Systems and methods for assisting orthopedic surgery

Abstract

The present invention relates to a system and computer-implemented method (100) for intra-operatively predicting the outcome of a planar cut made with a planar surgical tool comprising a planar cutting surface on a target bone of a subject.

Description

[Technical Field]

[0001] The present invention relates to the field of image processing for orthopaedic surgery, and more particularly to a computer-implemented method and system configured to predict the results of planar cuts made with a planar surgical tool on a target bone of a subject during a surgical procedure. [Background technology]

[0002] Total knee arthroplasty (TKA) is a surgical procedure to replace knee surfaces damaged by arthritis. Metal implants are used to cover the ends of the bones that form the knee joint. During the bone preparation phase, the surgeon uses a surgical cutting instrument, usually a sagittal saw, to make five planar cuts on the femur and one planar cut on the tibia. In the case of navigated or robotic-assisted TKA, guidance software is used to position the cutting instrument within the desired planes on the bones before cutting.

[0003] A guidance system is used to align a planar cutting instrument with respect to the bone to be resected according to a target plane. Although such systems can guarantee a certain accuracy in bone cutting, several factors (patient morphology, user familiarity with the system, reference positioning errors) can still affect their performance, and the exact positioning of the cutting instrument cannot be completely satisfactory. There is no independent method to confirm the accuracy of bone resection without actually performing the cut and to obtain qualitative or quantitative information to predict the shape of the anatomical structure after the cut.

[0004] The present invention aims to fill this void by providing a method and system for verifying planar cuts and visualizing their future effects before making the cuts, which can be used in conjunction with robotic and / or navigation systems. Summary of the Invention

[0005] The present invention provides a computer-implemented method for intra-operatively predicting the outcome of a planar cut made on a target bone of a subject using a planar surgical tool comprising a planar cutting surface, the method comprising: receiving at least one previously acquired 3D image from at least one 3D imaging sensor, said 3D image being a 3D point cloud including at least one portion of a target bone and at least one portion of a planar cut surface of a surgical tool; segmenting the 3D image to obtain points of the 3D image that belong to the planar cutting plane of the surgical tool and points of the 3D image that belong to the target bone; - obtaining the spatial orientation and position of the osteotomy plane by fitting a plane to the segmented points belonging to the planar cutting surface of the surgical tool; - superimposing the osteotomy plane onto the segmented points belonging to the target bone and selecting the points belonging to the portion of the target bone to be removed with the surgical tool; outputting points belonging to the portion of the target bone to be removed by the surgical tool; The present invention relates to a method comprising:

[0006] Advantageously, the method allows the future outcome of the planar cut to be confirmed and its future effect to be visualized for medical staff before the cut is made, thus providing valuable information for collecting any alignment errors etc. Furthermore, thanks to the external measurement device (i.e. 3D imaging sensor), the method allows an independent confirmation that does not rely on any kinematic or positioning data from the robotic arm or navigation system used during the surgical procedure, and is therefore not affected by their initial positioning errors.

[0007] According to one embodiment, the method further comprises generating a simulated 3D model of the bone portion to be removed using points belonging to the target bone portion to be removed with the surgical tool.

[0008] According to one embodiment, the method comprises: receiving a preoperative plan including a 3D model of a bone and an equation of a planned cutting plane in a reference coordinate system of the 3D model of the bone; - obtaining a planned 3D model of the bone portion to be removed by applying the equation of the cutting plane to the 3D model of the bone; comparing the simulated 3D model with the planned 3D model of the bone portion to be removed using 3D shape analysis and outputting the results of the comparison; Further includes:

[0009] The 3D model of the bone and the simulated 3D model may be a 3D digital model as a planned 3D model obtained from the 3D model of the bone.

[0010] According to one embodiment, the result of the comparison is a 3D shape similarity measure or matching error. This output of the method advantageously provides medical staff with information regarding the accuracy of the positioning of the surgical tool relative to the pre-operative plan.

[0011] According to one embodiment, the method further comprises the steps of calculating the principal components of the simulated 3D model, defining a bounding box of the bone portion to be removed from the principal components, and estimating the thickness of the bone portion to be removed from the bounding box. This embodiment advantageously allows calculating the thickness of the bone fragment (i.e. the bone portion to be resected) before actually making the cut.

[0012] According to one embodiment, the method further comprises the steps of comparing said estimated thickness of the bone portion to be removed with a planned thickness of the bone portion to be removed and outputting an alarm whenever a deviation from the planned thickness is detected, which advantageously alerts medical staff so that corrections to the positioning of the surgical tool can be made.

[0013] According to one embodiment, the surgical tool includes fiducial markers to aid in obtaining the spatial orientation and location of the osteotomy surface.

[0014] According to one embodiment, the target bone is the femur or the tibia.

[0015] The invention also relates to a computer program comprising instructions that, when executed by a computer, cause the computer to carry out the steps of the method according to any one of the above embodiments.

[0016] The invention also relates to a computer-readable medium comprising instructions that, when executed by a computer, cause the computer to carry out the steps of the method according to any one of the above embodiments.

[0017] The present invention provides a system for intra-operatively predicting the outcome of a planar cut made on a target bone of a subject using a planar surgical tool including a planar cutting surface, the system comprising: at least one input adapted to receive at least one previously acquired 3D image from at least one 3D imaging sensor, said 3D image being a 3D point cloud including at least one portion of a target bone and at least one portion of a planar cut surface of a surgical tool; at least one processor, Segment the 3D image to obtain points of the 3D image that belong to the planar cutting surface of the surgical tool and points of the 3D image that belong to the target bone; Obtain the spatial orientation and position of the osteotomy plane by 3D fitting the segmented points belonging to the planar cutting surface of the surgical tool; Overlay the osteotomy plane onto the segmented points belonging to the target bone, and select the points that belong to the part of the target bone that will be removed with the surgical tool. a processor configured to: at least one output adapted to provide a point belonging to a portion of a target bone to be removed with a surgical tool; The present invention also relates to a system comprising:

[0018] According to one embodiment, the processor is further configured to generate a simulated 3D model of the bone portion to be removed using points belonging to the target bone portion to be removed with the surgical tool.

[0019] According to one embodiment, the processor further comprises: receiving a preoperative plan including a 3D model of the bone and equations of the cutting plane in the reference coordinate system of the 3D model of the bone; Obtaining a planned 3D model of the bone portion to be removed by applying the cutting plane equation to the 3D model of the bone; comparing the simulated 3D model of the bone portion to be removed and the planned 3D model using 3D shape analysis, and outputting the results of the comparison; It is structured as follows.

[0020] According to one embodiment, the result of the comparison is a 3D shape similarity measure or matching error.

[0021] According to one embodiment, the processor is further configured to calculate principal components of the simulated 3D model, define a bounding box of the bone portion to be removed from the principal components, and estimate a thickness of the bone portion to be removed from the bounding box.

[0022] According to one embodiment, the processor is further configured to compare said estimated thickness of the bone portion to be removed with a planned thickness of the bone portion to be removed and to output an alarm whenever a deviation from the planned thickness is detected.

[0023] definition In the present invention, the following terms have the following meanings:

[0024] "Bone resection thickness" refers to the smaller dimension of the resected portion of the bone.

[0025] "Adapted" and "configured" are used in this disclosure to broadly encompass the initial configuration of the device, subsequent adaptation or supplementation, or any combination thereof, whether done through material or software means (including firmware).

[0026] "Processor" should not be construed as being limited to hardware capable of executing software, but generally refers to a processing device, such as a computer, microprocessor, integrated circuit, or programmable logic device (PLD). A processor may also encompass one or more graphics processing units (GPUs), whether utilized for computer graphics and image processing or other functions. Furthermore, instructions and / or data capable of performing the relevant and / or resulting functions may be stored on any processor-readable medium, such as an integrated circuit, a hard disk, a CD (compact disc), a DVD (digital versatile disc), an optical disk such as a RAM (random access memory) or a ROM (read-only memory). Instructions may specifically be stored in hardware, software, firmware, or any combination thereof.

[0027] "Reference coordinate system" refers to a coordinate system that uses one or more numbers or coordinates to uniquely determine the location of points or other geometric elements on a manifold, such as Euclidean space.

[0028] "3D digital model" refers to a 3D digital (or virtual) model that is a three-dimensional virtual object, the position and orientation of which are known in an associated digital frame of reference.

[0029] In the context of surgery, "preoperative planning" refers to a list of actions to be performed during different stages of surgery. This surgical plan may be obtained using a simulation program performed prior to the procedure using a 3D digital model of the patient's bones that are the target of the surgery. In the case of knee arthroplasty, for example, preoperative planning involves defining the cutting planes and drill axes for the 3D models of the femur and tibia, respectively.

[0030] Detailed Description The following detailed description will be better understood when read in conjunction with the drawings. For purposes of illustration, the method steps are shown in preferred embodiments. It should be understood, however, that the invention is not limited to the precise arrangement, structure, features, embodiments, and aspects shown. The drawings are not drawn to scale, and are not intended to limit the claims to the depicted embodiments. Accordingly, it should be understood that, where features recited in the appended claims are labeled, such labels are included solely to enhance comprehension of the claims, and in no way limit the scope of the claims.

[0031] The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared.

[0032] It will be appreciated that the elements shown in the figures may be implemented in various forms of hardware, software, or a combination thereof. Preferably, these elements are implemented in a combination of hardware and software on one or more appropriately programmed general-purpose devices, which may include a processor, memory, and input / output interfaces.

[0033] Features and advantages of the invention will become apparent from the following description of an embodiment of the system, which description is given by way of example only and with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a block diagram illustrating the main steps of a method according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a color image of a target bone and a planar surgical tool positioned prior to making a planar cut. [Figure 3] 3 is a depth image corresponding to the color image in FIG. 2. [Figure 4] Figure 4a shows the point cloud belonging to both the planar cutting surface of the surgical tool and the target bone after segmentation, Figure 4b shows the bone resection surface superimposed on the point cloud belonging to the planar cutting surface of the surgical tool and the target bone after segmentation, and Figure 4c shows the points belonging to the target bone portion to be removed by the surgical tool. [Figure 5] 1 shows the removed bone portion and a planned 3D model of the bone to be resected. [Figure 6] The tibia after performing the planar cut is shown on the right and the appropriate prosthesis on the left. [Figure 7] The femur after performing the planar cut is shown on the right and the appropriate prosthesis on the left. [Figure 8] The bone removed after anterior femoral resection and the thickness of the removed bone measured with a slidometer are shown. DETAILED DESCRIPTION OF THE INVENTION

[0035] While various embodiments have been described and illustrated, the detailed description should not be construed as limiting thereof. Various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the present disclosure, as defined by the claims.

[0036] As shown in FIG. 1, a first aspect of the present invention relates to a computer-implemented method 100 including multiple steps for intraoperatively predicting the outcome of at least one planar cut made with a planar surgical tool on a target bone Bt of a subject.

[0037] 2 shows a schematic diagram of a target bone Bt with a planar surgical tool positioned such that the planar cutting surface Sc has a spatial orientation and position adapted to perform the planar cut according to the preoperative plan. The surgical tool may be attached to a kinematic chain configured to position the surgical tool according to the preoperative plan.

[0038] According to the embodiment of Figure 1, a first step 110 of the method consists of receiving at least one 3D image including at least one portion of the target bone Bt and at least one portion of the planar cutting surface Sc of the surgical tool, acquired from at least one 3D imaging sensor before making a cut on the target bone Bt. Figure 3 shows a depth image of the scene depicted in Figure 2.

[0039] The 3D image obtained from the 3D imaging sensor contains the distance between each point of the scene captured in the 3D image and the information of the 3D imaging sensor. Therefore, the raw 3D image obtained by the 3D imaging sensor is also called a depth map or depth image, which can be provided in the form of a two-dimensional array representing a grayscale image or an RGB image, the size of which depends on the type of camera and the sensor dimensions.

[0040] According to one embodiment, the 3D image acquisition is performed using at least two cameras for stereoscopic acquisition, and according to another embodiment, a projector is used to project a pattern onto the scene that aids in matching the stream data from the two cameras.

[0041] The use of a 3D imaging sensor advantageously allows for obtaining bone surface information in an easy, non-invasive and rapid manner, as one image captures the entire surgical field without contacting the patient (as with palpation techniques).

[0042] The at least one 3D imaging sensor 30 may have a fixed position relative to the target 10 in the operating room, or alternatively, it may be kinematically coupled to a surgical navigation or robotic system.

[0043] The method may further comprise a pre-processing step in which a noise reduction algorithm is implemented.

[0044] According to one embodiment, the second step 120 comprises segmenting the point clouds of the 3D image to obtain one point cloud containing points belonging to the planar cutting surface Sc of the surgical tool and one point cloud containing points of the target bone Bt. Figure 4a shows the point clouds belonging to the planar cutting surface Sc of the surgical tool and the target bone Bt.

[0045] As shown in FIG. 4b, in one embodiment, a subsequent step 130 involves obtaining the spatial orientation and position of the osteotomy plane P by fitting a plane to the segmented points belonging to the planar cutting plane Sc of the surgical tool.

[0046] In one embodiment, step 140 of the method comprises selecting points belonging to a portion Pr of the target bone to be removed with the surgical tool by superimposing 140 the bone resection plane P onto the segmented points belonging to the target bone Bt. Figure 4c shows the cloud of points belonging to the portion of the target bone to be removed obtained in step 140. This advantageously allows segmentation of the portion of the target bone to be removed as if a planar cut were made along the proposed plane P.

[0047] In one embodiment, the method includes a step 150 of outputting points belonging to the portion of the target bone to be removed with the surgical tool. This output may simply be information transferred to at least one data storage medium or database or a digital-to-analog conversion module, which may be a display device for visualizing the portion of the target bone to be removed.

[0048] According to one embodiment, the method further comprises generating a simulated 3D model of the bone portion to be removed by rendering points belonging to the portion of the target bone to be removed with the surgical tool.

[0049] According to one embodiment, the method includes retrieving, from a computer-readable storage medium, a server, or the like, a 3D model of a target bone Bt to be treated during a surgical procedure using a surgical tool, said 3D model being a three-dimensional virtual representation of the target bone Bt.

[0050] In one embodiment, the 3D model of the target bone Bt is generated using imaging data acquired using a computed tomography or MRI system. Other imaging techniques, such as x-ray, fluoroscopy, ultrasound, or other imaging modalities, may also be used. In this case, the three-dimensional digital model is obtained prior to the surgical procedure.

[0051] In one embodiment, the 3D model of the target bone Bt is generated using two-dimensional radiography including the target, a statistical shape model of the target, and / or 3D images acquired intraoperatively by a 3D imaging sensor. This embodiment advantageously allows for the generation of a 3D model even when 3D imaging data (i.e., computed tomography or MRI) is not available.

[0052] In one embodiment, the 3D model of the target bone Bt is modified to simulate measurement noise or the presence of cartilage, said modifications may be calculated from training data or biomechanical simulation data.

[0053] Along with the 3D model, the method is configured to receive a preoperative plan, which can also be retrieved from a computer-readable storage medium or a medical server. The preoperative plan includes a cutting plane equation in the same reference coordinate system of the bone model. The cutting plane equation can then be used to apply the cutting plane to the 3D model of the bone to obtain a planned 3D model of the bone portion to be removed. The simulated 3D model of the bone portion to be removed and the planned 3D model are then compared using 3D shape analysis. The result of this comparison can be a matching error or a 3D shape similarity measure. The matching error can be performed by matching the 3D models using an ICP (iterative closest point)-based method and estimating the angular deviation between the simulated cutting plane and the planned cutting plane. For the shape similarity measure, shape measures such as the Hausdorff distance or the Jaccard distance can be used after matching. Finally, the result of the comparison is provided as an output. Figure 5 shows an example of visualization of the planned 3D model of the bone portion to be removed.

[0054] According to one embodiment, the method further comprises calculating the principal components of the simulated 3D model and determining a bounding box of the bone to be removed from the principal components. One side of the bounding box coincides with the simulated bone resection plane. The bounding box is used to estimate the thickness of the bone portion to be removed. This step advantageously allows the thickness of the bone fragment (i.e., the bone portion to be resected) to be calculated before the actual cut is made. Figure 8 provides an exemplary representation of the thickness of the bone fragment that this method allows to calculate before the intervention and that can be measured with a gliometer after the surgical resection.

[0055] According to an advantageous embodiment, the method comprises the steps of comparing the estimated thickness of the bone portion to be removed with the planned thickness of the bone portion to be removed, and outputting an alarm whenever a deviation is detected to inform medical staff that a discrepancy exists between the pre-planned cutting plane and the actual position of the surgical tool.

[0056] In one embodiment, the surgical tool includes fiducial markers visible to the imaging sensor to aid in estimating the bone resection plane. Depending on the imaging sensor, these markers can be very easy to detect in the stream data. In the present application, infrared reflective markers may be used with a stereo vision sensor including an infrared sensor, or contrasting black and white markers such as Aruco markers may be used with an RGB-D camera. Advantageously, the fiducial markers are easy to detect in the image, making it easier to segment points belonging to the planar surgical tool. Thus, when fiducial markers are used, the segmented points belonging to the planar cutting plane of the surgical tool contain few or no outliers, resulting in a more accurate bone resection plane equation.

[0057] Advantageously, the information obtained by the method of the present invention allows independent confirmation of the realization of the preoperative plan.

[0058] According to one embodiment, the method includes visualizing the output of different steps in real time. In particular, the visualization is configured to show the surface of the simulated 3D model of the bone segment to be removed simultaneously with the surface of the planned 3D model of the bone segment to be removed in real time. These two models may be superimposed in a consistent manner (alignment and / or positioning of the main components of the 3D models), and the visualization may be configured to highlight differences between them. These superimposed models may be displayed simultaneously with values ​​obtained from their comparison using 3D shape analysis to provide qualitative and quantitative feedback to the user. Using such visual feedback, the surgeon can advantageously adapt surgical tool positions to minimize differences so that the surface of the simulated 3D model of the bone segment to be removed matches the surface of the planned 3D model of the bone segment to be removed.

[0059] The method may be used in conjunction with a navigation system, where the planar surgical tool and the portion of the target bone to be removed with the surgical tool are calculated independently of, and therefore not dependent on, the navigation system, and advantageously, the method may provide independent confirmation and assessment of the accuracy of the projected bone resection.

[0060] The method may also be used with a robotic system, in which case the method does not use knowledge of the robot's kinematics and surgical tool position calculated from sensors, and thus can advantageously provide independent confirmation and assessment of the accuracy of the projected bone resection.

[0061] The method of the present invention may be used for target bones that are the tibia or femur.

[0062] Examples of tibias after a single cut with and without an implant are shown in Figure 6 .

[0063] According to one embodiment, steps 110-150 are repeated each time the surgical tool is repositioned relative to the target bone according to a new cutting plane included in the pre-operative plan. In practice, as in the example of the femur shown in Figure 7, the femur is cut according to five planes to ensure a precise fit of the implant.

[0064] The present invention also relates to a system comprising means for carrying out the steps of the method described above. In particular, the system of the present invention comprises: at least one input adapted to receive at least one previously acquired 3D image from at least one 3D imaging sensor, said 3D image being a 3D point cloud including at least one portion of a target bone and at least one portion of a planar cut surface of a surgical tool; at least one processor, Segmentation of the 3D image points belonging to the planar cutting surface of the surgical tool and the target bone, Obtain the spatial orientation and position of the osteotomy plane by 3D fitting the segmented points belonging to the planar cutting surface of the surgical tool; Overlay the osteotomy plane onto the segmented points belonging to the target bone, and select the points that belong to the part of the target bone that will be removed with the surgical tool. a processor configured to: at least one output adapted to provide a point belonging to a portion of a target bone to be removed with a surgical tool; Equipped with.

[0065] In another embodiment, the system is integrated into robotic guidance software that automatically corrects the saw trajectory to ensure the cutting plane matches the surgical plan.

[0066] The embodiments disclosed herein include various operations implemented in different steps of the methods described herein. As discussed above, these operations may be performed by hardware components and / or embodied in machine-executable instructions that cause a general-purpose or special-purpose processor programmed with the instructions to perform the operations. Alternatively, the operations may be performed by a combination of hardware, software, and / or firmware.

[0067] Performance of one or more of the operations described herein may be distributed across one or more processors, i.e., spread across many machines rather than residing within a single machine. In some examples, one or more processors or processor-implemented modules may be located in a single geographic location (e.g., in a home environment, a work environment, or a server farm). In other embodiments, one or more processors or processor-implemented modules may be distributed across many geographic locations.

[0068] The present invention further includes a computer program product for intra-operatively predicting the outcome of a planar cut, the computer program product comprising instructions that, when the program is executed by a computer, cause the computer to perform the steps of the method according to any one of the embodiments described above.

[0069] A computer program product for performing the methods described above may be described as a computer program, code segments, instructions, or any combination thereof, individually or collectively instructing or configuring a processor or computer to operate as a machine or special-purpose computer to perform the operations performed by the hardware components. In one example, the computer program product includes machine code that is executed directly by the processor or computer, such as machine code generated by a compiler. In another example, the computer program product includes higher-level code that is executed by the processor or computer using an interpreter. A programmer skilled in the art can easily write instructions or software based on the block diagrams and flowcharts shown in the drawings and corresponding descriptions herein, which disclose algorithms for performing the operations of the methods described above.

[0070] The present invention further includes a computer-readable storage medium comprising instructions that, when the program is executed by a computer, cause the computer to perform the steps of the method according to any one of the embodiments described above.

[0071] According to one embodiment, the computer readable storage medium is a non-transitory computer readable storage medium.

[0072] Computer programs for implementing the methods of the present invention can generally be distributed to users via computer-readable storage media for distribution, such as, but not limited to, SD cards, external storage devices, microchips, flash memory devices, portable hard drives, and software websites. From the distribution media, the computer programs can be copied to a hard disk or similar intermediate storage medium. The computer programs can be executed by loading computer instructions from either the distribution media or the intermediate storage medium into the computer's execution memory and configuring the computer to operate according to the methods of the present invention. All of these operations are well known to those skilled in the art of computer systems.

[0073] The instructions or software and any associated data, data files, and data structures for controlling a processor or computer to execute the hardware components and perform the methods described above are recorded, stored, or fixed in or on one or more non-transitory computer-readable storage media, including, for example, read-only memory (ROM), random-access memory (RAM), flash memory, CD-ROM, CD-R, CD+R, CD-RW, CD+RW, DVD-ROM, DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-RAM, BD-ROM, BD-R, BD-R LTH, BD-RE, magnetic tape, floppy disk, magneto-optical data storage device, optical data storage device, hard disk, solid-state disk, or any device known to those skilled in the art that can non-transitoryly store the instructions or software and any associated data, data files, and data structures and provide the instructions or software and any associated data, data files, and data structures to a processor or computer so that the processor or computer can execute the instructions. In one example, the instructions or software and any associated data, data files and data structures are distributed over a network coupled computer system such that the instructions and software and any associated data, data files and data structures are stored, accessed and executed by the processors or computers. [Example]

[0074] The present invention is further illustrated by the following example, which applies the method and system of the present invention to a robotic total knee arthroplasty (TKA) procedure and specifically to femoral surface preparation.

[0075] A CT scan of the patient's lower limb is taken in the preoperative phase. The data is segmented to obtain a 3D model of the femur (i.e., the target bone). Using dedicated planning software, the 3D implant model is placed on the 3D femur model. In this way, the equations for the plane cut are defined in the coordinate system of the 3D femur model.

[0076] During the bone preparation stage, after exposing the femur, a planar cutting instrument is positioned within the planned osteotomy plane as included in the preoperative plan estimated by the guidance software with accuracy uncertainty. A depth camera is used to photograph the exposed femur and the saw. Step 120 of the method is used to detect and segment depth data belonging to the femur and the saw. Due to the planarity of the planar cutting surface of the saw, the osteotomy plane is estimated by fitting a 3D plane to the segmented point cloud belonging to the saw. Given the equation of the osteotomy plane, the depth data belonging to the femur is segmented by selecting points that belong to the portion of the target bone to be removed with the surgical tool.

[0077] The method thus makes it possible to obtain a 3D representation of the simulated removal that would result if the cut were made after preoperative planning. 3D shape analysis then compares the simulated bone fragments with the bone fragments planned from the preoperative phase. The surgeon can visualize the simulated bone fragments, the simulated resected bone, and the comparison with the preoperative plan on a dedicated graphical user interface displayed on the screen.

[0078] This system and method allows for the comparison of whether a simulated 3D model of the bone segment to be removed matches the preoperative plan just before making the actual cut (which is irreversible). The system also provides a metric to quantitatively assess the similarity between the simulated 3D model of the bone segment to be removed and the planned 3D model. This comparison is independent of the guidance system itself (e.g., a robotic arm) and is therefore an independent method of verifying the accuracy of surgical execution.

[0079] Surgical guidance systems often also allow visualization of the osteotomy plane (on-screen or using augmented reality) before cutting. However, this feature uses the exact same information used to position the saw in the first place, nothing more. Therefore, if there was already an error in the positioning of the surgical tool (i.e., if the robot records it as being positioned at point A, when it is actually at point B), the same error will be reproduced in the pre-cut verification mechanism.

[0080] Typical robotic systems for orthopedic surgery and TKA in particular use planning, initial positioning, and embedded sensors to direct the physical positioning of surgical tools in space relative to the bone being resected, and therefore do not prevent errors by using the same information to verify whether the surgical tools are properly positioned.

[0081] In contrast, the present system and method advantageously allows for independent verification relying on external measurement devices (depth cameras) that do not rely on any kinematic or positioning data from the robot or navigation system, and are therefore not affected by their initial positioning errors.

Claims

1. 1. A computer-implemented method (100) for intra-operatively predicting the outcome of a planar cut made on a target bone of a subject using a planar surgical tool comprising a planar cutting plane (Sc), the method comprising: receiving (110) at least one 3D image (Im) acquired from at least one 3D imaging sensor, said 3D image (Im) being a 3D point cloud comprising at least one portion of said target bone (Bt) and at least one portion of a planar cutting surface (Sc) of said surgical tool; - segmenting (120) the 3D point cloud to obtain 3D point cloud points belonging to a planar cutting plane (Sc) of the surgical tool and 3D point cloud points belonging to the target bone (Bt); - obtaining (130) the spatial orientation and position of the osteotomy plane (P) by fitting a plane to the segmented points belonging to the planar cutting surface (Sc) of said surgical tool; - superimposing (140) the osteotomy plane (P) on the segmented points belonging to the target bone (Bt) and selecting points belonging to the part of the target bone (Pr) to be removed with the surgical tool; - outputting (150) points belonging to the part of the target bone (Pr) intended to be removed with said surgical tool; A method comprising:

2. The method of claim 1 , further comprising generating a simulated 3D model of the bone portion to be removed using points belonging to the target bone portion (Pr) to be removed with the surgical tool.

3. receiving a pre-operative plan including a 3D model of the target bone and an equation of a planned cutting plane in a reference coordinate system of the 3D model of the target bone; - obtaining a planned 3D model of the bone portion to be removed by applying the equation of the cutting plane to a 3D model of the target bone; - comparing the simulated 3D model and the planned 3D model of the bone portion to be removed using 3D shape analysis and outputting the results of the comparison; The method of claim 2 further comprising:

4. The method of claim 3 , wherein the result of the comparison is a 3D shape similarity measure or a matching error.

5. - Calculating the principal components of the simulated 3D model; - determining a bounding box of the bone portion to be removed from the principal components; - estimating the thickness of the bone portion to be removed from the bounding box; The method of any one of claims 2 to 4, further comprising:

6. - comparing the estimated thickness of the bone portion to be removed with the planned thickness of the bone portion to be removed; - issuing an alarm whenever a deviation from said planned thickness is detected; The method of claim 5 further comprising:

7. 7. The method according to any one of claims 1 to 6, wherein the surgical tool includes fiducial markers to aid in obtaining the spatial orientation and position of the osteotomy plane (P).

8. The method of any one of claims 1 to 7, wherein the target bone is a femur or a tibia.

9. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to any one of claims 1 to 8.

10. A computer readable medium comprising instructions which, when executed by a computer, cause the computer to perform the steps of the method of any one of claims 1 to 8.

11. 1. A system for intra-operatively predicting the outcome of a planar cut made on a target bone of a subject using a planar surgical tool comprising a planar cutting plane (Sc), the system comprising: at least one input adapted to receive at least one 3D image (Im) acquired from at least one 3D imaging sensor, said 3D image (Im) being a 3D point cloud comprising at least one portion of said target bone (Bt) and at least one portion of a planar cutting surface (Sc) of said surgical tool; at least one processor, segmenting the 3D point cloud to obtain 3D point cloud points belonging to a planar cutting surface (Sc) of the surgical tool and 3D point cloud points belonging to the target bone (Bt); Obtaining the spatial orientation and position of the osteotomy plane (P) by 3D fitting the segmented points belonging to the planar cutting plane (Sc) of said surgical tool; and superimposing the osteotomy plane (P) on the segmented points belonging to the target bone (Bt) and selecting the points belonging to the part of the target bone (Pr) that is to be removed with the surgical tool; a processor configured to at least one output adapted to provide a point belonging to a portion (Pr) of the target bone intended to be removed with said surgical tool; A system comprising:

12. 12. The system of claim 11, wherein the at least one processor is further configured to generate a simulated 3D model of the bone portion to be removed using points belonging to the target bone portion to be removed with the surgical tool.

13. The at least one processor further comprises: receiving a pre-operative plan including a 3D model of the target bone and an equation of a planned cutting plane in a reference coordinate system of the 3D model of the target bone; obtaining a planned 3D model of the bone portion to be removed by applying the cutting plane equation to a 3D model of the target bone; and comparing the simulated 3D model and the planned 3D model of the bone portion to be removed using 3D shape analysis, and outputting the results of the comparison; The system of claim 12 configured to:

14. The at least one processor further comprises: - calculating the principal components of the simulated 3D model; determining a bounding box of the bone portion to be removed from the principal components; and The system according to claim 12 or 13, configured to estimate the thickness of the bone portion to be removed from the bounding box.

15. The at least one processor further comprises: comparing the estimated thickness of the bone portion to be removed with the planned thickness of the bone portion to be removed; and - Issues an alarm whenever a deviation from the planned thickness is detected The system of claim 14 configured to:

16. 14. The system of claim 13, wherein the at least one processor is further configured to generate a 3D shape similarity measure or matching error as a result of the comparison between the simulated 3D model and the planned 3D model.

Images