Cutting device for installing knee prostheses

Abstract

The present invention relates to a cutting device (1) for the installation of a knee prosthesis, comprising a bracket (4) and a cutting guide (2) movably mounted relative to said bracket (4), the bracket (4) comprising a first marker (43) for its identification and a fixation element (42) for fixing it to the bone, the cutting guide (2) comprising a second marker (23) for its identification and a slot (21) defining a cutting plane suitable for guiding a cutting tool. The present invention also relates to a system including an auxiliary device and the cutting device. The present invention further relates to an auxiliary method, as well as a computer program product and a data storage medium for carrying out the method.

Description

Detailed Description of the Invention

[0001] The present invention relates to a cutting device for installing a knee prosthesis. The present invention also relates to a cutting assistance device comprising such a cutting device. The present invention also relates to a method for assisting the installation of a knee prosthesis and the use of said device. The present invention further relates to an assistance system for implementing said method, a computer program product for implementing said method and a storage medium comprising the steps of said method.

[0002] To install a knee prosthesis in a patient, it is first necessary to cut the tibia and femur at their ends adjacent the knee. The bone cuts are delicate and the surgeon must be careful to remove as little bone as possible, but enough bone to provide a flat surface and sufficient space for the placement of the prosthesis components. Furthermore, the cutting angle is very important. Lack of precision in the operation causes significant risks of pain felt by the patient, instability, premature wear, or dislocation. For this purpose, very complex devices exist with numerous auxiliary instruments, and these systems have the disadvantage of being very expensive and not widely available.

[0003] It is an object of the present invention to provide an apparatus and method to assist a surgeon in identifying cut planes in the tibia or femur for the placement of a knee prosthesis, in particular to simplify the identification of the cut planes with optimization of accuracy.

[0004] According to a first aspect, the present invention relates to a cutting device for the installation of a knee prosthesis comprising a bracket and a cutting guide movably attached to said bracket, the bracket having a first marker for its positioning and a fixing element for attaching it to the bone, and the cutting guide having a second marker for its positioning and a slot defining a cutting surface suitable for guiding a cutting tool.

[0005] In one embodiment, the cutting guide is movably mounted to the bracket according to at least one translational degree of freedom. In one embodiment, the cutting guide is movably mounted to the bracket according to at least two rotational degrees of freedom.

[0006] In one embodiment, the cutting guide is movably mounted to the bracket via an articulation assembly that allows movement of the cutting guide relative to the bracket. In one embodiment, the first marker and the second marker have a rectangular plane that includes at least one pattern.

[0007] In one embodiment, the cutting guide includes a fixation element for attachment to bone. According to a second aspect, the present invention relates to a cutting assistant device for installing a knee prosthesis comprising at least one cutting device according to the first aspect of the invention and at least one point inspection tool having a positioning point and a third marker for identifying the position thereof.

[0008] In one embodiment, the auxiliary device comprises a first cutting device according to the first aspect of the invention designed for cutting the tibia and a second cutting device according to the first aspect of the invention designed for cutting the femur.

[0009] No. 3 According to one aspect, the present invention relates to a method for assisting in the placement of a knee prosthesis. The method comprises: - a first step of positioning a cutting device according to a first aspect of the invention, the cutting device comprising a cutting guide movable in three degrees of freedom relative to a bracket of the cutting device; a second step of assisting in positioning the cutting guide relative to the bracket, a step of visualization by one camera of a first marker of the bracket and creation of a reference coordinate system [reference marker] defined relative to the first marker; visualizing the first marker and the second marker; communicating and displaying to the surgeon the three-dimensional relative positioning of the cutting guide and / or its cutting surface with respect to a reference coordinate system [fiducial marks]; A second stage including: Includes.

[0010] In one embodiment, the reference coordinate system [fiducial marker] has two reference axes. In one embodiment, the formation of the reference coordinate system [reference marker] includes: - generating a reference point; - forming a first reference axis passing through the reference point and a predetermined point relative to the first marker; - forming a second reference axis determined by projecting the known axis of the bracket onto a plane perpendicular to the first reference axis; Includes.

[0011] In one embodiment, the method is suitable for cutting the tibia and the reference point is placed on the mechanical axis of the tibia. In one embodiment, the generation of the reference point is performed by visualizing a third marker of a point inspection tool relative to the first marker for locating said reference point.

[0012] In one embodiment, the method is suitable for cutting a femur and the reference point is placed on the mechanical axis of the femur. In one embodiment, generating the reference point includes the sub-steps of moving a patient's leg to identify a center of rotation of said leg, and visualizing multiple images of the first marker and a third marker fixed relative to the patient's pelvis while moving the leg.

[0013] According to a fourth aspect, the invention relates to a system for assisting the placement of a prosthesis, comprising a cutting device according to the first aspect of the invention, a moveable monocular camera, in particular attached to a pair of glasses or a portable object such as a phone, display means and means for implementing the assistance method according to the third aspect of the invention.

[0014] In one embodiment, the visualizing step is performed by said camera and the communicating step is performed by said display means. According to a fifth aspect, the present invention relates to a computer program product comprising program code instructions stored on a computer readable medium for performing the steps of the method according to the third aspect of the invention when said program is executed on a computer, or to a computer program product downloadable from a communications network and / or stored on a computer readable medium and / or a computer executable data carrier, the computer program product comprising instructions for causing the computer to perform the method according to the third aspect of the invention when said program is executed by a computer.

[0015] According to a sixth aspect, the present invention relates to a data storage medium having recorded thereon a computer program readable by a computer and comprising program code instructions for carrying out the method according to the third aspect of the invention, or a computer readable storage medium comprising instructions which, when executed by a computer, direct the computer to carry out the method according to the third aspect of the invention.

[0016] The accompanying drawings show, by way of example, an embodiment of a cutting device according to the invention and an embodiment of a system according to the invention. [Brief description of the drawings]

[0017] [Figure 1] 1 shows a perspective view of a cutting device according to one embodiment of the present invention; [Diagram 2] 1 shows a front view of a cutting device according to an embodiment of the present invention. [Diagram 3] 1 shows a front view of the cutting device with the cutting guide being moved by the first means for operating the articulating assembly; [Figure 4] 1 shows a side view of a cutting device according to one embodiment of the present invention. [Diagram 5]1 illustrates a side view of an apparatus according to one embodiment of the present invention, where the cutting guide is moved by a second means for operating the articulation assembly. [Figure 6] 1 shows a perspective view of a pointer for implementing a method according to an embodiment of the present invention; [Figure 7] 1 shows a perspective view of a clamp for carrying out a method according to an embodiment of the present invention; [Figure 8] FIG. 8 shows a perspective view of the clamp of FIG. [Figure 9] 1 illustrates a perspective view of a cutting guide according to one embodiment of the present invention. [Figure 10] 1 shows a schematic diagram of an auxiliary system according to one embodiment of the present invention. [Figure 11] FIG. 2 shows a schematic diagram of steps performed by a computer of an auxiliary system according to an embodiment of the present invention. [Figure 12] 1 shows a profile view of a tibia with a cutting device attached according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An example of a cutting device 1 for installing a knee prosthesis according to one embodiment of the present invention is described below with reference to FIG. The cutting device 1 comprises a positioning frame 3 and a cutting guide 2. The positioning frame 3 allows the device 1 to be fixed to the bone to be cut, and the movable cutting guide 2 has a slot 21 through which a cutting tool can be guided to perform the cut in the bone.

[0019] The positioning frame 3 comprises a bracket 4 and an articulating assembly 5. The bracket 4 is designed to be attached to the bone to be cut. The cutting guide 2 is movably attached to said bracket 4. The articulating assembly 5 is designed to be movable relative to the bracket 4 and to support the cutting guide 2.

[0020] The bracket 4 comprises attachment means 41 for providing a stable attachment with no degrees of freedom between the bracket 4 and the bone to be cut. 1, the attachment means 41 may have at least one first hole 42 designed to receive a first threaded pin or nail. The bracket 4 is placed against the bone to be cut at the attachment point, and the first threaded pin or nail is inserted through the first hole 42 in the bracket 4 into the bone.

[0021] Advantageously, the bracket 4 enables the positioning frame 3 to be fixed adjacent to the cutting surface of the cutting guide 2 which will be described below. In one embodiment, the bracket 4 has at least one second hole 44 designed to receive a second screw pin or nail for fixing the bracket 4 to the bone. The longitudinal axis of the at least one second hole 44 is inclined with respect to the longitudinal axis of the first hole 42. In other words, the second hole 44 is designed such that the screw pin or nail received therein is inclined with respect to the direction of the first screw. This advantageously allows the inclined orientation of the at least one second hole 44 to prevent separation and / or rattle of the bracket 4 once attached to the bone to be cut. The second hole 44 may have a diameter smaller than the diameter of the first hole 42.

[0022] The bracket 4 is mechanically connected to an articulating assembly 5 of the positioning frame 3. The mechanical connection between the bracket 4 and the articulating assembly 5 has at least one degree of freedom. Preferably, the mechanical connection between the bracket 4 and the articulating assembly 5 has at least one rotational degree of freedom, and preferably two rotational degrees of freedom and one translational degree of freedom.

[0023] Preferably, the bracket 4 comprises a mast 45. The mast 45 has a longitudinal extension designed to receive the articulating assembly 5. The mast 45 may have a groove that forms a sliding connection with the articulating assembly 5. Preferably, the mast 45 is designed to receive a carriage 531 of the articulating assembly 5 such that the carriage 531 is slidable along the longitudinal axis of the mast 45.

[0024] Advantageously, the mobility of the cutting guide 2 relative to the bracket 4 allows the displacement of the cutting guide 2 relative to the associated bone to be controlled in order to optimally position the cutting guide 2 for cutting the bone.

[0025] In one embodiment, the positioning frame 3 comprises at least one means for controlling the articulating assembly with the bracket 4. Said control means allows the displacement of the articulating assembly 5 relative to the bracket 4 according to at least one degree of freedom.

[0026] More generally, the articulation assembly 5 and the bracket 4 are provided with at least two, or multiple, control means each capable of controlling the mobility of the articulation assembly 5 or the cutting guide 2 relative to the bracket 4 according to one degree of freedom.

[0027] The at least one control means allows displacement of the articulation assembly 5 relative to the bracket 4 according to at least one rotational or translational degree of freedom. As shown in Figures 1 to 5, the articulation assembly 5 comprises first control means 51 allowing rotation of the articulation assembly along a first axis B, second control means 52 allowing rotation of the articulation assembly along a second axis C, and third control means 53 allowing mobility of the articulation assembly 5 relative to the bracket by translation along a third axis A.

[0028] The control means may comprise a locking mechanism and / or a rack. As shown in more detail in Figures 2 and 3, the first control means 51 comprises a drive wheel 510 coupled to a screw 514. A movable element 513 is arranged on the threaded part of said screw 514. When the screw 514 is rotated, the movable element 513 is therefore moved to one side or the other of the screw 514 depending on the direction of rotation of the screw 514. The displacement of the movable element 513 results in the rotation shown in Figure 3 of the articulated assembly 5 along the B axis.

[0029] Preferably, the displacement of the movable element 513 along the thread 514 is translated into a rotational displacement of a drive element 512 of the cutting guide 2 by a sliding connection 511 between the movable element 513 and the drive element 512. Said drive element 512 is mechanically connected to the cutting guide 2 via a pivot connection 516, thereby causing its rotation along a first axis B (shown in FIG. 4 ) passing through the pivot connection 516.

[0030] The first control means 51 preferably comprises a drive wheel 510 for the screw 514, very preferably two drive wheels 510 for the screw 514, one on each side of the screw. As shown in more detail in Figures 4 and 5, the second control means 52 comprises a drive wheel 520 which drives a screw 521 which is integral with the drive wheel 520. A tip 522 of the screw 521 abuts against the carriage 531. Said end 522 is preferably spherical. Said spherical shape allows the end of the screw 522 and the carriage 531 to move in a circular arc. 531 The purpose is to ensure a point-to-point connection between

[0031] The second control means 52 comprises a tilt pivot 524. The tilt pivot 524 has a threaded portion 525. The screw 521 is screwed into the threaded portion 525. More specifically, the threaded portion 525 may have a threaded through hole. A rotation of the screw 521 therefore causes a longitudinal displacement of the threaded portion 525 along the thread 521. The tilt pivot 524 further has a connection to the cutting guide 2 such that a rotation of the tilt pivot 524 causes a rotation of the cutting guide 2. The tilt pivot 524 also has a pivot connection 523 to the bracket 4 or to the carriage 531. Said pivot connection 523 is preferably arranged between the threaded portion 525 and the connection to the cutting guide. A longitudinal displacement of the threaded portion 525 along the thread 521 therefore causes a rotational movement of the tilt pivot 524 about the pivot 523 and, consequently, of the cutting guide 2 along the second axis C as shown in FIG. 2. The second axis passes through pivot 523 .

[0032] The first control means 51 and the second control means 52 are preferably arranged such that the first axis B and the second axis C are perpendicular and / or secant at the pivot point 523 . The third control means 53 comprises a sliding connection between the mast 45 of the bracket 4 and a carriage 531 of the articulating assembly 5. Said sliding connection may comprise means for stopping said translation. For example, a set screw 532 is arranged at the end of the mast 45.

[0033] The set screw 532 screws into the end of the mast 45 for displacement along the translation axis A. The set screw 532 then locks the translation in one direction of the carriage 531 at a desired height or position. In an embodiment not shown, the third control means 53 may comprise a second stop means for preventing translation of the carriage 531 in the opposite direction to the set screw 532.

[0034] The sliding connection preferably allows translational displacement of the cutting guide 2 along an axis parallel to the longitudinal axis of the first bore 42 . In an embodiment not shown, the positioning frame 3 may also comprise connection elements forming a rack. The rack has a sliding connection between the articulation assembly and the bracket. The sliding connection comprises a first threaded arm and a second arm in sliding connection with the first arm. The rack comprises a gear between the first and second arms, the rotational movement of the gear about the first threaded arm being converted into a linear movement along said first arm, said linear movement of the gear driving the second arm. The rack may also be designed such that one complete revolution of the gear corresponds to a linear movement of a predetermined distance.

[0035] Therefore, the mobility of the cutting guide 2 relative to the bracket 4 is controlled to allow the surgeon to position the cutting guide 2 at a desired location and / or orientation in a precise and stable manner.

[0036] Preferably, the articulating assembly 5 and the bracket 4 are removable. Indeed, the articulating assembly 5 may be removed from the bracket 4 once the cutting guide 2 is attached to the bone.

[0037] As shown in Fig. 9, the cutting guide 2 has a slot 21. The slot 21 is designed to abut the bone to be cut. It forms a through passage designed to allow a cutting tool to penetrate the cutting guide 2 to cut the bone. The slot 21 therefore defines a cutting plane suitable for guiding a cutting tool through said slot 21. In the following description, the plane passing through said slot may be called the "cutting plane".

[0038] The articulation assembly 5 comprises at least one connection element 54 with the cutting guide 2, and the cutting guide 2 comprises at least one connection element 25, e.g., male-female, that complements the at least one connection element 54 of the articulation assembly 5. This fixed connection allows the cutting guide to be operated by the articulation assembly 5.

[0039] Preferably, the connection is removable to allow the articulating assembly 5 to be removed from the cutting guide 2 when the cutting guide 2 is attached to an associated bone. The articulating assembly 5 may include a fastening key 515. The fastening key 515 is integral with a screw (not shown) that extends through the mast 45 of the bracket 4 to the connecting element 54 or the cutting guide 2. The purpose of the fastening key 515 is to secure the cutting guide 2 to its connecting element 54.

[0040] Therefore, the surgeon may remove the positioning frame 3 (brackets 4 and articulating assemblies 5) from the bone prior to cutting the bone by unscrewing the fastening key 515. In this manner, the pins or nails used to secure the positioning frame 3 to the bone are removed and will not interfere with the cutting.

[0041] In one embodiment, the cutting guide 2 also includes at least one fixation element 22. The cutting guide fixation element 22 allows the cutting guide 2 to be fixed to the bone to be cut. In this manner, once the surgeon has positioned the cutting guide 2 at a desired location via the articulating assembly, the surgeon may fix the cutting guide 2 to the bone prior to performing the bone cut.

[0042] In one embodiment, the cutting guide 2 may be removed from the device. The fixing element 22 of the cutting guide 2 may comprise a surface designed to be placed on the surface of the bone and a first hole designed to receive a first screw in the same way as the positioning frame of the bracket. Preferably, the fixing element of the cutting guide is positioned such that the screw does not interfere with the cutting of the bone.

[0043] Preferably, the cutting guide comprises at least two fixation elements, each having a hole for a screw to pass through to penetrate the bone to be cut, and each hole may extend in a different direction to prevent back movement of the cutting guide.

[0044] In one embodiment, the cutting guide 2 is adapted to the morphology of the bone to be cut. In the case of a cutting guide suitable for cutting the tibia, the cutting guide may be asymmetric. The cutting guide may further comprise at least one means for attaching a physical probe 24 .

[0045] In addition, the bracket 4 is provided with at least one first position marker 43 for identifying its position, and the cutting guide 2 is provided with a second position marker 23 for identifying its position. The first marker 43 and the second marker 23 are designed and positioned to be located by an optical sensor, such as a camera.

[0046] The image of the position markers acquired by the camera allows their position and orientation to be detected by the algorithm. Each marker has a predefined size, shape and pattern. The algorithm identifies the shape, size and optionally the pattern of the marker. To do this, the algorithm has access to an electronic memory in which digital data representing the geometry of the element it analyzes are stored. In particular, by comparing them with the shape, size and pattern of the marker on the image, the algorithm is able to estimate its position and orientation. For example, if a marker has a square surface pattern and this same pattern appears as a trapezoid on the image, the angle of the trapezoid allows the algorithm to estimate the orientation of said surface. In addition, the number of pixels between two opposite sides of the square allows the algorithm to estimate the distance between the marker and the camera. Each marker can have a different pattern and the algorithm, by recognizing the pattern, can associate an instrument with a position marker and, for example, a cutting guide with a second position marker. Since the position markers are attached to the tool without any degrees of freedom, the acquired images of the first and second markers can therefore be used to identify the respective positions and orientations of the first and second markers and thus the bracket and cutting guide.

[0047] In fact, the use of such markers makes it possible to refine its position in the repository of one or more cameras and its three-dimensional pose each time an image is acquired. These markers can be of various sizes and shapes.

[0048] The pattern may be three-dimensional or two-dimensional. Preferably, the marker has a flat surface suitable for reception, for example by adhering a label containing the pattern. In another example, the pattern is screen-printed on said flat surface. The pattern may be black and white, but the pattern may also be in color.

[0049] This pattern is different from those commonly used by infrared surgical navigation systems in that it is reusable - in fact, it can be sterilized by autoclaving - allowing for savings on consumables.

[0050] The patterns can have simple or complex geometric shapes, which makes the markers easier to identify, and also allows for improved estimation of the markers' position and pose by processing images from one or more cameras.

[0051] In practice, a marker according to an embodiment of the invention described herein has a rectangular plane that includes at least one pattern. The specific shapes of the first and second markers therefore make it possible to determine the respective positions and orientations of the bracket and cutting guide, as described above, which provides a simple means of positioning and orientation of the first and second markers, and thus the bracket and cutting guide.

[0052] An advantage of this particular shape of the marker is also that estimation of the position and orientation of the bracket and cutting guide can be performed with a single optical sensor, such as a camera. Another advantage is that the images to be processed can be acquired by a monocular optical sensor, in particular a camera, preferably in the visible range. By "optical sensor in the visible range" we mean optical sensors that record images visible to the human eye, including so-called "black and white" cameras and so-called "color" cameras. This makes it possible to choose a cheaper camera than the systems consisting of infrared cameras commonly used by surgical navigation devices.

[0053] The optical sensor can be integrated with a variety of devices such as a phone, a tablet, smart glasses, or any other system with one or more cameras integrated. A set of surgical navigation algorithms can be implemented on an embedded platform or a remote computer.

[0054] However, the at least one pattern can also be located by a monocular optical sensor that is used to locate the shape of the marker. By processing the image of the pattern in a manner similar to the image processing of the shape of the marker, the position and orientation of the first and second markers, and thus of the bracket and cutting guide, respectively, can also be determined. This therefore easily constitutes a complementary means of positioning and orientation of the first and second markers, and thus of the bracket and cutting guide.

[0055] An advantage of this pattern or these patterns is that the estimation of the position and orientation of the first and second markers, and thus the bracket and cutting guide, is done by two different means, which further improves the accuracy of positioning and orientation of the first and second markers, and thus the bracket and cutting guide.

[0056] Therefore, better positioning and orientation of the first and second markers, and thus the bracket and cutting guide, is achieved with a single camera shot in the visible area. The invention also relates to a cutting aid for placing knee prostheses, characterized in that it comprises at least one cutting device as described above and at least one point inspection tool as described below, which has a measuring point and a third marker for its localization. This cutting aid may comprise a first cutting device designed for cutting the tibia and a second cutting device designed for cutting the femur. The aid also comprises at least one additional tool, which we will call a "point inspection tool", for localizing a specific position, in particular an anatomical position. The said point inspection tool also comprises a third marker for its localization, similar to the first and / or second marker. The third marker has a specific shape and a unique pattern for its identification in the image by an algorithm.

[0057] In a first embodiment shown in FIG. The pointer 6 has a shaft 61, a contact point 62 and a third position marker 63. The algorithm uses data representative of the geometry of the pointer 6 to recognize the position of the contact point 62 relative to the third position marker 63. This data can be stored in an electronic memory of an auxiliary system that will be explained later. Therefore, to generate a point in a given coordinate system [landmark], it is sufficient to point with the contact point 62 to the point to be recorded and then to acquire images of the third marker 63 and other markers associated with the above formed coordinate system [landmark].

[0058] In a second embodiment shown in FIGS. The clamp 7 comprises a base 70 and two arms 71 movable relative to the base 70. Each arm 71 of the clamp 7 may comprise a pad 72 at its end for positioning. Said pad 72 may have a pivot degree of freedom with the arms 71 of the clamp. In an embodiment, the pad 72 is preferably designed to receive the malleolus of the ankle.

[0059] The base 70 of the clamp 7 is provided with a third positioning marker 73. Said marker 73 is integral with the base 70. The two arms 71 are connected to each other by a pivot connection 74. Said pivot connection comprises a central pinion 75 designed to slide in a central groove 76.

[0060] Each arm 71 further includes a lateral groove designed to cooperate with a lateral pinion 78 of the base 70. As the arm 71 moves relative to the base 70, the lateral pinion 78 slides along the lateral groove 77.

[0061] The lateral grooves 77 and the central groove 76 are designed such that the projection of the pad 72 on an axis x parallel to the longitudinal axis of the central groove 76 remains constant during the different movements of the arms 71 of the clamp 7 . In addition, the central pivot connection 74 imposes a similar movement on the first arm as on the second arm, so that the point located in the middle of the section between the two pads 72 is always in the same position relative to the base and thus relative to the position marker of the clamp.

[0062] As the arm 71 moves to shorten the distance between the two pads 72, the rotational movement of the arm 71 about the pivot connection 74 causes the lateral pinions 78 to move along the lateral grooves 77 and the central pinion 75 to move linearly along the linear central groove 76, so that the central point O of the portion between the two pads is fixed relative to the base 70 and therefore relative to the third marker 73.

[0063] Preferably, the clamp 7 comprises a return element (not shown) that allows the central pinion 75 to be supported at one of the two ends of the central groove 76, very preferably at the end closest to the pad. Said element can be a return spring or a rubber band that is placed in the groove. This return element allows the ends of the clamp to return towards each other.

[0064] The algorithm uses the position data of the point O in the middle of the part between the two pads 72 relative to the third position marker 73. Therefore, to generate the point O in a given reference coordinate system, it is sufficient to position the pad 72 and image the third marker 73 and another marker related to said given reference coordinate system.

[0065] In a third embodiment, not shown, the point inspection tool has markers attached to a flat surface. An algorithm uses data of the inspection fixture's geometry to identify the location of a point on the plane relative to a third position marker.

[0066] The invention therefore relates to an auxiliary device comprising a cutting device as described above and a point inspection tool as described above. For the generation of a plane in a given reference coordinate system of the algorithm, it is therefore sufficient to place the plane of the inspection tool on the surface to be recorded and then image the third marker and the further markers related to said given reference coordinate system.

[0067] An example of an auxiliary system 100 comprising the cutting device 1 is described below with reference to FIG. The invention relates to an auxiliary system 100 comprising the cutting device 1 described above, optical capture means 200, in particular a camera, and information transmission means 400.

[0068] Advantageously, the system makes it possible to determine the position of the cutting surface relative to the bracket, or the O of the inspection object, 62 of the point inspection instrument, by incorporating position markers. An information transmission means 400 is used to transmit information about the position and orientation of the cutting plane to the surgeon.

[0069] Preferably, the optical capture means 200 is a video capture means such that the position of the cutting guide can be monitored in real time. The optical capture means may be a camera or a still camera. In one embodiment, the auxiliary system 100 preferably comprises only one monocular capture means of the visible range. By "visible range capture means" is meant optical capture means that record images visible to the human eye, including both so-called "black and white" cameras and so-called "color" cameras.

[0070] The assistance system 100 also comprises a communication means 400. Said communication means 400 may be a visual or an audio communication means. The information transmission means 400 may be any means for transmitting cutting plane position and / or orientation information from the image captured by the optical capture means 200 to the surgeon.

[0071] The information transmission means 400 may be a display means, and may include a screen, an image projection means, a speaker, and an audio headphone. Preferably, the information transmission means 400 comprises glasses or a monocular worn by the surgeon. Said glasses or monocular may have optical capture means 200, for example in the form of a camera integrated in a frame or arm, and information transmission means 400, for example in the form of a means for projecting information into the field of view of the surgeon onto the lenses of the glasses.

[0072] The assistance system 100 also comprises a computer 300 connected to a data storage medium 301 containing algorithms for assisting in the placement of the prosthesis. The computer 300 is connected to optical capture means for receiving captured images and to communication means for controlling said communication means.

[0073] The auxiliary system 100 may also comprise an interaction means 250 for the operator to interact with the software. The interaction means 250 may be located on the glasses or monocular. The interaction means may include a microphone, control buttons, a tactile surface, an eye tracking camera.

[0074] The interaction means 250 may include a pointer 6. In one embodiment, the glasses or monocular display a graphical interface including icons or pictograms. The user may manipulate these icons or pictograms and thereby interact with the software via a pointing device. The pointing device may include a pointer 6, a mouse, etc. The user may also interact with the graphical interface via a hand gesture recognition system or an accelerometer.

[0075] Preferably, the auxiliary system is activated by voice commands or a body movement, e.g., a head movement. Once the system is activated, the glasses or monocular displays a graphical interface including icons or pictograms. The user can manipulate these icons or pictograms and thus interact with the auxiliary system software via a pointing device, such as the pointer mentioned above, or via a hand gesture recognition system.

[0076] The graphical interface may include virtual interaction buttons. Preferably, the graphical interface includes a rosette, the virtual interaction buttons being represented on the rosette around a center of said rosette. A user can manipulate the buttons of the rosette and thus interact with the software via a pointing device, such as the pointer mentioned above, or via a hand gesture recognition system.

[0077] The present invention also relates to a method of assisting in the placement of a knee prosthesis using the cutting device 1 and / or the assist system 100 described above. The method aims to assist the surgeon, for example by providing him with information about the position and / or orientation of the cutting plane of the device relative to the formed coordinate system [reference marks]. It should be noted that the inventive assistance method per se concerns an upstream step of the surgical procedure. It concerns only the correct positioning of the auxiliary tools for the upcoming operation. The method is therefore only related to the correct use of the device, without preventing the surgeon from performing the surgical procedure in a different way without using said device.

[0078] The method comprises a first stage of positioning the positioning frame 3 of the above-mentioned cutting device 1. This step includes not only mounting the cutting guide 2 to the articulating assembly 5 but also mounting the bracket 4 to the bone to be cut via at least one fixation element.

[0079] The method then includes using an optical capture means 200, such as a monocular camera in the visible range, so that said camera can detect the first marker on the bracket and the second marker on the cutting guide. The information transmission means 400 is also arranged to transmit information to a user.

[0080] The cutting device 1 is placed relative to the tibia or femur. The cutting device may also be placed on the knee joint surface of any of the aforementioned bones. The cutting device is positioned on the tibia or femur in such a way that the cutting surface allows a cut to be made with a thickness between 2 mm and 20 mm, preferably between 6 mm and 10 mm.

[0081] In this manner, the bracket is secured to the bone, while the cutting guide remains movable relative to the bracket and to the bone to which the bracket is secured. The method then includes a second step of assisting in positioning the cutting guide relative to the bracket, and therefore relative to the bone.

[0082] To this end, the method comprises a step of visualising the first marker 43 and the second marker 23 by optical capture means. The method may implement an algorithm for recognizing a marker in an image captured by an optical capture means, the algorithm may identify the position and orientation of said marker in three-dimensional space by the particular shape of the marker and / or a unique pattern applied to the marker.

[0083] From the visualizing step, the method then includes the step of forming a coordinate system [landmarks]. The coordinate system formed is a coordinate system with two or three orthogonal reference axes.

[0084] The formed coordinate system [landmark] has a first reference axis, a second reference axis perpendicular to the first reference axis, and optionally a third reference axis perpendicular to the first and second reference axes. The first reference axis N shown in Fig. 12 is the mechanical axis of the bone to be cut. By mechanical axis is meant the axis that supports the mechanical forces of the bone in question. The mechanical axis is distinct from the anatomical or longitudinal axis of the bone, which extends along the shaft of the bone concerned.

[0085] A first reference axis N is formed by identifying the positions of a first point and a second point. The position of the first point is generated relative to a first marker of the cutting device. In fact, the bracket of the cutting device is in a reference position, which is visualized through its first marker. The algorithm can therefore generate a first point representing the fixation of the bracket to the bone, the position of which is fixed relative to the marker of the bracket. The first point is fixed relative to the bracket. The bracket is therefore designed such that when the bracket is attached to the bone, the first point passes through the mechanical axis of the bone to be cut.

[0086] In the case of the tibia, the position of the second point can be determined using a point inspection tool. As shown in Fig. 12 for the example of the tibia 10, the first point K is determined by the position and orientation of the first marker.

[0087] The mechanical axis of the tibia 10 passes through a point equidistant from the lateral points of the left and right malleoli of the associated leg, where lateral point means here the point on the surface of the malleoli that is furthest from the anatomical axis of the tibia. In one embodiment, the second point M is generated by inspecting a point on the outside of each of the patient's ankles, preferably with the above-mentioned pointer 6. From these two points, the algorithm generates the second point M as a point that is equidistant from the point on the outside of each of the patient's ankles.

[0088] In another embodiment, the above-mentioned clamp 7 is used to identify the second point M. The two pads 72 of the clamp 7 are respectively placed at the lateral points of the respective malleoli. The second point M thereby coincides with a point O equidistant from the two pads of the clamp 7. Such a clamp therefore makes it possible to reliably, easily and automatically identify the central (or medial) anatomical point from each of the two lateral supports on two easily locatable anatomical regions with one reading. In the described embodiment, the clamp is designed as two supports on each of the respective malleoli of the ankle. It goes without saying that such a clamp can be used instead to locate numerous other anatomical points.

[0089] Therefore, the present invention provides a solution to the technical problem of localizing anatomical points within the body in an accessible and reliable manner. The solution is based on a clamp characterized by two articulated arms 71 each equipped with a pad 72 allowing positioning on an anatomical region of the human body. The clamp is equipped with a fixed marker 73 that allows to automatically identify its position and to estimate an internal anatomical point deducible from the two pads 72 of the clamp. In particular, the invention relates to a clamp comprising a base and a first arm and a second arm each equipped with a pad, the first arm and the second arm being connected to each other by a movable articulated joint, whereby the movement of one arm moves the movable articulated joint along a groove in the base such that the middle of the part connecting the two arms is fixed relative to the base.

[0090] In the case of the femur, the mechanical axis passes through the femoral head of the femur. To generate the second point, we use the fact that the femoral head forms the center of rotation of the femur to estimate the location of the second point.

[0091] In a first step, the user places a location marker on a fixed support relative to the patient's pelvis. Preferably, the location marker is placed on the patient's pelvis, but it could also be placed on a table on which the patient lies, or on another fixed support within the field of view of the camera.

[0092] In a second step, the camera takes different images of the fixed position marker and the first position marker, in each image the patient's knee is moved to different positions. In each image, the algorithm generates and records a first point on the mechanical axis of the femur by locating the first position marker 43 relative to the fixed position markers.

[0093] The algorithm then calculates a sphere that contains the set of machine axis points, which may be the sphere that approximates all the points as closely as possible through statistical methods. The algorithm further identifies the center of the sphere as a second reference point.

[0094] The position of the second reference point according to the first position marker is therefore stored in memory. The algorithm then generates a first reference axis relative to the first position marker that passes through the first point and the second point.

[0095] The second reference axis is generated by projecting the known axis of the bracket 4 onto a plane perpendicular to the first reference axis N. The second reference axis preferably passes through the center or first point K of the knee. The first reference axis N and the second reference axis are therefore identified by the first fiducial marker 43. For each image captured by the camera in this step, the algorithm can therefore generate an orthonormal coordinate system [orthonormal reference coordinate system] defined by the first and second reference axes from the image of the first fiducial marker.

[0096] The intersection of the cutting plane with the first reference axis makes it possible to evaluate the height of the cutting plane relative to the mechanical axis of the bone to be cut. The cutting plane projected onto the first axis is used to determine the cutting thickness. For this purpose, an algorithm determines the distance between the intersection of the cutting plane with the first reference axis and the thickness reference point.

[0097] The thickness reference point is a point located on the knee joint surface, preferably at the extreme of the articular bone surface. In the example of the femur, said point is located at the extreme of one of the prominent condyles, i.e. at the most distal point of the prominent curve of the condyle. In the example of the tibia, said point is the bottom point of the cup of the tibial plateau or the most distal point of the convex lateral condyle.

[0098] In a first embodiment, the thickness reference point is generated by a point inspection tool. A user points the condyle extremity with a pointer, while a camera captures images of the pointer position marker and the first position marker. The position of the thickness reference point relative to the first marker is therefore recorded.

[0099] In a second embodiment, the cutting guide comprises a physical probe 24. The physical probe 24 is designed such that its end 26 can be placed at the condyle extremity. For example, as the articulating assembly 5 moves relative to the bracket 4 via the sliding connection, the projection of the cutting plane onto the mechanical axis N changes until the end 26 of the probe reaches the condyle extremity. As shown in FIG. 4, the probe may have two ends 26, 27. The probe is designed such that a first end may be placed at the concave extremity and a second end may be placed at the convex extremity.

[0100] The cutting guide is preferably designed such that the intersection of the cutting plane with the first reference axis is a predetermined distance from the tip of said probe and thus from the thickness reference point, preferably about 9 mm, and may comprise means for varying this distance between 6 and 10 mm.

[0101] The coordinate system [marker] is therefore formed from the first position marker. Once the coordinate system [markers] is formed, the method determines the position and orientation of the cutting plane relative to said formed coordinate system [markers] or to a reference coordinate system [reference markers]. Preferably, the position and orientation of the cutting guide are controlled by the control means 51, 52, 53 of the positioning frame 3.

[0102] The method includes capturing an image including the first position marker and a second position marker of the cutting guide. From such an image, and from the pose of the two markers, this step allows the localization of the cutting plane in the reference coordinate system.

[0103] The algorithm identifies a first marker and estimates a reference coordinate system [reference marker]. By identifying a second marker on the cutting guide in the same image, the position and orientation of the cutting guide or cutting plane in the reference coordinate system is determined.

[0104] The method is therefore advantageously compatible with moving cameras or moving optical capture means due to the fact that the first marker serves as a reference coordinate system [reference marker] for the position and orientation of the cutting plane.

[0105] Once a reference coordinate system [reference markers] is identified, the position and orientation of the cutting plane is identified in said reference coordinate system and the method generates at least one parameter of the position and / or orientation of the cutting guide surface relative to said reference coordinate system [reference markers].

[0106] The parameter may indicate an angle of the cutting plane relative to a first reference axis and / or relative to a second reference axis of a reference coordinate system [fiducial marker]. The step of generating at least one parameter is preferably computer-implemented.

[0107] The first generated parameter may be, for example, the angle between the cutting plane and the second reference axis, or a value dependent on the angle, representing the varus / valgus angle. The second generated parameter may be, for example, the angle between the cutting plane and the first reference axis, or an angular function, representing the anterior / posterior tilt of the knee articular surface relative to the tibia, or the flexion / extension parameter of the femur.

[0108] A third generated parameter may be the cutting thickness, which is specified by the coordinates of the cutting plane projected onto the first reference axis or the distance between said coordinates and the thickness reference point mentioned above.

[0109] Thus, when the surgeon moves the cutting guide by means of the articulating assembly and by means of the control means, the camera records the first and second position markers. From the captured images and the reference coordinate system [reference markers], an algorithm calculates in real time the position and orientation parameters of the cutting plane.

[0110] In one embodiment in which the information conveying means comprises a representation of the axes forming the reference coordinate system [fiducial markers], this representation is preferably superimposed on a real image of the knee. This representation can be generated with mixed reality glasses.

[0111] Furthermore, the method includes a step of transmitting the above mentioned parameters to the operator, said transmission being made by the information transmission means 400 of the auxiliary system 100 according to the invention. The optical capture means may be movable. Indeed, since the first marker 43 acts as a reference, the camera may be moved without unduly impeding the method. Hence, the method is compatible with the use of a camera placed on a portable object such as a mobile phone or a pair of glasses.

[0112] The invention also relates to a method for tracing cutting planes according to the second step of the method described above. After the cutting surface is positioned at the surgeon's desired location, the surgeon attaches the cutting guide to the bone using the cutting guide attachment. The positioning frame 3 can then be separated from the cutting guide 2, and the positioning frame 3 is removed from the bone. Thus, only the cutting guide 2 remains attached to the bone.

[0113] In one embodiment, this step includes the preceding sub-step of replacing the reference coordinate system. For this purpose, said reference coordinate system formed relative to the first position marker is then replaced relative to the second position marker associated with the cutting guide that remains uniquely positioned. In this way, the reference coordinate system is maintained by the auxiliary system, despite the removal of the bracket and the first marker.

[0114] After the method has been performed, the surgeon may then perform the actual surgical procedure and cut the bone according to the cutting plane using the pre-positioned cutting guide. In one embodiment, after the bone is cut, the method includes the step of verifying the cut surface.

[0115] The verification step includes the provision of a point inspection tool including a marker attached to the plane as described above. The surface of the tool is placed on the surface where the cut has been completed. The position and orientation of the tool's marker relative to the second position marker is used to compare the cut plane with the created coordinate system [landmarks]. An algorithm may then calculate the parameters as described above. The operator may therefore advantageously verify that the cut plane indeed resembles the cut plane as intended.

[0116] The assist system comprises hardware and / or software elements that implement or manage a method for assisting in the installation of a knee prosthesis. In particular, the system comprises hardware and / or software elements that implement the steps of a method for assisting in the installation of a knee prosthesis. These various elements may include software modules.

[0117] For example, hardware and / or software elements include: - optical capture means 200, such as a camera; at least one cutting device 1 according to the invention, - interaction device 250, - computer 300, - means for transmitting information 400, a memory or data storage medium 301, at least one point inspection tool, such as a pointer 6 or a clamp 7, It may comprise all or some of the above.

[0118] In one embodiment, the data storage medium 301 includes the following: receiving 1100 a first image including a first marker; - forming 1200 a Cartesian coordinate system [marker] from an image of the first marker; receiving 1300 a second image including a first marker and a second marker; a step 1400 of identifying a cutting plane in the space of a coordinate system formed from the position and orientation of the second marker relative to the first marker in the second image [reference coordinate system], - a step 1500 of determining at least one position and / or orientation parameter of the cutting plane relative to the formed coordinate system [markers], a step 1600 of transmitting information of at least one determined parameter to a communication means; The method includes instructions 1000 for carrying out the method.

[0119] In one embodiment, the step 1200 of forming the coordinate system [marker] includes the following steps: - substep 1210 of identifying a first point in space relative to a first marker; - a substep 1220 of identifying a second point in space on the mechanical axis of the bone to be cut; - substep 1230 of creating a first axis passing through the first point and the second point; - forming a coordinate system (reference coordinate system) 1240 including a first axis and, in particular, a second orthogonal axis formed by projecting the known axis of the bracket onto a plane perpendicular to the first axis; Includes.

[0120] In a first embodiment applied to the tibia, the sub-step of identifying the second point includes the following steps: - receiving at least one image comprising a first marker and a third marker; - determining the position of a second point in space relative to the position of a third marker relative to the first marker in the image; Includes.

[0121] In a second embodiment suitable for a femur, the sub-step of identifying the second point comprises the following: - receiving a plurality of images, each of which includes a first marker and another marker; - determining from the image a center of rotation of a first marker relative to another marker; - identifying a second point as a centre of rotation of the first marker; Includes.

Claims

1. A cutting device (1) for installation of a knee prosthesis, comprising a bracket (4) and a cutting guide (2) movably attached to said bracket (4), The bracket (4) is a first marker (43) for localization, - a fixation element (42) for fixing to the bone, having The cutting guide (2) is a second marker (23) for localization, a slot (21) defining a cutting surface suitable for guiding a cutting tool; having The first marker (43) and the second marker (23) have a rectangular plane including at least one pattern; The cutting guide (2) is attached to the bracket (4) so ​​as to be movable according to at least one translational degree of freedom; The cutting guide (2) is mounted on the bracket (4) so ​​as to be movable according to at least two rotational degrees of freedom; the cutting guide (2) is movably attached to the bracket (4) via an articulation assembly (5) that allows movement of the cutting guide (2) relative to the bracket (4); The bracket (4) comprises a mast (45) having a longitudinal extension designed to receive the articulation assembly (5); said articulation assembly (5) comprises first control means (51) allowing rotation of said articulation assembly (5) along a first axis (B), second control means (52) allowing rotation of said articulation assembly (5) along a second axis (C), and third control means (53) allowing mobility of said articulation assembly (5) relative to said bracket (4) by translation of said articulation assembly (5) along a third axis (A), the first control means (51) comprises a movable element (513) arranged on a threaded portion of a screw (514) and movable to one side or the other side in a longitudinal direction of the screw (514) when the screw (514) rotates, and as a result of this movement, a drive element (512) of a cutting guide (2) which is driven to rotate around the first axis (B) is moved; the second control means (52) comprises a screw (521) integral with a drive wheel (520), the tip (522) of which is in contact with a carriage (531) of the articulating assembly (5), the screw (521) moving in a thread (525) of a tilting pivot (524) having a connection part connecting the cutting guide (2) so as to allow the cutting guide (2) to rotate about the second axis (C), as a result of which movement causes a rotational movement of the cutting guide (2) about the second axis (C); the third control means (53) comprises a sliding connection part between the mast (45) of the bracket (4) and the carriage (531) along the third axis (A), Cutting device (1).

2. 2. The cutting device (1) according to claim 1, wherein the cutting guide (2) comprises a fixing element (22) for fixing to a bone.

3. 1. A cutting aid for installing a knee prosthesis, comprising a cutting device (1) according to claim 1 or 2 and at least one point inspection device (6, 7) having a third marker for identifying a specific position.

4. 4. The cutting assistant device according to claim 3, comprising a first cutting device as a cutting device (1) according to claim 1 or 2 designed for cutting the tibia and a second cutting device as a cutting device (1) according to claim 1 or 2 designed for cutting the femur.

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