Markers for tracking objects in medical procedures

Abstract

At least one example is a method of tracking an object in a medical procedure, the method including holding a bone marker on a distal end of a placement tool, the bone marker including a polyhedron having a fiducial pattern on each of at least three outwardly facing faces of the polyhedron, an externally threaded screw extending distally from the polyhedron, and a flange proximate to an intersection of the polyhedron and the externally threaded screw, positioning a distal end of the externally threaded screw relative to the bone at the marker location, threading the externally threaded screw via the placement tool into the bone, and constraining tissue to the bone directly below the flange.

Description

[Background technology]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application Serial No. 63 / 257,196, filed October 19, 2021, entitled "Methods and Systems of Tracking Objects in Medical Procedures," which is incorporated by reference herein as if reproduced in full below.

[0002] Arthroscopic surgery is a minimally invasive procedure in which a surgical site within the body is accessed through a small keyhole or port passed through the patient's skin. Various tissues within the surgical site are visualized by an arthroscope placed through the port, and the internal view is displayed on an external display device. Tissues can be repaired or replaced through the same port or through additional ports.

[0003] In computer-assisted surgery (e.g., anterior cruciate ligament (ACL) replacement, femoroacetabular impingement reduction), the position of various objects relative to the surgical site can be tracked by images captured by an arthroscope. In particular, related art systems teach tracking the position of objects (e.g., medical instruments, bones) based on reading a Quick Response Code (QR Code), determining the orientation of the QR Code in three-dimensional coordinate space, and then determining the position and / or orientation of an accessory instrument or bone in the three-dimensional coordinate space.

[0004] However, the surgical site may be filled with debris, loose tissue, and other objects that may block the QR code attached to the device, and when the QR code is blocked, it cannot receive computer assistance. Summary of the Invention

[0005] One example is a method that includes holding a bone marker on a distal end of a placement tool, the bone marker including a polyhedron having a reference pattern on each of at least three outwardly facing surfaces of the polyhedron, an externally threaded screw extending distally from the polyhedron, and a flange proximate to an intersection of the polyhedron and the externally threaded screw, positioning the distal end of the externally threaded screw relative to the bone at the marker location, threading the externally threaded screw through the placement tool into the bone, and constraining tissue against the bone just below the flange.

[0006] In an exemplary method, retaining the bone marker may include fitting a polyhedron into an internal volume at a distal end of the installation tool, the bone marker including a retention hole having an entry opening through a top surface of the polyhedron, and may further include disposing a retention fixation member in the retention hole that holds the bone marker in an engaged relationship to the installation tool. The exemplary method may further include removing the retention fixation member from within the retention hole after threading the externally threaded screw into the bone. In an exemplary method, disposing the retention fixation member in the retention hole may further include threading the external threads of the retention fixation member in an engaged relationship with the internal threads of the retention hole. The exemplary method may further include unthreading the external threads of the retention fixation member from the internal threads of the retention hole after threading the externally threaded screw into the bone. Threading the externally threaded screw into the bone may further include applying a force against at least three outwardly facing surfaces of the polyhedron. Applying a force to the at least three outwardly facing surfaces of the polyhedron may further include applying a force on each of the at least three outwardly facing surfaces to a position that does not overlap with a corresponding reference pattern on each of the at least three outwardly facing surfaces. Driving the externally threaded screw into the bone may further include applying a force to the flange but not to the polyhedron.

[0007] In an exemplary method, constraining the tissue against the bone may further include constraining the tissue between an outer surface of the bone and a bottom surface of the flange that is made of a polymeric material.

[0008] In an exemplary method, constraining the tissue against the bone may further include constraining the tissue between an outer surface of the bone and a bottom surface of the flange that is of a metallic material.

[0009] In an exemplary method, constraining the tissue against the bone may further include constraining the tissue with a flange, wherein a vector perpendicular to a plane defined by a portion of the flange and directly underlying the polyhedron forms an acute angle with respect to a central longitudinal axis of the externally threaded screw.

[0010] In an exemplary method, constraining the tissue against the bone may further include constraining the tissue between an outer surface of the bone and a bottom surface of the flange defining at least one of a circular and an oval contour.

[0011] Yet another example is a bone marker including a polyhedron defining a first outwardly facing surface, a second outwardly facing surface, and a third outwardly facing surface; an externally threaded screw protruding from a surface of the polyhedron, the externally threaded screw being integral with the polyhedron; a retention hole having an entrance opening through the polyhedron, the retention hole defining a retention feature on an inner surface of the retention hole; a first reference pattern on the first outwardly facing surface, a second reference pattern on the second outwardly facing surface, and a third reference pattern on the third outwardly facing surface, the first reference pattern, the second reference pattern, and the third reference pattern being distinct from one another; and a flange disposed proximate an intersection of the polyhedron and the externally threaded screw.

[0012] In the exemplary bone marker, the polyhedron may be a cube.In the exemplary bone marker, the externally threaded screw may be a self-tapping screw.

[0013] In the exemplary bone marker, the retention features may further include threads defined on an inner surface of the retention hole. The exemplary bone marker may further include an externally threaded screw that is right-hand threaded, and the threads on the inner surface of the retention hole are left-hand threaded.

[0014] In the exemplary bone marker, each of the first fiducial pattern, the second fiducial pattern, and the third fiducial pattern may be a three-dimensional pattern.

[0015] In an exemplary bone marker, the flange may further include a polymeric material and defines a top surface, a bottom surface opposite the top surface, a through hole defining a through hole axis, and a thickness measured parallel to the through hole axis, the through hole being fitted onto the externally threaded screw, and the flange being disposed at an intersection of the bottom surface of the polyhedron and a proximal end of the externally threaded screw. The flange may further include at least one material selected from the group consisting of a polymeric material, a metallic material, and a silicone. The flange may further include at least one shape selected from the group consisting of a circular shape and an oval shape.

[0016] An exemplary bone marker may further include an annular trough located at the intersection of the polyhedron and the proximal end of the externally threaded screw, surrounding a central longitudinal axis of the externally threaded screw, and an inner diameter of a through hole in the flange forming a friction fit against the annular trough.

[0017] An exemplary bone marker may further include an annular trough disposed at the intersection of the polyhedron and the proximal end of the externally threaded screw, the annular trough circumscribing a central longitudinal axis of the externally threaded screw, a mounting thread defined between the threads of the externally threaded screw and the annular trough, and an inner diameter of a through hole disposed within the annular trough.

[0018] In an exemplary bone marker, the flange may further include a top surface intersecting the first outward surface, the second outward surface, and the third outward surface, a bottom surface intersecting the externally threaded screw, and a diameter greater than a maximum dimension of the polyhedron as measured perpendicular to a central longitudinal axis of the externally threaded screw, wherein the flange, the polyhedron, and the externally threaded screw are integral. The exemplary bone marker may further include an interface feature defined by the flange, the interface feature being at least one selected from the group consisting of an outer surface of the flange, and a recess on the top surface of the flange.

[0019] Another example is an intraoperative method that includes receiving, by a surgical controller, an image of a surgical site viewed by an endoscope and an attached camera head during surgery, the image including an image related to an instrument having a plurality of fiducial patterns associated with the instrument; selecting, by the surgical controller, an unobstructed fiducial pattern from among the plurality of fiducial patterns visible in the image; calculating, by the surgical controller, a value indicative of a position of the instrument within the surgical site based on the unobstructed fiducial patterns; and performing, by the surgical controller, an intraoperative task based on the value indicative of the position.

[0020] In an exemplary intraoperative method, receiving the image may further include receiving an image related to at least one instrument selected from the group consisting of a touch probe and a sight.

[0021] In an exemplary intra-operative method, performing the intra-operative tasks may further include at least one selected from the group consisting of registering a location on the bone visible in the image, selecting a location for a corrected tunnel entrance for the tunnel through the bone, selecting a location for a corrected tunnel exit for the tunnel through the bone, determining a location of a distal end of the sight relative to the bone visible in the image, and determining an orientation of a central longitudinal axis of the sight relative to a central axis of a planned tunnel through the bone.

[0022] In an exemplary intraoperative method, selecting the unoccluded fiducial pattern may further include selecting the unoccluded fiducial pattern having a normal vector closest to being coaxial with respect to the viewing direction of the arthroscope.

[0023] In an exemplary intraoperative method, receiving the image may further include receiving an image of an instrument having at least three reference surfaces, each of the at least three reference surfaces being parallel to a central longitudinal axis of the instrument, and each of the at least three reference surfaces having a reference pattern on a top surface thereof.

[0024] In an exemplary intraoperative method, receiving the image may further include receiving an image of an instrument having a first reference surface having a first fiducial pattern thereon, a second reference surface having a second fiducial pattern thereon, and a third reference surface having a third fiducial pattern thereon, the first, second, and third reference surfaces forming, at least in part, an outer surface about a central longitudinal axis of the instrument. Receiving the image may further include receiving an image of a fourth reference surface having a fourth fiducial pattern thereon, the first, second, third, and fourth reference surfaces forming an outer surface about a central longitudinal axis of the instrument. Receiving the image may further include receiving an image of an instrument where each of the first, second, and third reference surfaces is parallel to the central longitudinal axis of the instrument.

[0025] In an exemplary intraoperative method, receiving the images may further include receiving images of an instrument having a first reference surface having a plurality of fiducial patterns on an upper surface at distinct axial positions relative to the central longitudinal axis of the instrument, a second reference surface having a plurality of fiducial patterns on an upper surface at distinct axial positions relative to the central longitudinal axis, and a third reference surface having a plurality of fiducial patterns on an upper surface at distinct axial positions relative to the central longitudinal axis. Receiving the images may further include receiving images of an instrument having a fourth reference surface having a plurality of fiducial patterns on an upper surface at distinct axial positions relative to the central longitudinal axis. In an exemplary intraoperative method, each of the plurality of fiducial patterns on the first reference surface may be identical. In an exemplary intraoperative method, each of the plurality of fiducial patterns on the first reference surface may be different.

[0026] Yet another example is a medical device including an elongate shaft defining a proximal end, a distal end and a central longitudinal axis, a first datum surface disposed proximate to the distal end and a first datum pattern disposed on the first datum surface, a second datum surface disposed proximate to the distal end and a second datum pattern disposed on the second datum surface, a third datum surface disposed proximate to the distal end and a third datum pattern disposed on the third datum surface, the first datum surface, the second datum surface and the third datum surface at least partially defining an exterior surface about the central longitudinal axis.

[0027] The exemplary medical device may further include an elongate shaft defining a through hole extending from the proximal end to the distal end. The exemplary medical device may further include a fourth reference surface disposed proximate to the distal end and a fourth reference pattern disposed on the fourth reference surface, the first reference surface, the second reference surface, the third reference surface, and the fourth reference surface defining an outer surface about the central longitudinal axis. The exemplary medical device may further include a first reference surface defining a plane perpendicular to the second reference surface, a second reference surface defining a plane perpendicular to the third reference surface, a third reference surface defining a plane perpendicular to the fourth reference surface, and a fourth reference surface defining a plane perpendicular to the first reference surface. The first reference pattern, the second reference pattern, the third reference pattern, and the fourth reference pattern may be identical.

[0028] The exemplary medical instrument may further include a probe end defining a probe axis, the probe axis forming an acute angle with respect to the central longitudinal axis, the acute angle being measured beyond the distal end of the medical instrument. The exemplary medical instrument may further include a first datum plane defining a plane intersecting with a plane defined by the second datum plane, a plane defined by the second datum plane intersecting with a plane defined by the third datum plane, and a plane defined by the third datum plane intersecting with the plane defined by the first datum plane, and a cross-sectional shape when viewed perpendicular to the central longitudinal axis is triangular. A geometric center of the cross-sectional shape may have a non-zero offset from the central longitudinal axis.

[0029] An exemplary medical device may further include a first reference surface including a first plurality of fiducial patterns, the first fiducial pattern being a component of the first plurality of fiducial patterns, each fiducial pattern in the first plurality of fiducial patterns being located at a distinct axial position relative to the central longitudinal axis, a second reference surface including a second plurality of fiducial patterns, the second fiducial pattern being a component of the second plurality of fiducial patterns, each fiducial pattern in the second plurality of fiducial patterns being located at a distinct axial position relative to the central longitudinal axis, and a third reference surface including a third plurality of fiducial patterns, the third fiducial pattern being a component of the third plurality of fiducial patterns, each fiducial pattern in the third plurality of fiducial patterns being located at a distinct axial position relative to the central longitudinal axis. Each of the first, second, and third plurality of fiducial patterns may be identical. Each of the first plurality of reference patterns may be different from each other and from each of the second and third reference patterns.

[0030] Another example is a surgical controller including a processor configured to couple to a display device and a memory coupled to the processor. The memory may store instructions that, when executed by the processor, cause the processor to receive images of a surgical site viewed by an endoscope and an attached camera head during surgery, the images including an instrument having a plurality of fiducial patterns associated with the instrument, select an unobstructed fiducial pattern from among the plurality of fiducial patterns visible in the images, calculate a value indicative of a position of the instrument within the surgical site based on the unobstructed fiducial patterns, and perform an intra-operative task based on the value indicative of the position.

[0031] In an exemplary surgical controller, when the processor receives the image, the instructions may further cause the processor to receive an image relating to at least one instrument selected from the group consisting of a touch probe and a sight.

[0032] In an exemplary surgical controller, when the processor performs an intraoperative task, the instructions may further cause the processor to perform at least one selected from the group consisting of: registering a location on the bone visible in the image; selecting a location for a corrected tunnel entrance for the tunnel through the bone; selecting a location for a corrected tunnel exit for the tunnel through the bone; determining a position of a distal end of the sight relative to the bone visible in the image; and determining an orientation of a central longitudinal axis of the sight relative to a central axis of a planned tunnel through the bone.

[0033] In an exemplary surgical controller, when the processor selects an unobstructed reference pattern, the instructions may further cause the processor to select the unobstructed reference pattern having a normal vector closest to the axis relative to the arthroscope's viewing direction.

[0034] In an exemplary surgical controller, when the processor receives the image, the instructions may further cause the processor to receive an image relating to an instrument having at least three reference surfaces, each of the at least three reference surfaces being parallel to a central longitudinal axis of the instrument, and each of the at least three reference surfaces having a reference pattern on an upper surface thereof.

[0035] In an exemplary surgical controller, when the processor receives the image, the instructions may further cause the processor to receive an image of an instrument having a first datum surface having a first fiducial pattern thereon, a second datum surface having a second datum pattern thereon, and a third datum surface having a third datum pattern thereon, the first datum surface, the second datum surface, and the third datum surface defining, at least in part, an outer surface about a central longitudinal axis of the instrument. When the processor receives the image, the instructions may further cause the processor to receive an image of a fourth datum surface having a fourth datum pattern thereon, the first datum surface, the second datum surface, the third datum surface, and the fourth datum surface forming an outer surface about a central longitudinal axis of the instrument.

[0036] In an exemplary surgical controller, when the processor receives the image, the instructions may further cause the processor to receive an image of the instrument in which the first, second, and third reference planes are each parallel to a central longitudinal axis of the instrument.

[0037] In the exemplary surgical controller, when the processor receives the image, the instructions may further cause the processor to receive an image for an instrument having a first datum surface having a plurality of fiducial patterns on its upper surface at distinct axial positions relative to the central longitudinal axis of the instrument, a second datum surface having a plurality of fiducial patterns on its upper surface at distinct axial positions relative to the central longitudinal axis, and a third datum surface having a plurality of fiducial patterns on its upper surface at distinct axial positions relative to the central longitudinal axis. When the processor receives the image, the instructions may further cause the processor to receive an image for an instrument having a fourth datum surface having a plurality of fiducial patterns on its upper surface at distinct axial positions relative to the central longitudinal axis. Each of the plurality of fiducial patterns on the first datum surface may be identical. Each of the plurality of fiducial patterns on the first datum surface may be different. [Brief description of the drawings]

[0038] For a detailed description of the exemplary embodiments, reference is now made to the accompanying drawings.

[0039] [Figure 1] FIG. 1 illustrates a surgical system according to at least some embodiments.

[0040] [Diagram 2] FIG. 2 illustrates a perspective side view of a bone marker in accordance with at least some embodiments.

[0041] [Diagram 3] FIG. 3 illustrates a perspective side view of a bone marker in accordance with at least some embodiments.

[0042] [Figure 4] FIG. 4 illustrates a perspective side view of a bone marker in accordance with at least some embodiments.

[0043] [Diagram 5] FIG. 5 illustrates a perspective view of a bone marker in accordance with at least some embodiments.

[0044] [Figure 6A] 6A and 6B show perspective views of a bone marker held on a distal end of a placement tool, according to at least some embodiments. [Figure 6B] Same as above.

[0045] [Figure 7] FIG. 7 illustrates an exploded perspective view of the distal end of the installation tool and bone marker, according to at least some embodiments.

[0046] [Figure 8] FIG. 8 illustrates a perspective view of a bone marker in accordance with at least some embodiments.

[0047] [Figure 9] FIG. 9 illustrates a perspective view of a bone marker in accordance with at least some embodiments.

[0048] [Figure 10] FIG. 10 illustrates a perspective view of a distal end of a sight according to at least some embodiments.

[0049] [Figure 11] FIG. 11 illustrates a perspective side view of a touch probe according to at least some embodiments.

[0050] [Figure 12] FIG. 12 illustrates a cross-sectional view of a distal end of a touch probe according to at least some embodiments.

[0051] [Figure 13] FIG. 13 shows a cross-sectional view looking distally through the probe assembly, according to at least some embodiments.

[0052] [Figure 14] FIG. 14 illustrates a side view of an arthroscope and multiple fiducial patterns in accordance with at least some embodiments.

[0053] [Figure 15] FIG. 15 illustrates a method according to at least some embodiments.

[0054] [Figure 16] FIG. 16 illustrates a method according to at least some embodiments.

[0055] [Figure 17] FIG. 17 illustrates a computer system according to at least some embodiments.

[0056] [Figure 18]FIG. 18 illustrates a perspective side view of another exemplary bone marker.

[0057] [Figure 19] FIG. 19 illustrates a perspective side view of another exemplary bone marker.

[0058] definition Various terms are used to refer to particular system components. Although different companies may refer to a component by different names, this document does not intend to distinguish between components that differ in name but not function. In the following discussion and claims, the terms "including" and "comprises" are used in an open-ended manner and should be interpreted to mean "including, but not limited to." Additionally, the terms "couple" or "couples" are intended to mean either an indirect or direct connection. Thus, when a first device is coupled to a second device, the connection may be by a direct connection or an indirect connection via another device or other connection.

[0059] "Through hole" is intended to mean an opening or passageway through an underlying object. However, the term "through hole" should not be construed as implying any method of formation. Thus, through holes may be formed in any suitable manner, such as drilling, punching, laser drilling, casting, etc.

[0060] "Counterbore" is intended to mean an opening or passage into an underlying object. Where the counterbore intersects with another opening (e.g., a through hole), the counterbore may thereby define an internal shoulder. However, the term "counterbore" should not be construed as implying any method of formation. Counterbore holes may be formed in any suitable manner, such as by drilling, punching, laser drilling, casting, etc. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] The following discussion is directed to various embodiments of the present invention. Although one or more of these embodiments may be preferred, the disclosed embodiments should not be interpreted as limiting the scope of the present disclosure, including the claims, and should not be used in other ways. In addition, those skilled in the art will understand that the following description has a broad range of applications, and that the discussion of any embodiment is intended to be merely an example of that embodiment, and is not intended to imply that the scope of the present disclosure, including the claims, is limited to that embodiment.

[0062] Various examples are directed to methods and systems for tracking objects in medical procedures. More particularly, various examples are directed to methods and associated systems for reducing the occurrence of debris and / or tissue occluding fiducial patterns attached to objects (e.g., bone markers, medical instruments) in arthroscopic surgery. Even more particularly, exemplary methods and systems replicate fiducial patterns at various locations around and / or along the tracked object such that to the extent that debris and / or tissue occludes one fiducial pattern, another fiducial pattern is still visible and thus computer assistance may still be available. In the exemplary case of a bone marker, the bone marker may include a polyhedron with fiducial patterns on multiple outwardly facing surfaces. Additionally, the bone marker may include flanges for compressing or constraining underlying tissue to reduce the occurrence of the underlying tissue occluding the fiducial pattern. In the exemplary case of a medical instrument positioned within a surgical site, the medical instrument may include multiple fiducial patterns positioned around the medical instrument and / or at various axial locations along the medical instrument. Implementing multiple fiducial patterns reduces the occurrence of the computer aid losing track of the position of the medical instrument within the surgical site due to debris and / or tissue obscuring the fiducial patterns. To orient the reader, an exemplary system is first described herein.

[0063] FIG. 1 illustrates a surgical system (not to scale) according to at least some embodiments. In particular, the exemplary surgical system 100 includes a tower or device cart 102, an exemplary mechanical cutting instrument 104, an exemplary plasma-based cauterization instrument (hereinafter simply cauterization instrument 106), and an endoscope in an exemplary configuration consisting of an arthroscope 108 and an attached camera head 110. The device cart 102 may include a camera 112 (illustratively shown as a stereoscopic camera), a display device 114, a resection controller 116, and a camera control unit (CCU), along with an endoscope light source and a video controller. In the exemplary case, the CCU, endoscope light source, and video controller provide light for the arthroscope 108 and display images received from the camera head 110, as well as implement various additional aspects such as tracking the position of objects within a surgical site. Thus, the CCU, endoscope light source, and video controller are hereinafter referred to as a surgical controller 118. However, in other cases, the CCU, endoscope light source, and video controller may be separate systems that are separate from the controller that handles aspects of intraoperative tracking, but the separate devices are still operably coupled.

[0064] The exemplary device cart 102 further includes a pump controller 120 (e.g., a single or dual peristaltic pump). Fluid connections between the mechanical ablation instrument 104 and the cauterization instrument 106 are not shown to avoid overcomplicating the drawing. Similarly, fluid connections between the pump controller 120 and the patient are not shown to avoid overcomplicating the drawing. In the exemplary system, both the mechanical ablation instrument 104 and the cauterization instrument 106 are coupled to the ablation controller 116, which is a dual function controller. However, in other cases, a separate and distinct mechanical ablation controller may be provided to the ablation controller. The exemplary devices and controllers associated with the device cart 102 are merely illustrative; other examples include vacuum pumps, robotic arms that hold various instruments, ultrasonic cutting devices and associated controllers, patient positioning controllers, and robotic surgical systems.

[0065] FIG. 1 further illustrates additional instruments that may be present during arthroscopic surgery. In particular, FIG. 1 illustrates an exemplary touch probe 122, sight 124, and bone marker 126. The touch probe 122 may be used during surgery to provide information to the surgical controller 118, such as information for registering the three-dimensional bone model to the underlying bone visible in the images captured by the arthroscope 108 and camera head 110, and information regarding revised tunnel entry and / or exit positions when the surgeon chooses to deviate from the preoperative tunnel plan. The sight 124 may be used as a guide for drill wire placement and drilling to form an initial or pilot tunnel through the bone. The bone marker 126 may be rigidly attached to the bone and may serve as an anchor location for the surgical controller 118 to know the orientation of the bone (e.g., after registration to the three-dimensional bone model). There will be additional tools and instruments such as drill wires, various reamers for creating the through hole and countersunk versions of the tunnel through the bone, and various tools such as for suturing and anchoring the graft, etc. These additional tools and instruments are not shown so as not to further complicate the drawing.

[0066] FIG. 2 illustrates a perspective side view of an exemplary bone marker 126. In particular, the exemplary bone marker 126 includes a polyhedron 200, an externally threaded screw 202, and a flange 204. The exemplary polyhedron defines a top or upper surface 206 and a number of outwardly facing surfaces, such as outwardly facing surface 208 and outwardly facing surface 210. In the example of FIG. 2, the polyhedron 200 is a cube, and thus two additional outwardly facing surfaces are present but are not visible in the view of FIG. 2. However, the polyhedron 200 may take any suitable shape that defines the top surface 206, at least three outwardly facing surfaces, and a location (e.g., a lower surface) from which the externally threaded screw 202 protrudes. Each of the outwardly facing surfaces, such as outwardly facing surfaces 208, 210, visible in FIG. 2, has a fiducial pattern disposed on the top surface, such as fiducial pattern 212, 214, respectively. Representatively referring to fiducial pattern 214, fiducial pattern 214 is a machine-readable code that uniquely identifies outwardly facing surface 210 of polyhedron 200. That is, upon receiving images captured by arthroscope 108 (FIG. 1) and camera head 110 (FIG. 1), surgical controller 118 (FIG. 1) may read values ​​represented by fiducial pattern 214. Moreover, fiducial pattern 214 is designed and configured such that by analyzing the physical relationships between three-dimensional features or patterns of fiducial pattern 214 (e.g., outer corners, inner corners, relative line widths) within an image of fiducial pattern 214, surgical controller 118 may thereby determine the physical orientation of the fiducial pattern in three-dimensional coordinate space within the field of view of arthroscope 108, and thus the physical orientation of bone marker 126. Thus, when bone marker 126 is bonded to a bone, surgical controller 118 may determine the physical orientation of the bonded bone in three-dimensional coordinate space within the field of view of arthroscope 108. In the exemplary system, the reference patterns on each of the outwardly facing surfaces are unique and separate patterns.

[0067] In this example, the externally threaded screw 202 protrudes from the surface of the polyhedron 200 opposite the top surface 206. In an exemplary case, the polyhedron 200 and the externally threaded screw 202 are of one piece construction, such as a continuous piece of metal material (e.g., aluminum). For example, the polyhedron 200 and the externally threaded screw 202 may be cast together in a mold or machined from a single piece of aluminum, stainless steel, or titanium. The exemplary externally threaded screw 202 is a self-drilling or self-tapping screw, meaning that the distal end 216 of the externally threaded screw 202 includes a drilling feature for forming an initial opening into the bone. The externally threaded screw 202 further includes a thread 218 extending from near the distal end 216 of the externally threaded screw 202 toward the proximal end. In some cases, the threads 218 are right-hand threads, meaning that when the bone marker 126 is screwed into a bone, the bone marker 126 is rotationally driven clockwise about its central longitudinal axis 220 when viewed from above the polyhedron 200 along the central longitudinal axis toward the externally threaded screw. The threads 218 may alternatively be left-hand threads.

[0068] The bone marker 126 is a relatively small object, and in one example, the outer diameter of the externally threaded screw 202 is about 2.5 millimeters (mm), although larger and smaller sizes are contemplated. In an exemplary case, the polyhedron 200 may define a face that is about 4 mm long (as measured parallel to the central longitudinal axis 220). In some cases, the fiducial patterns on each face are the same size, but in other cases, the fiducial patterns need not be the same size (even overlapping patterns). The overall length of the exemplary bone marker may be 10 mm to 15 mm, inclusive, and in one example, 12 mm.

[0069] 2, the exemplary bone marker 126 further includes a flange 204. The exemplary flange 204 is located proximate to the intersection of the polyhedron 200 and the externally threaded screw 202. The exemplary flange 204 is a separate and distinct component from the integral structure of the polyhedron 200 and the externally threaded screw 202. The flange 204 may be made of a metallic material (e.g., aluminum); however, in other cases, the flange 204 may be made of a polymeric material (e.g., silicone) to allow the flange 204 to conform to the shape of the underlying bone when the bone marker 126 is screwed into the bone. The flange 204 has a top surface 222, a bottom surface 224 opposite the top surface 222, a through hole (not visible in FIG. 2) defining a through hole axis, a diameter (e.g., about 9 mm), and a thickness T measured parallel to the through hole axis. FLANGE In the exemplary embodiment, the thickness T of the flange 204 is as shown. FLANGE is uniform from the through hole to the outer edge of the flange 204. In other cases, however, a non-uniform thickness may be used, such as a tapered thickness having a greater thickness near the through hole and a thinner thickness with distance from the through hole toward the outer edge.

[0070] FIG. 3 shows a perspective view of the exemplary bone marker 126. Specifically visible in FIG. 3 are the polyhedron 200 and a portion of the externally threaded screw 202. The outwardly facing surfaces 208, 210 are also visible along with their respective fiducial patterns (not specifically labeled). However, in the view of FIG. 3, a through hole 226 through the flange 204 is visible along with an annular trough 228 located at the intersection of the polyhedron 200 and the proximal end of the externally threaded screw 202. After placement and / or formation, the inner diameter of the through hole 226 is located within the annular trough 228. As shown in FIGS. 2 and 3, the exemplary flange 204 may move within the annular trough 228 to accommodate the orientation of the underlying bone or soft tissue during placement of the bone marker 126.

[0071] 3, the exemplary bone marker 126 further includes a retention hole 230 having an entrance opening 232 through the top surface 206 of the polyhedron 200. The retention hole 230 defines a retention feature 234, illustratively shown as threads on the interior surface of the retention hole 230. The retention feature 234 may be used to hold the bone marker 126 in operative relationship to a placement tool (not shown in FIG. 3) so that the unplaced bone marker 126 may be deployed from a port through the patient's skin and then screwed into place within the bone. Once screwed into place, the placement tool may be removed from the retention feature 234, allowing the placement tool to be withdrawn and the bone marker 126 to remain in place. The flange 204 may be opaque, transparent, or something in between.

[0072] FIG. 4 shows a perspective side view of the exemplary bone marker 126 with the flange 204 displaced away from the polyhedron 200. Particularly well visible in FIG. 4 is the annular trough 228. The annular trough 228 is disposed between the polyhedron 200 and the proximal end of the externally threaded screw 202, with the exemplary annular trough 228 located around the central longitudinal axis 220 of the bone marker 126. In the exemplary case where the flange 204 is a rigid material, the exemplary bone marker 126 may include a mounting thread 400 that provides a channel from the outside of the annular trough 228 to the inside of the annular trough 228. The mounting thread 400 allows the flange 204 to be mounted such that the inner diameter of the through hole 226 is located inside the annular trough 228. However, in other cases, the mounting thread 400 may be omitted. For example, when the flange 204 is made from a polymeric material, the flange 204 may be elastically deformed during installation to position the inner diameter of the flange 204 within the annular trough 228. In yet other cases, the flange 204 may be cast in place along with the annular trough 228, which may form part of the mold used to cast the flange 204. Any suitable technique or system may be used to install the flange 204 relative to the bone marker 126.

[0073] FIG. 5 illustrates a perspective view of another exemplary bone marker 126, illustrating various alternatives. In particular, the exemplary bone marker 126 of FIG. 5 includes a flange 204, however the exemplary flange 204 in FIG. 5 is illustrated as having an elliptical or oval shape. That is, when viewed from above along the through-hole axis, the outer edge or surface defines an oval shape. Although the through-hole 226 is illustrated off-center relative to the oval shape (e.g., at the focus of the ellipse), the through-hole may be located in any suitable location. The exemplary flange 204 of FIG. 5 further includes through-holes 500, 502 located at both ends of the length dimension of the flange 204. The through-holes 500 and / or 502 may be used to assist in positioning the flange 204 in an orientation desired by the surgeon prior to final fastening of the bone marker 126 into the bone. The exemplary oval shaped flange 204 may be of particular use in arthroscopic ACL repair where the bone marker 126 is placed on the tibial plateau. In such locations, there may be tissue protruding from the plateau surface, and the oval shape may allow the flange to capture or restrain tissue between the bone and the bottom surface of the flange 204 directly beneath the polyhedron 200. In one example, the maximum dimension of the oval shape of the exemplary flange 204 of FIG. 5 is approximately 16 mm.

[0074] FIG. 5 further illustrates that in other examples, the through hole 226 need not be held within an annular trough. As shown, the through hole 226 is fitted onto the externally threaded screw 202, but the relative orientation of the through hole axis 504 of the through hole 226 and the central longitudinal axis 220 of the polyhedron 200 may be greater in the exemplary system of FIG. 5. Furthermore, FIG. 5 illustrates that the through hole 226 itself need not be circular. The inner surface of the exemplary through hole 226 of FIG. 5 may form an oval shape when viewed along the through hole axis 504 to allow for greater relative orientation between the central axis 504 and the central longitudinal axis 220.

[0075] The alternatives of FIG. 5 should not be read as mutually exclusive. For example, an oval shaped flange may be designed and constructed such that the through hole 226 has an inner diameter that is disposed within the annular trough 228 (FIG. 2). Conversely, a circular shaped flange may be designed and constructed such that the through hole is floating as shown in FIG. 5, including the through hole defining an oval shape. Additionally, the oval shaped flange 204 shown in FIG. 5 may rotate about the marker axis 220 or may be rotatably keyed relative to the marker 202. Now, an exemplary bone marker 126 will be described for holding within a placement tool during placement of the bone marker 126 within a bone.

[0076] FIG. 6A shows a perspective view of a bone marker 126 held on the distal end of an exemplary installation tool. In particular, FIG. 6A shows an exemplary installation tool 600 including an elongate shaft 602 defining a distal end 604 and a proximal end 606. The elongate shaft 602 is coupled to a handle 608 at the proximal end 606. Although not visible in FIG. 6A, the elongate shaft 602 and the handle 608 define a coaxial throughbore. Also visible in FIG. 6A is an exemplary bone marker 126, with the flange omitted so as not to obscure the intersection of the bone marker 126 with the distal end 604 of the installation tool 600. FIG. 6B shows a close-up view of the distal end 604 including the bone marker 126. In this example, the bone marker 126 is held within the installation tool 600 by fitting a polyhedron 200 within an interior volume at the distal end 604 of the installation tool 600. As shown and described in more detail below, the bone marker 126 is held in a mating relationship by a retaining fixation member (not visible in FIGS. 6A or 6B ) disposed in mating relationship with a retaining feature 234 ( FIG. 2 ) in the retention hole 230 ( FIG. 2 ). The retaining fixation member provides an axial force tending to hold the bone marker 126 in the mating relationship. By retaining the bone marker 126 within the installation tool, the bone marker 126 can be installed directly, eliminating the related art approach of drilling a pilot tunnel with a guidewire and then guiding the bone marker to the proper location on the bone by sliding the bone marker along a guide.

[0077] In use, the distal end 604 of the installation tool 600 and the retained bone marker 126 are placed into the surgical site, such as through a port through the patient's skin. The installation tool 600 can then be used to not only place the bone marker 126 in the appropriate location for installation (e.g., in the intercondylar recess in the case of ACL repair / replacement), but also to provide a rotational drive to the bone marker 126 for driving an externally threaded screw into the bone and securing the bone marker 126 to the bone. To reduce the possibility of denting or damaging the fiducial patterns on the outwardly facing surfaces of the polyhedron 200, in the exemplary case, the rotational drive applied by the installation tool 600 to the polyhedron 200 is located on each outwardly facing surface at a position that does not contact or overlap the respective corresponding fiducial patterns on the outwardly facing surface. In other words, the rotational drive for installation of the bone marker 126 is applied at a position outside the boundaries of the respective corresponding fiducial patterns on each outwardly facing surface.

[0078] 7 shows an exploded perspective view of the distal end of the installation tool 600 and the bone marker 126. In particular, the distal end 604 of the elongate shaft 602 defines an inner surface designed and constructed to fit over the polyhedron 200 of the bone marker 126. In the exemplary case where the polyhedron 200 is a cube, the inner surface of the distal end 604 of the elongate shaft therefore defines a square cross-sectional shape. The elongate shaft 602 further defines a through hole along a central longitudinal axis 610 of the elongate shaft 602. The through hole intersects with the inner surface and forms a shoulder region (not specifically shown) that limits axial translation of the polyhedron 200 into the distal end 604. Fitted into the through hole along the central longitudinal axis 610 is a retaining fixation member 612, illustratively shown as an externally threaded portion of an elongate rod 614. The elongate rod 614 may extend into a handle 608 (FIG. 6A) and may extend through the handle 608 to the distal end 604.

[0079] Thus, retaining the bone marker 126 on the distal end 604 of the installation tool 600 may include fitting the polyhedron 200 into an internal volume defined by the interior surface at the distal end 604 of the installation tool 600. The retaining fastener 612 may then be coupled to a retaining feature 234 (FIG. 2) located within a retaining hole 230 (FIG. 2) on the top surface of the polyhedron 200. In the illustrated example, the retaining fastener 612 configured with an external thread may be threadably coupled to the retaining feature 234 configured with an internal thread located within the retaining hole 230. The elongate rod 614 may thus provide a force tending to retain the bone marker 126 in an engaged relationship to the installation tool 600. In this example, when the bone marker 126 is held in mating relationship with the installation tool, the central longitudinal axis 220 of the bone marker 126 is coaxial with the central longitudinal axis 610 of the throughbore of the elongate shaft 602 and with the central longitudinal axis of the elongate rod 614. However, in other cases, the central longitudinal axes need not be coaxial.

[0080] After the bone marker 126 is placed in the bone, the retaining fixation member 612 may be removed from the retaining hole 230 (FIG. 2). In particular, in the exemplary case where the retaining fixation member 612 is externally threaded, the installation tool 600 may be used to hold the bone marker 126 in a constant rotational orientation as the external threads of the retaining fixation member 612 are unthreaded from engagement. In some cases, the threads of the exemplary retaining fixation member 612 are right-handed threads, but the bone marker 126 is not unthreaded from the bone when the threads of the exemplary retaining fixation member 612 are unthreaded, given that the bone marker 126 may be held in place by the installation tool 600. However, in other cases, the threads of the exemplary retaining fixation member 612 may be left-handed threads and the threads of the externally threaded screw 202 may be right-handed threads (or vice versa), such that the act of unscrewing the threads of the exemplary retaining fixation member 612 will tend to more firmly connect the bone marker 126 to the underlying bone.

[0081] FIG. 18 illustrates a perspective side view of another exemplary bone marker 126. In particular, the exemplary bone marker 126 includes a polyhedron 200 and an externally threaded screw 202. Although the bone marker 126 of FIG. 18 is shown without a flange, it may still be used with a flange if desired. The exemplary polyhedron 200 defines a top or upper surface 206 and a number of outwardly facing surfaces, such as outwardly facing surface 208 and outwardly facing surface 210. In the example of FIG. 18, the polyhedron 200 is a cube, but in this case the cube is angled and the externally threaded screw 202 extends from a "corner" of the cube. Each of the outwardly facing surfaces, such as outwardly facing surfaces 208, 210 visible in FIG. 18, has a fiducial pattern disposed thereon.

[0082] In this example, the externally threaded screw 202 protrudes from the face of the polyhedron 200 opposite the top face 206. In other words, the longitudinal center axis of the externally threaded screw 202 extends through two opposite corners of the exemplary cube. As above, in the exemplary case, the polyhedron 200 and the externally threaded screw 202 are of one piece construction, such as a continuous member of a metallic material (e.g., aluminum, stainless steel, titanium). The exemplary externally threaded screw 202 is a self-drilling or self-tapping screw. Again, as above, the bone marker 126 of FIG. 18 is a relatively small object, and in one example, the outer diameter of the externally threaded screw 202 is about 2.5 millimeters (mm), although larger and smaller sizes are contemplated. In the exemplary case, the polyhedron 200 may form a face that is about 4 mm long (measured parallel to the longitudinal center axis 220). Exemplary bone markers may have a total length of 10 mm to 15 mm inclusive, and in one example, 12 mm.

[0083] FIG. 19 illustrates a perspective side view of another exemplary bone marker 126. In particular, the left portion of FIG. 19 illustrates a side view, and the right portion of FIG. 19 illustrates a top view. The exemplary bone marker 126 of FIG. 19 similarly includes a polyhedron 200 and an externally threaded screw 202. Although the bone marker 126 of FIG. 19 is shown without a flange, it may still be used with a flange if desired. The exemplary polyhedron 200 defines a top or upper surface 206 and a number of outwardly facing surfaces, such as outwardly facing surface 208 and outwardly facing surface 210. In the example of FIG. 19, the polyhedron 200 is a hexahedron. Each of the outwardly facing surfaces, such as outwardly facing surfaces 208, 210, visible in FIG. 19 has a fiducial pattern disposed thereon.

[0084] In this example, the externally threaded screw 202 protrudes from the bottom surface of the hexahedron opposite the top surface 206. In other words, the central longitudinal axis of the externally threaded screw 202 extends through the bottom of the hexahedron. As above, in an exemplary case, the polyhedron 200 and the externally threaded screw 202 are of one piece construction, such as a continuous member of a metallic material (e.g., aluminum, stainless steel, titanium). The exemplary externally threaded screw 202 is a self-drilling or self-tapping screw. Again, as above, the bone marker 126 of FIG. 19 is a relatively small object, and in one example, the outer diameter of the externally threaded screw 202 is about 2.5 millimeters (mm), although larger and smaller sizes are contemplated. In an exemplary case, the polyhedron 200 may form a surface that is about 4 mm long (measured parallel to the central longitudinal axis 220). Exemplary bone markers may have a total length of 10 mm to 15 mm inclusive, and in one example, 12 mm.

[0085] In the example shown in FIG. 19, the hexahedron may be associated with lower corner notches, such as notches 1900, 1902, 1904, 1906. Each notch may define a closed bottom, an open top, and a notch axis. In the example shown, the notch axes may be parallel to one another and to a central axis (not specifically shown) of the externally threaded screw 202. The notches may be used by an installation tool (not specifically shown) to provide a location for applying a rotational installation force to the bone marker 126 of FIG. 19. Additionally, similar to the above, the top surface 206 may be associated with a retention hole 230 having a retention feature (not specifically shown in FIG. 19) disposed therein, the retention feature taking any of the various forms described above.

[0086] In the various exemplary bone markers described thus far, the flange (if present) has been described as a separate and distinct component to the polyhedron and to the externally threaded screw protruding from the polyhedron, however, in still further examples, the flange may be an integral component to the polyhedron and the externally threaded screw, and in the exemplary case, the flange may be integral to the polyhedron and the externally threaded screw.

[0087] FIG. 8 illustrates a perspective view of an exemplary bone marker 126. In particular, the exemplary bone marker 126 in FIG. 8 includes a polyhedron 200 and an externally threaded screw 202. As in the previous example, the polyhedron 200 defines a top surface 206 that defines a retention hole 230 therein that includes an exemplary retention feature 234 in the form of a thread. As in the previous example, the externally threaded screw 202 protrudes from a side of the polyhedron 200 opposite the top surface 206. As in the previous example, a flange 204 is disposed proximate to an intersection of the polyhedron 200 and a proximal end of the externally threaded screw 202. However, in the example of FIG. 8, the flange 204 is an integral component of the externally threaded screw 202. Thus, the flange 204 is rigidly coupled to the polyhedron and the externally threaded screw 202. In some cases, the polyhedron 200, flange 204, and externally threaded screw 202 are of one piece construction, such as a continuous piece of metallic material (e.g., aluminum). For example, the polyhedron 200, flange 204, and externally threaded screw 202 may be cast together in a mold or machined from a single piece of aluminum. Nonetheless, the exemplary flange 204 may capture or constrain tissue against the bone directly below the flange 204 to reduce the occurrence of debris and / or tissue obscuring the fiducial pattern associated with the polyhedron 200. The exemplary bone marker 126 of FIG. 8 may find beneficial use when the underlying bone is relatively flat or when the underlying bone slopes away from the attachment point. For example, the bone marker 126 of FIG. 8 may find beneficial use in treating femoroacetabular impingement when the bone marker 126 is placed on the anterior superior iliac spine of the pelvis.

[0088] Moreover, the exemplary flange 204 of FIG. 8 may be the location where a rotational drive is applied to place the bone marker 126 in the bone. To that end, the exemplary flange 204 of FIG. 8 defines a number of recesses or notches 800 on the face of the flange 204. Thus, a placement tool (not shown) may be designed and constructed to fit onto the polyhedron 200 and interact with the notches 800. Applying a rotational drive for placement at the notches 800 reduces the possibility of damaging the fiducial pattern on the outwardly facing face of the polyhedron 200. However, applying a rotational drive for placement at the notches 800 may also increase the diameter of the distal end of the placement tool. Notch 800 is merely one example of a feature associated with flange 204 to which an installation tool may be coupled to apply a rotational driving force for installation and retrieval of bone marker 126, and notch 800 may take any suitable form, such as one or more countersunk holes of any suitable shape disposed on flange 204 in a non-intersecting position relative to the outer surface of flange 204, or one or more through holes of any suitable shape disposed on flange 204 in a non-intersecting position relative to the outer surface of flange 204.

[0089] In the example of FIG. 8, the polyhedron 200 may be a separate component relative to the externally threaded screw 202 and relative to the flange 204. In particular, the exemplary bone marker 126 of FIG. 8 may include a tube or nipple extending proximally from the flange 204, where the inner surface of the nipple forms the retention hole 230 and the retention feature 234. Thus, the nipple, flange 204, and externally threaded screw 202 may be an integral component (e.g., made of metal), while the polyhedron 200 may be a separate, distinct component (e.g., a polymeric material such as plastic) that is snapped onto the nipple during assembly of the bone marker 126. By using the flange 204 as the mechanical structure against which a rotational drive force for installation is applied, the polyhedron may be made from different materials and possibly using different, less expensive construction techniques.

[0090] FIG. 9 illustrates a perspective view of an exemplary bone marker 126. In particular, the exemplary bone marker 126 in FIG. 9 includes a polyhedron 200 and an externally threaded screw 202. As in the previous example, the polyhedron 200 defines a top surface 206 that defines a retaining hole 230 therein that includes an exemplary retaining feature 234 in the form of a thread. As in the previous example, the externally threaded screw 202 protrudes from a face of the polyhedron 200 opposite the top surface 206. As in the previous example, a flange 204 is disposed adjacent to an intersection of the polyhedron 200 on a proximal end of the externally threaded screw 202. In the example of FIG. 9, the flange 204 is an integral component of the bone marker 126. Thus, the flange 204 is rigidly coupled to the polyhedron and the externally threaded screw 202. In some cases, the polyhedron 200, flange 204, and externally threaded screw 202 are of one piece construction, such as a continuous member of a metallic material (e.g., aluminum). As above, the exemplary flange 204 can capture or restrain tissue against the bone directly below the flange 204, reducing the occurrence of debris and / or tissue obscuring the fiducial pattern associated with the polyhedron 200. As with the bone marker of FIG. 8, the exemplary bone marker 126 of FIG. 9 can find beneficial use when the underlying bone is relatively flat or when the underlying bone is angled away from the attachment point.

[0091] Moreover, the exemplary flange 204 of FIG. 9 may be the location where a rotational drive is applied to place the bone marker 126 in the bone. To that end, the outer surface of the exemplary flange 204 of FIG. 9 defines a hexagon. Thus, a placement tool (not shown) may be designed and constructed to fit onto the polyhedron 200 and further fit onto and interact with the hexagonal outer surface 900. Applying a rotational drive for placement at the hexagonal outer surface 900 reduces the possibility of damaging the fiducial pattern on the outwardly facing surface of the polyhedron 200. However, applying a rotational drive for placement at the hexagonal outer surface 900 may also increase the diameter of the distal end of the placement tube. The hexagonal outer surface 900 is only one example of a feature that a placement tool may mate with to apply a rotational drive for placement and retrieval of the bone marker 126.

[0092] In the example of FIG. 9, the polyhedron 200 may also be a separate component relative to the externally threaded screw 202 and relative to the flange 204. In particular, the exemplary bone marker 126 of FIG. 9 may include a tube or nipple extending proximally from the flange 204, where the inner surface of the nipple forms the retention hole 230 and the retention feature 234. The nipple, flange 204, and externally threaded screw 202 may be an integral component (e.g., made of metal), while the polyhedron 200 may be a separate, distinct component (e.g., a polymeric material such as plastic). Thus, again, the polyhedron may be made of different materials, using the flange 204 as the mechanical structure to which the rotational drive force for installation is applied. Other examples of methods and systems for reducing debris and / or tissue obscuring a fiducial pattern are now described herein in the exemplary context of a sight.

[0093] FIG. 10 illustrates a perspective view of the distal end of the exemplary sight 124. In particular, FIG. 10 illustrates that the exemplary sight 124 includes an elongate shaft 1000 defining a distal end 1002, a proximal end (not visible), and a central longitudinal axis 1004. In the exemplary sight 124, the distal end 1002 is sharpened to assist in holding the sight 124 in place relative to the bone during placement and drilling, although in other cases the sharpening may be omitted. The exemplary sight 124 includes a plurality of fiducial patterns associated with it to enable the surgical controller 118 (FIG. 1) to determine the position of the sight 124 relative to the bone visible in the images viewed by the arthroscope 108 (FIG. 1) and the camera head 110 (FIG. 1). More specifically, the exemplary sight 124 defines a reference surface 1006 disposed proximate to the distal end 1002. The reference surface 1006 includes a plurality of reference patterns on an upper surface at different axial locations. For example, the reference surface 1006 includes a distal reference pattern 1008, a central reference pattern 1010, and a proximal reference pattern 1012. The distal reference pattern 1008 is located at a distal axial location along the central longitudinal axis 1004. The central reference pattern 1010 is disposed proximal to the distal reference pattern 1008. The proximal reference pattern 1012 is disposed proximal to the central reference pattern 1010. Although three reference patterns are shown in association with the reference surface 1006, more than two reference patterns may be implemented on the reference surface 1006 to reduce the occurrence of debris and / or tissue obscuring the reference patterns during arthroscopic surgery. In some cases, the reference surface 1006 defines a plane on which the fiducial pattern is formed or attached. The fact that the reference surface 1006 defines a plane provides an additional linear feature that the surgical controller 118 may rely on in determining the orientation of the fiducial pattern. However, in still other cases, the reference surface need not be planar, but may take on other suitable shapes (e.g., cylindrical).

[0094] In some procedures, the relationship between the reference plane 1006 and the viewing angle of the arthroscope 108 (FIG. 1) may be such that the reference plane 1006 is always located within the field of view of the arthroscope 108. However, in other procedures (e.g., ACL replacement), the rotational orientation of the sight 124 relative to the field of view of the arthroscope 108 may not be guaranteed. Thus, in still further cases, the exemplary sight 124 includes additional reference planes, where each of the additional reference planes also has multiple fiducial patterns. In particular, FIG. 10 illustrates another reference plane 1014 that includes a distal fiducial pattern 1016, a central fiducial pattern 1018, and a proximal fiducial pattern 1020. Although the exemplary sight 124 includes four reference planes, only the reference planes 1006, 1014 are visible in the view of FIG. 10. When four reference planes are implemented, the reference planes may define a plane perpendicular to the plane defined by adjacent reference planes. For example, datum plane 1006 defines a plane that is perpendicular to the plane defined by datum plane 1014. The four exemplary datum planes form an outer surface about the exterior surface of elongate shaft 1000, and thus about central longitudinal axis 1004.

[0095] Having four reference surfaces forming an outer surface about the central longitudinal axis 1004 is merely one example. In other cases, fewer than three reference surfaces may be used. For example, three reference surfaces may be used, which may form an outer surface about the central longitudinal axis 1004. Still further, the reference surfaces need not form an outer surface that completely surrounds the central longitudinal axis 1004. For example, in cases where it can be relatively certain that the field of view of the arthroscope will be within a range of rotational orientations relative to the central longitudinal axis 1004, one or more of the reference surfaces and corresponding reference patterns may be omitted (e.g., a reference surface on the back of the object).

[0096] In the exemplary sight 124, the fiducial pattern 1008 is located at the same axial position relative to the fiducial pattern 1016, but at a different radial position about the central longitudinal axis 1004. With respect to the fiducial plane not visible in FIG. 10, the distal fiducial pattern may similarly be located at the same axial position relative to the fiducial patterns 1008, 1016, but again at separate radial positions about the central longitudinal axis 1004. Similarly, the fiducial pattern 1010 is located at the same axial position relative to the fiducial pattern 1018, but at a different radial position about the central longitudinal axis 1004. The central fiducial pattern on the non-visible fiducial plane may be located at the same axial position. The fiducial pattern 1012 is located at the same axial position relative to the fiducial pattern 1020, but at a different radial position about the central longitudinal axis 1004. The proximal fiducial patterns on the non-visible reference surfaces may be located at the same axial position. In yet another example, the axial positions of the fiducial patterns need not be the same across reference surfaces.

[0097] 10, for the exemplary sight 124, the reference surfaces (e.g., 1006, 1014) may be constructed and associated with the elongate shaft 1000 in any suitable manner. For example, in some cases, the reference surfaces and the corresponding reference patterns may be integral with the elongate shaft 1000. In other cases, the reference surfaces and the corresponding reference patterns may be separate and distinct components that are fitted onto the elongate shaft 1000. For example, the reference surfaces and the corresponding reference patterns may be part of a reference assembly that defines a through hole. The reference assembly may be fitted onto the elongate shaft 1000, where the inner diameter of the through hole is designed and constructed to form a friction fit with the outer surface of the elongate shaft 1000. Thus, the reference assembly may be a disposable member made of a polymeric material (e.g., plastic), and the underlying sight 124 may be made of metal and therefore sterilized by autoclaving.

[0098] The operational information for the sight 124 is the orientation of the central longitudinal axis 1004 relative to other objects in the images captured by the arthroscope 108 (FIG. 1) and the camera head 110 (FIG. 1). That is, if the surgical controller 118 (FIG. 1) can determine the orientation of the central longitudinal axis 1004 in the three-dimensional coordinate space of the field of view of the arthroscope 108, no further spatial relationship may be necessary. For example, once the surgical controller 118 knows the orientation of the central longitudinal axis 1004, it can determine the orientation of the sight 124 relative to other tracked objects (e.g., bones). For this reason, for the sight 124, the exact location of the distal tip 1022 does not need to be defined relative to the fiducial pattern. For that reason, the fiducial pattern does not need to be distinct along the fiducial plane, nor does the fiducial pattern need to be distinct between the fiducial planes. Stated another way, when only the orientation of the central longitudinal axis 1004 is of interest, all of the fiducial patterns may be identical, as shown in Figure 10. For other medical instruments, such as a touch probe 122 (Figure 2), it may be necessary to know the exact location of the distal tip.

[0099] FIG. 11 illustrates a perspective view of the distal end of an exemplary touch probe 122. In particular, FIG. 11 illustrates that the exemplary touch probe 122 includes an elongate shaft 1100, a proximal end (not visible), and a central longitudinal axis 1102. The exemplary touch probe 122 has a distal end 1104 including a probe end 1106 having a probe axis 1108. In the exemplary case, the probe end 1106 defines a truncated cone having a narrow distal end that is rounded to form a touch surface 1110 and a wider proximal end located closer to the central longitudinal axis 1102. In the exemplary case, the probe axis 1108 forms an acute angle with the central longitudinal axis 1102, the acute angle being measured beyond the distal end 1104 of the touch probe 122. In use, the touch surface 1110 is contacted against a bone to provide positional information to the surgical controller 118 (FIG. 1), for example to provide data for registering a three-dimensional bone model to the bone, or to provide corrected tunnel entrance and exit positions when changing the tunnel path during surgery.

[0100] In order for the surgical controller 118 (FIG. 1) to determine the location of the touch surface 1110 relative to the bones viewed in the images viewed by the arthroscope 108 (FIG. 1) and the camera head 110 (FIG. 1), the exemplary touch probe 122 includes a number of fiducial patterns associated with the touch probe 122. More specifically, the exemplary touch probe 122 defines a fiducial surface 1112 disposed proximate to the touch surface 1110. The fiducial surface 1112 includes a number of fiducial patterns on an upper surface thereof at different axial positions relative to the central longitudinal axis 1102. For example, the fiducial surface 1112 includes a distal fiducial pattern 1114, a central fiducial pattern 1116, and a proximal fiducial pattern 1118. The distal fiducial pattern 1114 is located at a distal axial position along the central longitudinal axis 1102. The central fiducial pattern 1116 is located more proximal than the distal fiducial pattern 1114. The proximal fiducial pattern 1118 is disposed proximal to the central fiducial pattern 1116. Although three fiducial patterns are shown in association with the fiducial surface 1112, more than one fiducial pattern may be implemented on the fiducial surface 1112 to reduce the occurrence of debris and / or tissue obscuring the fiducial patterns during arthroscopic surgery. In some cases, the fiducial surface 1112 defines a plane on which the fiducial patterns are formed or attached. The fact that the fiducial surface 1112 defines a plane provides an additional linear feature that the surgical controller 118 may rely on in determining the orientation of the fiducial patterns. However, in still other cases, the fiducial surface need not be planar, but may take on other suitable shapes (e.g., cylindrical).

[0101] In some procedures, the relationship between the reference surface 1112 and the viewing angle of the arthroscope 108 (FIG. 1) may be such that the reference surface 1112 is always located within the viewing angle of the arthroscope 108. More likely, however, the rotational orientation of the touch probe 122 may vary significantly during an intraoperative procedure. Thus, in still further instances, the touch probe 122 includes additional reference surfaces, where each of the additional reference surfaces also includes multiple reference patterns. In particular, FIG. 11 illustrates another reference surface 1120 that includes a distal reference pattern 1122, a central reference pattern 1124, and a proximal reference pattern 1126. Although the exemplary touch probe 122 includes three reference surfaces, only the reference surfaces 1112, 1120 are visible in the view of FIG. 11. The exemplary three reference surfaces form an outer surface about the central longitudinal axis 1102. In other cases, the reference surface need not form an exterior surface that completely surrounds the central longitudinal axis 1102.

[0102] In the exemplary touch probe 122, the fiducial pattern 1114 is located at the same axial position relative to the fiducial pattern 1122, but at a different radial position about the central longitudinal axis 1102. With respect to a fiducial surface not visible in FIG. 11, the distal fiducial pattern may similarly be located at the same axial position relative to the fiducial patterns 1114, 1122, but again at separate radial positions about the central longitudinal axis 1102. Similarly, the fiducial pattern 1116 is located at the same axial position relative to the fiducial pattern 1124, but at a different radial position about the central longitudinal axis 1102. The central fiducial pattern on the non-visible reference surface may be located at the same axial position. The fiducial pattern 1118 is located at the same axial position relative to the fiducial pattern 1126, but at a different radial position about the central longitudinal axis 1102. Proximal fiducial patterns on non-visible reference surfaces may be located at the same axial position. In yet another example, the axial positions of the fiducial patterns need not be the same across reference surfaces.

[0103] The motion information for the touch probe 122 is the position of the touch surface 1110 relative to other objects in the images captured by the arthroscope 108 (FIG. 1) and the camera head 110 (FIG. 1). Due to the offset of the touch surface 1110 from the central longitudinal axis 1102 (as measured perpendicular to the central longitudinal axis 1102), the linear distances between each fiducial pattern and the touch surface 1110 are different. For example, the distance between the fiducial pattern 1118 and the touch surface 1110 is greater than the distance between the fiducial pattern 1114 and the touch surface 1110. Similarly, the distance between the fiducial pattern 1126 and the touch surface 1110 is greater than the distance between the fiducial pattern 1122 and the touch surface 1110. Still further, the linear distance between the fiducial pattern 1126 and the touch surface 1110 is different than the linear distance between the fiducial pattern 1118 and the touch surface 1110. Due to the different distances between each fiducial pattern and the touch surface 1110, each implemented fiducial pattern may be distinct and unique with respect to all other fiducial patterns implemented by the touch probe 122. Thus, the surgical controller 118 (FIG. 1) determines the location of the touch surface 1110 within the three-dimensional coordinate space of the field of view of the arthroscope 108 by reading at least one of the fiducial patterns visible in the received image. When debris and / or tissue obscures one or more of the fiducial patterns, the surgical controller 118 may nonetheless determine the location of the touch surface 1110 based on the one or more fiducial patterns that are still visible. An example of how the surgical controller selects a particular fiducial pattern when more than one fiducial pattern is visible in an image is described in more detail herein below.

[0104] Figure 12 shows a cross-sectional view of an exemplary touch probe 122, with the cross-section taken along the central longitudinal axis 1102 and through the center of the reference surface 1112. In particular, visible in Figure 12 are the elongate shaft 1100, the probe end 1106, the touch surface 1110, the probe axis 1108, the reference surface 1112, the distal reference pattern 1114, the central reference pattern 1116, and the proximal reference pattern 1118. Since three reference surface are used in the exemplary touch probe 122, only the reference surface 1112 is shown in the cross-sectional view.

[0105] The exemplary touch probe 122 includes at least two components, namely, at least an elongate shaft 1100 and a probe assembly 1200. In particular, the exemplary elongate shaft 1100 defines a threaded stem 1202 extending along a central longitudinal axis 1102. In addition, the elongate shaft 1100 defines a flange region 1204 having an outer diameter greater than an outer diameter of the elongate shaft 1100. The flange region 1204 defines a shoulder 1206 disposed between the outer diameter of the threaded stem 1202 and the outer diameter of the flange region 1204. The interface between the probe assembly 1200 and the shoulder 1206 may be used to increase the force required to unscrew the probe assembly 1200 from the threaded stem 1202, thereby reducing the likelihood of the probe assembly 1200 coming loose during an intraoperative procedure.

[0106] The probe end 1106 extends away from the central longitudinal axis 1102 at an acute angle α when measured distally from the touch probe 122. Additionally, the touch surface 1110 has an offset O when measured perpendicularly from the central longitudinal axis 1102. A The touch surface 1110 has an offset O from the reference surface 1112. F (again, measured perpendicularly from the central longitudinal axis 1102). In various examples, the offset O A , O Fis designed and constructed such that the probe assembly 1200 defines a cut-out area 1208. The cut-out area 1208 may allow the surgeon to reach "around" various objects within the surgical field and still be able to contact the bone surface. A is about 7 mm, and the offset O F The offset O of the flange region 1204 is approximately 5 mm, and the outer diameter of the flange region 1205 is approximately 10 mm. Thus, the cutout region 1208 provides an offset O of approximately 5 mm while maintaining the displacement of the probe end 1106 exceeding the outer diameter of the flange region 1204 by approximately 2 mm. F This makes it possible.

[0107] In the exemplary touch probe 122 of FIG. 12, the probe assembly 1200 has a counterbore defining an internal thread that mates with the external thread of the threaded stem 1202. However, the mechanical configuration is only one example. Other examples include the probe assembly 1200 defining a proximally projecting threaded stem, the elongated shaft 1100 defining a counterbore having an internal thread, into which the threaded stem of the probe assembly is coupled. Still further, the probe assembly 1200 may itself be a two-piece component, where the probe end 1106 defines a threaded stem that mates with the elongated shaft, and the datum is a member having a through hole that fits onto the threaded stem. Another example is a one-piece shaft with a reduced diameter distal portion including the tip. A triangular datum section is slid onto the reduced diameter section and rotatably keyed to the shaft. The reduced diameter section projecting distally from the datum is ultimately bent at an angle α. Many variations are possible.

[0108] FIG. 13 shows a cross-sectional view through the probe assembly 1200 looking distally towards the probe end 1106. In particular, FIG. 13 shows a cross-section of the probe assembly 1200, which illustratively includes a reference surface 1112, a reference surface 1120, and a third reference surface 1300. In this example, the reference surfaces 1112, 1120, 1300 form an outer surface about the central longitudinal axis 1102 (shown as a dot in the view of FIG. 13 since the central longitudinal axis 1102 is perpendicular to the plane of the page). The outer surface formed is triangular, despite the rounded or curved corners between the reference surfaces. In the cross-section, a portion of the reference pattern on the reference surface 1120 is also visible, which may be any of the reference patterns 1114, 1116, or 1118. Additionally, in cross section, a portion of the fiducial pattern on reference surface 1120 is also visible, which may be any of fiducial patterns 1122, 1124, or 1126. In the exemplary case, reference surface 1300 similarly has three fiducial patterns, and the view of FIG.

[0109] In the exemplary triangular probe assembly 1200, a cross section of the triangular portion defines a geometric center 1302. Stated another way, the triangular portion of the probe assembly 1200 defines a central longitudinal axis, which in the view of FIG. 13 is shown as the geometric center 1302 because it is perpendicular to the plane of the page. In the exemplary case, the geometric center 1302 has a non-zero offset from the central longitudinal axis 1102. Stated another way, the reference plane 1112 is located closer to the central longitudinal axis 1102 than the geometric center 1302, where both distances are measured perpendicular to the central longitudinal axis 1102. Due to the relationship of the reference plane 1112 to the central longitudinal axis 1102, and the offset O F This forms cutout area 1208 (FIG. 12).

[0110] The exemplary bone marker 126, sight 124, and touch probe 122 all have multiple fiducial patterns. The fiducial patterns extend radially around the central longitudinal axis of the object, and in the case of sight 124 and touch probe 122, the fiducial patterns extend axially along the central longitudinal axis. The goal is to have at least one fiducial pattern visible even if debris and / or tissue obscures some of the fiducial patterns during surgery. However, in many instances, the surgical controller 118 (FIG. 1) can see multiple fiducial patterns in images captured by the arthroscope 108 (FIG. 1) and camera head 110 (FIG. 1). More specifically, the surgical controller 118 receives images that the arthroscope 108 and attached camera head 110 view during surgery, including images of instruments having multiple fiducial patterns. The surgical controller 118 then selects an unobstructed fiducial from among the fiducial patterns visible in the image and calculates a value indicative of the position of the instrument within the surgical site based on the unobstructed fiducial. The position value may take a variety of forms. In the case of a bone marker 126, the position value may be a position in the three-dimensional coordinate space of the arthroscopic field of view that provides an anchor position for the bone marker 126 with respect to a three-dimensional bone model that has been preregistered. In the case of a sight 124, the position value may be an orientation of a central longitudinal axis of the sight 124. In the case of a touch probe 122, the position value may be a position of the touch surface 1110 within the three-dimensional coordinate space of the arthroscopic field of view.

[0111] Regardless of the exact calculated position value, in the exemplary system, the surgical controller 118 then performs an intraoperative task based on the position value. The intraoperative task may take many forms. For example, the surgical controller may register a location on a bone visible in the image that is selected or specified by the touch probe 122. As another example, the surgical controller 118 may use the position value to select a corrected tunnel entrance for a tunnel through the bone or a corrected tunnel exit for a tunnel through the bone. The position value, such as in the form of a central longitudinal axis of the sight 124, may be used to determine the position of the distal end of the sight with respect to the bone visible in the image and / or the relative orientation of the central longitudinal axis of the sight 124 with respect to the central axis of a planned tunnel through the bone.

[0112] FIG. 14 illustrates a side view of an arthroscope 108 and multiple fiducial patterns to illustrate fiducial pattern selection when more than one fiducial pattern is visible in a received image. In particular, FIG. 14 illustrates a fiducial plane 1400 including fiducial patterns 1402, 1404, and 1406. Because the figure is a side view, the actual patterns for fiducial patterns 1402, 1404, and 1406 are not visible in FIG. 14. Each fiducial pattern 1402, 1404, and 1406 defines a normal vector 1408, 1410, and 1412, respectively. In each case, a "normal vector" is a vector that is perpendicular to the outer surface of the fiducial pattern and, in some cases, perpendicular to the underlying fiducial plane 1400. The exemplary arthroscope 108 defines a viewing angle enclosed by exemplary arrows 1414, 1416. Additionally, the exemplary arthroscope 108 defines a viewing direction 1418 that is a vector that defines a range of viewing angles. In the example of Figure 14, fiducial pattern 1402 is not visible at all within the viewing angle of the arthroscope 108, while fiducial patterns 1404, 1406 are visible within the viewing angle.

[0113] The question is, which of the unoccluded fiducial patterns 1404 or 1406 should be selected for further processing. In an exemplary system, the surgical controller 118 selects the unoccluded fiducial pattern with a normal vector that is closest to the axis relative to the line of sight 1418 of the arthroscope 108. In the example of FIG. 14, the normal vector 1410 of the fiducial pattern 1404 is closest to the axis relative to the line of sight 1418, so even though both fiducial patterns 1404, 1406 are visible, the surgical controller 118 selects the one to proceed with. The exemplary FIG. 14 is two-dimensional, just the plane of the page. However, in reality, the line of sight 1418 of the arthroscope 108 may vary in three dimensions relative to the normal vector of the fiducial pattern being viewed. Selecting a reference pattern that had a normal vector closest to the line of sight direction may mean that the orientation of the reference pattern, and therefore the orientation of an object located below, will have less uncertainty, for example, compared to a reference pattern observed at a small acute angle (e.g., a large angle between the line of sight angle and the normal vector).

[0114] 15 illustrates a method according to at least some embodiments. In particular, the method begins (block 1500) and includes holding a bone marker on a distal end of a placement tool (block 1502), the bone marker including a polyhedron having a fiducial pattern on each of at least three outwardly facing surfaces of the polyhedron, an externally threaded screw extending distally from the polyhedron, and a flange proximate to an intersection of the polyhedron and the externally threaded screw, positioning the distal end of the externally threaded screw relative to the bone at the marker location (block 1504), threading the externally threaded screw into the bone via the placement tool (block 1506), and constraining tissue relative to the bone directly below the flange (block 1508). The exemplary method then ends (block 1510).

[0115] FIG. 16 illustrates a method according to at least some embodiments. In particular, the exemplary method of FIG. 16 may be implemented, at least in part, by instructions executed by a processor, such as the surgical controller 118 (FIG. 1), in a computer system. The exemplary method begins (block 1600) and includes receiving images (1602) that are viewed by an endoscope and an attached camera head during surgery and that include images of an instrument having a plurality of fiducial patterns associated with the instrument, selecting an unobstructed fiducial pattern from among the plurality of fiducial patterns visible in the image (block 1604), calculating a value indicative of the position of the instrument within the surgical site based on the unobstructed fiducial pattern (block 1606), and performing an intraoperative task based on the value indicative of the position (block 1608). The exemplary method then ends (block 1610) and is resumed by receiving a next set of images.

[0116] FIG. 17 illustrates an exemplary computer system 1700. In one example, computer system 1700 may correspond to a surgical controller 118, a tablet device in an operating room, or any other system implementing any or all of the various methods described herein. Computer system 1700 may be connected (e.g., networked) to other computer systems within a local area network (LAN), an intranet, and / or an extranet (e.g., device cart 102 network), or at certain times, the Internet (e.g., when not being used in surgery). Computer system 1700 may be a server, a personal computer (PC), a tablet computer, or any device capable of executing a set of instructions (sequential or otherwise) that specify actions to be performed by the device. Additionally, although only a single computer system is illustrated, the term "computer" shall also be construed to include any collection of computers that individually or jointly execute a set (or sets) of instructions to perform any one or more methods described herein.

[0117] The computer system 1700 includes a processing device 1702, a main memory 1704 (e.g., read only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM)), a static memory 1706 (e.g., flash memory, static random access memory (SRAM)), and a data storage device 1708, which communicate with each other via a bus 1710.

[0118] The processing device 1702 represents one or more general-purpose processing devices, such as a microprocessor, a central processing unit, or the like. More specifically, the processing device 1702 may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, or a processor implementing other instruction sets or a combination of instruction sets. The processing device 1702 may also be one or more application-specific processing devices, such as an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), a network processor, or the like. The processing device 1702 is configured to execute instructions to perform any of the operations and steps described herein. After being programmed with specific instructions, the processing device 1702, and thus the entire computer system 1700, becomes an application-specific device, such as the surgical controller 118.

[0119] The computer system 1700 may further include a network interface device 1712 for communicating with any suitable network (e.g., the device cart 102 network). The computer system 1700 may also include a video display 1714 (e.g., the display device 114), one or more input devices 1716 (e.g., a microphone, keyboard, and / or mouse), and one or more speakers 1718. In one example, the video display 1714 and the input device(s) 1716 may be combined into a single component or device (e.g., an LCD touch screen).

[0120] The data storage device 1708 may include a computer-readable storage medium 1720 having stored thereon instructions 1722 that embody any one or more of the methodologies or functions described herein. The instructions 1722 may also reside, completely or at least partially, within the main memory 1704 and / or within the processing device 1702 during execution thereof by the computer system 1700. Thus, the main memory 1704 and the processing device 1702 also constitute computer-readable media. In certain cases, the instructions 1722 may also be transmitted or received over a network via the network interface device 1712.

[0121] Although computer readable storage medium 1720 is shown in the illustrated example as being a single medium, the term "computer readable storage medium" shall be interpreted to include a single or multiple media (e.g., a centralized or distributed database and / or associated caches or servers) having one or more sets of instructions stored thereon. The term "computer readable storage medium" shall also be interpreted to include any medium that can store, encode or carry a set of instructions for execution by a machine, and that cause a machine to perform any one or more methodologies in this disclosure. Thus, the term "computer readable storage medium" shall be interpreted to include, but is not limited to, solid state memory, optical media, and magnetic media.

[0122] The above discussion is intended to illustrate the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.

Claims

1. A bone marker, a polyhedron defining a first outward facing surface, a second outward facing surface, and a third outward facing surface; an externally threaded screw protruding from a face of the polyhedron, the externally threaded screw being integral with the polyhedron; a retention hole having an entrance opening through said polyhedron, said retention hole defining retention features on an interior surface of said retention hole; a first reference pattern on the first outward surface, a second reference pattern on the second outward surface, and a third reference pattern on the third outward surface, the first reference pattern, the second reference pattern, and the third reference pattern being distinct from one another; a flange positioned proximate to an intersection of said polyhedron and said externally threaded screw.

2. The bone marker of claim 1 , wherein the polyhedron is a cube.

3. The bone marker of claim 2 , wherein the externally threaded screw is a self-tapping screw.

4. The bone marker of claim 3 , wherein the retention feature further comprises a thread defined on an inner surface of the retention hole.

5. 5. The bone marker of claim 4, further comprising: the externally threaded screw comprises right-hand threads; and the threads on the interior surface of the retention hole comprise left-hand threads.

6. The bone marker of claim 5 , further comprising: each of the first reference pattern, the second reference pattern, and the third reference pattern being a three-dimensional pattern.

7. 7. The bone marker of claim 6, wherein the flange further comprises a polymeric material and defines a top surface, a bottom surface opposite the top surface, a through hole defining a through hole axis, and a thickness as measured parallel to the through hole axis, the through hole being fitted onto the externally threaded screw, and the flange is positioned at the intersection of the bottom surface of the polyhedron and a proximal end of the externally threaded screw.

8. The bone marker of claim 7 , wherein the flange comprises at least one material selected from the group consisting of a polymeric material, a metallic material, and a silicone.

9. The bone marker of claim 7 , wherein the flange further comprises at least one shape selected from the group consisting of a circle and an oval.

10. an annular trough disposed at the intersection of the polyhedron and the proximal end of the externally threaded screw, the annular trough surrounding a central longitudinal axis of the externally threaded screw; an inner diameter of the through hole in the flange forming a friction fit with the annular trough; The bone marker of claim 7 further comprising:

11. an annular trough disposed at the intersection of the polyhedron and the proximal end of the externally threaded screw, the annular trough surrounding a central longitudinal axis of the externally threaded screw; a mounting thread defined between the threads of the externally threaded screw and the annular trough; an inner diameter of the through hole disposed within the annular trough; The bone marker of claim 7 further comprising:

12. The flange is a top surface intersecting the first outward surface, the second outward surface, and the third outward surface; a lower surface intersecting the externally threaded screw; a diameter greater than a maximum dimension of the polyhedron as measured perpendicular to a central longitudinal axis of the externally threaded screw; The bone marker of claim 11 , wherein the flange, the polyhedron, and the externally threaded screw are integral.

13. 13. The bone marker of claim 12, further comprising an interface feature defined by the flange, the interface feature being at least one selected from the group consisting of an outer surface of the flange and a recess on the top surface of the flange.

Images