limited to, metals (including alloys), plastics, ceramics and various composite materials including two or more of metals, plastics and ceramics.

[0104] FIG. 3 illustrates an example system for performing multilevel glyph-based surgical navigation of a spinal procedure that facilitates intraoperative guidance of tracked medical instruments (e.g. tools) relative to the vertebrae and the intraoperative determination and assessment of vertebral alignment. The example system includes a set of glyph tracking structures 400 (the figure shows three example glyph tracking structures 400A, 400B and 400C), each including a glyph 410 that is defined or otherwise provided on glyph supportstructure 420 that is removably securable, either directly or indirectly, to a vertebral level (i.e. removably fixable or attachable to or within osseous tissue, or to a component already fixed on or within osseous tissue, such as a bone screw). In some example implementations, each glyph has a distinct structure to permit identification thereof via image processing.

[0105] In some example embodiments, at least one glyph tracking structure 400 of the set of glyph tracking structures that are employed in a navigated spinal surgical procedure (or which are provided as a kit from which one or more glyph tracking markers can be selected for use in a given navigated spinal surgical procedure) can include an elongate portion (which can be define, for example, a longitudinal axis), that provides spatial standoff between the anatomy to which the glyph tracking structure is secured, and a proximal surface on which the glyph is defined. This elongate portion can be beneficial for avoiding or reducing the likelihood of occlusion of the glyph by tissue, blood or other debris during the surgical procedure. The elongate portion can also be beneficial in positioning of the glyph remotely to facilitate access of to the vertebral surface when performing the surgical procedure.

[0106] In some example embodiments, at least one glyph tracking structure 400 of the set of glyph tracking structures that are employed in a navigated spinal surgical procedure (or which are provided as a kit from which one or more glyph tracking markers can be selected for use in a given navigated spinal surgical procedure) can be a monolithic glyph tracking structure. A non-limiting example of a monolithic glyph tracking structure is a bone screw having a glyph defined on one or more proximal surfaces that are not configured to be embedded into osseous tissue, such as a surface of a head portion of the bone screw.

[0107] In other example embodiments, at least one glyph tracking structure 400 of the set of glyph tracking structures that are employed in a navigated spinal surgical procedure (or which are provided as a kit from which one or more glyph tracking markers can be selected for use in a given navigated spinal surgical procedure) can be provided as an assembly of multiple components. An example of a glyph tracking structure assembly includes a base structure having a distal region that includes one or more attachment features suitable for removably securing the base structure to osseous tissue, and a proximal region that has secured thereto, or is configured to removably receive, a glyph member having at least one surface with a glyph defined thereon. The glyph member is a physical structure, such as, for example, a tile or cap, which can be secured, permanently or removably, to the base structure. The glyph member can be, in some example implementations, secured to the base structure by a friction fit between the glyph member and a proximal region of the base component. In another example implementation, the glyph member can be removably secured to the base component by magnetic forces produced byrespective permanent magnets provided on, embedded within, or recessed within the base structure and the glyph member.

[0108] In some example embodiments, the base structure of a glyph tracking assembly can itself include multiple components. For example, the base structure can include, or can be attachable to, a distal fixation component that is attachable to or embeddable within osseous tissue, an intermediate elongate member that provides a spatial standoff between the anatomy to which the distal fixation structure is secured, and the glyph member on which the glyph is defined. The intermediate elongate member positions the glyph at a location that is remote from the vertebral surface, which can be beneficial for reasons noted above.

[0109] It will be understood that the spatial offset between the vertebral surface and the glyph will impact the sensitivity or tolerance of glyph-based tracking to angular perturbations to the glyph that occur after an initial surface-based correlation / relationship / transformation is established between the glyph pose and the position and orientation of the vertebral level to which the glyph is secured. According, in some example implementations, the distance between a distal end of glyph tracking structure (that is secured to the vertebral surface, to an object already secured to the vertebral surface, such as a bone screw) and the proximal end of the glyph tracking structure (on which the glyph is defined, or which is configured to removably receive a glyph member), can be between 1 cm and 15 cm, between 1 cm and 12 cm, between 1 cm and 10 cm, between 1 cm and 8 cm, between 1 cm and 6 cm, between 1 cm and 4 cm, between 2 cm and 15 cm, between 2 cm and 12 cm, between 2 cm and 10 cm, between 2 cm and 8 cm, between 2 cm and 6 cm, between 2 cm and 4 cm, between 3 cm and 15 cm, between 3 cm and 12 cm, between 3 cm and 10 cm, between 3 cm and 8 cm, between 3 cm and 6 cm, between 3 cm and 4 cm, between 4 cm and 15 cm, between 4 cm and 12 cm, between 4 cm and 10 cm, between 4 cm and 8 cm, between 4 cm and 6 cm, or between 4 cm and 5 cm. In some example implementations, after securing the glyph tracking structure to a given vertebral level, the distance between the vertebral surface and the proximal end of the glyph tracking structure (on which the glyph is defined, or which is configured to removably receive a glyph member), can be between 1 cm and 15 cm, between 1 cm and 12 cm, between 1 cm and 10 cm, between 1 cm and 8 cm, between 1 cm and 6 cm, between 1 cm and 4 cm, between 2 cm and 15 cm, between 2 cm and 12 cm, between 2 cm and 10 cm, between 2 cm and 8 cm, between 2 cm and 6 cm, between 2 cm and 4 cm, between 3 cm and 15 cm, between 3 cm and 12 cm, between 3 cm and 10 cm, between 3 cm and 8 cm, between 3 cm and 6 cm, between 3 cm and 4 cm, between 4 cm and 15 cm, between 4 cm and 12 cm, between 4 cm and 10 cm, between 4 cm and 8 cm, between 4 cm and 6 cm, or between 4 cm and 5 cm. In some example implementations, after securing the glyph tracking structure to a given vertebral level, the distance between the vertebral surface and the most proximally located surface on which a glyph is defined,can be between 1 cm and 15 cm, between 1 cm and 12 cm, between 1 cm and 10 cm, between 1 cm and 8 cm, between 1 cm and 6 cm, between 1 cm and 4 cm, between 2 cm and 15 cm, between 2 cm and 12 cm, between 2 cm and 10 cm, between 2 cm and 8 cm, between 2 cm and 6 cm, between 2 cm and 4 cm, between 3 cm and 15 cm, between 3 cm and 12 cm, between 3 cm and 10 cm, between 3 cm and 8 cm, between 3 cm and 6 cm, between 3 cm and 4 cm, between 4 cm and 15 cm, between 4 cm and 12 cm, between 4 cm and 10 cm, between 4 cm and 8 cm, between 4 cm and 6 cm, or between 4 cm and 5 cm.

[0110] In some example implementations, a glyph resides on, is defined on, or is otherwise mechanically supported by a support structure that enables the glyph to be secured to a rigid structure residing on or in a body of a subject, such that the pose of the glyph remains fixed relative to the rigid structure (in the absence of an external perturbation to the glyph that would result in a loss of pose correspondence, e.g. in the absence of application of a torque to the glyph support structure, relative to the rigid structure to which the glyph support structure is secured, that would change the pose of the glyph relative to the rigid structure). The combination of a glyph and a support structure supporting the glyph is henceforth referred to as a glyph tracking structure.

[0111] Non-limiting examples of rigid structures to which a glyph tracking structure can be secured include rigid tissue, which is defined as solid tissue having sufficient mechanical stiffness and integrity to support a given glyph tracking structure in a stable pose, and can include, for example, both rigid and semi-rigid tissues such as osseous tissue (bone), ligaments, cartilage, tendons, sclera, interverbal discs, joint capsules, and other connective tissues. Other examples of rigid structures to which a glyph tracking structure can be secured include synthetic materials residing on or in the body such, but not limited to, synthetic implants such as bone screws and bone plates, and internal prostheses.

[0112] A glyph can be formed or defined on a non-rigid structure that is supported by an underlying rigid structure that forms at least a portion of the rigid glyph support structure. In one example, the glyph can comprise an adhesive-backed material such as Tyvek, plastic, cloth, polyester, nylon, woven material, or any combination thereof. The glyph can be adhesively affixed to, for example, a surface of an implanted bone screw, so that a user can first insert the bone screw into the appropriate bone or other surgical target site and then attach the printed code on the adhesive material to the bone screw head or shank, depending on the desired attachment point on the screw.

[0113] Similarly, a glyph can be adhesively affixed to or defined on a marker base, as described in further detail below. In one or more examples, a quick-connect mechanism can be employed to fixedly or removably attach a glyph to an attachment structure (also described in further detail below); the marker base can be attached via a quick-connect mechanism either before or after the attachment structure is inserted, attached or associatedwith the target anatomical site. In a further example, the glyph can be adhesively affixed to, for example, a bone clamp surface, so that a user can first associate the bone clamp with the appropriate bone or other surgical target site and then attach the printed code on the adhesive material to the bone clamp, depending on the desired attachment point on the bone clamp. While one or more examples describe a bone clamp, other types of clamps can also be used, depending on the relevant anatomical target site for affixing such a clamp.

[0114] In another example, the glyph can first be removably or fixedly attached to a screw (including a pedicle screw, other bone screw, and the like as described herein) and then the resulting glyph tracking structure is then fixedly or removably attached to the target anatomical site. Accordingly, in an example, the glyph can first be attached to the attachment structure before associating the glyph and attachment structure with a target anatomical site, or in another example the glyph can be attached to the attachment structure after the attachment structure is associated with a target anatomical site. In still another example, the glyph can be removably or fixedly attached to a target bone site or other target anatomical site, including adhesively attaching the glyph to the target anatomical site. In a further example, the glyph can be removably attached to a bone clamp, including an adhesively or magnetically affixed attachment. In yet another example, the glyph can be fixedly attached directly to a bone clamp, including a removable and / or adjustable angle bone clamp.

[0115] In another example, one or more glyphs can be applied directly to a target anatomical site, including printing or etching directly on or into the target site or structure. For example, a biocompatible ink or other biocompatible material, such as an inert ink or an adhesive-backed sheet with a biocompatible adhesive, can be applied to the target anatomical site, which can include, but is not limited to, bony or non-bone sites, as well as tissue sites which would not readily accommodate an attachment structure. Similarly, etched or laser inscribed glyphs can be applied directly to or into the target anatomical site.

[0116] As used herein, the phrase “marker base’’ refers to a rigid substrate on which a glyph can be defined or supported, where the substrate can be a solid, impermeable, semi-permeable, or permeable material, including, but not limited to, a plastic, PEEK, PEKK, PAEK, plastic composite, metal, metal alloy, ceramic, glass, acrylic, a woven material, or any combination of two or more of these materials. The marker base can be shaped into a configuration including, but not limited to, square, rectangular, oval, round, semicircular, convex, concave, or any combination of two or more of these shapes. In one or more embodiments, a marker base can also employ any type of threaded connection.

[0117] In one or more embodiments, a marker base and glyph can be configured to form a unitary structure wherein the unitary structure comprises a tile, a marker tile, a tile flag, a marker tile flag, or a combination thereof.

[0118] In one or more embodiments, a marker base and glyph can be configured to form a composite structure wherein the composite structure comprises a tile, a marker tile, a tile flag, a marker tile flag, or a combination thereof. A marker base, having a glyph supported or defined thereon, can be secured to a rigid structure via an attachment structure, with the marker base and the underlying attachment structure cooperating to mechanically support the glyph relative to the rigid structure, and the glyph, marker base and attachment structure forming a glyph tracking structure as defined above.

[0119] As used herein, the phrase “attachment structure” refers to a component for attaching a glyph and / or marker base to an anatomical structure or anatomical site. An attachment structure can be configured to be permanently secured to the rigid structure or removably attachable to the rigid structure. Examples of attachment structures include, but are not limited to: a pin; a screw; a tulip (also referred to as a tulip head, a receiver, or receiver head); a clamp; an associated extension or elongated component thereof; and any other orthopedic components for removably or fixedly attaching to an anatomical structure or anatomical site. Examples of screws include, but are not limited to: bone screws; pedicle screws; polyaxial screws; monoaxial screws; cancellous bone screws; cortical screws; cannulated and non-cannulated screws; fenestrated screws; threaded or partially-threaded screws; low- or reduced-torque screws; hybrid thread screws; smooth shank screws; lag screws; compression screws (including headless compression screws); Herbert screws; malleolar screws; self-tapping screws; self-drilling screws; self-starting screws; stylet tip screws; screws with uniform or variable thread pitch; low-profile screws; screws with a threaded, partially threaded, or non-threaded head; reduction head screws; locking screws; spinal implant screws; magnetic core bone screws; trauma and deformity screws; fixation screws, including, but not limited to, spinal fixation screws; break-away screws; drug eluting screws; coated screws, including HA-coated screws, drug-coated screws, screws coated with antibiotics, anti-inflammatory compound(s), growth factors, and the like; bio-absorbable screws, including, but not limited to, screws constructed from polylactic acid, polyglycolic acid, poly-L-lactic acid screws, any combination thereof, and the like; 3D-printed screws, including custom-designed and fabricated screws tailored to individual patient anatomy; and other screws used in orthopedic procedures. An orthopedic screw can be constructed of stainless steel, titanium, titanium alloy, cobalt chrome, other metal alloys, or any combination thereof.

[0120] Examples of tulips include, but are not limited to: polyaxial tulips; motion-limiting tulips; variable angle tulips; fixed angle tulips; low-profile tulips; offset tulips; modified tulips; friction-fit tulips; tapered tulips; modular tulips; reduced height tulips; low-top tulips; reduction-top tulips; minimally invasive-top tulips; low profile tulips; standard or reduction tulips; configurable tulips; top-loading, side-loading, and angled tulips; extended orextended-tab tulips; or any combination thereof. One or more tulips can be constructed of stainless steel, titanium, titanium alloy, cobalt chrome, other metal alloys, or any combination thereof.

[0121] In some example embodiments, a marker base can be removably or fixedly attached to an attachment structure such as a screw head, the base of tulip, an extension attached into a tulip receiver channel, an extension protruding from the base, top or side portion of a tulip, direct threading of a marker base into a tulip threaded channel, including, but not limited to, other threaded connections, direct snap fit of a marker base into a tulip channel, or any combination thereof. In one or more embodiments, an offset tulip can also be employed. In one or more embodiments, an attachment mechanism facilitates association of a marker base with a relevant anatomical structure, for example, attachment to one or more to bones such as vertebrae or vertebral extensions. In one or more further embodiments, a marker base can be attached directly to a screw shank, or indirectly through one or more intermediary components. In still another example, a marker base can also connect directly to one or more bony target anatomical sites, or other non-bony target anatomical sites.

[0122] In an example embodiment, a spinous process screw with an integrated marker base can be directly attached to a target spinous process attachment point by directly screwing a threaded bone screw and associated marker base into the bone. Similarly, a pin with an integrated marker base can be directly attached to bone by driving the pin directly into the target bone. While a spinous process can be one such target bone site, other bone sites can also be targeted for insertion of an example threaded bone screw or pin, such as where the target site lacks an appropriate spinous process protrusion or other typical bony protrusion. In such examples, a target bone site is not limited to having a protrusion or other identifying “typical” target bone site. Other target anatomical sites that are not limited to bony sites can also serve as attachment sites for one or more marker bases.

[0123] Each marker base can have at least one unique glyph relative to the set of glyphs used in a surgical procedure. While the majority of marker bases contain a single unique glyph, a plurality of glyphs can be used on larger marker bases, as appropriate.

[0124] Examples of marker base material of construction include, but are not limited to, metal, metal alloy, ceramic, plastic, plastic composite, PEEK, any combination thereof, and the like. The marker base can be provided as a single use sterile pack device, a multi-use sterilizable device, a disposable device, or any combination thereof. In an embodiment, a printing material such as ink, including an inert ink for surgical use, can provide a suitable contrast from the marker base material for ease of optical detection of the glyph. In one or more examples, a marker base as described herein also includes, but is not limited to, a spring or spring-like material that can flex and subsequently return to a neutral position aftersuch flex. In one or more examples, a spring can flex if bumped or otherwise temporarily engaged before or during a surgical procedure, and the spring subsequently returns to an original position and the associated glyph position is reestablished.

[0125] In one or more example embodiments, the marker base can generally be oriented orthogonal to the attachment point of the patient anatomy to provide visibility of the marker base to the optical sensing system. For example, a marker base associated with an attachment component is oriented so that one or more optical sensors electronically recognize the glyph and its relative position in the surgical field of view. Also, the desired orientation of one or more marker bases can be oriented other than generally orthogonal to maximize readability by a user and also to maximize exposure to, and identification by, one or more optical sensors. For example, one or more marker bases according to the disclosure can also have customizable angulation relative to one or more optical sensors. In another example, a ball joint can be employed to effect customizable angulation. In a further example, multiple fixed angles can be employed relative to one or more optical sensors.

[0126] In an example use such as in a surgical setting, one or more attachment mechanisms supporting respective marker bases are associated with relevant anatomical structures (e g., attachment to one or more to bones such as vertebrae or vertebral extensions), providing optical tracking of glyphs via, for example, QR codes or other optical codes that are readable by the surgical navigation camera system. In an embodiment, one or more attachment mechanisms supporting respective marker bases are also or alternatively associated with extensions of relevant anatomical structures, such as spinal fixation devices including rods, towers, clamps, screws, tulips, and the like.

[0127] In another example embodiment, a marker base comprises a bone screw with a removably attachable marker base frame. In one embodiment, a user inserts a bone screw into a bony projection such as a vertebral spinous process by screwing the threaded screw directly into the bony projection. In an embodiment, the bone screw can be preloaded into a tool for ease of insertion into the bony projection. Once the screw is inserted, then the user can attach a snap-on marker base frame to the head of the bone screw. In an embodiment, the marker base can be attached via a magnetic coupling interface. In another embodiment, the marker base frame can be an open frame that supports a snap-in tile with integrated glyph on its external surface. The integrated glyph can be printed, stamped, molded, etched, carved, or even adhesively attached to the marker base external surface.

[0128] In one or more example embodiments, a marker base frame comprises an open inner cavity for insertion of a marker base having a glyph that is imprinted, stamped, molded, etched, or carved on or into the external surface thereof. The marker base frame is, for example, adjoined to the implanted screw head by a snap-fit, twist-on, magnetic attachment, or other suitable removable attachment. This example embodiment allows a user to accessthe screw head before attaching the removable (e.g., snap-in, snap-on, quick connect) glyph so that a user can adjust the insertion depth of the bone screw, as appropriate. Further, a removable marker base facilitates exchanging a marker base with a different marker base if the relevant lighting or orientation is not optimal to enable optical detection and reading of the glyph.

[0129] Further, a marker base (including a unitary marker base and a composite marker base) can independently be fixedly or removably connected to an attachment structure. In one example, a marker base can be connected to a bone fixation attachment structure, including, but not limited to, a spinous process clamp, a spinous process screw, a lamina screw, an expansion / clamp universal mount (also referred to as a tripod), a screw tulip (also known as a receiver or receiver head), a minimally invasive surgical (MIS) tower, an extended tab receiver head, and the like.

[0130] In one or more example embodiments, an attachment structure provides a fixed or removable connection to a target site or sites, including, but not limited to, a bone, a bony structure, a bone deformity site or sites, an osteophyte or plurality of osteophytes, one or more vertebrae, an intervertebral site or sites, multiple vertebral sites, as well as one or more pairs of vertebral levels. In one or more embodiments, marker bases and associated glyphs can be employed to track one or more soft tissue sites / regions (such as non-bony structures) including, but not limited to, representation of underlying bony structures such as, but not limited to, spinal structures, shoulders, and other underlying structures.

[0131] In one or more example embodiments, marker bases, attachment structures, and related components according to this disclosure can be single use devices provided in a sterile pack. In one or more embodiments, all components according to this disclosure can be multi-use devices comprised of materials which are able to withstand single or multiple autoclave sterilization processes.

[0132] As described herein, a marker base can be a unitary or composite structure, both of which can be directly or indirectly attachable to a single anatomical target site or multiple anatomical target sites. For example, in a surgical setting, a marker base that is a unitary structure can be directly and removably attached to a target anatomical site such as an individual bone or multi-bone structure. Similarly, in another surgical setting example, a marker base that is a composite structure can be directly and removably attached to a target anatomical site such as an individual bone or multi-bone structure. In another set of examples, in a surgical setting, a marker base that is a unitary structure can be directly and fixedly attached to a target anatomical site such as an individual bone or multi-bone structure. Similarly, in another surgical setting example, a marker base that is a multicomponent structure can be directly and fixedly attached to a target anatomical site such as an individual bone or multi-bone structure. A plurality of marker bases that are unitarystructures and / or multi-component structures can also be used in combination in a surgical setting, according to surgical needs and conveniences. In this disclosure, one or more target anatomical sites of a patient include, but are not limited to, a bony structure, a bone deformity site, an osteophyte or plurality of osteophytes, one or more vertebrae, an intervertebral site, multiple vertebral sites, as well as one or more pairs of vertebral levels.

[0133] One or more marker bases can also be removably attached to other surgical components, such as spinal fixation rods, including intermediate components placed between the marker bases and the fixation rod or other fixation components. In another example, one or more marker bases can also be removably attached to another attachment component, including additional extension or elongated attachment structure components.

[0134] In an example embodiment, a marker base can be fixedly or removably attached to a screw, including a bone screw. Attachment points of a marker base to a bone screw include removable or fixed attachment to a screw shank, screw head, top surface of screw head, and the like. In an embodiment, the screw head has external threads, and the corresponding marker base can have corresponding female threads to removably engage the external screw head threads.

[0135] In another example embodiment, the screw head is smooth (i.e., unthreaded), and the corresponding marker base can have a corresponding pop-on configuration with friction fit to engage the screw head.

[0136] In still another example embodiment, an attachment mechanism comprises a marker base quick-connect system. Examples of quick-connect attachment mechanisms include, but are not limited to, snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and the like.

[0137] In one example as shown in FIG. 4A, a unitary marker base structure 401 comprises a glyph 410 integrated with a marker base 430 into a single component. In this example, the unitary marker base structure 401 further comprises an attachment structure 440.

[0138] In another example as shown in FIG. 4B, a composite marker base structure 402 comprises a glyph 410 fixedly or removably integrated 430 with a marker base 430 into a combined structure. In this example, the composite marker base structure 402 further comprises an attachment structure 440.

[0139] An example shown in FIG. 5A provides a representative glyph as a QR code 411 wherein the marker base 431 is removably associated with an attachment structure shown as a screw 441 or bone screw. The removable glyph marker base 431 (also referred to as a tile) component can be attached via a quick-connect mechanism which enables the attachment structure to be inserted into a target anatomical site prior to attaching the glyphmarker base 431. A representative target site includes, but is not limited to, a spinous process 11 as shown in this example.

[0140] In one or more example embodiments, bone screws according to this disclosure can be of relatively smaller diameter and length for smaller stature patients, as compared to relatively larger sizes for adolescents and adults. Also, various screw diameters and lengths can be used in this disclosure for a variety of target bone sizes, such as for children through adults. Also, target bones include (but are not limited to) vertebrae, and other bones or bony structures can also be used in accordance with this disclosure.

[0141] In one or more example embodiments, screws can be fenestrated, cannulated, non-cannulated screw types, or any combination thereof. Also, screws according to this disclosure can be polyaxial, monoaxial, fixed, threaded head, non-threaded head, friction-fit, and the like.

[0142] In one or more example embodiments, a marker base can be attached to a posted screw via connection at a top surface of the screw post or sliding a marker base onto a post connector with a clamp to adjust the relative position of the marker base on the upper portion of the screw post.

[0143] In an example embodiment, a bone attachment mechanism comprises a spinous process clamp. One example of a spinous process clamp comprises a tension-based mechanism to provide a clamping force to opposing sides of a bony protrusion such as a spinous process to secure the mechanism onto the target bone. For example, as shown in the example of FIG. 5B , an internal spring or springs, or other tension mechanism, forces a pair of jaws 452 or similar opposing surfaces together to grip the bony protrusion. Once the clamp is applied to the bony protrusion, the spring tension holds the jaws in a closed position. The clamp can also be repeatedly removed and reattached, depending on user site preferences. In one or more embodiments, the example spinous process clamp allows for dual rod placement while assessing alignment according to the user preferences in the surgical setting.

[0144] In an example embodiment, a bone attachment mechanism comprises a spinous process clamp with an integrated marker base as a unitary device. In such an embodiment, a spinous process clamp comprises a tension-based mechanism to provide a clamping force to opposing sides of a bony protrusion such as a spinous process to secure the mechanism onto the target bone. A user applies the spinous process clamp to the bony protrusion, and the integrated glyph at the top surface of the clamp is displayed for recognition by an optical sensor.

[0145] In another example embodiment, a spinous process clamp according to the disclosure includes a slot or hole for receiving a marker base to be inserted therein. The receiving slot or hole can be located on a top surface of the clamp or on a side portion of theclamp. Once the marker base is inserted, the outer surface of the marker base is exposed to an optical sensor to recognize the glyph on the outer surface of the marker base.

[0146] In another example embodiment, a marker base comprises a removable cap that is attached over at least a top portion of the clamp, with an integrated printed, stamped or etched glyph on the outer top surface of the cap. A user applies the spinous process clamp to the bony protrusion or other target anatomical site, and then the user secures the removable cap around the perimeter of the top clamp surface, thereby exposing the glyph on the outer top surface of the cap for recognition by an optical sensor. In one or more examples, a quick connect mechanism enables tightening the clamp to the target anatomical site.

[0147] In another example embodiment, a spinous process clamp according to the disclosure includes a female threaded internal cavity for receiving a marker base with corresponding male threads on the lower portion of the marker base to be threaded into the internal cavity.

[0148] In one or more example embodiments, a spinous process clamp according to the disclosure includes a marker base that is located directly above the target bone site (such as the spinous process). In one or more embodiments, a spinous process clamp according to the disclosure also includes a marker base that is located in an offset location relative to the target bone site (e.g., offset relative to a target site of a patient’s spinous process).

[0149] As further shown in FIG. 5B, an attachment structure comprises a clamp, including, but not limited to, a spinous process clamp. In one or more embodiments, a clamp includes a quick attachment clamp, in which a tension mechanism of the attachment structure affords a removable clamping force around a target anatomical site, such as a spinous process site as exemplified. Further, in another example (shown in FIG. 5C), a clamp includes a tool 450 having a removably interconnected clamp 454. Also, in one or more embodiments, a clamp includes a rod clamp, such as for direct or indirect attachment to a spinal fixation rod, or direct or indirect attachment to any other fixation components or devices.

[0150] In an example shown in FIG. 5D, there is provided another view of a marker base 430 and attachment structure in an in situ position with a spinous process 11. This example also presents a unitary marker base structure with an attachment screw 441. In a further embodiment of FIG. 5D, a marker base 430 and attachment structure in an in situ position can be attached to other bony structures such as the sacral region, pedicle, or even the lamina. Accordingly, the exemplified attachment structure in an in situ position applies to other target anatomical sites including, but not limited to, bony structures.

[0151] In an example shown in FIG. 5E, there is provided a marker base 430 having a visible glyph 410 and an elongated attachment structure 440 with a screw / threadedattachment portion with the representative bone structure. This example illustration is similar to FIG. 5D, but with a screw / threaded elongated attachment component rather than a clamp.

[0152] In an example shown in FIG. 5F, there is provided an alternative marker base 430 having a visible glyph 410 and an elongated attachment structure 440 with a bone clamp 460 at the attachment portion with the representative bone structure. FIG. 5F is an example of a shallow bone screw 461 engaging only cortical bone, and stabilizing the base with a spiked tripod base. Tension is created by the screw pulling the tripod into the bone surface.

[0153] In an example shown in FIG. 5G, there is provided another alternative marker base 430 having a visible glyph 410 and an elongated attachment structure 440 with a bone clamp 461 at the attachment portion with the representative bone structure. The example in FIG. 5G and associated FIG. 5H detail provide an expandable wedge 462 (tripod in the figure), where actuating a screw 464 on the mount expands or retracts spikes (which can be telescoping or rotating), engaging with the bone. Tension is created by the force of the opposing spikes applying pressure to the bone.

[0154] In an example shown in FIG. 5I, there is provided a marker base 430 having a visible glyph 410 and an elongated attachment structure 440 interfacing with one example of a tulip 470. A tulip can also be referred to throughout this disclosure (and not in just this example ) as a receiver or receiver head. In yet another embodiment, an attachment structure comprises a screw tulip attachment 472 as shown in the example embodiment in FIG. 5I. In an example, a tulip comprises a pedicle screw system in which the tulip 470 is coupled to an installed screw 500. For example, the screw-tulip coupling can be an internally threaded tulip screwed onto an externally threaded screw head. Alternatively, the screw-tulip coupling can be a friction-fit engagement between the tulip and the screw head. Once the tulip is coupled onto the screw head, the rod receiver channel of the tulip above the screw head can then engage the bottom end of a tile marker post. For example, the bottom end of the tile marker post can be screwed into the threaded upper arm portions of the tulip to secure the lower portion of the tile marker post.

[0155] In one or more example embodiments, an associated screw (including a bone screw) allows the polyaxial motion of the screw-tulip connection to be locked so that the associate glyph is locked. In one or more of these embodiments, the marker base locks the polyaxial motion of the screw, therefore providing a rigid attachment of the glyph to the target anatomical site, including, but not limited to, a bony structure.

[0156] In another example embodiment, and as illustrated and described in further detail below, an attachment structure comprises a tulip in an offset configuration. In this example, a tulip (or receiver head) comprises a pedicle screw system in which the tulip is arranged in an offset configuration from the main screw shaft, so that the tulip and screwhead are not in direct axial alignment. In this example, the tulip receiving channel is located laterally from the head of the screw, thus allowing visualization and / or access to the screw head while simultaneously providing access to the tulip receiving channel. In an embodiment, a marker base is either directly threaded into the tulip receiving channel, or a threaded post is installed into the receiving channel and an integrated marker base atop the threaded post protrudes a distance from the tulip to maximize exposure / visualization of the glyph.

[0157] In a further example embodiment, also described and illustrated in further detail below, an attachment structure comprises a tulip having a receiving void, which can also comprise a slot, channel, hole, cavity, or any combination thereof, for insertion of a marker base therein. The receiving void can be oriented to an angle of about 0° to 65° relative to the axis of the threaded portion of the tulip.

[0158] In another example, FIG. 6A provides a marker base 430 with integrated glyph 410 positioned next to an example tower 480. In this example, the marker base 430 can be removably connected to one or more tower components 480, such as in a minimally invasive surgical (also known as MIS) setting. As illustrated in FIG. 6A, an example of a tile (marker base 430) attached to a screw tower 480, which can be attached / detached from the screw tulip. Further, unique base markers and associated glyphs can be used simultaneously or sequentially to track multiple vertebral levels as shown. In one or more embodiments, attachment of the tower or glyph can rigidly lock the tulip orientation of the vertebral body. In one or more further embodiments, attachment of the tower and / or attachment of the glyph creates a rigid transform to the bony structure (such as a vertebral body). In a further example, FIG. 6B provides a tower based reducer 490 that locks the polyaxial motion of the screw and also illustrates an example of the associated tile location.

[0159] In an example shown in FIG. 7A, there is provided a pair of marker base 430 embodiments with associated glyphs 410 and attachment structures 440. The representative attachment structures 440 are merely examples of one-piece and two-piece attachment structures, though other multi-piece attachment structures can also be used (not shown). Also, an example shown in FIG. 7B provides a demonstrative attachment structure 440 removably connected to a screw shank 505. Other mechanisms for removably connecting to a screw shank can also be used (not shown). Additionally, FIG. 7B provides an example screw 500 with no polyaxial motion (i.e. , a fixed screw); the example tile shown can be removably connected / disconnected from the screw. Further, an attachment structure can be connected to other points / areas of a screw or tulip, and such connection points are not limited to the example as shown in FIG. 7B. Attachment structures as described herein can also be connected to other fixation hardware components, such as spinal fixation rods, andthe example shown in FIG. 7B is not intended to limit any such further removable connection mechanisms.

[0160] In an example shown in FIG. 8, there is provided an alternative marker base 430 having a visible glyph 410 and an elongated attachment structure 440 with a rod clamp at the attachment portion with a representative spinal fixation rod 510 . While not shown in FIG.8, multiple marker bases with elongated attachment structures and rod clamps can be used at multiple spinal levels, and the representation of a single embodiment is not intended to limit the number of such marker bases with elongated attachment structures and rod clamps. In a situation in which multiple marker bases with elongated attachment structures and rod clamps are used, each associated glyph will comprise a unique code or other display for simultaneous or sequential tracking of glyph location in situ.

[0161] Both FIG. 9A and 9B provide examples of features on the screw shank to attach a mount 445 for the glyph 410. This allows for fixation of the glyph to the vertebral body while allowing polyaxial motion of the tulip 470 throughout the procedure. For example, FIG.9A demonstrates use of the screw shank to apply downward pressure on a “lock washer” with an integrated glyph mount. The mount 445 is free to rotate around the axis of the screw initially, allowing the user to optimally align the glyph 410 to the optical sensor, but as the screw is fully driven into the bone, it applies pressure between the screw and bone surface, rigidly fixing the mount 445 orientation to the vertebral body. FIG. 9B provides an example feature on the screw shank to be interfaced with a clamp. Once the screw is placed in bone, a mount 446 with a clamp 448 can be introduced. The user can orient the glyph 410 to the optical sensor, then clamp the mount 446 to the screw to provide fixation. This could be at several discrete positions, such as a hex shape on the screw, or non-discrete, such as a ball (pictured in FIG. 9B).

[0162] In a group of examples shown in FIGS. 9C to 9E, there are provided representative tulip attachment structures and their association with marker bases 430 and screws. In these examples, while bone screws shown are listed as polyaxial bone screws, other types of bone screws can also be similarly employed, including, but not limited to, monoaxial and fixed axis bone screws. For example, FIG. 9C shows an example tulip attachment structure 515A comprising a first receiver portion 520 that interfaces with a screw head 501 and includes a poly lock set screw 525 to lock orientation of the first receiver portion 520, a second receiver portion 530 featuring a rod slot 535 oriented adjacent. The first receiver portion receives the screw head 501 as well as a slot for receiving a marker base 430 (also referred to as a tile flag). The second receiver portion 530 is for receiving a fixation rod 532 and clamping the rod with rod set screw 536. In an example embodiment, the screw 500 can include, but is not limited to, a monoaxial, polyaxial, or fixed pediclescrew. In one or more examples, axial motion (including polyaxial and monoaxial motion) can be achieved independently of the associated fixation rod 532.

[0163] In another example, FIG. 9D shows an example tulip attachment structure 515B comprising a first receiver portion 520 that interfaces with a screw head 501 , a rod slot 535 axially aligned with the first receiver portion 520 for receiving a fixation rod 532, and a second receiver portion 530 angled relative to the first receiver portion 520 for receiving a marker base 430. In an embodiment, the screw 500 can be a monoaxial, polyaxial, or fixed pedicle screw.

[0164] In still another example, FIG. 9E shows an example tulip attachment structure 515C comprising a first receiver portion 520 that interfaces with a screw head 501 , a rod slot 535 axially aligned with the first receiver portion 520 for receiving a fixation rod 532, and a slot 550 for receiving a marker base 430. In an embodiment, the screw 500 can be a monoaxial, polyaxial, or fixed pedicle screw.

[0165] As noted above, a glyph can also be a distinguishable symbol, mark, character, pattern, or image, defined on and / or forming at least one surface of an object, for facilitating identification of the object and a determination of the pose of the object, by a computer vision system. Non-limiting examples of glyphs include letters, numerals, punctuation marks, icons, single or multi-dimensional barcodes, QR codes, ArUco (Augmented Reality University of Cordoba) markers and variations thereof, and other machine-readable or computer-recognizable features.

[0166] FIG. 10 is a flow chart illustrating an example of method of performing intraoperative-surface-based navigation of spinal surgical procedures a set of level-associated glyphs and the example system of FIG. 3. During an initial phase of the surgical procedure, the patient is prepared with two or more vertebral levels of the spine exposed, as shown at 1000. In step 1010, glyphs are secured, on a per-vertebral-level (per-level) basis, to two or more exposed vertebrae. This can be achieved, for example, by securing glyph tracking structures such as those described previously, or variations thereof. In example implementations in which one or more of the glyph tracking structures employed in the surgical procedure is provided in the form of a glyph tracking assembly that includes a base structure to which a glyph member is removably attachable, the base structure can be secured to a vertebral level prior to attaching the glyph member.

[0167] Step 1002 of FIG. 10, which involves associating the glyphs with the vertebral levels on a per-level basis, can be performed before or after securing the glyph tracking structures to their respective vertebrae, and is therefore also shown offset from the rightmost workflow of the flow chart. This association can be user-defined, for example, in a user interface, as illustrated in the Examples below (e.g. selecting a desired glyph from a drop-down list that contains a set of available glyphs, or glyphs detected in a current glyph tracking image).

[0168] In other example implementations, the glyph4evel association can be autonomous or semiautonomous (e.g. requiring user verification and confirmation). For example, autonomous glyph association can be performed by processing the glyph tracking images (e.g. a stereo pair of images of the surgical scene) to locate the positions of the glyphs and to determine, for each vertebral level detected during intraoperative surface imaging (e.g. in step 1020 in the example workflow shown in FIG. 10, as described below), the glyph that is closed to each acquired vertebral surface, and / or spatially sorting a set of detected glyphs from the inferior to superior directions, and associating each glyph with a respective level from a pre-determined spatial ordering of the vertebral levels (e.g. the superior and inferior directions in the stereo camera coordinate system can be deduced based on the position of the levels in the acquired surface).

[0169] In step 1004, an optical tracking reference structure that has optical tracking markers detectable by the optical tracking subsystem and surface features detectable by the surface detection subsystem can be employed to generate a calibration transformation, as described previously. This step is shown in a parallel workflow because it can be performed one or more times during the rightmost workflow in the flow chart, and need not be performed prior to steps 1010 or 1020, while it is generally beneficial to employ an updated calibration transformation when performing step 1040, and the use of the surface detection subsystem in step 1020 facilitates the collection of surface data and can also include employing the optical tracking system to detect the pose of the optical tracking reference structure in both frames of reference to generate the calibration transformation. In the present example workflow, the optical tracking reference structure need not be secured to the patient anatomy to generate a calibration transformation, and merely needs to be detectable by, and positioned stationary relative to, the surface detection subsystem and the optical tracking subsystem. In some example embodiments, however, the optical tracking reference structure can be secured to the patient anatomy or another object within the surgical field and can be employed to update the calibration transformation at one or more time points during the medical procedure.

[0170] After the glyphs have been secured to the anatomy such that the pose of each glyph is inherently and respectively tied to the position and orientation of each glyph-associated vertebral level, the surface detection subsystem is employed to obtain intraoperative surface data characterizing the exposed vertebral levels, as shown in step 1020. Additionally, in step 1020, stereo camera pair of the system, such as a stereo camera pair of the surface detection subsystem, or a stereo camera pair of the tracking subsystem, or an additional stereo camera pair of the system in addition to those of the surface detectionsubsystem and the optical tracking subsystem (and having an associated calibration transformation), is employed to obtain images of surgical field such that the acquired images include the glyphs (glyph tracking images). The imaging camera can be sensitive to a portion of the electromagnetic spectrum that includes one or more of visible, ultraviolet, nearinfrared, infrared, provided that the glyph is detectable. In step 1030, the glyph tracking images are processed to identify each glyph and to determine the pose of each glyph, and example algorithms for glyph identification and pose determination are described in detail below. The intraoperative surface data characterizing the exposed vertebral levels is also registered with per-level surface data segmented from the volumetric image data. This step provides an association between the intraoperative positions and orientations of the vertebral levels, as prescribed by the per-level surface registration transformations (and also, for example, pre-established alignment parameters or measures associated with volumetric image data, examples of which are described in the Examples below) and the glyph poses (which are referred to below as initial glyph poses).

[0171] This relationship is schematically illustrated in FIG. 11, which shows a given vertebral level 1100, for which the intraoperative position and orientation, in the frame of reference of the surface detection subsystem, which is represented in the figure by Tvert (where “vert” denotes vertebrae), is known via the surface registration transformation. The figure also shows the glyph 410, for which the intraoperative pose, in the frame of reference of the surface detection subsystem, and which is represented byTgiyPh, is known via the glyph pose determination performed by processing the glyph tracking images (e.g. acquired via the stereo cameras of the surface detection subsystem). Since both of these quantities (vertebral level position and orientation, and glyph pose) are known in a common coordinate system (intraoperative frame of reference), the pose of the glyph relative to the vertebral level, shown in the figure as transformation Tgiyph-to-vert, is known and will remain constant, during motion of the patient relative to the system, and after a surgical intervention performed on the vertebral level that changes the intraoperative position and orientation of the vertebral level, provided that position orientation of the glyph relative to the vertebral level is not inadvertently perturbed. Accordingly, having established the aforementioned relationship for each glyph-level pair, between the intraoperative position and orientation of the vertebral level and the pose of the glyph, and provided that each glyph remains rigidly secured to its respective vertebral level such that intraoperative changes in the position and orientation of vertebral are equivalent to changes in the pose of the corresponding glyph, intraoperative tracking of the pose of each glyph can be employed as a surrogate or proxy for the determination of the intraoperative position and orientation (pose) of each vertebral level. The example method illustrated in FIG. 10 employs repeated acquisition of glyph tracking images and the processing of the glyph tracking images to determine changes inthe intraoperative pose of the glyphs, as illustrated in steps 1040, 1050, 1065 and 1070. Each time the loop 1065 is performed, glyph tracking images are acquired and processed to determine the updated poses of the glyphs, as per step 1070. The poses of tracked medical instruments, tracked repeatedly by the optical tracking subsystem, are also updated, as per step 1040.

[0172] The glyph poses are employed to determine updated intraoperative poses of the vertebral levels, given the known transformation TgiyPh-to-vert, as shown in FIG. 11, which is presumed to remain valid. Knowing the updated intraoperative poses of the vertebral levels, the registration transforms, which map the volumetric image data to each vertebral level, and the calibration transformation, which relates the coordinate systems (frames of reference) of the optical tracking subsystem and the surface detection subsystem, the pose of the medical instrument 40 can be represented in the same intraoperative coordinate system as the perlevel volumetric image data, enabling the generation navigation images in step 1050 showing the optically tracked medical instrument relative to volumetric image data associated with one or more of the tracked vertebral levels.

[0173] As also shown in step 1060 of FIG. 10, the updated positions and orientations of the vertebral levels, as determined based on the changes in the glyph poses, can be employed to generate vertebral alignment parameters (measures) and / or visualizations, optionally provided as continuous or real-time updates. Non-limiting examples involving the display of updated alignment parameters and visualizations of vertebral alignment are provided in the examples below. The dashed box 1055 in FIG. 10 illustrates how, at any given time during the rapidly updated (e.g. continuous) detection of the pose of the glyphs and the tracked medical instruments, either one, or both, of steps 1050 and 1060 can be performed.

[0174] It is noted that while step 1070 is performed each time the loop 1065 is performed, this step can be skipped when initiating the loop, as shown at 1038, since the glyph poses (and the intraoperative poses of the vertebral levels) are already known from step 1030. Alternatively, the loop 1065 can be initiated with step 1070.

[0175] The present example method can solve the aforementioned problems associated with previous surface-detection-based navigation methods that rely heavily on repeated intraoperative acquisition of surface data characterizing the exposed surface of the vertebra, which, as noted above, can be hampered or precluded by the occlusion of the vertebral surface by tissue and / or blood, and / or from surgical modifications to the surface of the exposed vertebra, resulting in poor registration or an inability to achieve a desired registration accuracy or quality. In stark contrast, the present example method employs glyph pose detection as a proxy for detection of the vertebral surface, enhancing clinicalworkflow and making the navigation procedure more robust, using small-form-factor glyphs that do not clutter the surgical field.

[0176] It is noted, however, that ability to employ to glyphs pose as a surrogate for intraoperative vertebral surface data, and the assumed validity of the transformation TgiyPh-to- vert relies on the assumption that the pose of each glyph does not change relative to the underlying vertebral structure. A risk nonetheless exists that the glyphs could be displaced during the course of the surgical procedure, such that the stored transformation TgiyPh-to-vert no longer reflects the physical reality.

[0177] This assumption can be verified, for example, by the user, by positioning a tracked medical instrument, such as the instrument 40 shown in FIG. 11 , relative to a known target location, such as a known location on the vertebral surface (e.g. a landmark, optionally pre-defined) that will not be removed by the planned procedure. If the navigation images fail to show the tracked medical device being properly positioned relative to the known target location, then the user can conclude that the existing Tg|yph-to-vert transformations, and / or the calibration transformation, are no longer valid. The user can then take remedial action, such as, for example, performing a re-registration (i.e. returning to step 1020), and / or acquiring an updated calibration transformation.

[0178] In some example embodiments, the repeated acquisition of glyph tracking images and the updating of the glyph poses can be automated to occur at a pre-selected time points that may or may not be periodic. For example, the repeated acquisition of glyph tracking images and the updating of the glyph poses can occur at periodic time intervals. The intervals can be selected to be short enough such that the updating is perceived by a human observer to be continuous or real-time (e.g. at a frame rate exceeding, for example 20 Hz or 25 Hz). For example, the update interval can be less than 60 seconds, less than 40 seconds, less than 30 seconds, less than 20 seconds, less than 10 seconds, less than 5 seconds, less than 2 seconds, or less than 1 second. The time interval between updates can depend on the computing resources available for performing glyph identification and pose detection. In one example implementation, the time interval between updating the registration transforms can be equal to the time interval required for computing registration plus a time delay margin (where the time delay margin can be a fraction of the time interval required for computing registration).

[0179] In some example implementations, when processing re-acquired glyph tracking images to update the pose of the glyphs, the previous poses of the glyphs can be employed as initial estimates for the calculation of the updated poses, which can beneficially facilitate an updated rate of pose determination, and can optionally facilitate the omission of the glyph identification step in the image processing workflow.

[0180] In some example implementations, one or more navigation images can be generated based on tracking of the pose of a selected vertebral level (e.g. a vertebral level associated with a specific glyph), as opposed to the full set of glyph-associated vertebral levels. For example, the selection of a specific vertebral level, at a given point in time during the navigated procedure, can be based on proximity of a tracked tool relative to each vertebral level. For example, in the case of a spinal surgical procedure involving two vertebral levels and a tracked awl, a proximity measure associated with a tracked location of the awl tip can be employed to determine which vertebral level to render in a given navigation image. In another example embodiment, the dynamic selection of a vertebral level (and glyph pose) for use when generating navigation images can be determined according to user input. For example, a user input device, such as a foot pedal, keyboard, mouse, touch screens, external gesture control devices such as the Myo armband, Kinect or by internally integrating gesture control algorithms into the navigational camera systems (tracking or visible camera(s)) can be employed to facilitate the intraoperative selection of a suitable registration transform.

[0181] Glyph identification and pose detection, as performed in steps 1030 and 1040 of FIG. 10, can be performed according to a wide range of available algorithms. An example glyph pose detection algorithm using the processing of stereo glyph tracking images is illustrated in FIG. 12A. The left and right glyph tracking images 1200 and 1205 (e.g. obtained via the stereo camera pair of the surface detection subsystem or the optical tracking subsystem) are processed to detect and identify the glyph (steps 1210 and 1215) and locate (e.g. select) glyph key features (e.g. features suitable for glyph localization), such as, but not limited to, corners and saddle points, as shown at steps 1220 and 1225. Detection can be achieved in various ways. For example, a thresholding step can be performed to find all the edges in the images. Specific design choices of the glyphs, such as the use of highly contrasting colors (e.g. black and white) can improve the accuracy of this step. Following this, contours can be generated from the edges, and those that are convex and have the right shape matching that of the marker (e.g. square) can be selected. The selected regions are then further processed to match to that of a dictionary of predefined glyph patterns. One method for matching is to take the detected region, which can be a square, and subdivide it based on the known geometry in the dictionary of glyphs. For a square glyph with chessboard like patterns, the subdivided region can be 2x2, 3x3, 4x4, etc. A threshold can be applied to the subdivided image regions to create a binary pattern which can be matched to the dictionary of glyphs. The left and right images can be processed in parallel, as shown in the example workflow. Once markers matching those present in the predefined dictionary of glyphs are detected, the predefined features on them can be identified. One example feature is one or more corners, which includes, but is not limited to, saddle points. For eachglyph, the corresponding features from the left and right images are matched in step 1230. One example method for matching is to ensure that only features from the same glyph (as seen in the left and right image) are paired. Additional constraints can be used, such as the feature on the left image must be on the same row, or to within a tolerance (e.g. they cannot differ by more than two rows) as the right image, when the left and right camera are stereo rectified (after rectification, a row in the left image will correspond to the same row in the right image). Other constraints can include discarding glyphs that appear more than once due to potential uncertainties this introduces in the paring process. In step 1240, the matched features are employed to triangulate their 3D positions (for example, using camera calibration data). The predefined feature set associated with the detected and identified glyph is then registered with the triangulated points to determine or estimate the pose (6DOF position and orientation) of the glyph, as shown in step 1250. FIG. 12B schematically illustrates the steps from the flowchart of FIG. 12A, showing the various processing steps in terms of the feature identification and correlation in the stereo glyph images, and the steps of triangulation and registration.

[0182] It will be understood that the example workflow shown in FIG. 12A is intended to provide a non-limiting example algorithm for glyph identification and pose determination, and that many other algorithms can be employed in the alternative. Furthermore, while the workflow illustrated in FIG. 12A pertains to the processing of stereo glyph tracking images, in other example implementations, a single glyph tracking image can be processed to identify the glyph and estimate the glyph pose, where pose estimation is performed using a method such as, but not limited to, a perspective-n-point (PnP) algorithm (which can be implemented, for example, using cues such as the known size of the marker square in the image).

[0183] FIG. 13A illustrates a non-limiting example of a glyph in the form of an Arllco marker 1300. Arllco markers are 2D fiducial patterns encoded in binary, which were created for rapid detection by computer vision systems. These marker patterns can be stored in a binary dictionary within the software that allow for rapid identification of pattern IDs and pose estimation from analyzed images. In some example implementations, a first portion of a glyph, such as an Arllco marker, can be augmented with one or more surrounding features, such as the border 1310 surrounding the Arllco marker in FIG. 13A, and the example outer features 1320 and 1330 shown beyond the Arllco marker 1300 in FIG. 13B. In some examples implementations, a set of glyphs that are available for use during or employed during a given spinal surgical procedure can include one or more uniquely identifiable glyph portions (for example, the Arllco marker 1300) shown in FIG. 13B and one or more additional features that are common among two or more glyphs (for example, the additional features 1310, 1320 and 1330 shown in FIGS. 13A and 13B), with the one or moreadditional features being employed for pose determination but not for glyph identification. In such an example implementation, the one or more uniquely identifiable glyph portions can be employed only for glyph identification, and / or can be employed for glyph identification and glyph pose determination (where glyph pose determination is performed based on both the one or more uniquely identifiable glyph portions and the one or more additional features).

[0184] In some example embodiments, surface detection can be employed in combination with conventional glyph tracking images to determine the pose of a glyph. For example, the system can be employed to acquire stereo glyph tracking images that include the glyph, and surface data characterizing at least one surface of the glyph tracking structure on which the glyph is defined (in some example implementations, the surface detection subsystem can be employed to acquire both datasets). The glyph tracking images can be employed, for example, to obtain an approximate estimation of the glyph location and / or pose, and the approximate location and / or pose can be employed as an input for segmenting the acquired surface data and / or to generate an initial alignment between the acquired surface data and reference surface associated with a model of at least a portion of the glyph tracking structure. Subsequent surface-to-surface registration can be performed to determine and / or refine the pose of the glyph. This example embodiment is illustrated in FIG.13C, which shows the top 1350 and side 1360 surfaces of an example glyph tile being employed to perform surface registration with a reference surface of a model 1370 of the glyph component. Accordingly, in some example implementations, a component on which a glyph is defined can include one or more 3D landmarks, e.g. three-dimensional surface features detectable by a surface detection subsystem, where the three-dimensional surface features can be employed for one or both of (i) identification of the glyph and (ii) determination or refinement of the pose of the glyph. Detected 3D surface features can be employed in combination with detected of 2D markings for identification and / or pose determination.

[0185] FIGS. 14A-14C show screenshots of an example navigation user interface for performing multilevel glyph-based surgical navigation of a spinal procedure. FIG. 14A shows a screenshot of an initial phase of the surgical procedure in which the glyphs are being associated with their respective tracked vertebral levels. The example navigation user interface displays alignment parameters determined from the volumetric image data (including sagittal Cobb angle and coronal Cobb angle). FIGS. 14B, 14C and 14D show the glyph-level associations along with visualizations that are updated based on the tracked pose of each glyph during the procedure.

[0186] Referring again to FIG. 3, the example system includes a surface detection subsystem 10 and an optical tracking subsystem 20. In some example implementations, a separate (not shown in the figure) monocular camera or separate set stereo camera pair(separate from the surface detection subsystem 10 and the optical tracking subsystem 20) can be employed for the acquisition of intraoperative images that are suitable for glyph identification and glyph pose determination. In other example implementations, a single camera or a pair of cameras from either of the surface detection subsystem 10 and the optical tracking subsystem 20 can be employed to obtain intraoperative images suitable for glyph identification and pose determination. In example implementations in which the surface detection subsystem 10 is a structured light surface detection subsystem, intraoperative images of the glyphs that are suitable for glyph identification and pose determination can be obtained in the absence of projection of structured light patterns.

[0187] The surface detection subsystem 10 and the optical tracking subsystem 20 can be rigidly secured to one another, for example, by a frame 15. Non-limiting examples of integrated surface detection subsystems and optical tracking subsystems are disclosed in International Patent Application No. PCT / CA2013 / 050819, titled “INTEGRATED ILLUMINATION AND OPTICAL SURFACE TOPOLOGY DETECTION SYSTEM AND METHODS OF USE THEREOF”, filed October 13, 2013, which is incorporated herein by reference in its entirety. The system can be employed to facilitate intraoperative surgical navigation and display, on a user interface, the pose of one or more tracked medical instruments 40 relative to pre-operative volumetric image data 30.

[0188] FIG. 3 also illustrates an example implementation of control and processing hardware 100, which includes one or more processors 110 (for example, a CPU / microprocessor), bus 105, memory 115, which can include random access memory (RAM) and / or read only memory (ROM), a data acquisition interface 120, a display 125, external storage 130, one more communications interfaces 135, a power supply 140, and one or more input / output devices and / or interfaces 145 (e.g. a speaker, a user input device, such as a keyboard, a keypad, a mouse, a position tracked stylus, a position tracked probe, a foot switch, and / or a microphone for capturing speech commands).

[0189] It is to be understood that the example system shown in FIG. 3 is illustrative of a non-limiting example embodiment and is not intended to be limited to the components shown. Furthermore, one or more components of the control and processing hardware 100 can be provided as an external component that is interfaced to a processing device. For example, as shown in the figure, one or both of the surface detection subsystem 10 and the optical tracking subsystem 20 can be included as a component of control and processing hardware 100 or can be provided as one or more external devices.

[0190] Although only one of each component is illustrated in FIG. 3, any number of each component can be included in the control and processing hardware 100. For example, a computer typically contains a number of different data storage media. Furthermore, although bus 105 is depicted as a single connection between all of the components, it will beappreciated that the bus 105 can represent one or more circuits, devices or communication channels which link two or more of the components. For example, in personal computers, bus 105 often includes or is a motherboard. Control and processing hardware 100 can include many more or less components than those shown.

[0191] Control and processing hardware 100 can be implemented as one or more physical devices that are coupled to processor 110 through one of more communications channels or interfaces. For example, control and processing hardware 100 can be implemented using application specific integrated circuits (ASICs). Alternatively, control and processing hardware 100 can be implemented as a combination of hardware and software, where the software is loaded into the processor from the memory or over a network connection.

[0192] Some aspects of the present disclosure can be embodied, at least in part, in software. That is, the techniques can be carried out in a computer system or other data processing system in response to its processor, such as a microprocessor, executing sequences of instructions contained in a memory, such as ROM, volatile RAM, non-volatile memory, cache, magnetic and optical disks, or a remote storage device. Further, the instructions can be downloaded into a computing device over a data network in a form of compiled and linked version. Alternatively, the logic to perform the processes as discussed above could be implemented in additional computer and / or machine readable media, such as discrete hardware components as large-scale integrated circuits (LSI's), applicationspecific integrated circuits (ASIC's), or firmware such as electrically erasable programmable read-only memory (EEPROM's) and field-programmable gate arrays (FPGAs).

[0193] A computer readable medium can be used to store software and data which when executed by a data processing system causes the system to perform various methods. The executable software and data can be stored in various places including for example ROM, volatile RAM, non-volatile memory and / or cache. Portions of this software and / or data can be stored in any one of these storage devices. In general, a machine readable medium includes any mechanism that provides (i.e., stores and / or transmits) information in a form accessible by a machine (e.g., a computer, network device, personal digital assistant, manufacturing tool, any device with a set of one or more processors, etc.).

[0194] Examples of computer-readable media include but are not limited to recordable and non-recordable type media such as volatile and non-volatile memory devices, read only memory (ROM), random access memory (RAM), flash memory devices, floppy and other removable disks, magnetic disk storage media, optical storage media (e.g., compact discs (CDs), digital versatile disks (DVDs), etc.), among others. The instructions can be embodied in digital and analog communication links for electrical, optical, acoustical or other forms of propagated signals, such as carrier waves, infrared signals, digital signals, and the like. Asused herein, the phrases “computer readable material” and “computer readable storage medium” refer to all computer-readable media, except for a transitory propagating signal per se.

[0195] Embodiments of the present disclosure can be implemented via processor 110 and / or memory 115. For example, the functionalities described below can be partially implemented via hardware logic in processor 110 and partially using the instructions stored in memory 115. Some embodiments are implemented using processor 110 without additional instructions stored in memory 115. Some embodiments are implemented using the instructions stored in memory 115 for execution by one or more microprocessors, which can be general purpose processors or specialty purpose processors. Thus, the disclosure is not limited to a specific configuration of hardware and / or software.

[0196] The control and processing hardware 100 is programmed with subroutines, applications or modules 150, that include executable instructions, which when executed by the one or more processors 110, causes the system to perform one or more methods described in the present disclosure. Such instructions can be stored, for example, in memory 115 and / or other internal storage. In particular, in the example embodiment shown, glyph ID and pose detection module 152 includes executable instructions for processing glyph tracking images to identify and determine the pose of one or more glyphs, registration module 154 includes executable instructions for registering segmented surface data (obtained from the volumetric image data 30) with intraoperative surface data that is obtained using the surface detection subsystem 10, and for determining measures and feedback associated with an intraoperative orientation of the vertebrae (e.g. relative to the vertebrae orientation in the volumetric image data). The navigation user interface module 156 includes executable instructions for displaying a user interface for performing, for example, image-guided surgical procedures that show tracked medical devices relative to volumetric image data and facilitate the intraoperative assessment of vertebral alignment parameters.

[0197] It will be understood that the example system shown in FIG. 3, and the associated example workflow illustrated in FIG. 10, are not intended to be limiting, and that other system configurations and associated workflows can be employed in the alternative. For example, FIG. 15 illustrates an example system in which the medical instrument 40 has a glyph 410D that is tracked by the surface detection subsystem 10, obviating the need for the optical tracking subsystem and avoiding the need for an optical tracking reference structure and calibration transform. Such a system can be employed using a workflow similar to the workflow illustrated in FIG. 10, but where both the pose of the medical instrument 40 and the pose of the glyphs 400A-400C are tracked continuously to generate the navigation user interface images and the updating of the relevant vertebral alignment parametersand / or visualizations. The medical instrument 40 can, in some example embodiments, include multiple glyphs orientated at different respective angles to facilitate glyph-based pose detection as the medical instrument is moved relative to the surface detection system 20.

[0198] FIG. 16 illustrates an alternative system configuration in which the optical tracking reference structure 50 (shown having a geometric reference feature 52 that facilitates the acquisition of a calibration transform) is secured to the vertebrae to facilitate alternative workflows.

[0199] For example, FIG. 17 illustrates a modified version of the workflow illustrated in FIG. 10 in which glyph-based pose detection is performed intermittently as opposed to continuously, with the optical tracking support structure being continuously tracked to facilitate navigation in between the intermittent glyph-based pose detection events.Differences in the present workflow, relative to the workflow illustrated in FIG. 10, are shown by reference labels in bold.

[0200] As can be seen in the figure, steps 1010, 1020 and 1030, can be performed as in the workflow shown in FIG. 11, thereby establishing the transformation Tg|yph-to-vert, optionally performing an updated calibration in step 1725 after having acquired the intraoperative surface data. Likewise, the association of the glyphs and with respective vertebral levels is performed in step 1002, as in FIG. 10.

[0201] Unlike the workflow of FIG. 10, however, the alternative workflow illustrated in FIG. 17 does not rely on continuous imaging of the glyphs and continuous updating of the intraoperative poses of the glyphs. Instead, as evidenced by step 1740 in FIG. 17, the acquisition of glyph tracking images, and the updating of the glyph poses, is only performed intermittently (noting the absence, in FIG. 17, of the repeat loop that was connected to step 1070 in FIG. 10), and change in the pose of the optical tracking support structure is employed as a global surrogate for changes poses of the glyphs.

[0202] As can be seen in FIG. 17, the pose of the optical tracking reference structure, which is secured to a selected vertebral level in initial step 1704, is initially determined (using the optical tracking system) when acquiring the glyph images in step 1740, and is subsequently repeatedly tracked by the optical tracking subsystem (as shown at step 1745) in between updates of the glyph poses to enable a repeated (e.g. rapidly repeated) determination of its pose, as per the inner loop shown at 1720. Furthermore, when performing step 1750 to generate navigation images, the current (i.e. most recently determined) pose of the optical tracking structure is employed, along with the previous pose of the optical tracking reference structure that was recorded when the most recent glyph pose update was acquired (i.e. when performing step 1740), to determine a correction transformation, based on the change in the pose of the optical tracking reference structure,that accounts for relative motion between the tracked anatomy and the detection subsystems.

[0203] As can be seen in FIG. 17, in some example implementations, the frequency of updating the pose of the optical tracking structure exceeds that of the intermittent updating of the glyph poses (via acquisition of glyph images), as the inner loop 1720 is executed at least two times prior to reacquiring a new set of glyph poses. In some example embodiments, the repeated acquisition of pose of the optical tracking structure can be automated to occur at pre-selected time points that may or may not be periodic. For example, the repeated acquisition of the pose of the optical tracking structure and the updating of the glyph poses can occur at periodic time intervals. The intervals can be selected to be short enough such that the updating is perceived by a human observer to be continuous or real-time (e.g. at a frame rate exceeding, for example 20 Hz or 25 Hz). In some example implementations, the update interval can be less than 60 seconds, less than 40 seconds, less than 30 seconds, less than 20 seconds, less than 10 seconds, less than 5 seconds, less than 2 seconds, or less than 1 second. The time interval between updates can depend on the computing resources available for performing pose detection. In one example implementation, the time interval between the pose of the optical tracking structure can be equal to the time interval required for computing updated navigation images plus a time delay margin (where the time delay margin can be a fraction of the time interval required for computing registration).

[0204] The ability to employ the optical tracking reference structure as a surrogate for the poses of the glyphs, in between the acquisition of glyph tracking images and the detection of glyph poses, relies in the assumption that the optical tracking reference structure maintains a rigid position and orientation relative to the glyphs. This validity of this assumption will generally depend on both space and time, and can be understood with reference to FIG. 19A, which shows how changes in the pose of the optical tracking reference 50 can be employed to infer changes in the intraoperative position of the vertebral level 1100, provided that TgiyPh-to-ref and TgiyPh-to-vert remain constant. As time progresses forward from the most recent glyph pose detection event, and the surgical procedure progresses and involves modification of vertebral alignment, the assumption will become invalid and misalignment errors can develop. The magnitude of the misalignment errors will, in general, increase with distance from the optical tracking reference structure, as previously described. Conversely, misalignment errors will likely remain low for vertebral levels near the vertebral level to which the optical tracking reference structure is secured. Accordingly, in some cases, one can navigate, during the time in between successive glyph pose detection events, at the vertebral level to which the optical tracking reference structure is secured, and optionally at one or more nearby vertebral levels, and can still achieve sufficient navigation accuracy for a given task.

[0205] For the reasons described above, it is clear that the inner loop 1720 cannot facilitate detection and updating of glyph poses, and therefore the intraoperative vertebral alignment parameters and the intraoperative vertebral alignment visualization can only be updated once after each glyph pose detection event. Accordingly, this step is shown at 1760, outside of the inner loop 1720.

[0206] As shown in FIG. 17, the glyph poses are intermittently updated, as per the outer loop 1710. The intermittent updating of the glyph poses can be performed at a prescribed frequency, or, for example, initiated by the user, for example, according to one or more events during the surgical procedure, such as, for example, after a therapeutic action has been taken that is likely to result in a perturbation to vertebral alignment, or, for example, prior to initiating a therapeutic intervention on a new vertebral level, or, for example, transitioning to a new phase of a surgical procedure, or, for example, after determining that the navigation accuracy is insufficient.

[0207] As shown in step 1735, the optical tracking reference structure can optionally be moved prior to updating the glyph poses, as the ability to perform 1750 only requires that the position and orientation of the optical tracking reference structure remain fixed, relative to the glyphs, after acquisition of the updated glyph poses (as evidenced by the relationships illustrated in FIG. 19A). Accordingly, prior to updating the glyph poses, it can be advantageous to remove and reattach the optical tracking reference structure to a vertebral level that is to be navigated in the next phase of the surgical procedure, or is near a set of vertebral levels that are to be navigated in the next phase of the surgical procedure.

[0208] As described above, the assumption of validity of the accuracy of navigation (i.e. assumptions regarding the rigidity of the relationship between the glyph, optical tracking reference structure, and vertebral level) can be verified by observing navigation images for accuracy when contacting, with a tracked medical instrument, a selected vertebral location, where observed absence of or insufficiency of navigation accuracy can be employed to determine when to update the determination of the glyph poses (i.e. when to repeat step 1740) or when a new surface registration is required (i.e. when to repeat step 1030).

[0209] It is also noted that while step 1760 is performed each time the loop 1710 is performed, this step can be skipped when initiating the loop, as shown at 1738, since the glyph poses (and the intraoperative poses of the vertebral levels) are already known from step 1030. Alternatively, the loop 1710 can be initiated with step 1740 (and / or step 1735).

[0210] It is noted that the spatial relationships shown in FIG. 19A can be treated as a connected graph. For example, to determine the pose of one object relative to another, one can traverse this graph, where on passage of each edge, a transformation is appended. For example, Tpointer-to-vert ~ Tpointer X Tpointer-to-ref X Tref-to-vert, WtlGTG Tref-to-vert ~ Tef X ( / ert) ■ It IS noted that this traversal is not unique, and a different path can be chosen, employing a different setof transformations, to arrive at the same result. Accordingly, while various example embodiments are described in the present disclosure with reference to one example combination of transformations (traversal), it will be understood that alternative combinations of transformations that achieve the same result can be employed without departing from the intended scope of the present disclosure.

[0211] Referring now to FIG. 18A, an alternative example workflow is illustrated that employs the optical tracking reference structure as an intermediary during the initial phase when acquiring the surface image data and glyph tracking images that facilitate a determination of the transformation Tgiyph-to-vert. Unlike the workflow of FIG. 17, in the present workflow, the optical tracking reference structure is secured to the subject (e.g. an exposed vertebral level), as shown at step 1810, prior to attachment of the glyphs to the vertebral levels. This alternative workflow can be beneficial in cases in which the glyphs can partially obscure the bone surface from being imaged by the surface detection system. Accordingly, acquiring the intraoperative surface data prior to securing the glyphs to the vertebral levels can result in a higher quality and / or more comprehensive intraoperative surface dataset (e.g. point cloud).

[0212] As shown in the figure, intraoperative surface data characterizing the exposed vertebral levels is acquired in step 1820 (optionally after having instructed the operator to secure the optical tracking reference structure (but not yet the glyphs) to the subject, and / or receiving input confirming that the optical tracking reference structure has been secured to the subject), and an initial pose of the optical tracking reference structure is detected. As described below, the detection of this initial pose of the optical tracking reference structure provides a basis for linking the glyph poses to the intraoperative pose of the vertebral levels.

[0213] As shown in the figure, having acquired both the intraoperative surface data and employed the optical tracking system to detect the pose of optical tracking reference structure, a calibration transformation can be generated or updated, as shown at optional step 1825.

[0214] In step 1830, the intraoperative surface data characterizing the exposed vertebral levels is registered with per-level surface data segmented from the volumetric image data, thereby obtaining the per-level registration transformations. Since the initial pose of the optical tracking reference structure has also been determined, this initial pose of the optical tracking reference structure can be employed, with the per-level registration transformations, to obtain a transformation Tref-to-vert, for each vertebral level, as illustrated in FIG. 19A.

[0215] The glyphs (e.g. glyph-bearing supports or tracking structures) are then secured to respective vertebral levels in step 1835, with the glyph association step 1802 having been performed at any time up until this point. In step 1840, glyph tracking images (one or moreimages) are acquired, and the optical tracking system is also employed to determine an updated pose of the optical tracking reference structure, optionally after instructing the operator to secure the glyphs (e.g. glyph marker bases, glyph tracking structures) to the vertebral levels and / or receiving input confirming that the glyphs have been secured to the vertebral levels.

[0216] As shown in step 1840, and as can be seen with reference to FIG. 19A, the change in the pose of the optical tracking reference structure between the pose that was initially acquired when acquiring the intraoperative surface data and the pose that was acquired when acquiring the glyph tracking images can be employed, using the per-level registration transformations (or alternatively, using the transformation Tref-to-vert, to obtain the transformations TgiyPh.to-vert that link the glyph poses to the intraoperative poses of the vertebral levels). For example, the poses of the glyphs and the updated pose of the optical tracking reference structure can be employed to determine Tgiyph-to-ref, and the transformation Tgiyph-to-vert can be calculated as Tgiyph-to-vert = TgiyPh-to-refX Tref-to-vert. It is noted that the present example workflow assumes the vertebral levels are not moving relative to one another during the time interval between steps 1820 (intraoperative surface data acquisition) and 1840 (initial glyph imaging). This risk is commonly minimal and can be mitigated, as noted above, by detecting tracking / navigation / calibration inaccuracies by moving a tracked medical instrument to a known location and verifying accuracy in the navigation images.

[0217] The remaining steps in the workflow follow those shown in FIG. 17, as described above, including intermittent updating of the glyph poses in step 1740 according to outer loop 1710, generating updated alignment measures and / or visualizations in step 1760, and employing the tracked pose of the optical tracking reference structure as a proxy for glyph pose detection in steps 1745 as per inner loop 1750, with the exception that the optional moving of the optical tracking reference structure is shown at step 1836 in the outer loop 1710.

[0218] If a glyph is detached, Tgiyph.to-vert would need to be recalculated. In the case of FIG 17, an intraoperative surface characterizing the exposed vertebral levels would be needed, step 1020, to acquire data to update Tgiyph-to- ert. This would only need to be performed on the particular glyph that is detached. Note that as a surgery progresses, bone may be removed, and there may not be enough structure left to perform 1030 accurately. In that case, the system can be instructed to no longer track and update the alignment measures associated with that level. Similarly for FIG 18A, if a glyph is inadvertently detached, step 1820 would need to be performed.

[0219] This alternative workflow that employs the optical tracking reference structure when generating the transformation Tgiyph-to-vert that maps the glyph poses to the intraoperative surface data, and, through the registration transforms (and known pre-operative alignment parameters of the vertebral levels in the volumetric image data), the intraoperative poses of the vertebral levels, is also schematically illustrated in FIG. 19B. FIG. 19C illustrates the intraoperative calculation of a pose offset between two tracked vertebral levels, with navigation accuracy verification optionally being performed by contacting a tracked tool with a known location on the exposed vertebrae.

[0220] FIG. 18B illustrates yet another example workflow that is a hybrid between the workflow shown in FIG. 10 and the workflow shown in FIG. 18A. As can be seen in the figure, the workflow follows the steps shown in FIG. 18A up to step 1835, in which the optical tracking reference structure is secured to the subject and intraoperative surface detection is performed prior to securing the glyphs to the vertebral levels. After performing step 1835, the workflow follows that shown in FIG. 10 for the execution of the inner loop 1006, in which glyph-based-tracking is employed to generate the navigation images. Notably, the inner loop 1006 in FIG. 18B does not require the use of the optical tracking reference structure, unless it is desired to interrupt the loop to re-acquire a calibration transformation.

[0221] In example embodiments described herein in which two different modalities or subsystems are shown as performing image or data acquisition in a common step of a flow chart, or, for example, in example embodiments described herein in which image or data acquisition performed using one modality or subsystem is described as occurring “when” image or data acquisition is performed using another modality or subsystem, these steps are to be understood as occurring within a time duration or interval that is sufficiently short to facilitate the establishment of a valid transformation, for example, in the presence of breathing motion of a subject or other change in pose (e.g. a change in pose between imaged objects and the imaging system). For example, the time duration between such events can be less than 1 second, less than 500 ms, less than 250 ms, less than 100 ms, less than 50 ms, less than 25 ms, less than 10 ms, less than 5 ms, less than 2 ms, or less than 1 ms. For example, when acquiring glyph image data and intraoperative surface data for the determination of a transformation TgiyPh-t0-vert in embodiments described below, the glyph image data and intraoperative surface data can be acquired with a time interval therebetween that is sufficiently short that breathing motion of the patient does not invalidate the calculated transformation TgiyPh-to-vert. Likewise, when acquiring intraoperative surface data and optical tracking data, e.g. for the calculation of a calibration transformation, intraoperative surface data and the optical tracking data can be acquired with a time interval therebetween that is sufficiently short that breathing motion of the patient does not invalidate the calculated calibration transformation. Likewise, in example embodiments in which glyph tracking images are obtained when acquiring optical tracking data to characterize an initial pose of the optical tracking reference structure (so that the optical tracking reference structure can be employed as a proxy for tracking glyph poses between intermittentlydetermined glyph poses), the glyph tracking images and optical tracking data for determining an initial pose of the optical tracking reference structure can be acquired with a time interval therebetween that is sufficiently short that breathing motion of the patient does cause an error in the determination of the glyph poses relative to the initial pose of the optical tracking reference structure.

[0222] Although many of the preceding example embodiments have been illustrated with example workflows involving the flow charts shown in FIGS. 10, 17, 18A and 18B, it will be understood that subsets of steps within these example workflows can be adapted and employed in other workflows. For example, the inner loop shown at 1065 in FIG. 10 involving repeated (e.g. continuous) glyph tracking for surgical navigation can be employed in and / or adapted to a wide range of alternative workflows. Likewise, for example, the inner loop 1720 and / or outer loop 1710 shown in FIG. 17 can be employed in and / or adapted to a wide range of alternative workflows. Moreover, for example, the determination of the transformation Tgiph-to-vert, as illustrated in steps 1010 to 1030 of FIG. 10, can be employed in and / or adapted to a wide range of alternative workflows. Furthermore, for example, the use of the optical tracking reference structure as a proxy to facilitate the determination of the transformation Tgiph-to vert, as illustrated in steps 1820-1840 of FIG. 18A, can be employed in and / or adapted to a wide range of alternative workflows.

[0223] While the preceding example embodiment have been described as employing a combination of using an imaging camera to perform glyph imaging and a surface detection system to perform intraoperative surface detection, for directly or indirectly obtaining information sufficient for determining the transformation TgiyPh-to-vert, it will be understood that in other example embodiments, a different imaging modality, such as X-ray, CT or MRI could be employed to intraoperatively acquire image data characterizing the tissue surfaces to which the glyphs are attached (or to which the glyphs will be attached), and / or to intraoperatively acquire image data facilitating pose detection of the glyphs (provided that the glyphs were suitably modified to be detectable via such modalities).

[0224] The preceding example embodiments have been disclosed within the example context of spinal surgical procedures, non-limiting examples of which include procedures to decompress, align, stabilize, and / or fuse spinal sections or regions. Further, such examples can address relieving pressure on nerve roots and / or spinal cord caused by bone, tissue, or tumors. Also, addressing alignment can help to provide sagittal and coronal balance.Stabilization can temporarily stabilize the appropriate spinal segment via combinations of screws, rods, plates, and other related systems. Moreover, fusion can provide permanent stabilization of the relevant spinal segment / region via bone union form one vertebra to the next. It will be understood that the example embodiments disclosed herein can be adapted to and / or applied to other types of medical procedures that involve anatomical regions (e.g.rigid tissue structures, as described above) that can move relative to one another during the medical procedure, and which can be tracked via attachment of a glyph. Non-limiting examples of such other medical procedures and anatomical regions include orthopedic procedures, for example, including limb reconstruction procedures (for example, attaching a glyph to the two ends of a limb to be re-positioned, such as the femur and tibia), ophthalmological procedures, and craniofacial procedures.Enumerated Embodiments

[0225] Embodiment 1. A surgical navigation optical tracker marker subsystem comprising:a glyph;a marker base; andan attachment structure.

[0226] Embodiment 2. A surgical navigation optical tracker marker subsystem according to embodiment 1 , wherein said glyph and said marker base comprise a unitary structure.

[0227] Embodiment 3. A surgical navigation optical tracker marker subsystem according to embodiment 2, wherein said unitary structure comprises a tile, a marker tile, a tile flag, a marker tile flag, or any combination thereof.

[0228] Embodiment 4. A surgical navigation optical tracker marker subsystem according to embodiment 1 , wherein said glyph and said marker base are configured to form a unitary structure.

[0229] Embodiment 5. A surgical navigation optical tracker marker subsystem according to embodiment 4, wherein said unitary structure comprises a tile, a marker tile, a tile flag, a marker tile flag, or any combination thereof.

[0230] Embodiment 6. A surgical navigation optical tracker marker subsystem according to embodiment 1 , wherein said glyph and said marker base are configured to form a composite structure.

[0231] Embodiment 7. A surgical navigation optical tracker marker subsystem according to embodiment 6, wherein said composite structure comprises a tile, a marker tile, a tile flag, a marker tile flag, or any combination thereof.

[0232] Embodiment 8. A surgical navigation optical tracker marker subsystem according to embodiment 1 , wherein said glyph, said marker base and said attachment structure comprise separate structures.

[0233] Embodiment 9. A surgical navigation optical tracker marker subsystem according to embodiment 1 , wherein said glyph is removably or fixedly attached to said marker base.

[0234] Embodiment 10. A surgical navigation optical tracker marker subsystem according to embodiment 1 , wherein said glyph is removably or fixedly attached to said attachment structure.

[0235] Embodiment 11. A surgical navigation optical tracker marker subsystem according to embodiment 2, wherein said unitary structure is removably attached to an attachment structure via a quick-connect mechanism.

[0236] Embodiment 12. A surgical navigation optical tracker marker subsystem according to embodiment 11, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

[0237] Embodiment 13. A surgical navigation optical tracker marker subsystem according to embodiment 2, wherein said composite structure is removably attached to an attachment structure via a quick-connect mechanism.

[0238] Embodiment 14. A surgical navigation optical tracker marker subsystem according to embodiment 13, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

[0239] Embodiment 15. A surgical navigation optical tracker marker subsystem according to embodiment 4, wherein said unitary structure is removably affixed to an attachment structure via a quick-connect mechanism.

[0240] Embodiment 16. A surgical navigation optical tracker marker subsystem according to embodiment 15, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

[0241] Embodiment 17. A surgical navigation optical tracker marker subsystem according to embodiment 6, wherein said marker base is removably affixed to an attachment structure via a quick-connect mechanism.

[0242] Embodiment 18. A surgical navigation optical tracker marker subsystem according to embodiment 17, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

[0243] Embodiment 19. A surgical navigation optical tracker marker subsystem according to embodiment 1 , wherein said marker base comprises a material selected from plastic, polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK), plastic composite, metal, metal alloy, ceramic, glass, acrylic, a woven material, and any combination thereof.

[0244] Embodiment 20. A surgical navigation optical tracker marker subsystem according to embodiment 1 , wherein said attachment structure comprises a screw, a tulip, a clamp, or any combination thereof.

[0245] Embodiment 21. A surgical navigation optical tracker marker subsystem according to embodiment 20, wherein said screw comprises:a bone screw; a pedicle screw; a polyaxial screw; a monoaxial screw; a cancellous bone screw; a cortical screw; a cannulated or non-cannulated screw; a fenestrated screw; a threaded or partially-threaded screw; a low- or reduced-torque screw; a hybrid thread screw; a smooth shank screw; a lag screw; a compression screw; a Herbert screw; a malleolar screw; a self-tapping screw; a self-drilling screw; a self-starting screw; a stylet tip screw; a screw with uniform or variable thread pitch; a low-profile screw; a screw with a threaded, partially threaded, or non-threaded head; a reduction head screw; a locking screw; a spinal implant screw; a magnetic core bone screw; a trauma screw; a deformity screw; a spinal fixation screw; a break-away screw; a drug eluting screw; a coated screw; an HA-coated screw; a drug-coated screw; a screw coated with antibiotics, anti-inflammatory compound(s), or growth factors; a bio-absorbable screw; a 3D-printed screw; or any combination thereof.

[0246] Embodiment 22. A surgical navigation optical tracker marker subsystem according to embodiment 20, wherein said tulip comprises:a polyaxial tulip; a motion-limiting tulip; a variable angle tulip; a fixed angle tulip; a low-profile tulip; an offset tulip; a modified tulip; a friction-fit tulip; a tapered tulip; a modular tulip; a reduced height tulip; a low-top tulip; a reduction-top tulip; a minimally invasive-top tulip; a low profile tulip; a standard or reduction tulip; a configurable tulip; a top-loading, sideloading, or angled tulip; an extended or extended-tab tulip ; or any combination thereof.

[0247] Embodiment 23. A surgical navigation optical tracker marker subsystem according to embodiment 20, wherein said clamp comprises a bone clamp, a spinous process clamp, or a combination thereof.

[0248] Embodiment 24. A surgical navigation optical tracker marker subsystem comprising:a unitary marker component comprising a marker base and a glyph; andan attachment structure.

[0249] Embodiment 25. A surgical navigation optical tracker marker subsystem according to embodiment 24, wherein said unitary marker component comprises a tile, a marker tile, a tile flag, a marker tile flag, or any combination thereof.

[0250] Embodiment 26. A surgical navigation optical tracker marker subsystem according to embodiment 25, wherein said unitary structure is removably attached to an attachment structure via a quick-connect mechanism.

[0251] Embodiment 27. A surgical navigation optical tracker marker subsystem according to embodiment 26, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

[0252] Embodiment 28. A surgical navigation optical tracker marker subsystem according to embodiment 24, wherein said attachment structure comprises a screw, a tulip, a clamp, or any combination thereof.

[0253] Embodiment 29. A surgical navigation optical tracker marker subsystem according to embodiment 28, wherein said screw comprises:a bone screw; a pedicle screw; a polyaxial screw; a monoaxial screw; a cancellous bone screw; a cortical screw; a cannulated or non-cannulated screw; a fenestrated screw; a threaded or partially-threaded screw; a low- or reduced-torque screw; a hybrid thread screw; a smooth shank screw; a lag screw; a compression screw; a Herbert screw; a malleolar screw; a self-tapping screw; a self-drilling screw; a self-starting screw; a stylet tip screw; a screw with uniform or variable thread pitch; a low-profile screw; a screw with a threaded, partially threaded, or non-threaded head; a reduction head screw; a locking screw; a spinal implant screw; a magnetic core bone screw; a trauma screw; a deformity screw; a spinal fixation screw; a break-away screw; a drug eluting screw; a coated screw; an HA-coated screw; a drug-coated screw; a screw coated with antibiotics, anti-inflammatory compound(s), or growth factors; a bio-absorbable screw; a 3D-printed screw; or any combination thereof.

[0254] Embodiment 30. A surgical navigation optical tracker marker subsystem according to embodiment 28, wherein said tulip comprises:a polyaxial tulip; a motion-limiting tulip; a variable angle tulip; a fixed angle tulip; a low-profile tulip; an offset tulip; a modified tulip; a friction-fit tulip; a tapered tulip; a modular tulip; a reduced height tulip; a low-top tulip; a reduction-top tulip; a minimally invasive-top tulip; a low profile tulip; a standard or reduction tulip; a configurable tulip; a top-loading, sideloading, or angled tulip; an extended or extended-tab tulip ; or any combination thereof.

[0255] Embodiment 31. A surgical navigation optical tracker marker subsystem according to embodiment 28, wherein said clamp comprises a bone clamp, a spinous process clamp, or a combination thereof.

[0256] Embodiment 32. A surgical navigation optical tracker marker subsystem comprising:a composite marker component comprising a marker base and a removable glyph; andan attachment structure.

[0257] Embodiment 33. A surgical navigation optical tracker marker subsystem according to embodiment 32, wherein said unitary marker component comprises a tile, a marker tile, a tile flag, a marker tile flag, or any combination thereof.

[0258] Embodiment 34. A surgical navigation optical tracker marker subsystem according to embodiment 33, wherein said unitary structure is removably attached to an attachment structure via a quick-connect mechanism.

[0259] Embodiment 35. A surgical navigation optical tracker marker subsystem according to embodiment 34, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

[0260] Embodiment 36. A surgical navigation optical tracker marker subsystem according to embodiment 32, wherein said attachment structure comprises a screw, a tulip, a clamp, or any combination thereof.

[0261] Embodiment 37. A surgical navigation optical tracker marker subsystem according to embodiment 36, wherein said screw comprises:a bone screw; a pedicle screw; a polyaxial screw; a monoaxial screw; a cancellous bone screw; a cortical screw; a cannulated or non-cannulated screw; a fenestrated screw; a threaded or partially-threaded screw; a low- or reduced-torque screw; a hybrid thread screw; a smooth shank screw; a lag screw; a compression screw; a Herbert screw; a malleolar screw; a self-tapping screw; a self-drilling screw; a self-starting screw; a stylet tip screw; a screw with uniform or variable thread pitch; a low-profile screw; a screw with a threaded, partially threaded, or non-threaded head; a reduction head screw; a locking screw; a spinal implant screw; a magnetic core bone screw; a trauma screw; a deformity screw; a spinal fixation screw; a break-away screw; a drug eluting screw; a coated screw; an HA-coated screw; a drug-coated screw; a screw coated with antibiotics, anti-inflammatory compound(s), or growth factors; a bio-absorbable screw; a 3D-printed screw; or any combination thereof.

[0262] Embodiment 38. A surgical navigation optical tracker marker subsystem according to embodiment 36, wherein said tulip comprises:a polyaxial tulip; a motion-limiting tulip; a variable angle tulip; a fixed angle tulip; a low-profile tulip; an offset tulip; a modified tulip; a friction-fit tulip; a tapered tulip; a modular tulip; a reduced height tulip; a low-top tulip; a reduction-top tulip; a minimally invasive-top tulip; a low profile tulip; a standard or reduction tulip; a configurable tulip; a top-loading, sideloading, or angled tulip; an extended or extended-tab tulip ; or any combination thereof.

[0263] Embodiment 39. A surgical navigation optical tracker marker subsystem according to embodiment 36, wherein said clamp comprises a bone clamp, a spinous process clamp, or a combination thereof.

[0264] Embodiment 40. A surgical navigation system comprising:a surgical imaging system comprising a surface detection subsystem and an optical tracking subsystem;a plurality of glyph marker bases, each glyph marker base comprising a glyph, wherein each glyph marker base is removably attachable, directly or indirectly, to rigid tissue such that a pose of the glyph remains fixed relative to a pose of the rigid tissue; andcontrol and processing circuitry operably coupled to the surgical imaging system, the control and processing circuitry comprising one or more processors and associated memory, the memory comprising instructions executable by the one or more processors for performing operations comprising:controlling the surface detection subsystem to acquire intraoperative surface data characterizing an intraoperatively exposed portion of a plurality of rigid tissue structures associated with a subject, and employing surface registration between the intraoperative surface data and segmented surface data obtained from volumetric image data associated each rigid tissue structure to generate, for each rigid tissue structure, a corresponding registration transformation associating the volumetric image data pertaining to the rigid tissue structure with an intraoperative pose of the rigid tissue structure;obtaining glyph association information establishing an association between each glyph and attachment of the corresponding glyph marker base to a respective rigid tissue structure, thereby associating each glyph with a respective rigid tissue structure;a) acquiring image data from at least one imaging camera of the surgical imaging system, the at least one imaging camera being capable of imaging the glyphs when the glyphs reside within a field of view of the at least one imaging camera;b) processing the image data to identify at least two glyphs and to determine a respective glyph pose associated with each identified glyph;c) for at least one rigid tissue structure having an identified glyph associated therewith, employing the glyph pose of the identified glyph, the registration transformation associated with the rigid tissue structure, and a pre-determined relationship between the glyph pose and an intraoperative pose of the rigid tissue structure to generate navigation images displaying, in an intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with the rigid tissue structure, the intraoperative pose of the trackable medical instrument being determined via the optical tracking subsystem;wherein the navigation images are generated based on a known calibration transformation between the optical tracking subsystem and the surface detection subsystem and a known spatial relationship between the at least one camera and one or both of the surface detection subsystem and the optical tracking subsystem.

[0265] Embodiment 41. The system according to embodiment 40 wherein the control and processing circuitry is further configured to employ, for a plurality of rigid tissue structure having identified glyphs respectively associated therewith, the pre-determined relationship between the glyph pose and the intraoperative pose of the rigid tissue structure to determine a current intraoperative pose of the rigid tissue structure, and to employ the current intraoperative poses to generate updated alignment parameters associated with the rigid tissue structures having identified glyphs respectively associated therewith.

[0266] Embodiment 42. The system according to embodiment 40 wherein the control and processing circuitry is further configured to employ, for a plurality of rigid tissue structures having identified glyphs respectively associated therewith, the pre-determined relationship between the glyph pose and the intraoperative pose of the rigid tissue structure to determine a current intraoperative pose of the rigid tissue structure, and to employ the current intraoperative poses to generate and display an image facilitating visualization of alignment of the plurality of rigid tissue structures having identified glyphs respectively associated therewith.

[0267] Embodiment 43. The system according to any one of embodiments 40 to 42 wherein the control and processing circuitry is further configured such that step c) is performed for each rigid tissue structure having an identified glyph associated therewith.

[0268] Embodiment 44. The system according to any one of embodiments 40 to 42 wherein the control and processing circuitry is further configured such that step c) is performed for a rigid tissue structure that is closed in proximity to the trackable medical instrument, the rigid tissue structure having an identified glyph associated therewith.

[0269] Embodiment 45. The system according to any one of embodiments 40 to 44 wherein the control and processing circuitry is further configured such that the pre-determined relationship is generated by:acquiring initial image data when acquiring the intraoperative surface data to determine initial glyph poses of the at least two glyphs; andemploying the intraoperative surface data and the initial glyph poses to generate, for each glyph of the at least two glyphs, a transformation between the initial glyph pose and an intraoperative pose of the rigid tissue structure associated with the glyph.

[0270] Embodiment 46. The system according to any one of embodiments 40 to 45 wherein the control and processing circuitry is configured to instruct an operator to secure the glyph marker bases to the rigid tissue structures before the intraoperative surface data has been acquired.

[0271] Embodiment 47. The system according to any one of embodiments 40 to 44 further comprising an optical tracking reference structure having a pose trackable by the opticaltracking subsystem, the optical tracking reference structure being removably attachable to rigid tissue for tracking motion of the subject;wherein the control and processing circuitry is further configured such that the predetermined relationship is generated by:prior to acquiring the intraoperative surface data, instructing the operator to secure the optical tracking reference structure to the subject, and / or receiving input confirming that the optical tracking reference structure is secured to the subject,subsequently acquiring the intraoperative surface data and an initial pose of the optical tracking reference structure;prior to acquiring the image data fortracking of the glyphs, instructing the operator to secure the glyph marker bases to the rigid tissue structures and / or receiving input confirming that the glyph marker bases have been secured to the rigid tissue structures;subsequently determining an updated pose of the optical tracking reference structure when acquiring the image data fortracking of the glyphs; andemploying the initial pose and updated pose of the optical tracking reference structure to determine a transformation between the glyph pose and an intraoperative pose of the rigid tissue structure.

[0272] Embodiment 48. The system according to embodiment 47 wherein the optical tracking reference structure includes one or more geometric references facilitating pose detection by the surface detection subsystem in addition to pose detection by the optical tracking subsystem, and wherein the optical tracking reference structure is employed to perform a calibration transform after acquiring the intraoperative surface data.

[0273] Embodiment 49. The system according to any one of embodiments 40 to 48 wherein the one or more imaging cameras are components of the surface detection subsystem.

[0274] Embodiment 50. The system according to any one of embodiments 40 to 48 wherein the one or more imaging cameras are components of the optical tracking subsystem.

[0275] Embodiment 51. The system according to any one of embodiments 40 to 50 wherein the control and processing circuitry is configured such that steps a) through c) are repeated to update the navigation images based on updated determinations of the glyph poses.

[0276] Embodiment 52. The system according to embodiment 51 wherein the control and processing circuitry is configured such that steps a) through c) are repeated at a frequency that is sufficiently high to facilitate updating of the navigation images in real time.

[0277] Embodiment 53. The system according to any one of embodiments 40 to 46 further comprising an optical tracking reference structure having a pose trackable by the optical tracking subsystem, the optical tracking reference structure being removably attachable to rigid tissue for tracking motion of the subject;wherein the control and processing circuitry is configured such that steps a) through c) are repeated intermittently to update the glyph poses, and wherein the control and processing circuitry is configured such that the navigation images are updated between intermittent updates of the glyph poses by performing operations comprising:repeatedly tracking the optical tracking reference structure secured to the subject; andemploying a tracked pose of the optical tracking reference structure to update the navigation images.

[0278] Embodiment 54. The system according to embodiment 53 wherein tracking of the pose of the optical tracking reference structure is performed at a frequency that is sufficiently high to facilitate updating of the navigation images in real time.

[0279] Embodiment 55. The system according to embodiment 53 wherein the control and processing circuitry is configured such that at least one intermittent update of the glyph poses is autonomously triggered.

[0280] Embodiment 56. The system according to embodiment 55 wherein the control and processing circuitry is configured such that at least one intermittent update of the glyph poses is autonomously triggered according to a prescribed time interval.

[0281] Embodiment 57. The system according to embodiment 53 wherein the control and processing circuitry is configured such that at least one intermittent update of the glyph poses is triggerable in response to input received from an operator.

[0282] Embodiment 58. The system according to embodiment 57 wherein the control and processing circuitry is configured such that an intermitted update of the glyph poses is triggered after receiving input from an operator indicating insufficient navigation accuracy.

[0283] Embodiment 59. The system according to embodiment 57 wherein the control and processing circuitry is configured such that an intermitted update of the glyph poses is triggered after receiving input from an operator indicating initiation of a new phase of a surgical procedure.

[0284] Embodiment 60. The system according to any one of embodiments 53 to 59 wherein the optical tracking reference structure includes one or more geometrical features facilitating pose detection by the surface detection subsystem in addition to pose detection by the optical tracking subsystem, and wherein the optical tracking reference structure is employed to perform a calibration transform after acquiring the intraoperative surface data.

[0285] Embodiment 61. The system according to any one of embodiments 40 to 60 wherein the control and processing circuitry is configured such that the surface detection subsystem is employed to acquire additional intraoperative surface data when performing step a), and wherein surface registration is performed between the additional intraoperative surface data and reference surface data associated with a known model at least one glyph marker baseto obtain or refine a determination of the pose of the glyph associated with the at least one glyph marker base.

[0286] Embodiment 62. The system according to embodiment 61 wherein the control and processing circuitry is configured such that the pose of the glyph associated with the at least one glyph marker base, as determined from step b), is employed as an input for performing segmentation of the additional intraoperative surface data prior to performing surface registration.

[0287] Embodiment 63. The system according to any one of embodiments 40 to 62 wherein the control and processing circuitry is configured such that the glyph association information is determined autonomously, by performing operations comprising:employing the known intraoperative poses of the rigid tissue structures, as determined from surface registration between the intraoperative surface data and the segmented surface data obtained from volumetric image data of each rigid tissue structure, and the glyph poses and glyph identification determined from step b), to locate a glyph that is closest in spatial proximity to each rigid tissue structure.

[0288] Embodiment 64. The system according to any one of embodiments 40 to 63 wherein the control and processing circuitry is configured such that the glyph association information is determined autonomously, by performing operations comprising:after performing step b), spatially sorting the set of identified glyphs, and associating each glyph with a respective rigid tissue structure according to a known spatial ordering of the rigid tissue structures.

[0289] Embodiment 65. The system according to any one of embodiments 40 to 64 wherein the control and processing circuitry is configured such that the glyph association information establishes an association between each glyph and attachment of the corresponding glyph marker base to a respective vertebral level, thereby associating each glyph with a respective vertebral level, and wherein the navigation images display, in the intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with at least one vertebral level.

[0290] Embodiment 66. A method of controlling a surgical navigation system to performing autonomous surgical navigation, the system comprising a surgical imaging system comprising a surface detection subsystem and an optical tracking subsystem, and a plurality of glyph marker bases, each glyph marker base comprising a glyph, wherein each glyph marker base is removably attachable, directly or indirectly, to rigid tissue such that a pose of the glyph remains fixed relative to a pose of the rigid tissue, the method comprising:controlling the surface detection subsystem to acquire intraoperative surface data characterizing an intraoperatively exposed portion of a plurality of rigid tissue structures associated with a subject, and employing surface registration between the intraoperativesurface data and segmented surface data obtained from volumetric image data associated each rigid tissue structure to generate, for each rigid tissue structure, a corresponding registration transformation associating the volumetric image data pertaining to the rigid tissue structure with an intraoperative pose of the rigid tissue structure;obtaining glyph association information establishing an association between each glyph and attachment of the corresponding glyph marker base to a respective rigid tissue structure, thereby associating each glyph with a respective rigid tissue structure;a) acquiring image data from at least one imaging camera of the surgical imaging system, the at least one imaging camera being capable of imaging the glyphs when the glyphs reside within a field of view of the at least one imaging camera;b) processing the image data to identify at least two glyphs and to determine a respective glyph pose associated with each identified glyph;c) for at least one rigid tissue structure having an identified glyph associated therewith, employing the glyph pose of the identified glyph, the registration transformation associated with the rigid tissue structure, and a pre-determined relationship between the glyph pose and an intraoperative pose of the rigid tissue structure to generate navigation images displaying, in an intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with the rigid tissue structure, the intraoperative pose of the trackable medical instrument being determined via the optical tracking subsystem;wherein the navigation images are generated based on a known calibration transformation between the optical tracking subsystem and the surface detection subsystem and a known spatial relationship between the at least one camera and one or both of the surface detection subsystem and the optical tracking subsystem.

[0291] Embodiment 67. A method of performing surgical navigation during a surgical procedure, the method comprising:providing a surgical imaging system comprising a surface detection subsystem and an optical tracking subsystem, and a plurality of glyph marker bases, each glyph marker base comprising a glyph, wherein each glyph marker base is removably attachable, directly or indirectly, to rigid tissue such that a pose of the glyph remains fixed relative to a pose of the rigid tissue;employing the surface detection subsystem to acquire intraoperative surface data characterizing an intraoperatively exposed portion of a plurality of rigid tissue structures associated with a subject, and employing surface registration between the intraoperative surface data and segmented surface data obtained from volumetric image data associated each rigid tissue structure to generate, for each rigid tissue structure, a correspondingregistration transformation associating the volumetric image data pertaining to the rigid tissue structure with an intraoperative pose of the rigid tissue structure;providing glyph association information establishing an association between each glyph and attachment of the corresponding glyph marker base to a respective rigid tissue structure, thereby associating each glyph with a respective rigid tissue structure;employing at least one imaging camera of the surgical imaging system to acquire image data, the at least one imaging camera being capable of imaging the glyphs when the glyphs reside within a field of view of the at least one imaging camera;employing the image data to identify at least two glyphs and to determine a respective glyph pose associated with each identified glyph;for at least one rigid tissue structure having an identified glyph associated therewith, employing the glyph pose of the identified glyph, the registration transformation associated with the rigid tissue structure, and a pre-determined relationship between the glyph pose and an intraoperative pose of the rigid tissue structure to generate navigation images displaying, in an intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with the rigid tissue structure, the intraoperative pose of the trackable medical instrument being determined via the optical tracking subsystem;wherein the navigation images are generated based on a known calibration transformation between the optical tracking subsystem and the surface detection subsystem and a known spatial relationship between the at least one camera and one or both of the surface detection subsystem and the optical tracking subsystem.

[0292] Embodiment 68. The method according to embodiment 67 wherein the glyph marker bases are secured to the respective rigid tissue structures prior to acquiring the intraoperative surface data.

[0293] Embodiment 69. The method according to embodiment 66 further comprising: prior to the glyph marker bases being secured to the respective rigid tissue structures, and after an optical tracking reference structure is secured to rigid tissue of the subject, the optical tracking reference structure having a pose trackable by the optical tracking subsystem;subsequently acquiring the intraoperative surface data and an initial pose of the optical tracking reference structure; andafter the glyph marker bases are secured to the respective rigid tissue structures: subsequently determining an updated pose of the optical tracking reference structure when acquiring the image data fortracking of the glyphs; andemploying the initial pose and updated pose of the optical tracking reference structure to determine a transformation between the glyph pose and an intraoperative pose of the rigid tissue structure.

[0294] Embodiment 70. A surgical navigation system comprising:a surgical imaging system comprising a surface detection subsystem and an optical tracking subsystem;control and processing circuitry operably coupled to the surgical imaging system, the control and processing circuitry comprising one or more processors and associated memory, the memory comprising instructions executable by the one or more processors for performing operations comprising:controlling the surface detection subsystem to acquire intraoperative surface data characterizing an intraoperatively exposed portion of a plurality of rigid tissue structures associated with a subject, and employing surface registration between the intraoperative surface data and segmented surface data obtained from volumetric image data associated each rigid tissue structure to generate, for each rigid tissue structure, a corresponding registration transformation associating the volumetric image data pertaining to the rigid tissue structure with an intraoperative pose of the rigid tissue structure;obtaining glyph association information establishing an association between: a plurality of glyph marker bases, each glyph marker base comprising a glyph, wherein each glyph marker base is removably attachable, directly or indirectly, to rigid tissue such that a pose of the glyph remains fixed relative to a pose of the rigid tissue; and attachment of the corresponding glyph marker base to a respective rigid tissue structure, thereby associating each glyph with a respective rigid tissue structure;a) acquiring image data from at least one imaging camera of the surgical imaging system, the at least one imaging camera being capable of imaging the glyphs when the glyphs reside within a field of view of the at least one imaging camera;b) processing the image data to identify at least two glyphs and to determine a respective glyph pose associated with each identified glyph;c) for at least one rigid tissue structure having an identified glyph associated therewith, employing the glyph pose of the identified glyph, the registration transformation associated with the rigid tissue structure, and a pre-determined relationship between the glyph pose and an intraoperative pose of the rigid tissue structure to generate navigation images displaying, in an intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with the rigid tissue structure, the intraoperative pose of the trackable medical instrument being determined via the optical tracking subsystem;wherein the navigation images are generated based on a known calibration transformation between the optical tracking subsystem and the surface detection subsystem and a known spatial relationship between the at least one camera and one or both of the surface detection subsystem and the optical tracking subsystem.

[0295] Embodiment 71. A surgical navigation system comprising:control and processing circuitry operably connectable to a surgical imaging system having a surface detection subsystem and an optical tracking subsystem, the control and processing circuitry comprising one or more processors and associated memory, the memory comprising instructions executable by the one or more processors for performing the following operations when the control and processing circuitry is operably coupled to the surgical imaging system:controlling the surface detection subsystem to acquire intraoperative surface data characterizing an intraoperatively exposed portion of a plurality of rigid tissue structures associated with a subject, and employing surface registration between the intraoperative surface data and segmented surface data obtained from volumetric image data associated each rigid tissue structure to generate, for each rigid tissue structure, a corresponding registration transformation associating the volumetric image data pertaining to the rigid tissue structure with an intraoperative pose of the rigid tissue structure;obtaining glyph association information establishing an association between: a plurality of glyph marker bases, each glyph marker base comprising a glyph, wherein each glyph marker base is removably attachable, directly or indirectly, to rigid tissue such that a pose of the glyph remains fixed relative to a pose of the rigid tissue; andattachment of the corresponding glyph marker base to a respective rigid tissue structure, thereby associating each glyph with a respective rigid tissue structure;a) acquiring image data from at least one imaging camera of the surgical imaging system, the at least one imaging camera being capable of imaging the glyphs when the glyphs reside within a field of view of the at least one imaging camera;b) processing the image data to identify at least two glyphs and to determine a respective glyph pose associated with each identified glyph;c) for at least one rigid tissue structure having an identified glyph associated therewith, employing the glyph pose of the identified glyph, the registration transformation associated with the rigid tissue structure, and a pre-determined relationship between the glyph pose and an intraoperative pose of the rigid tissue structure to generate navigation images displaying, in an intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with the rigidtissue structure, the intraoperative pose of the trackable medical instrument being determined via the optical tracking subsystem;wherein the navigation images are generated based on a known calibration transformation between the optical tracking subsystem and the surface detection subsystem and a known spatial relationship between the at least one camera and one or both of the surface detection subsystem and the optical tracking subsystem.EXAMPLES

[0296] The following examples are presented to enable those skilled in the art to understand and to practice embodiments of the present disclosure. They should not be considered as a limitation on the scope of the disclosure, but merely as being illustrative and representative thereof.Example 1: Example Workflow for Glyph-Based Level Tracking and Intraoperative Assessment of Spinal AlignmentExamples 1A-1H illustrate, via a non-limiting example implementation, an example workflow presented in the form of user interface screenshots obtained from an example navigation system. It will be understood that the example workflow illustrated in the user interface screenshots presented herein is not intended to limit the scope of the present disclosure.Example 1A: User-Interface-Guided Alignment Parameter Planning based on Preoperative Image Data (FIGS. 20A-20D)

[0297] FIGS. 20A-20D illustrate an example user-interface driven workflow for selecting and defining alignment parameters, which can be employed to display and quantify the intraoperative pose of the vertebral levels based on glyph pose detection. While any number of alignment parameters may be employed, the present example employs three common example alignment parameters: 1. Pelvic Incidence, 2. Pelvic Angle, and 3. Cobb Angle (Sagittal and Coronal). Example 2 provides examples of other example alignment parameters that may be defined and employed. FIG. 20A shows an example user interface screen for selecting an alignment parameter.

[0298] If Pelvic Incidence is selected as an alignment parameter, then two vertebral levels can be defined for calculation of the parameter - Femoral Heads and S1 (superior endplate), as shown in FIG. 20B

[0299] If Pelvic Angle is selected, then two levels are pre-determined for defining the alignment parameter - namely the femoral heads and S1 (superior endplate), as shown in FIG. 20C, and an additional is identified based on user selection. The user interface can permit the midpoint of the user-selected level to be defined.

[0300] If the sagittal or coronal Cobb angle is selected, the user can select 2 levels for calculation and can specify whether the superior or inferior endplate will be used for each of the selected levels, as shown in FIG. 20D.Example 1B: User-Interface-Guided Level Definition for Preoperative Image Data (FIGS. 21A-21Cand 22)

[0301] According to the present example workflow, after an alignment parameter has been added, the user can perform level definition. In some example user interface implementations, a user can add an alignment parameter, define its levels, and then repeat the process for additional alignment parameters, or the user can select multiple alignment parameters and subsequently define the levels for all parameters.

[0302] While the present example implementation involves manual workflows for level definition, it will be understood that level definition can be performed autonomously or semi-autonomously.

[0303] In the example case of defining femoral heads, the midpoints of the two femoral heads are prescribed. In the present example implementation, this is performed by placing spheres to overlay the femoral heads. The point in the middle of the sphere can represent the midpoint that will be used for calculations. It will be understood that other methods can be employed in the alternative to define the femoral head midpoints, such as, for example, placing points at the center of each femoral head.

[0304] To define endplates (inferior and superior), one example implementation involves use of an MPR (multiplanar reconstruction / reformation) tool. According to one example implementation, three interactable orthogonal planes are manipulated by the user to define the location and orientation of the endplate. It will be understood that other methods of defining the endplate of levels can be employed in the alternative, such as, for example, placing 3-4 points and fitting a plane to define the location and orienting the plane by a last point placed at the spinous process.

[0305] To define the midpoint of a level, the MPR tool can be used in one example implementation. For example, three interactable orthogonal planes can be manipulated by the user to place the center of the 3 planes at the center of the spine level. It will be understood that other methods of defining the midpoint of levels can be employed in the alternative, such as, for example, placing points to capture the bounds of the endplate and calculating the center.

[0306] Once the definition of each level is completed for an alignment parameter, the parameter can be calculated. In the present example workflow, after the user completes all level definitions, the user can proceed to the segmentation phase of the workflow, which is described below.

[0307] FIGS. 21A, 21B, and 21C shows an example user interface screen for selecting a parameter and performing level definition, and FIG. 22 shows the resulting calculation of example alignment parameters based on the selected parameters and defined levels.Example 1C: User-Interface-Guided Segmentation of Levels from Pre-Operative Volumetric Image Data (FIGS. 23A-23C)

[0308] In the present example, segmentation of volumetric image data is performed to facilitate level-specific registration with intraoperative surface data, and level-specific rendering of navigation images. In one example implementation, default bounding boxes are shown when entering segmentation for each of the defined levels. These default bounding boxes can be provided as set sizes and can be calculated, for example, based on the endplate or midpoint definitions. Since the local coordinate system of each level is known (see Example 2 below; the origin and the local x,y,z where the origin corresponds to the midpoint of the level or the center of the superior or inferior endplate), a set sized box can be calculated.

[0309] In an example implementation involving midpoint definition, the default box can be centered at the midpoint.

[0310] In an example implementation involving superior endplate definition, the center of the top plane of the default box can correspond to the center of the superior endplate.

[0311] In an example implementation involving inferior endplate definition, the center of the bottom plane of the default box can correspond to the center of the inferior endplate.

[0312] In some example implementations, the user can crop by interacting with the points or rotate by interacting with the handles to refine the bounding box. It is noted that although the example segmentation methods here involve manual intervention, in other example implementations, one or more of the segmentation steps can be automated.

[0313] It is also noted that this step of the workflow can be optional, as it does not affect measurements and can be used to generate the visualization of the levels during the alignment tracking stage described below.

[0314] According to the present example implementation, the segmentation stage is completed by saving the segmentation for use in the alignment parameter stage. This can be performed, for example, by extracting the geometry within bounding box and exporting it as an STL file, or using other methods such as, for example, using the bounds to crop the volumetric image data for each level for visualization.

[0315] Example segmentation user interface screens are shown in FIGS. 23A-23C.Example 1E: Image Registration Between Intraoperatively Acquired Surface Data and Segmented Pre-Operative Image Data (FIGS. 24A-24G)

[0316] In the present example workflow, the user can interact with a user interface screen for registration involving the spine levels populated by the levels that were defined in planning, as shown in FIG. 24A.

[0317] In an initial registration step, the user can pick points on the volumetric data, optionally prior to acquisition of the structured light image data (the present non-limiting example implementation employs structured light for the surface detection modality), as shown in FIG. 24B.

[0318] Proceeding to the structured light acquisition stage, the user can be presented with a live video view, which can include two views corresponding to the left and right cameras of the structured light system. The user can then initiate acquisition of the structured light image dataset, and in the present example implementation, the point cloud is generated and shown next to the volumetric image data (e.g. CT data), as shown, for example, in FIG. 24C.

[0319] According to one example implementation, the user can select three points per level and proceed to the glyph association stage if the point cloud is deemed to have captured sufficient data, or one or more additional structured light image datasets can be acquired and stitched.

[0320] In some example implementations, the registration user interface screen can show the number of structured light acquisitions taken and stitched, and the user interface can allow the user to discard the latest structured light acquisition, as shown in FIG. 24E.

[0321] For example, when additional structured light acquisitions are to be performed, the user can be presented with the live video views. After another acquisition, the point clouds can be merged and shown on the user interface, as shown, for example, in FIG. 24F. The user can continue acquiring and merging points clouds or proceed after confirming the latest merged point cloud. In the present example implementation, the user selects, in the user interface for each level, three points on volumetric image data and the point cloud, as shown in FIG. 24F, and the surface registration is then performed.

[0322] The user interface can prompt the user to accept the registration of all levels.Registration can be confirmed by navigating an optically tracked tool, as shown in FIG. 24G. The user interface can show the registered level closest to the tip of the optically tracked tool in navigation images.Example 1F: Association of Tracking Glyphs with Vertebral levels (FIGS. 25A and 25B)

[0323] For glyph-level association, the user is instructed to attach the glyphs (e.g. glyphs provided on support structures attachable to the vertebral levels). In the example implementation shown in FIG. 25A, the user is presented with live video views to facilitate the glyph association phase. When the glyphs are secured to levels that the user would like to track and are in view of the structured light camera pair, images are acquired withcontrolled lighting using the projector. In some example implementations, all glyphs are imaged and tracked in a single glyph image acquisition. However, other example implementations can employ stitching of multiple glyph tracking images.

[0324] Furthermore, while the present example workflow involves the acquisition of intraoperative surface data for registration prior to glyph attachment and association (e.g. as in the workflow illustrated in FIGS. 18A and 18B), other workflows can employ attachment of glyphs prior to registration (e.g. as illustrated in the workflow of FIG. 10 and 17), and in such cases, the surface image data and glyph images can be acquired in a common step (e.g. immediately after one another). Example workflows thus include [acquire surface image data] -> [register] -> [acquire glyph images] -> [associate glyphs with levels], or, for example, [acquire surface image data and glyph images] -> [register] -> [associate glyphs with levels],

[0325] With the acquired glyph images and the identification of the glyphs, the glyph poses can be tracked, and overlays can be generated showing the different glyphs, as shown, for example in FIG. 25B, and the user can associate the glyphs with respective vertebral levels in the user interface.Example 1G: Intraoperative Level Tracking and Assessment of Spinal Alignment via Tracking Glyphs (FIGS. 26A-26D)

[0326] After associating the glyphs with respective vertebral levels, the updated alignment parameter measurements can be shown in the user interface, as generated based on registration and the most recent glyph images, with the glyph images acting as a proxy for surface detection and registration, as shown, for example in FIG. 26A. The user can reassess the alignment with subsequent glyph image acquisitions, which facilitate updated glyph pose determination, which in turn facilitates the updating of the alignment parameter measurements. FIG. 26B shows an example live view that is generated when acquiring a glyph tracking image.

[0327] In some example implementations, the user can verify (optionally in response to a prompt by the user interface) that the glyph poses relative to the vertebrae are still correct. For example, an optically tracked medical instrument can be employed to determine whether the position of the instrument tip, for every level with a glyph attached thereto (with the glyph being captured in the glyph tracking image) is accurate, as shown in FIG. 26C. If navigation of a level of interest is no longer accurate, the user can perform a re-registration (involving re-acquisition of surface data), e.g. by selection of the registration workflow from the alignment tracking user interface shown in FIG. 26D.

[0328] The alignment tracking measurements can be updated with each subsequent glyph image acquisition and determination of glyph pose. In some example implementations, the user can view one or more previous glyph tracking images.

[0329] The user interface can display a set of goal parameters associated with desired or planned alignment parameters, and these goal parameters can be shown adjacent to the relevant updated alignment parameters for comparison.Example 2: Examples of Alignment Parameters and their DefinitionIntroduction

[0330] Spinal alignment surgery aims to restore proper sagittal, coronal and / or axial balance by correcting abnormal curvature while optimizing anatomical posture (FIG. 27 shows an example of abnormal spine curvature). To achieve precise surgical outcomes, multiple alignment parameters are utilized both preoperatively to assess the extent of correction required and intraoperatively to evaluate progress toward the desired alignment. These parameters include, but are not limited to, Pelvic Incidence (PI), Pelvic Angle (PA), and Cobb Angle, each of which provides critical biomechanical insights into spinal and pelvic orientation.Alignment Parameters

[0331] Pelvic Incidence (PI) is a fixed anatomical parameter representing the angular relationship between the sacral endplate and the bicoxofemoral axis in a sagittal plane. The bicoxofemoral axis is the line connecting the centers of femoral heads. PI is measured as the angle between the line connecting the midpoint of sacral endplate to the midpoint of the bicoxofemoral axis and the line perpendicular to the sacral endplate at its midpoint, as shown in FIG. 28 in panel (a).

[0332] Pelvic Angle (PA) measures the orientation of the pelvis relative to another vertebra such as L1, aiding in sagittal balance assessment. It is measured between a line extending from the midpoint of bicoxofemoral axis to the reference vertebra (for example L1) and the line connecting the midpoint of sacral endplate to the midpoint of the bicoxofemoral axis, as shown in FIG. 28 in panel (b).

[0333] Cobb Angle quantifies the degree of spinal curvature by measuring the angle between the superior endplate of the most tilted superior vertebra and the inferior endplate of the most tilted inferior vertebra within a deformity region, as shown in FIG. 28 in panel (c). The cobb angle measurement can be made in both sagittal and coronal planes depending on the type of deformity that needs to be assessed.

[0334] FIG. 28 also shows the coronal plane Cobb angle between two vertebrae in panel (d), the distance measurement between the centroids of a pair of vertebrae in panel (e).

[0335] These measurements are typically performed on 2D X rays that provide only a single view orientation, which cannot capture the 3D variability in the orientations of individual vertebrae. Volumetric imaging modalities including but not limited to CT or MRI provide an accurate map of the full 3D structure of the spine, allowing comprehensive assessment for surgical correction. However, extending these measurements to 3D requires careful selection of parameter measurement plane to obtain sensible measurements that can be correlated with existing metrics. The parameter measurement plane is a 2D plane within the parameter measurement coordinate system where the angle computation occurs.Parameter Measurement Coordinate System

[0336] Object tracking employs understanding various coordinate systems and their relationships. A coordinate system defines an object's position, orientation, or movement within a reference frame. It can be absolute, relative, global, local, or follow Cartesian, polar, cylindrical, or other predefined or dynamic models, comprising axes, reference points, or transformation rules for mapping between frames.

[0337] Any volumetric data has an intrinsic coordinate system, referred herein as the 'Global Coordinate System' (FIG. 29, panel (a)). In DICOM, the typical CT coordinate system aligns the X-axis with the patient's left-right axis, the Y-axis with the anterior-posterior axis, and the Z-axis with the inferior-superior axis. However, abnormalities in spine curvature can cause misalignment between the global coordinate system and individual vertebrae. In such cases, more specific coordinate systems may be needed for accurate measurements in the region of interest.

[0338] Depending on the parameter being measured, it may be more appropriate to use a local coordinate system specific to an individual vertebra (FIG. 29, panel (c)). Alternatively, a regional coordinate system can be derived from two or more local coordinate systems using processing techniques, such as averaging or other methods (FIG. 29, panel (b)). Both the local and regional coordinate systems may be established automatically or through user input.

[0339] Each alignment parameter may utilize any variation of the coordinate systems described above, including different methods of encoding such systems, such as Cartesian, polar, cylindrical, or other variations.

[0340] The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments can be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.

Claims

CLAIMS1. A surgical navigation optical tracker marker subsystem comprising:a glyph;a marker base; andan attachment structure.

2. A surgical navigation optical tracker marker subsystem according to claim 1 , wherein said glyph and said marker base comprise a unitary structure.

3. A surgical navigation optical tracker marker subsystem according to claim 2, wherein said unitary structure comprises a tile, a marker tile, a tile flag, a marker tile flag, or any combination thereof.

4. A surgical navigation optical tracker marker subsystem according to claim 1 , wherein said glyph and said marker base are configured to form a unitary structure.

5. A surgical navigation optical tracker marker subsystem according to claim 4, wherein said unitary structure comprises a tile, a marker tile, a tile flag, a marker tile flag, or any combination thereof.

6. A surgical navigation optical tracker marker subsystem according to claim 1 , wherein said glyph and said marker base are configured to form a composite structure.

7. A surgical navigation optical tracker marker subsystem according to claim 6, wherein said composite structure comprises a tile, a marker tile, a tile flag, a marker tile flag, or any combination thereof.

8. A surgical navigation optical tracker marker subsystem according to claim 1 , wherein said glyph, said marker base and said attachment structure comprise separate structures.

9. A surgical navigation optical tracker marker subsystem according to claim 1 , wherein said glyph is removably or fixedly attached to said marker base.

10. A surgical navigation optical tracker marker subsystem according to claim 1 , wherein said glyph is removably or fixedly attached to said attachment structure.

11. A surgical navigation optical tracker marker subsystem according to claim 2, wherein said unitary structure is removably attached to an attachment structure via a quick-connect mechanism.

12. A surgical navigation optical tracker marker subsystem according to claim 11 , wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

13. A surgical navigation optical tracker marker subsystem according to claim 2, wherein said composite structure is removably attached to an attachment structure via a quickconnect mechanism.

14. A surgical navigation optical tracker marker subsystem according to claim 13, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

15. A surgical navigation optical tracker marker subsystem according to claim 4, wherein said unitary structure is removably affixed to an attachment structure via a quick-connect mechanism.

16. A surgical navigation optical tracker marker subsystem according to claim 15, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

17. A surgical navigation optical tracker marker subsystem according to claim 6, wherein said marker base is removably affixed to an attachment structure via a quick-connect mechanism.

18. A surgical navigation optical tracker marker subsystem according to claim 17, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

19. A surgical navigation optical tracker marker subsystem according to claim 1 , wherein said marker base comprises a material selected from plastic, polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK), plastic composite, metal, metal alloy, ceramic, glass, acrylic, a woven material, and any combination thereof.

20. A surgical navigation optical tracker marker subsystem according to claim 1 , wherein said attachment structure comprises a screw, a tulip, a clamp, or any combination thereof.

21. A surgical navigation optical tracker marker subsystem according to claim 20, wherein said screw comprises:a bone screw; a pedicle screw; a polyaxial screw; a monoaxial screw; a cancellous bone screw; a cortical screw; a cannulated or non-cannulated screw; a fenestrated screw; a threaded or partially-threaded screw; a low- or reduced-torque screw; a hybrid thread screw; a smooth shank screw; a lag screw; a compression screw; a Herbert screw; a malleolar screw; a self-tapping screw; a self-drilling screw; a self-starting screw; a stylet tip screw; a screw with uniform or variable thread pitch; a low-profile screw; a screw with a threaded, partially threaded, or non-threaded head; a reduction head screw; a locking screw; a spinal implant screw; a magnetic core bone screw; a trauma screw; a deformity screw; a spinal fixation screw; a break-away screw; a drug eluting screw; a coated screw; an HA-coated screw; a drug-coated screw; a screw coated with antibiotics, anti-inflammatory compound(s), or growth factors; a bio-absorbable screw; a 3D-printed screw; or any combination thereof.

22. A surgical navigation optical tracker marker subsystem according to claim 20, wherein said tulip comprises:a polyaxial tulip; a motion-limiting tulip; a variable angle tulip; a fixed angle tulip; a low-profile tulip; an offset tulip; a modified tulip; a friction-fit tulip; a tapered tulip; a modular tulip; a reduced height tulip; a low-top tulip; a reduction-top tulip; a minimally invasive-top tulip; a low profile tulip; a standard or reduction tulip; a configurable tulip; a top-loading, sideloading, or angled tulip; an extended or extended-tab tulip ; or any combination thereof.

23. A surgical navigation optical tracker marker subsystem according to claim 20, wherein said clamp comprises a bone clamp, a spinous process clamp, ora combination thereof.

24. A surgical navigation optical tracker marker subsystem comprising:a unitary marker component comprising a marker base and a glyph; andan attachment structure.

25. A surgical navigation optical tracker marker subsystem according to claim 24, wherein said unitary marker component comprises a tile, a marker tile, a tile flag, a marker tile flag, or any combination thereof.

26. A surgical navigation optical tracker marker subsystem according to claim 25, wherein said unitary structure is removably attached to an attachment structure via a quickconnect mechanism.

27. A surgical navigation optical tracker marker subsystem according to claim 26, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

28. A surgical navigation optical tracker marker subsystem according to claim 24, wherein said attachment structure comprises a screw, a tulip, a clamp, or any combination thereof.

29. A surgical navigation optical tracker marker subsystem according to claim 28, wherein said screw comprises:a bone screw; a pedicle screw; a polyaxial screw; a monoaxial screw; a cancellous bone screw; a cortical screw; a cannulated or non-cannulated screw; a fenestrated screw; a threaded or partially-threaded screw; a low- or reduced-torque screw; a hybrid thread screw; a smooth shank screw; a lag screw; a compression screw; a Herbert screw; a malleolar screw; a self-tapping screw; a self-drilling screw; a self-starting screw; a stylet tip screw; a screw with uniform or variable thread pitch; a low-profile screw; a screw with a threaded, partially threaded, or non-threaded head; a reduction head screw; a locking screw; a spinal implant screw; a magnetic core bone screw; a trauma screw; a deformity screw; a spinal fixation screw; a break-away screw; a drug eluting screw; a coated screw; an HA-coated screw; a drug-coated screw; a screw coated with antibiotics, anti-inflammatory compound(s), or growth factors; a bio-absorbable screw; a 3D-printed screw; or any combination thereof.

30. A surgical navigation optical tracker marker subsystem according to claim 28, wherein said tulip comprises:a polyaxial tulip; a motion-limiting tulip; a variable angle tulip; a fixed angle tulip; a low-profile tulip; an offset tulip; a modified tulip; a friction-fit tulip; a tapered tulip; a modular tulip; a reduced height tulip; a low-top tulip; a reduction-top tulip; a minimally invasive-top tulip; a low profile tulip; a standard or reduction tulip; a configurable tulip; a top-loading, sideloading, or angled tulip; an extended or extended-tab tulip ; or any combination thereof.

31. A surgical navigation optical tracker marker subsystem according to claim 28, wherein said clamp comprises a bone clamp, a spinous process clamp, ora combination thereof.

32. A surgical navigation optical tracker marker subsystem comprising:a composite marker component comprising a marker base and a removable glyph; andan attachment structure.

33. A surgical navigation optical tracker marker subsystem according to claim 32, wherein said unitary marker component comprises a tile, a marker tile, a tile flag, a marker tile flag, or any combination thereof.

34. A surgical navigation optical tracker marker subsystem according to claim 33, wherein said unitary structure is removably attached to an attachment structure via a quickconnect mechanism.

35. A surgical navigation optical tracker marker subsystem according to claim 34, wherein said quick-connect mechanism is selected from snap-on, snap-in, snap-fit, press-fit, twist-on, swage lock, magnetic, adhesive, and any combination thereof.

36. A surgical navigation optical tracker marker subsystem according to claim 32, wherein said attachment structure comprises a screw, a tulip, a clamp, or any combination thereof.

37. A surgical navigation optical tracker marker subsystem according to claim 36, wherein said screw comprises:a bone screw; a pedicle screw; a polyaxial screw; a monoaxial screw; a cancellous bone screw; a cortical screw; a cannulated or non-cannulated screw; a fenestrated screw; a threaded or partially-threaded screw; a low- or reduced-torque screw; a hybrid thread screw; a smooth shank screw; a lag screw; a compression screw; a Herbert screw; a malleolar screw; a self-tapping screw; a self-drilling screw; a self-starting screw; a stylet tip screw; a screw with uniform or variable thread pitch; a low-profile screw; a screw with a threaded, partially threaded, or non-threaded head; a reduction head screw; a locking screw; a spinal implant screw; a magnetic core bone screw; a trauma screw; a deformity screw; a spinal fixation screw; a break-away screw; a drug eluting screw; a coated screw; an HA-coated screw; a drug-coated screw; a screw coated with antibiotics, anti-inflammatory compound(s), or growth factors; a bio-absorbable screw; a 3D-printed screw; or any combination thereof.

38. A surgical navigation optical tracker marker subsystem according to claim 36, wherein said tulip comprises:a polyaxial tulip; a motion-limiting tulip; a variable angle tulip; a fixed angle tulip; a low-profile tulip; an offset tulip; a modified tulip; a friction-fit tulip; a tapered tulip; a modular tulip; a reduced height tulip; a low-top tulip; a reduction-top tulip; a minimally invasive-top tulip; a low profile tulip; a standard or reduction tulip; a configurable tulip; a top-loading, sideloading, or angled tulip; an extended or extended-tab tulip ; or any combination thereof.

39. A surgical navigation optical tracker marker subsystem according to claim 36, wherein said clamp comprises a bone clamp, a spinous process clamp, ora combination thereof.

40. A surgical navigation system comprising:a surgical imaging system comprising a surface detection subsystem and an optical tracking subsystem;a plurality of glyph marker bases, each glyph marker base comprising a glyph, wherein each glyph marker base is removably attachable, directly or indirectly, to rigid tissue such that a pose of the glyph remains fixed relative to a pose of the rigid tissue; andcontrol and processing circuitry operably coupled to the surgical imaging system, the control and processing circuitry being configured to perform operations comprising:controlling the surface detection subsystem to acquire intraoperative surface data characterizing an intraoperatively exposed portion of a plurality of rigid tissue structures associated with a subject, and employing surface registration between the intraoperative surface data and segmented surface data obtained from volumetric image data associated each rigid tissue structure to generate, for each rigid tissue structure, a corresponding registration transformation associating the volumetric image data pertaining to the rigid tissue structure with an intraoperative pose of the rigid tissue structure;obtaining glyph association information establishing an association between each glyph and attachment of the corresponding glyph marker base to a respective rigid tissue structure, thereby associating each glyph with a respective rigid tissue structure;a) acquiring image data from at least one imaging camera of the surgical imaging system, the at least one imaging camera being capable of imaging the glyphs when the glyphs reside within a field of view of the at least one imaging camera;b) processing the image data to identify at least two glyphs and to determine a respective glyph pose associated with each identified glyph;c) for at least one rigid tissue structure having an identified glyph associated therewith, employing the glyph pose of the identified glyph, the registration transformationassociated with the rigid tissue structure, and a pre-determined relationship between the glyph pose and an intraoperative pose of the rigid tissue structure to generate navigation images displaying, in an intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with the rigid tissue structure, the intraoperative pose of the trackable medical instrument being determined via the optical tracking subsystem;wherein the navigation images are generated based on a known calibration transformation between the optical tracking subsystem and the surface detection subsystem and a known spatial relationship between the at least one camera and one or both of the surface detection subsystem and the optical tracking subsystem.

41. The system according to claim 40 wherein the control and processing circuitry is further configured to employ, for a plurality of rigid tissue structure having identified glyphs respectively associated therewith, the pre-determined relationship between the glyph pose and the intraoperative pose of the rigid tissue structure to determine a current intraoperative pose of the rigid tissue structure, and to employ the current intraoperative poses to generate updated alignment parameters associated with the rigid tissue structures having identified glyphs respectively associated therewith.

42. The system according to claim 40 wherein the control and processing circuitry is further configured to employ, for a plurality of rigid tissue structures having identified glyphs respectively associated therewith, the pre-determined relationship between the glyph pose and the intraoperative pose of the rigid tissue structure to determine a current intraoperative pose of the rigid tissue structure, and to employ the current intraoperative poses to generate and display an image facilitating visualization of alignment of the plurality of rigid tissue structures having identified glyphs respectively associated therewith.

43. The system according to claim 40 wherein the control and processing circuitry is further configured such that step c) is performed for each rigid tissue structure having an identified glyph associated therewith.

44. The system according to claim 40 wherein the control and processing circuitry is further configured such that step c) is performed for a rigid tissue structure that is closed in proximity to the trackable medical instrument, the rigid tissue structure having an identified glyph associated therewith.

45. The system according to claim 40 wherein the control and processing circuitry is further configured such that the pre-determined relationship is generated by:acquiring initial image data when acquiring the intraoperative surface data to determine initial glyph poses of the at least two glyphs; andemploying the intraoperative surface data and the initial glyph poses to generate, for each glyph of the at least two glyphs, a transformation between the initial glyph pose and an intraoperative pose of the rigid tissue structure associated with the glyph.

46. The system according to claim 40 wherein the control and processing circuitry is configured to instruct an operator to secure the glyph marker bases to the rigid tissue structures before the intraoperative surface data has been acquired.

47. The system according to claim 40 further comprising an optical tracking reference structure having a pose trackable by the optical tracking subsystem, the optical tracking reference structure being removably attachable to rigid tissue fortracking motion of the subject;wherein the control and processing circuitry is further configured such that the predetermined relationship is generated by:prior to acquiring the intraoperative surface data, instructing the operator to secure the optical tracking reference structure to the subject, and / or receiving input confirming that the optical tracking reference structure is secured to the subject,subsequently acquiring the intraoperative surface data and an initial pose of the optical tracking reference structure;prior to acquiring the image data fortracking of the glyphs, instructing the operator to secure the glyph marker bases to the rigid tissue structures and / or receiving input confirming that the glyph marker bases have been secured to the rigid tissue structures;subsequently determining an updated pose of the optical tracking reference structure when acquiring the image data fortracking of the glyphs; andemploying the initial pose and updated pose of the optical tracking reference structure to determine a transformation between the glyph pose and an intraoperative pose of the rigid tissue structure.

48. The system according to claim 47 wherein the optical tracking reference structure includes one or more geometric references facilitating pose detection by the surface detection subsystem in addition to pose detection by the optical tracking subsystem, and wherein the optical tracking reference structure is employed to perform a calibration transform after acquiring the intraoperative surface data.

49. The system according to claim 40 wherein the one or more imaging cameras are components of the surface detection subsystem.

50. The system according to claim 40 wherein the one or more imaging cameras are components of the optical tracking subsystem.

51. The system according to claim 40 wherein the control and processing circuitry is configured such that steps a) through c) are repeatedto update the navigation images based on updated determinations of the glyph poses.

52. The system according to claim 51 wherein the control and processing circuitry is configured such that steps a) through c) are repeated at a frequency that is sufficiently high to facilitate updating of the navigation images in real time.

53. The system according to claim 40 further comprising an optical tracking reference structure having a pose trackable by the optical tracking subsystem, the optical tracking reference structure being removably attachable to rigid tissue fortracking motion of the subject;wherein the control and processing circuitry is configured such that steps a) through c) are repeated intermittently to update the glyph poses, and wherein the control and processing circuitry is configured such that the navigation images are updated between intermittent updates of the glyph poses by performing operations comprising:repeatedly tracking the optical tracking reference structure secured to the subject; andemploying a tracked pose of the optical tracking reference structure to update the navigation images.

54. The system according to claim 53 wherein tracking of the pose of the optical tracking reference structure is performed at a frequency that is sufficiently high to facilitate updating of the navigation images in real time.

55. The system according to claim 53 wherein the control and processing circuitry is configured such that at least one intermittent update of the glyph poses is autonomously triggered.

56. The system according to claim 55 wherein the control and processing circuitry is configured such that at least one intermittent update of the glyph poses is autonomously triggered according to a prescribed time interval.

57. The system according to claim 53 wherein the control and processing circuitry is configured such that at least one intermittent update of the glyph poses is triggerable in response to input received from an operator.

58. The system according to claim 57 wherein the control and processing circuitry is configured such that an intermitted update of the glyph poses is triggered after receiving input from an operator indicating insufficient navigation accuracy.

59. The system according to claim 57 wherein the control and processing circuitry is configured such that an intermitted update of the glyph poses is triggered after receiving input from an operator indicating initiation of a new phase of a surgical procedure.

60. The system according to claim 40 wherein the optical tracking reference structure includes one or more geometrical features facilitating pose detection by the surface detection subsystem in addition to pose detection by the optical tracking subsystem, and wherein the optical tracking reference structure is employed to perform a calibration transform after acquiring the intraoperative surface data.

61. The system according to claim 40 wherein the control and processing circuitry is configured such that the surface detection subsystem is employed to acquire additional intraoperative surface data when performing step a), and wherein surface registration is performed between the additional intraoperative surface data and reference surface data associated with a known model at least one glyph marker base to obtain or refine a determination of the pose of the glyph associated with the at least one glyph marker base.

62. The system according to claim 61 wherein the control and processing circuitry is configured such that the pose of the glyph associated with the at least one glyph marker base, as determined from step b), is employed as an input for performing segmentation of the additional intraoperative surface data prior to performing surface registration.

63. The system according to claim 40 wherein the control and processing circuitry is configured such that the glyph association information is determined autonomously, by performing operations comprising:employing the known intraoperative poses of the rigid tissue structures, as determined from surface registration between the intraoperative surface data and the segmented surface data obtained from volumetric image data of each rigid tissue structure, and the glyph poses and glyph identification determined from step b), to locate a glyph that is closest in spatial proximity to each rigid tissue structure.

64. The system according to claim 40 wherein the control and processing circuitry is configured such that the glyph association information is determined autonomously, by performing operations comprising:after performing step b), spatially sorting the set of identified glyphs, and associating each glyph with a respective rigid tissue structure according to a known spatial ordering of the rigid tissue structures.

65. The system according to claim 40 wherein the control and processing circuitry is configured such that the glyph association information establishes an association between each glyph and attachment of the corresponding glyph marker base to a respective vertebral level, thereby associating each glyph with a respective vertebral level, and wherein the navigation images display, in the intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with at least one vertebral level.

66. A method of controlling a surgical navigation system to performing autonomous surgical navigation, the system comprising a surgical imaging system comprising a surface detection subsystem and an optical tracking subsystem, and a plurality of glyph marker bases, each glyph marker base comprising a glyph, wherein each glyph marker base is removably attachable, directly or indirectly, to rigid tissue such that a pose of the glyph remains fixed relative to a pose of the rigid tissue, the method comprising:controlling the surface detection subsystem to acquire intraoperative surface data characterizing an intraoperatively exposed portion of a plurality of rigid tissue structures associated with a subject, and employing surface registration between the intraoperative surface data and segmented surface data obtained from volumetric image data associated each rigid tissue structure to generate, for each rigid tissue structure, a corresponding registration transformation associating the volumetric image data pertaining to the rigid tissue structure with an intraoperative pose of the rigid tissue structure;obtaining glyph association information establishing an association between each glyph and attachment of the corresponding glyph marker base to a respective rigid tissue structure, thereby associating each glyph with a respective rigid tissue structure;a) acquiring image data from at least one imaging camera of the surgical imaging system, the at least one imaging camera being capable of imaging the glyphs when the glyphs reside within a field of view of the at least one imaging camera;b) processing the image data to identify at least two glyphs and to determine a respective glyph pose associated with each identified glyph;c) for at least one rigid tissue structure having an identified glyph associated therewith, employing the glyph pose of the identified glyph, the registration transformation associated with the rigid tissue structure, and a pre-determined relationship between the glyph pose and an intraoperative pose of the rigid tissue structure to generate navigation images displaying, in an intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with the rigid tissue structure, the intraoperative pose of the trackable medical instrument being determined via the optical tracking subsystem;wherein the navigation images are generated based on a known calibration transformation between the optical tracking subsystem and the surface detection subsystem and a known spatial relationship between the at least one camera and one or both of the surface detection subsystem and the optical tracking subsystem.

67. A method of performing surgical navigation during a surgical procedure, the method comprising:providing a surgical imaging system comprising a surface detection subsystem and an optical tracking subsystem, and a plurality of glyph marker bases, each glyph marker base comprising a glyph, wherein each glyph marker base is removably attachable, directly or indirectly, to rigid tissue such that a pose of the glyph remains fixed relative to a pose of the rigid tissue;employing the surface detection subsystem to acquire intraoperative surface data characterizing an intraoperatively exposed portion of a plurality of rigid tissue structures associated with a subject, and employing surface registration between the intraoperative surface data and segmented surface data obtained from volumetric image data associated each rigid tissue structure to generate, for each rigid tissue structure, a corresponding registration transformation associating the volumetric image data pertaining to the rigid tissue structure with an intraoperative pose of the rigid tissue structure;providing glyph association information establishing an association between each glyph and attachment of the corresponding glyph marker base to a respective rigid tissue structure, thereby associating each glyph with a respective rigid tissue structure;employing at least one imaging camera of the surgical imaging system to acquire image data, the at least one imaging camera being capable of imaging the glyphs when the glyphs reside within a field of view of the at least one imaging camera;employing the image data to identify at least two glyphs and to determine a respective glyph pose associated with each identified glyph;for at least one rigid tissue structure having an identified glyph associated therewith, employing the glyph pose of the identified glyph, the registration transformation associated with the rigid tissue structure, and a pre-determined relationship between the glyph pose and an intraoperative pose of the rigid tissue structure to generate navigation images displaying, in an intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with the rigid tissue structure, the intraoperative pose of the trackable medical instrument being determined via the optical tracking subsystem;wherein the navigation images are generated based on a known calibration transformation between the optical tracking subsystem and the surface detection subsystem and a known spatial relationship between the at least one camera and one or both of the surface detection subsystem and the optical tracking subsystem.

68. The method according to claim 67 wherein the glyph marker bases are secured to the respective rigid tissue structures prior to acquiring the intraoperative surface data.

69. The method according to claim 66 further comprising:prior to the glyph marker bases being secured to the respective rigid tissue structures, and after an optical tracking reference structure is secured to rigid tissue of the subject, the optical tracking reference structure having a pose trackable by the optical tracking subsystem;subsequently acquiring the intraoperative surface data and an initial pose of the optical tracking reference structure; andafter the glyph marker bases are secured to the respective rigid tissue structures: subsequently determining an updated pose of the optical tracking reference structure when acquiring the image data fortracking of the glyphs; andemploying the initial pose and updated pose of the optical tracking reference structure to determine a transformation between the glyph pose and an intraoperative pose of the rigid tissue structure.

70. A surgical navigation system comprising:a surgical imaging system comprising a surface detection subsystem and an optical tracking subsystem;control and processing circuitry operably coupled to the surgical imaging system, the control and processing circuitry being configured to perform operations comprising:controlling the surface detection subsystem to acquire intraoperative surface data characterizing an intraoperatively exposed portion of a plurality of rigid tissue structures associated with a subject, and employing surface registration between the intraoperative surface data and segmented surface data obtained from volumetric image data associated each rigid tissue structure to generate, for each rigid tissue structure, a corresponding registration transformation associating the volumetric image data pertaining to the rigid tissue structure with an intraoperative pose of the rigid tissue structure;obtaining glyph association information establishing an association between: a plurality of glyph marker bases, each glyph marker base comprising a glyph, wherein each glyph marker base is removably attachable, directly or indirectly, to rigid tissue such that a pose of the glyph remains fixed relative to a pose of the rigid tissue; and attachment of the corresponding glyph marker base to a respective rigid tissue structure, thereby associating each glyph with a respective rigid tissue structure;a) acquiring image data from at least one imaging camera of the surgical imaging system, the at least one imaging camera being capable of imaging the glyphs when the glyphs reside within a field of view of the at least one imaging camera;b) processing the image data to identify at least two glyphs and to determine a respective glyph pose associated with each identified glyph;c) for at least one rigid tissue structure having an identified glyph associated therewith, employing the glyph pose of the identified glyph, the registration transformation associated with the rigid tissue structure, and a pre-determined relationship between the glyph pose and an intraoperative pose of the rigid tissue structure to generate navigation images displaying, in an intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with the rigid tissue structure, the intraoperative pose of the trackable medical instrument being determined via the optical tracking subsystem;wherein the navigation images are generated based on a known calibration transformation between the optical tracking subsystem and the surface detection subsystem and a known spatial relationship between the at least one camera and one or both of the surface detection subsystem and the optical tracking subsystem.

71. A surgical navigation system comprising:control and processing circuitry operably connectable to a surgical imaging system having a surface detection subsystem and an optical tracking subsystem, the control and processing circuitry being configured to perform the following operations when the control and processing circuitry is operably coupled to the surgical imaging system:controlling the surface detection subsystem to acquire intraoperative surface data characterizing an intraoperatively exposed portion of a plurality of rigid tissue structures associated with a subject, and employing surface registration between the intraoperative surface data and segmented surface data obtained from volumetric image data associated each rigid tissue structure to generate, for each rigid tissue structure, a corresponding registration transformation associating the volumetric image data pertaining to the rigid tissue structure with an intraoperative pose of the rigid tissue structure;obtaining glyph association information establishing an association between: a plurality of glyph marker bases, each glyph marker base comprising a glyph, wherein each glyph marker base is removably attachable, directly or indirectly, to rigid tissue such that a pose of the glyph remains fixed relative to a pose of the rigid tissue; and attachment of the corresponding glyph marker base to a respective rigid tissue structure, thereby associating each glyph with a respective rigid tissue structure;a) acquiring image data from at least one imaging camera of the surgical imaging system, the at least one imaging camera being capable of imaging the glyphs when the glyphs reside within a field of view of the at least one imaging camera;b) processing the image data to identify at least two glyphs and to determine a respective glyph pose associated with each identified glyph;c) for at least one rigid tissue structure having an identified glyph associated therewith, employing the glyph pose of the identified glyph, the registration transformation associated with the rigid tissue structure, and a pre-determined relationship between the glyph pose and an intraoperative pose of the rigid tissue structure to generate navigation images displaying, in an intraoperative frame of reference, an intraoperative pose of a trackable medical instrument relative to volumetric image data associated with the rigid tissue structure, the intraoperative pose of the trackable medical instrument being determined via the optical tracking subsystem;wherein the navigation images are generated based on a known calibration transformation between the optical tracking subsystem and the surface detection subsystem and a known spatial relationship between the at least one camera and one or both of the surface detection subsystem and the optical tracking subsystem.

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