BONE TRACKER SET, BONE TRACKING SYSTEM AND BONE TRACKING PROCEDURE

Abstract

The disclosure relates to a bone tracker set (1) for a bone tracking system (100) for tracking, preferably further for registering, at least two bones relative to one another, comprising: at least two bone fixations, in particular two pins (2), which are provided and adapted to be fastened directly to or in a bone of a patient (P) by means of a distal bone anchor (4), wherein a proximal end section (6) of the bone fixation, in particular of the pin (2), in each case has a coupling section (8), and at least two reference adapters, in particular two sleeves (10), which have or carry a proximal optical reference marker (12), and the reference adapters, in particular sleeves (10), are adapted to be able to be coupled to or uncoupled from the coupling section (8) of the bone fixation, in particular of the pin (2), without the need for tools, in particular having a counter-coupling structure (14).In addition, the present disclosure relates to a bone tracking system according to the independent claim.

Description

Technical FieldThe present disclosure relates to a bone tracker set (having at least two bone trackers) for a bone tracking system for tracking, and further preferably for registering, at least two bones (multiple bones) relative to one another, in particular two vertebrae (columns) bones relative to one another. In addition, the present disclosure relates to a bone tracking system and a bone tracking method according to the preambles of the subordinate claims.Background ArtSpinal navigation and spinal robotics are now established methods in a surgical procedure on a patient. Most current navigation systems, however, only permit spatial tracking of a single (spinal) bone at a time, if any, because they are too large in size and also too invasive (with concomitant tissue damage to the patient) to attach reference frames (reference frames) to the bone, which in most cases are attached to the spinous process. This allows the individual pedicle screws to be implanted precisely in the spinal column, but it is not possible to monitor the actual reconstruction of the spinal column in order to restore the functioning of the spinal column of the patient.For multi-plane spinal tracking, the use of EM (Electromagnetic Tracking / Electro-Magnetic Tracking) has been proposed, however, EM tracking often suffers from limited accuracy due to EM interference from other devices in the surgical device. These electrical devices, due to the material or self-radiation, influence the electromagnetic field, so that the tracking is not robust enough or a high calibration effort has to be operated in order to obtain at least halfway acceptable results.Reference optical bodies have also been proposed, such as rigid bodies with markers which are attached to a plurality of planes. However, in order to locate each following vertebral body with six degrees of freedom (6 DOF / six degrees of freedom) (three degrees of freedom position--approximately x,y,z; three degrees of freedom orientation--approximately three angles), the reference body (approximately rigid body) as tracker needs a bulky and large design and has, for example, mechanical clamps or pins with an additional claw for rotational fixation. Also, due to the geometrically large structure, a visual connection is made more difficult and a (disadvantageous) line-of-sight problem (visual line problem) becomes very relevant. In addition, the reference body must have sufficient three-dimensional (3D) extent to allow precise spatial six-degree-of-freedom (6 DOF) tracking. However, a bulky tracker increases patient invasiveness, particularly during multi-level operations, such as three or more levels (3+), and a reference body of greater extent also risks collisions between the reference bodies of the individual vertebral bodies, as well as collisions between the reference bodies and a surgical instrument.US 2022 / 0192752 A1, for example, discloses a system for registration with an X-ray apparatus and a visible light camera. The x-ray apparatus captures a first x-ray image and the visible light camera simultaneously captures another visible light image. In addition, a further recording with a set positioning marker is recorded and a computer system provides a navigation interface.US 2021 / 0174950 A1 discloses a stereoscopic marking device with a polyhedral cube. This cube has at least four flat surfaces, the at least four flat surfaces being used as a primary marker. The primary marker comprises a primary graphical code, while three secondary markers individually comprise a first secondary graphical code, a second secondary graphical code, and a third secondary graphical code, and the primary graphical code is used to provide spatial coordinate information used for a six degree of freedom (6 DOF) location data calculation. The polyhedral cube is configured to be attachable to a vertebral body at an operative site.SUMMARY OF THE PRESENT DISCLOSUREIt is therefore the object of the present disclosure to avoid or at least reduce the disadvantages from the prior art and in particular to provide a bone tracker set and a bone tracking system with which even better bones can be tracked relative to one another. A sub-task can be seen in particular in performing a registration by means of an optical detection and an X-ray detection.The object of the present disclosure is achieved according to the invention by the features of claim 1 with respect to a bone tracker system, according to the invention by the features of claim 11 with respect to a bone tracking system and according to the invention by the features of claim 20 with respect to a bone tracking method.A basic idea of the present disclosure can therefore be seen in providing a system for (spatially) tracking a plurality of bones in relation to one another, in particular for spinal surgery, in which at least two bones, in particular vertebrae (bones), are tracked by fastening / anchoring or inserting a bone fixation, in particular as or in the form of a pin (as a particular embodiment), (for example in the spinous process), without a rotational stability being required. The bone fixations, in particular the pins, have a proximal end section (which is in particular adapted to protrude from the skin of the patient) to which a reference adapter, in particular a sleeve, can be coupled, in particular fastened. This reference adapter, in particular the sleeve as a particular embodiment of the reference adapter, has or carries an optical reference marker. Each optical reference marker enables a pose determination or position determination with a maximum of five, in particular four or five degrees of freedom (at least one rotation is still indeterminate). To determine the (at least) missing sixth degree of freedom for a one-to-one position determination, the optical reference marker of an, in particular adjacent, bone fixation and reference adapter, in particular a pin and sleeve, is used.Preferably, the system also allows registration of the patient when using a 3D intraoperative x-ray scanner by correlating the distal portion of the pencil in the x-ray image with the optical marker tracked by an optical camera system. In particular, no optical reference markers can be used for a registration and thus also the optical camera system cannot be used. Registration can be effected solely by bone fixation and a corresponding determination (for example via a software algorithm) which recognizes the position of the bone fixation in the bone, preferably of the pin as bone fixation, in the spinous process.In other words, according to the present disclosure, a bone tracker set is thus provided for a bone tracking system for tracking, and preferably further for registering, at least two bones (a plurality of bones) relative to one another, having: at least two bone fixations, in particular pins which are provided and adapted to be fastened directly to or in a bone of a patient (rigidly or in constant relation to the bone) by means of a distal bone anchor, wherein in each case a proximal end section has bone fixation, in particular of the pin, a coupling section (or fastening section), and at least two reference adapters, in particular sleeves, which each have or bear a proximal optical reference marker and the reference adapters, in particular sleeves, are adapted to be fastened to the coupling section of the respective bone fixation, In particular, the respective pin can be coupled or decoupled without tools.The advantage of this disclosure is in particular that the relative positions, in particular positions, of the bones, in particular of a plurality of vertebral bodies, can be tracked intraoperatively in real time, as a result of which the renewed positioning of the bones, in particular of the spinal column, into a desired state can be monitored. The disclosure further makes it possible to register a plurality of vertebral bodies at the same time by an X-ray scan and also prevents a renewed scanning of the patient with an X-ray scanner, for example, if the bones, in particular vertebral bodies, have moved relative to one another. The disclosure makes it possible to remove the reference adapters, in particular sleeves, with the optical reference markers (as trackers) at any time during the operation when the navigation is not currently required, and to reattach the optical reference markers without losing the registration, which in particular makes minimally invasive tracking possible.In yet other words, a bone tracker set with at least two bone trackers is proposed, wherein each bone tracker in this case has at least two separate components, namely a bone fixation device which is adapted to be fixed to or in a respective bone, and a reference adapter with an optical reference marker which can be coupled to and decoupled from the bone fixation device without tools by means of a coupling "interface". Thus, an optical reference marker can be attached and removed rapidly intra-operatively. The respective bone can be optically tracked (with the aid of the second bone tracker) via the optical reference marker. While an individual bone tracker is still underdetermined (approximately 4OF or 5OF), the bone tracker and thus the respective bone can be tracked unambiguously by means of two bone trackers.Thus, in particular, a form-fitting coupling "interface" is provided between the bone fixation on the one hand and the (separate but couplable and uncoupled) reference adapter / tracking adapter on the other hand, wherein the form-fitting does not have to include the rotation, whereby there is no complete determination with six degrees of freedom (6OF). In the case of rotatable / rotatable reference adapters, the coordinate system is constructed in particular on the analysis of two, preferably adjacent, reference adapters (each with the optical reference marker), that is to say on the basis of two times four determinable degrees of freedom (2x4 DOF) to form a complete set of specific degrees of freedom (1x6 DOF) and thus the tracked position of the respective bone (belonging to the reference adapter).Spatial tracking (tracking) can therefore be provided, wherein registration can additionally take place as a further option. However, it is also possible to register differently, for example by following a 3D scanner.According to an independent aspect, an associated analog method is provided which can determine the 6 DOF coordinate system of each individual bone, in particular vertebral body, on the basis of two (coupled) reference adapters (as tracker).With the present disclosure, the reference adapters and the optical reference markers can be determinable not only over five degrees of freedom (5 DOF) but also only over four degrees of freedom (4 DOF), if e.g. only the axis in space is known but not a specific point on the axis. By combining two axes each having 4 DOF, a 6 DOF coordinate system (and thus the position) can then be determined. It can also be said that each tracker has a maximum of five degrees of freedom (5 DOF), it then always being possible to determine 6 DOF by combination. An essential basic idea is thus that a single bone fixation with coupled reference adapter (as a single tracker) does not have six degrees of freedom (6 DOF), i.e. it does not have to be rotation-fixed and can be smaller.Advantageous embodiments are claimed in the dependent claims and are explained in particular below.According to one embodiment, at least one bone fixation, preferably all bone fixations, in particular a pin or the pins, can have a screw shaft with a (screw) screw thread as distal bone anchor in order to be screwed into the bone. In particular, the screw shank can be designed similar to a screw shank of a pedicle screw, for example with different thread pitches and / or a hollow shank and / or sharp cutting edges. The screw shaft extends distally and preferably coaxially with the remaining portion of the bone fixation, in particular of the pin. In particular, the bone fixation, in particular the pin (as a particular embodiment of the bone fixation), has two opposing "end" sections, on the one hand the distal screw shaft and on the other hand the proximal coupling section. In particular, bone fixations, in particular the pins, can have a helical distal end. Alternatively, the bone fixation, in particular the pin, can have a pin as a distal bone anchor in order to be fixed in the bone, preferably in a spinous process. Such a fixing by means of a pin can be carried out easily and efficiently, in particular since the fixing of the degree of freedom about the axis of rotation by the (bone) transducer, which has, for example, five degrees of freedom (5-DOF), is not required. Rotation about the longitudinal axis of the pin is possible as free and is not necessarily required for tracking. In one embodiment, the bone tracker set may also comprise a set with two bone fixations, wherein a first bone fixation has a screw shank and the second bone fixation has a pin as a bone anchor. Thus, for example, in a large bone, the first bone fixation can be screwed in by means of the screw shank, which is seated in a particularly fixed and stable manner, and in a smaller bone, the second bone fixation can be fixed with the pin, which is preferably designed in the form of a nail.Preferably, the bone fixations, in particular pins, have a (radially protruding) collar as a stop at the proximal end section. In particular, the collar is the termination or end stop of the coupling section, so that reference adapters, in particular sleeves, in particular the optical reference marker, coupled to the bone fixation, in particular the pin always have a fixed geometric relationship to the bone fixation, in particular the pin and the distal bone anchor. As a result, by detecting the optical reference pattern via the static, fixed relationship, it is possible to draw a conclusion directly on the distal bone anchor and thus on the bone. In particular, only one rotation remains as a degree of freedom, that is to say the sleeve with the optical reference markers can be rotated about its own axis on the pin. In particular, the pins have a collar at or near the proximal end so that the coupled sleeve has a fixed geometric relationship to the pin and the distal bone anchor. Thus, five degrees of freedom (5 DOF) can be determined with the stop, whereas only four degrees of freedom can be determined without a stop (4 DOF). In both cases, the rotation is open, so that two trackers or bone fixations with reference adapters are always required in order to determine the complete position with six degrees of freedom (6OF position).According to a further embodiment, the pins can have a cylindrical outer contour as coupling section and the sleeve can have a hollow cylindrical counter-coupling section which is correspondingly adapted to be plugged or can be plugged on over the cylindrical outer contour without tools, in particular by means of a clearance fit approximately or ) for easy coupling and decoupling (with pushing on and off) or a transition fit for stable coupling (for example wherein an external thread is preferably provided in the region of the end side of the cylindrical outer contour of the coupling section and a complementary internal thread is provided in the hollow cylindrical counter-coupling structure in order to provide a toolless secure coupling and decoupling. In particular in combination with a thread, the sleeve can first be pushed on and secured by means of approximately half a revolution or a whole revolution. By means of the cylindrical outer contour (of the coupling section) of the pin, in particular with a collar at a distal end of the coupling section, and the hollow cylindrical sleeve, which can be easily pushed on, an efficient and secure system or set can be provided. In particular, a diameter of the coupling section is at least 2 mm, preferably 4 mm and / or at most 10 mm, preferably at most 5 mm. The sleeve can thus be easily coupled (mounted) and uncoupled (dismounted) without tools during the engagement, so that the sleeve is coupled only when navigation is required.In particular, the coupling section (as or with the coupling structure) and the counter-coupling structure in the coupled state can form a magnetic connection / coupling (out), preferably at least one of the two coupling structures has a magnet which forms the magnetic connection. In the case of two magnets, these must have an opposite polarity; in the case of one magnet, a metallic (magnetically attracting) structure on the opposite side reaches. Thus, by means of the magnetic attachment, a risk of a relative movement in the axial direction can be prevented or at least minimized. In other words, a magnetic coupling is thus provided which is independent of the shape of the coupling section and of the counter-coupling structure (as a form-fitting interface). The magnetic coupling permits a stable connection without a tool. It can also be said that a type of closure securing means is provided by means of the magnetic coupling.Preferably, a dimension of the cylindrical coupling structure in the axial direction is at least 15 mm, preferably at least 30 mm, so that the coupling structure provides a sufficient length for a coupling.According to another embodiment, the bone fixation can also have a proximal sleeve and the reference adapter can be designed as a pin, wherein the optical reference marker is preferably attached to a proximal head. In this embodiment, the pin and sleeve are thus reversed with respect to the (special) embodiment described above.Preferably, a dimension of the end portion of the bone fixation, in particular of the pin, is at least 30 mm, in order to protrude from a skin of the patient in the implanted state.According to one embodiment, the sleeve can have a proximal sleeve head, in particular a conically shaped sleeve head (similar to a screen), with which optical reference markers are provided, on the outer surface (of the sleeve head) of which an optical pattern, in particular a circumferential QR code, is applied or entered, for example printed or engraved, as an optical reference marker. The optical reference body can thus be an optical pattern with characteristic visual features.According to a further embodiment, the reference adapter, in particular the sleeve, can have a proximal head, in particular a sleeve head, in the form of a flat disk (flat disk) with the optical reference marker, on the (proximal) outer surface of which (the flat disk toward the proximal) an optical pattern, in particular a circumferential QR code, is introduced or applied as an optical reference marker, for example printed on or engraved. A flat disk is cost-effective to produce and offers a good view from proximal to the optical reference marker. The flat disk is arranged concentrically to the longitudinal axis, and in particular symmetrically about the longitudinal axis. In one embodiment, the flat disk has a circular contour. Alternatively, the flat disk can also have an oval circumferential contour.In particular, the reference adapter can have a proximal head with two spaced apart marker balls arranged coaxially to a longitudinal axis of the reference adapter, which balls together form the proximal optical reference marker. Two marker spheres located on the longitudinal axis of the reference adapter are thus used as optical reference markers. with these marker spheres it is possible to determine a straight line in space through a reference point (i.e. 4D), further preferably even with a reference point (5OF).According to a further embodiment, the reference adapter, in particular the sleeve, can have a proximal head, in particular a sleeve head with at least two concentric rings, in particular have exactly two rings which are spaced apart from one another and are arranged both concentrically with respect to one another and with respect to a longitudinal axis of the sleeve, such that the rings, when the reference adapter is coupled to the bone fixation, in particular the sleeve to the pin, also have their center point in the axis of the bone fixation, in particular the pin. The optical reference body can thus have or consist of two rings in particular, wherein both rings ultimately have their center point in the axis (in particular of the pin) in the coupled state. In order to be able to track the rings better, it is sufficient if only one position of the ring can be detected by the optical camera, so that the ring can be extrapolated (by means of the adapted control unit) and the center point of the ring can be determined.Preferably, the at least two concentric rings may each have a unique optical pattern and / or have a different diameter to improve optical tracking. This makes it possible to directly infer a distal and proximal ring, as a result of which the position can be determined unambiguously, apart from approximately one degree of rotation. Each ring may in particular have a unique optical pattern to facilitate the localization of the ring with the optical camera.The present disclosure is achieved with respect to a bone tracking system for tracking, and further preferably for registering, at least two bones (a plurality of bones) relative to one another, in particular at least two spinal bones, in that it comprises: a bone tracker set according to the present disclosure, an optical camera for optically capturing the optical reference markers of the bone tracker set and for spatially tracking by a navigation system, a visual display device, in particular an OP monitor, and a control unit which is specifically adapted to capture and spatially track the at least two optical reference markers via the optical camera and for each optical reference marker (the reference adapter coupled to the bone fixation, in particular the sleeve coupled to the pin) a position determination with a maximum of five, in particular four or five, The method is configured to perform degrees of freedom (5D) and the control unit is adapted to determine the remaining sixth degree of freedom (at 5OF) or even fifth and sixth degrees of freedom (at 4D) on the basis of two, in particular adjacent, optical reference markers, and to visually output the position of the bones relative to one another via the display device in a live tracking mode, in particular with inserted anatomical parameters, such as preferably a sagittal plane or balance. In this disclosure, a bone tracking system is thus proposed which enables the tracking of a plurality of bones with minimally invasive bone anchors and (optical) reference bodies with a small profile.A particularly pin-shaped bone anchor (pin with distal bone anchor as an embodiment of bone fixation) is inserted into the bone, for example a spinous process, until sufficient longitudinal stability is achieved. While the distal section of the pin is anchored (as a bone fixation) to or in the bone, in particular is seated inside the bone, the proximal section of the pin projects outside the skin of the patient in an implanted state. In this case, rotational stability is not required. In the present case, at least two bones (for example vertebral bodies) are anchored. The proximal portion of the pin is configured to be couplable to a separate sleeve, in particular to fit within a separate sleeve inserted over the proximal portion of the pin with a fixed geometric relationship to the distal portion of the pin. The sleeve in turn carries an optical reference marker or reference body which enables tracking with an optical camera. Thus, in particular, the pin can be screwed into the bone, wherein an end rotational position / end rotation of the pin does not necessarily have to be observed and flexibility and handling on the operating table are increased.However, only (at most) five degrees of freedom can be determined for each bone (5 DOF), in particular four or five degrees of freedom (4 DOF or 5 DOF), since the bone tracking system or the bone tracking set have a rotational symmetry about an axis of the pin or can be rotated about the axis. More specifically, an axis is particularly located in space, with a reference point, i.e., five degrees of freedom (5 DOF). The optical reference marker, in particular the optical pattern, can therefore be symmetrical about the axis of the pen and have a low profile relative to the axis of the pen. In order to determine all six degrees of freedom (i.e. the full 6 DOF), a pin and a sleeve (as a reference body) of a bone, in particular a neighbouring bone, are used in order (at least) to determine the missing rotational degree of freedom, i.e. to include the missing rotational degree of freedom (rotational DOF). Therefore, the tracking of the location and the two rotation parameters of the first bone is not affected by the location of the second bone. Since the rotation of the first bone about the axis of the pin within the given spine is very unlikely, i.e. very small, errors of such movement can be neglected. In order to further reduce the error of the sixth degree of freedom (6 DOF) determined by a further, in particular adjacent, bone, a plurality of, in particular adjacent, bones can be used or used for determining the missing sixth degree of freedom of the first bone. The bones need not necessarily be directly adjacent. For example, the next but one bone, in particular next but one vertebral body, can also be used to determine the missing degree of freedom (by means of the optical reference marker).Preferably, the bone tracking system can have an intraoperative 3D x-ray scanner, and the control unit can be adapted to spatially capture (and optionally preferably also track) the pencil, in particular a distal section thereof, in a 3D x-ray image and to correlate the pencil in the x-ray image with the optical reference marker of an optical image of the optical camera, in order in particular to carry out a registration, preferably of the patient. Thus, the bone tracking system is also capable of registering a patient with a 3D intraoperative x-ray scanner. For example, the pegs are first inserted into all vertebral bodies to be treated. A 3D x-ray scan / 3D x-ray image is then recorded. The position of the distal end of the pins is then determined using the 3D x-ray dataset or the 3D x-ray image. In the 3D data set, the vertebral bodies must be segmented and registered separately. The correlation between the distal end of the pins and the sleeve fitted thereon is known by design. With the optical camera, the sleeves are localized with the optical reference marker (or body). Five degrees of freedom (5 DOF) can be determined with each pin (only one rotation about the pin is missing). Using two pens, the full six degrees of freedom (6 DOF) can be determined so that full spatial tracking is possible. Thus, two pins and sleeves are also required for the spatial tracking (tracking) of at least two bones. Moreover, registration may be performed, if necessary, by means of additional features on the pen or pens visible in the 3D x-ray scan. However, it is the case that the sleeve can only be detected with five degrees of freedom (5 DOF) even in the 3D x-ray scan.In particular, registration with two bone fixations, in particular pins, can be performed in the 3D x-ray scan ("X-ray image"). In this case, the bone fixations, in particular pins, initially provide only four degrees of freedom (4 DOF) (a straight line in space). By evaluating two bone fixations, in particular two pins, a 6 DOF registration can then be determined from 2x4 DOF (2 skew straight lines span a coordinate system). However, this only occurs if the lines are not parallel. Otherwise, a point on the straight line must also be determined for at least one of the straight lines-this can be the distal end in particular. Five degrees of freedom have thus been determined (5 DOF) and registration can be carried out unambiguously even in the case of parallel straight lines.In one embodiment, the control unit can be adapted to capture the position, in particular position, of each ring by the optical camera in the case of optical reference markers in the form of at least two rings and to determine the first center point of the first ring and the second center point of the second ring by means of calculation, in particular extrapolation, in order to determine the position of the pin (and thus the position of the associated bone) by means of the determination of the two centers.According to an embodiment, the optical camera may be a white light camera or an infrared camera.In particular, the bone tracking system may comprise a medical mobile cart which carries the optical camera and which is in particular adapted to be placed next to an operating table. Thus, the optical camera can be mounted on a carriage which can be located next to the surgical table.Preferably, during the X-ray recording, the position of the optical reference markers can also be detected with a microscope, and the position of the 3D X-ray scanner / X-ray system can likewise be detected with the microscope, wherein the X-ray system or X-ray device is calibrated. In this way, the position of the reference markers can be determined via two acquisition modes.Preferably, the bone tracking system may comprise a medical robot and the optical camera may be attached to a robot arm of the robot, wherein the camera is positionable over a patient by means of the robot arm to avoid or minimize line of sight problems. In other words, the optical camera can be mounted on a robotic arm positionable over the patient, thereby minimizing line of sight problems.In particular, the optical camera can be a surgical visualization system, in particular an exoscope, or can occur in such a system that carries out two functions, a surgical visualization as well as an optical tracking, or the optical camera is an optical camera that is separate from a surgical visualization system, such as an exoscope, and can be positioned in particular next to an exoscope. In other words, the optical camera can simultaneously be a surgical visualization system such as an exoscope or a separate camera, which can be positioned next to the exoscope.In one embodiment, in addition to the live tracking mode, the bone tracking system can also be operable in a scanning mode in which the control unit is adapted to move the optical camera by means of a robot arm in such a way that it scans the optical patterns and visually outputs the positions, in particular positions, of the vertebral bodies with respect to one another in a static display via the display device. In other words, in addition to the live tracking mode, a scanning mode can also be provided in which the optical camera travels and scans the optical reference markers, in particular the optical patterns, and displays the positions of the vertebral bodies with respect to one another in a static display. Such an operation can be repeated each time the bones, in particular the spinal column, are repositioned.In particular, the pin has dimensions such that at least 1 cm, preferably at least 3 cm, protrude from the skin of the patient in a state anchored in the bone.In particular, the optical camera can be easily positioned when mounted on a robot arm in order not to impair the ergonomy for the surgeons and at the same time to enable good tracking.Preferably, pre-OP planning software can be provided in a memory unit, which allows the navigation system to plan the desired positions between the bones, in particular the vertebral bodies, in advance.In particular, the control unit can be adapted to display the positions of the vertebral bodies relative to one another intra-operatively in a live tracking mode, wherein in particular anatomical parameters such as the sagittal balance are calculated and additionally displayed.In particular, surgical instruments can also be tracked as patient trackers with the bone tracking system, either using the same optical camera to track the reference optical bodies or reference optical bodies of the instruments, or tracking the instruments with a separate optical (instrument) camera, with both cameras having to be calibrated to one another or tracked with respect to one another.With regard to a bone tracking method for tracking at least two bones relative to one another, in particular at least two spinal bones, the object is achieved according to the present disclosure in that it comprises the steps:tracking, by means of a bone tracking system, in particular a bone tracking system according to the present disclosure, two bone trackers of a bone tracker set each having a bone fixation anda reference adapter, in particular a bone tracker set according to the present disclosure, wherein the reference adapter each has a proximal optical reference marker;determining an axis of the first bone fixation, in particular a unit vector of a first pin, which coincides with the main axis of the bone fixation;determining an origin of coordinates of the first bone fixation;determining a second line or axis that lies in the plane spanned by the first optical reference pattern intersecting the axis of the second bone fixation;determining the third axis by the vector product of the first axis and the second axis;determining a Cartesian coordinate system of the first bone fixation and thus of the first bone with the coordinate origin and the three axes for a tracking of the bone fixation and thus of the bone.Another aspect of the present disclosure relates to a computer readable storage medium and a computer program, each comprising instructions which, when executed by a computer, cause the computer to perform the method steps of the bone tracking method.In particular, the control unit (analog) of the bone tracking system may be adapted to perform the corresponding steps of the bone tracking method.Brief Description of the FiguresThe present disclosure will be explained below by way of preferred embodiments with reference to the accompanying figures. The following are shown: FIG. 1 is a schematic view of a bone tracking system of a preferred embodiment of the present disclosure including a bone tracker set according to a first preferred embodiment of the present disclosure; FIG. 2 is a detailed view of the bone tracker set of FIG. 1 ; FIG. 3 shows a schematic view of a bone tracker set according to a further preferred embodiment; FIG. 4 shows a schematic view of a pin of the bone tracker set in an x-ray image; FIG. 5 is another schematic view of pins of the bone tracker set; FIG. 6 is a schematic view of a bone tracking set illustrating calculations and relationships between pins and sleeves of individual bones; FIG. 7 shows a schematic view of a bone tracker set according to a further preferred embodiment with marker balls; FIG. 8 shows a schematic view of a bone tracker set according to a further preferred embodiment with a flat disc; and FIG. 9 is a flow diagram of a bone tracking method according to a preferred embodiment.The figures are schematic in nature and are intended only to aid in understanding the invention. Identical elements are provided with the same reference numerals. The features of the various embodiments may be interchanged.DETAILED DESCRIPTION OF PREFERRED EMBODIMENTSFIG. 1 shows a bone tracker set 1 according to a first preferred embodiment of the present disclosure and a bone tracking system 100 according to a first preferred embodiment of the present disclosure, wherein a detailed view of the bone tracker set 1 is illustrated in FIG. 2.Specifically, a bone tracker set 1 for the bone tracking system 100 is shown in FIG. 1 (and FIG. 2 ) for tracking and registering at least three vertebral (columnar) bones (as bones) relative to one another. The bone tracker set 1 has three pins 2 (as an embodiment of a bone fixation) which are each adapted to be fastened directly in a vertebral bone of a patient P by means of a distal bone anchor 4. Except for the bone anchor 4, the pins 2 are designed to be substantially rotationally symmetrical. Each pin 2 has a proximal end section 6 with a coupling section 8 for coupling a sleeve 10 (as an embodiment of a reference adapter). Specifically, three separate sleeves 10 are provided which carry a proximal optical reference marker 12 for optical (spatial) tracking. The sleeves 10 are correspondingly adapted to be coupled or decoupled to the coupling section 8 of the pin 2 without tools. Here, the sleeves 10 have a counter-coupling structure 14, which is described in more detail below.The bone tracking system 100 (hereinafter referred to only as system 100) for tracking and registering the three vertebrae (columns) bones relative to one another is designed in the form of a robot-guided surgical microscope and in turn has an optical camera 102 for optically capturing the optical reference markers 12 of the bone tracker set 1 for spatial tracking by a navigation system 104. In this case, the microscope head itself is used as an optical camera 102, with the result that the camera 102 is used both for surgical visualization and for optical tracking. The system 100 further has a visual display device 106 in the form of an surgical monitor, which can optionally also be supplemented by a head-mounted display. In addition, a control unit 108 of the system 100 is specifically adapted to capture the at least three optical reference markers 12 via the optical camera 102 and to track them spatially and to carry out a position determination with five degrees of freedom (5OF) for each optical reference marker 12. For this purpose, the control unit 108 is further adapted to determine the remaining sixth degree of freedom on the basis of two adjacent optical reference markers 12, and to visually output the position of the bones relative to one another via the display device 106 in a live tracking mode, in particular with inserted anatomical parameters, such as preferably a sagittal plane or balance. In particular, the control unit 108 is adapted to make such a determination as will be described with reference to FIG. 6.In addition to the optical camera 102, the system 100 also has a (separate) navigation camera 118 which tracks the optical camera 102 by means of a rigid body having four markers, among other things. The system 100 as a whole is arranged on a medical cart 112 so that it can be placed in a mobile manner in the operating room.In this embodiment, the system 100 has a medical robot 114 as a robot-guided surgical microscope, wherein the optical camera 102 is connected to a multi-link robot arm 116 of the robot 114, such that the camera 102 can be positioned over the patient P by means of the robot arm 116, as shown in FIG. 1, in order to avoid line-of-sight problems and ensure precise tracking.The bone tracker set 1 from FIGS. 1 and 2 will now be described in detail below. Specifically, in this embodiment of FIGS. 1 and 2, each pin 2 has a distal screw shank 16 with an external thread 18 as a distal bone anchor 4, which is screwed into a spinous process of the vertebral bone in each case. Thus, the pin 2 is securely fixed in the respective bone.Furthermore, the pins 2 have a collar 18 at the proximal end section 6 as an axial stop, here as an end stop of the coupling section 8, so that the sleeves 10 coupled to the pin 2 and the optical reference marker 12 thereof always have a fixed geometric relationship to the pin 2 and the distal bone anchor 4. Here, in particular a tip of the bone screw or of the screw shank is relevant as a reference. For example, a distance between the center of the one ring to the screw tip is 60 mm and from the center of the proximal ring is 65 mm. In this way, by means of the navigation system 104, the respective bone can be directly deduced by detecting the optical reference marker 12, in particular if a recording with implanted pins 2 (and optionally a registration with 3D data of the patient) has already been carried out by means of a 3D X-ray device 110.The pins 2 each have a cylindrical outer contour 20 as coupling section 8, and the sleeve 10 has a hollow cylindrical counter-coupling section 14, which is correspondingly adapted to be inserted manually by a medical professional such as a surgeon without tools via the cylindrical outer contour 20. As a result, the optical reference marker 12 can be coupled and decoupled easily and reliably. If navigation is therefore required, the sleeves 10 can be pushed on quickly and can also be removed again for a further intervention, in order, for example, to enlarge a field of view or to enable better handling of the surgeon in the region of the spinal column.In this embodiment, the sleeve 10 has a proximal sleeve head 24 with exactly two concentric rings 30, which are spaced apart from one another and are arranged both concentrically with respect to one another and with respect to a longitudinal axis 32 of the sleeve 10, so that the rings 30 in the coupled state of the sleeve 10 with the pin 2 also have their center point in the axis of the pin 2. As in the present case, the rings 30 can have a different color marking or have a specific optical pattern and / or a different diameter, for example the distal ring 30 can have a larger diameter than the other ring 30. For example, the rings 30 may be secured to the sleeve 10 by radial struts, such as three struts.The control unit 108 of the system 100 is correspondingly adapted to capture the position of each ring 30 by the optical camera 102 with the three optical reference markers 12 in the form of exactly two rings 30, and to determine the first center point of the first ring and the second center point of the second ring by means of calculation, in particular extrapolation, in order to determine the position of the pin 2 and thus of the associated vertebral bone by means of the determination of the two center points and the known reference to a tip of the pin 2.With the system 100, a spatial tracking of the three vertebral bones (relative to one another) of the patient P can thus be carried out with a minimally invasive bone anchor 4 in each case in the form of a screw shank 16 and connectable and decoupled optical reference markers 12 with a small construction. The pin 2 with distal bone anchor 4 is thus initially screwed into the spinous process until sufficient longitudinal stability is achieved. The proximal portion of the pin 2 projects out of the skin of the patient P due to the geometrical adjustment, as shown in FIGS. 1 and 2, in order to provide the coupling portion 8 outside the patient P. Each proximal section of the pin 2 can be coupled to the separate sleeve 10, which in turn carries the optical reference marker 12, respectively.Only five degrees of freedom can be determined for each vertebral bone by means of the optical camera 102, the control unit 108 and the navigation system 104, since the system 100 or the bone tracking set 1 respectively has a rotational symmetry about an axis of the stylus 2 or longitudinal axis 32. For each pen 2 with optical reference markers 12, the system 100 locates an axis in space with a reference point, in particular the screw shank tip, i.e. with five degrees of freedom.Now, in order to determine all six degrees of freedom for a one-to-one position (6OF), the pin 2 and the sleeve 10 of the adjacent vertebral bone are used to determine the lack of rotational degree of freedom. Since the rotation of the first vertebral bone about the axis of the pin 2 within the spinal column is very small, errors due to such a movement are neglected, since a sufficiently high precision of the spatial tracking can furthermore be achieved with the system 100. In this way, the system 100 can be used intraoperatively to track the spinal column or its bones easily and precisely.FIG. 3 shows another embodiment of the bone tracker set 1 according to the present disclosure. The bone tracker set 1 is designed substantially the same as the bone tracker set 1 of the first preferred embodiment from FIGS. 1 and 2, but differs from the first preferred embodiment in that the optical reference marker 12 is not designed in the form of two rings, but rather in the form of a sleeve 10 with a proximal conically shaped sleeve head 24, on the outer surface 26 of which an optical pattern 28 in the form of a symmetrical, encircling QR code is applied as optical reference marker 12. Thus, an optical pattern 28 can be detected with a flat profile. The bone tracker set 1 can be used alternatively or additionally to that from FIG. 1 in the system 100 from FIG. 1. Accordingly, the control unit 108 is adapted to also perform a position determination for a spatial tracking by means of the optical pattern 28 in addition to the rings.In particular, this bone tracker set 1 of FIG. 3 can have a magnet in the reference adapter (which is introduced, for example, inside the sleeve on a proximal side, so that a force-fit, magnetic tool-free connection (and thus also securing) is provided.FIG. 4 shows a schematic view of a pen 2 in an X-ray image. The screw shank 16 is screwed into the spinous process and (apart from the thread) the pin 2 is designed to be rotationally symmetrical about its longitudinal axis. In the X-ray image, it is therefore even possible to perform a registration of the patient by means of the pen 2, which in particular has metal as material in order to be well recognized in the X-ray image, by the control unit being adapted to locate the pens 2 in the X-ray image and to correlate them with the pens of the optical image by the optical camera 102 and thus track them and furthermore in particular to register the patient. After the detection of the pegs and the segmentation of the vertebral bodies, the registration is carried out by matching the intraoperative X-ray images with the already existing CT and MRI scans.Now, as shown in FIG. 5, when multiple pins 2 are screwed into the vertebral bodies, which may be performed conventionally, the system 100 may reduce the sixth degree of freedom (6 DOF) to be determined determined determined determined by an adjacent bone by using multiple adjacent bones to determine the missing sixth degree of freedom of the first bone, as will be explained below with reference to FIG. 6.In Figure 6, the relationships to each other are shown and the steps are shown, indicating how the coordinate systems are constructed for each vertebral bone (for tracking):Here, 0 1 is the (coordinate) center of the optical reference marker 12 of the first pin 2 screwed into the vertebral bone. The unit vector e z represents the principal axis of the optical reference marker 12 (which coincides with the axis of the pen 2). Specifically, the unit vector in y-direction e y is fixed to the line which lies in the plane defined by the first optical reference marker 12 (or its optical pattern; of the first pin 2) (0 1, normal to the unit vector in z-direction e z) and intersects the (second) axis (O 2, e z2) of the adjacent second pin 2. The remaining (and to be determined) unit vector in the x-direction e x is then unambiguously determined by the vector product of e z and e y. Thus, O 1, e x, e y, e z form a Cartesian coordinate system and the position of the optical reference marker 12 and thus also of the associated vertebral bone (a static determinable transformation is always present on account of the screwing into the latter).If the system 100 now determines the "local" KOS of the pencil for each optical reference marker 12, then a tracking of the pencil and thus of the respective vertebral bones can be carried out intraoperatively.The procedure for the determination can also be summarized as described below in formulae:Accordingly, the control unit 108 of the system 100 is adapted to determine the coordinate systems (KOS) to perform patient tracking and even registration.FIG. 7 shows another embodiment of a bone tracker set 1 of the present disclosure. In contrast to the above optical patterns as machine vision patterns, two passive marker balls 34 are now provided on the proximal head. This embodiment also allows simple, efficient tracking and also cost-effective production. In this embodiment, a magnet is provided in the reference adapter (within the sleeve) (not shown), so that a force-fit, magnetic connection is provided.FIG. 8 likewise shows a further embodiment of a bone tracker set 1 of the present disclosure, with the difference that a flat disk 36 is arranged on the proximal head, on the (proximal) upper side of which a visual pattern 28 is introduced (not illustrated here since a view onto the lower side of the flat disk 36).As an alternative to bone fixation in the form of a pin 2 with a screw shank 16 with an external thread 18, a pin can also be provided as a bone anchor, which is fixed in the bone. For example, the pin can be designed in the form of a nail which is pressed or driven into the bone.FIG. 9 illustrates a bone tracking method according to a preferred embodiment. The bone tracking method serves for tracking at least two bones relative to one another, in particular at least two spinal bones,In a first step S 1, a tracking takes place by means of a bone tracking system 100 according to the present disclosure, of two bone trackers of a bone tracker set having in each case a bone fixation and a reference adapter of a bone tracker set 1 according to the present disclosure, wherein the reference adapter in each case has a proximal optical reference marker. In step S 2, an axis e z1 of the first bone fixation, in particular a unit vector e z1 of a first pin, which coincides with the main axis of the bone fixation, is determined;In step S 3, a coordinate origin O 1 of the first bone fixation is determined, and in step S 4, a line or second axis e y1, which lies in the plane spanned by the first optical reference pattern O 1 Nomale e z1 and intersects the axis e z2 of the second bone fixation, is determined.In step S 5, a third axis e x1 is further determined by the vector product of the first axis e z1 and the second axis e y1; and finally a cartesian coordinate system of the first bone fixation and thus of the first bone is determined with the coordinate origin O 1 and the three axes e x1, e y1, e z1 for a tracking of the bone fixation and thus of the bone.List of reference characters1 Bone tracker set 2 Pin 4 Bone anchor 6 Proximal end section 8 Coupling section 10 Sleeve 12 Optical reference marker 14 Counter-coupling structure 16 Screw shaft 18 Collar 20 Cylindrical outer contour 22 External thread 24 Sleeve head 26 Outer surface 28 Optical pattern 30 Ring 32 Longitudinal axis 34 Marker ball 36 Flat disk 100 Bone tracking system / system 102 Optical camera 104 Navigation system 106 Display device 108 Control unit 110 3D X-ray scanner / 3D X-ray device 112 Medical carriage 114 Medical robot 116 Robot arm 118 Navigation camera P PatientReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedUS 2022 / 0192752 A1

[0005] US 2021 / 0174950 A1

[0006]

Claims

A bone tracker set (1) for a bone tracking system (100) for tracking, preferably further for registering, at least two bones relative to one another, comprising: at least two bone fixations, in particular two pins (2) which are provided and adapted to be fastened directly to or in a bone of a patient (P) by means of a distal bone anchor (4), wherein in each case a proximal end section (6) of the bone fixation, in particular of the pin (2), comprises a coupling section (8), and at least two reference adapters, in particular two sleeves (10) which comprise or carry a proximal optical reference marker (12) and the reference adapters, in particular sleeves (10), are adapted to be couplable or decoupled in each case at the coupling section (8) of the bone fixation, in particular of the pin (2), without tools, in particular, a counter-coupling structure (14).Bone tracker set (1) according to claim 1, characterised in that the bone fixations, in particular pins (2), have a screw shank (16) with an external thread (18) as distal bone anchors (4) in order to be screwed into the bone, or the bone fixations, in particular pins (2), have a pin as distal bone anchors (4) in order to be fixed into the bone, preferably in a spinous process.Bone tracker set (1) according to claim 1 or 2, characterised in that the bone fixations, in particular pins (2), have a collar (18) at the proximal end section (6) as an axial stop, in particular as an end stop of the coupling section (8), so that reference adapters, in particular sleeves (10), most particularly the optical reference marker (12), coupled to the bone fixation, in particular to the pin (2), always have a fixed geometric relationship to the bone fixation, in particular the pin (2), and the distal bone anchor (4).Bone tracker set (1) according to one of the preceding claims, characterized in that the bone fixations have as pins (2) a cylindrical outer contour (20) as coupling section (8) and the reference adapter has as sleeve (10) a hollow cylindrical counter-coupling section (14) which is adapted to be fitted over the cylindrical outer contour (20) without tools, in particular by means of a clearance fit for easy coupling and decoupling or a transition fit for stable coupling, wherein an external thread (22) is preferably provided in the region of the end face of the cylindrical outer contour (20) of the coupling section (8) and a complementary internal thread is provided in the hollow cylindrical counter-coupling structure (14) in order to provide a toolless secure coupling and decoupling by means of screwing.Bone tracker set (1) according to one of the preceding claims, characterized in that the reference adapter, in particular sleeve (10), has a proximal head, in particular sleeve head (24), in particular a conically shaped sleeve head (24), with the optical reference marker (12), on the outer surface (26) of which an optical pattern (28), in particular a circumferential QR code, is applied or introduced as an optical reference marker (12).Bone tracker set (1) according to one of claims 1 to 4, characterised in that the reference adapter has as a sleeve (10) a proximal sleeve head (24) with at least two concentric rings (30), which are spaced apart from one another and arranged both concentrically with respect to one another and with respect to a longitudinal axis (32) of the sleeve (10), so that the rings (30) in the coupled state of the sleeve (10) with the pin (2) also have their centre point in the axis of the pin (2).The bone tracker set (1) according to claim 6, characterized in that the at least two concentric rings (30) each have a one-to-one optical pattern and / or have a different diameter to improve optical tracking.Bone tracker set (1) according to one of the preceding claims, characterized in that the coupling section (8) of the bone fixation and a counter-coupling structure (14) of the reference adapter are adapted to form a magnetic connection with one another as a magnetic coupling in the coupled state, in particular the coupling section (8) and / or the counter-coupling structure (14) has a magnet for the magnetic connection in order to provide a toolless secure coupling and decoupling.Bone tracker set (1) according to one of the preceding claims, characterized in that the reference adapter has a proximal head in the form of a flat disc (36) with the optical reference marker (12), on the outer surface of which an optical pattern, in particular a revolving QR code, is applied or deposited as an optical reference marker, for example printed or engraved.Bone tracker set (1) according to one of the preceding claims, characterized in that the reference adapter has a proximal section with two marker balls which are spaced apart from one another and arranged coaxially with respect to a longitudinal axis of the reference adapter and together form the proximal optical reference marker (12).A bone tracking system (100) for tracking at least two bones relative to one another, in particular at least two spinal bones, comprising: a bone tracker set (1) according to one of the preceding claims, an optical camera (102) for optically capturing the optical reference markers (12) of the bone tracker set (1) for spatial tracking by a navigation system (104), a visual representation device (106), in particular an OP monitor or a head-mounted display, and a control unit (108) which is specifically adapted to capture and spatially track the at least two optical reference markers (12) via the optical camera (102) and to perform a position determination with a maximum of five degrees of freedom, in particular four or five degrees of freedom, for each optical reference marker (12), wherein the control unit (108) is further adapted to, based on two, in particular adjacent, optical reference markers (12), at least to determine the remaining sixth degree of freedom, and to visually output the position of the bones relative to one another via the display device (106) in a live tracking mode.Bone tracking system (100) according to claim 11, characterised in that the bone tracking system (100) comprises an intraoperative 3D X-ray scanner (110), and the control unit (108) is adapted to spatially capture and track the bone fixation, in particular the pin (2), in particular a distal section thereof, in a 3D X-ray image and to correlate the bone fixation, in particular the pin (2), in the X-ray image with the optical reference marker (12) of an optical image of the optical camera (102) in order to carry out a registration.Bone tracking system (100) according to claim 12, characterised in that the bone tracking system (100) is further adapted for registering at least two bones relative to one another, in particular at least two spinal bones, wherein the control unit is adapted to record the bone fixations, in particular the pins (2), in the 3D x-ray image, to determine four or five degrees of freedom each for these bone fixations, in order to determine the six degrees of freedom based thereon.Bone tracking system (100) according to one of claims 11 to 13, characterised in that the control unit (108) is adapted to record the position, in particular position, of each ring (30) by the optical camera (102) with optical reference markers (12) in the form of at least two rings (30) and to determine the first centre point of the first ring and the second centre point of the second ring by means of calculation, in particular extrapolation, in order to determine the position of the pin by means of the determination of the two centre points.The bone tracking system (100) according to any one of claims 11 to 14, characterized in that the optical camera (102) is a white light camera or an infrared camera.The bone tracking system (100) according to any one of claims 11 to 15, characterized in that the bone tracking system (100) comprises a medical mobile cart (112) which carries the optical camera (102) and which is in particular adapted to be placeable next to an operating table.The bone tracking system (100) of any of claims 11 to 16, characterized in that the bone tracking system (100) comprises a medical robot (114) and the optical camera (102) is linked to a multi-link robot arm (116) of the robot (114), wherein the camera (102) is positionable over a patient (P) by means of the robot arm (116) in order to avoid or minimize line-of-sight problems.Bone tracking system (1) according to one of claims 11 to 17, characterised in that the optical camera (102) is a surgical visualization system, in particular an exoscope or a surgical microscope, which carries out two functions of optical visualization and spatial tracking, or the optical camera is an optical camera separate from a surgical visualization system, such as an exoscope, which can be positioned in particular next to an exoscope.Bone tracking system (100) according to one of claims 17 or 18, characterised in that in addition to the live tracking mode, the bone tracking system (100) can also be operated in a scanning mode, in which the control unit (108) is adapted to move the optical camera (102) by means of a robot arm (116) in such a way that it scans the optical reference markers (12), in particular the optical patterns (28), and visually outputs the positions of the bones, in particular vertebral bodies, with respect to one another in a static display via the display device (106).A bone tracking method for tracking at least two bones relative to each other, in particular at least two spinal bones, characterized bythe steps: tracking (S1) by means of a bone tracking system, in particular a bone tracking system (100) according to any one of claims 11 to 19, two bone trackers of a bone tracker set each having a bone fixation and a reference adapter, in particular a bone tracker set (1) according to any one of claims 1 to 10, wherein the reference adapter each has a proximal optical reference marker (12); determining (S2) an axis (e z1) of the first bone fixation, in particular a unit vector (e z1) of a first pin, which coincides with the main axis of the bone fixation; determining (S3) an origin of coordinates (O 1) of the first bone fixation; determining (S4) a line or second axis (e y1), which lies in the plane spanned by the first optical reference pattern (O 1, Nomale e z1) and intersects the axis (e z2) of the second bone fixation; determining (S5) a third axis (e x1) by the vector product of the first axis (e z1) and the second axis (e y1); determining a Cartesian coordinate system of the first bone fixation and thus of the first bone with the coordinate origin (O 1) and the three axes (e x1, e y1, e z1) for a tracking of the bone fixation and thus of the bone.

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