Intraoperative resection planning for kinematic alignment

Abstract

A method for planning a surgery to a knee joint includes recording a target HKA for a patient and, based on an evaluation of wear of the knee joint, setting an initial resection plan including setting planned femoral resections and setting at least one planned tibial resection. The method includes determining a planned HKA of the patient based on the initial resection plan. The planned HKA is a function of a femoral coronal alignment provided by the planned femoral resections and a tibial coronal alignment of the patient provided by the planned at least one tibial resection. The method further includes selectively adjusting the initial resection plan based on the target HKA and the planned HKA by adjusting the planned tibial coronal alignment and / or the planned femoral coronal alignment to provide an adjusted resection plan with an adjusted planned HKA that is within a threshold of the target HKA.

Description

INTRAOPERATIVE RESECTION PLANNING FOR KINEMATIC ALIGNMENTBACKGROUND

[0001] Aspects described herein relate to surgical applications, and more specifically to processes for registration of patient anatomy and the planning of surgical resections for kinematic alignment.SUMMARY

[0002] Shortcomings of the prior art are overcome and additional advantages are provided through the provision of methods, systems and computer program products as described herein.

[0003] In an embodiment, a computer-implemented method for planning a surgery to a knee joint of a patient having a femur and tibia is provided. In such an embodiment, the method includes recording a target hip-knee-ankle angle (HKA) for the patient based on a preoperative assessment of the knee joint and, based on an evaluation of wear of the knee joint, setting an initial resection plan for resurfacing the patient femur and resurfacing the patient tibia. The setting the initial resection plan includes setting planned femoral resections to the patient femur to resurface the patient femur and setting at least one planned tibial resection to the patient tibia to resurface the patient tibia. The method further includes determining a planned postoperative HKA of the patient based on the initial resection plan, wherein the planned post-operative HKA is a function of a planned post-operative femoral coronal alignment of the patient provided by the planned femoral resections of the initial resection plan, and a planned post-operative tibial coronal alignment of the patient provided by the planned at least one tibial resection of the initial resection plan. The method further includes selectively adjusting the initial resection plan based on the target HKA and the planned post-operative HKA, wherein the selectively adjusting adjusts one or both of (i) the planned post-operative tibial coronal alignment by adjusting a planned tibial resection of the at least one planned tibial resection, and (ii) the planned post-operative femoral coronal alignment by adjusting a planned femoral resection of the planned femoral resections, and provides an adjusted resection plan with an adjusted planned post-operative HKA that is within a threshold of the target HKA.6361.005AWO Page 1 of 38

[0004] In some embodiments, the selectively adjusting adjusts one or both of the planned post-operative tibial coronal alignment and the planned post-operative femoral coronal alignment such that the adjusted planned post-operative HKA matches the target HKA.

[0005] In some embodiments, the selectively adjusting adjusts the planned postoperative tibial coronal alignment to provide the adjusted resection plan with the adjusted planned post-operative HKA and maintains the planned post-operative femoral coronal alignment the same as under the initial resection plan.

[0006] In some embodiments, the target HKA is determined intraoperatively as part of intraoperative registration of patient anatomy of the knee joint.

[0007] In some embodiments, the selectively adjusting includes determining whether to adjust the initial resection plan based on whether a difference between the target HKA and the planned post-operative HKA exceeds the threshold and performing processing based on the determining whether to adjust.

[0008] In some embodiments, the setting the planned femoral resections includes adjusting, based on evaluated femoral distal medial wear and femoral distal lateral wear, a femoral varus / valgus parameter for one or more planned distal femoral resections to be made to a distal portion of the patient femur and adjusting the one or more planned distal femoral resections proximally or distally based on a distal thickness of a femoral implant component. In such an embodiment, the setting the planned femoral resections further includes adjusting, based on evaluated femoral posterior medial and femoral posterior lateral wear, femoral implant component internal / extemal rotation to set a slope of one or more posterior femoral resections to be made to a posterior portion of the patient femur and adjusting femoral implant positioning to a desired position based on a posterior thickness of the femoral implant component. In such an embodiment, the setting the at least one planned tibial resection includes adjusting, based on evaluated tibial medial wear and tibial lateral wear, a tibial varus / valgus parameter for the planned at least one tibial resection to be made to the patient tibia and adjusting the at least one planned tibial resection proximally or distally based on thickness of one or more tibial implant components.6361.005AWO Page 2 of 38

[0009] In some embodiments, the setting the planned femoral resections and the setting at least one planned tibial resection is performed absent use of data describing balance of soft tissue of the knee joint.

[0010] Computer systems having memory and processing circuit(s) in communication with the memory, and configured to perform methods according to aspects described herein are also provided. Further provided are computer program products having a computer readable storage medium readable by processing circuit(s) and storing instructions for execution by the processing circuit(s) for performing aspects described herein.

[0011] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail herein (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter and may be used in different or alternative combinations as described to achieve the benefits and advantages described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Objects, features, and advantages of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

[0013] FIG. 1 depicts an example kinematic resection planning workflow for planning resections of a total knee arthroplasty, in accordance with aspects described herein;

[0014] FIG. 2 depicts an example workflow for planning femoral resection(s) in accordance with aspects described herein;

[0015] FIG. 3 depicts an example workflow for planning tibial resection(s) in accordance with aspects described herein;

[0016] FIGS. 4A-4B depict example conceptual representations of registering anatomical wear in a knee joint, in accordance with aspects described herein;6361.005AWO Page 3 of 38

[0017] FIG. 5 depicts yet another example resection planning workflow for planning resections of a total knee arthroplasty, in accordance with aspects described herein; and

[0018] FIG. 6 depicts an example computer system to perform aspects described herein.DETAILED DESCRIPTION

[0019] Aspects described herein provide an intraoperative surgical resection planning method or assistant, for instance one implemented as software for use in interoperative planning of a surgical procedure. In some aspects, an intraoperative algorithm is provided in, or at least partially implemented by, software to automate a process of identifying and achieving optimal targets in joint replacement surgeries. More specifically, aspects described herein are presented in the context of a total knee arthroplasty (“TKA”) by way of example, though it should be understood that aspects may be applied to other types of joint replacement surgeries.

[0020] Using intraoperatively generated / obtained patient-specific data, and requiring no pre-operative imaging or planning, aspects can algorithmically achieve balanced knee alignment (e.g., tibial-femoral alignment) and / or balanced hip-knee- ankle alignment (“HKA”) via the resection aspect of a TKA (by way of example) to provide a results-driven outcome. Aspects can correct varying degrees and severity of knee deformity, allowing for consistent and reproducible post-operative outcomes. Aspects may be implant-agnostic and / or robotic-system-agnostic, relying on intraoperative data collection of the wear on the bones of a patient’s knee. Aspects can extend beyond total knee arthroplasty into partial knee replacement aspects (as an example) as well.

[0021] Auto-solve aspects described herein can greatly improve efficiency, accuracy, and accessibility in this domain. This will lead to more consistent and reproducible surgical outcomes, and reduce the barriers to adopting data-driven approaches in surgery.

[0022] There are several problems associated with intraoperative data collection during surgical resection planning. For instance, there is no current intraoperative registration system in which the amount of wear on the cartilage and / or bone of a joint6361.005AWO Page 4 of 38(e.g., on the articular surfaces of the bones of the joint) can automatically be detected, nor are there systems which allow for the amount of wear to be input manually. Rather, present systems merely generate models of patients’ bones by using the raw dimensions of the bones, and are not able to capture the information necessary to calculate aspects of various resections. For instance, present systems are not able to independently determine the amount of resection needed or the angle such a resection must be made to correct knee deformity such as varus knee deformity or valgus knee deformity.

[0023] Aspects described herein address these and other problems. From a clinical outcome standpoint, processing described herein uses an algorithm that synchronizes with intraoperative data which includes data on wear to calculate optimized resection targets in real-time to consistently meet pre-operative expectations and deliver superior clinical outcomes. The automation of aspects of resection planning can lead to substantial cost savings by reducing the need for manual labor for both care facilities and industry. The automated process can also reduce or eliminate the need for training on the relevant segment(s) of the surgical process. Additionally, removing the uncertainty in identifying optimal resection targets, as well as how easily to achieve them, can reduce operating room times, provide clinician confidence, and encourage more widespread adoption of automated surgical systems to assist with surgeries.

[0024] Software incorporating aspects described herein can help simplify the surgical process by providing a single surgical solution (e.g., a best or optimal solution) based on clinical data to streamline the resection targeting process when balancing knee alignment and / or HKA. Software-driven solutions that address patient-specific needs can be built on a foundation of proven and successful clinical results, making them capable of being used on patients presenting with variable anatomic factors in order to deliver improved outcomes.

[0025] In the context of a TKA, there are a number of variables, dimensions and / or parameters which may be measured, or which must otherwise be known in order to generate a surgical resection plan. For example, the amount of wear on the femur (FW) and / or the amount of wear on the tibia (TW) may need to be determined. Further, the thickness(es) of any implant components (both medially and / or6361.005AWO Page 5 of 38posteriorly) to be inserted into the knee joint are relevant parameters. Some implant components may vary in thickness. Ultimately, the goal is for the amount to be resected from a given location plus the amount of wear at that location to equal the thickness of the component to be inserted at that location.

[0026] The amount to be resected from the femur and / or tibia in order to resurface the femur and / or tibia to their pre-arthritic state(s) may be referred to as the resection goal(s) (RG(s)). For the femur, there may be at least four resection goals - the femoral distal medial resection (FDMR), the femoral distal lateral resection (FDLR), the femoral posterior medial resection (FPMR) and the femoral posterior lateral resection (FPLR). For the tibia, there may be at least two resection goals - the tibial medial resection (TMR) and the tibial lateral resection (TLR).

[0027] FIG. 1 depicts an example kinematic planning workflow for planning resections of a total knee arthroplasty in accordance with aspects described herein. The resection planning may be set based on an intraoperative evaluation 102 of patient anatomy to determine some or all the dimensions and / or parameters outlined above. The workflow of FIG. 1 is discussed herein primarily in the context of a TKA for a patient with mild varus knee. However, it should be understood that the workflow of FIG. 1 may be useful in procedures for a variety of knee deformities. In the example, the femur and / or tibia of the varus knee may have mild medial wear, as discussed in more detail below. Aspects of the workflow could be performed manually (e.g., by a surgeon / user), automatically (e.g., by a computer system), or a combination of both.

[0028] Referring to FIG. 1, the process includes an intraoperative evaluation 102 of patient anatomy (e.g., knee joint anatomy such as the femur and / or tibia), particularly articular cartilage and / or bone wear therein. This may include, for instance, inspecting the patient’s knee joint intraoperatively to determine tibial wear (TW) and / or femoral wear (FW). In this example, femoral wear has components: distal medial femoral wear (FDMW), distal lateral femoral wear (FDLW), posterior medial femoral wear (FPMW), and / or posterior lateral femoral wear (FPLW). The FW, including FDMW, FDLW, FPMW, FPLW components, are parameters that may be used in planning one or more femoral resection(s). Also, in this example, tibial wear has the components of medial tibial wear (TMW) and lateral tibial wear (TLW).6361.005AWO Page 6 of 38The TW, including TMW and TLW components, are parameters that may be used in planning one or more tibial resection(s).

[0029] Another parameter that may be relevant, and thus may be evaluated and considered intraoperatively as explained herein, is the hip-knee-ankle angle or alignment (HKA) of the knee joint to be treated. The HKA is a measure of the alignment of the leg, before any cuts and / or resections are made.

[0030] In addition, and notably in comparison to conventional practices, there is no requirement and / or need to record or use data related to soft tissue as part of the process, such as data which may be collected with the use of a tensioner, nor is there a requirement and / or need to record or use a soft tissue balance graph.

[0031] For context, FIGS. 4A-4B depict example conceptual representations of registering anatomical wear in a knee joint, in accordance with aspects described herein. Cartilage 401 and bone 402 depicted in FIGS. 4A-4B may correspond to the patient’s femur or tibia. An amount of wear can be recorded as a selection from a collection of available wear levels corresponding to various points. FIGS. 4A-4B depict an example with six levels of wear at points A = 0 millimeters (mm) (no wear), B = 1 mm cartilage wear, C = 2 mm cartilage wear, D = 3 mm total wear (2 mm cartilage wear plus 1mm bone wear), E = 4 mm total wear (2 mm cartilage wear plus 2 mm bone wear), and F = 5 mm total wear (2 mm cartilage wear plus 3 mm bone wear). A typical femur or tibia initially has 2 mm of cartilage. Thus, at point C (representing 2 mm cartilage wear), the cartilage 401 is shown having worn through to the bone 402 - this location may be referred to as a “tidemark”. The tidemark may be viewed as a reproducible point at which 2 mm (in these examples) of wear may be assumed. Intraoperative evaluation of the patient’s knee (FIG. 1, 102) may include determining the level of wear at the relevant location(s) to be intraoperatively registered, including locating the tidemark, if present.

[0032] Thus, returning to FIG. 1, the process may further include intraoperative registration 104 of the patient anatomy. Intraoperative registration 104 may include multiple components and / or actions. For example, intraoperative registration 104 may include general registration using conventional processes, systems and / or technologies. The manner of registering the alignment and anatomy of the knee and leg (e.g., of the HKA) may be dependent on the particular technological system is6361.005AWO Page 7 of 38being utilized. For instance, this can be CT-based or non-CT-based, optical-based, ultrasound-based, or based on any other system that utilizes registration and navigation to aid in arthroplasty. General registration may be sufficient to generate a basic model (e.g., a computer model) of the patient’s femur and / or tibia. In some embodiments, this may include sweeping or brushing (e.g., “painting”) a tool over the bone(s) of the patient’s knee joint, the tool providing spatial data used to generate a basic model representing the dimensions of the patient’s femur and / or tibia.

[0033] One challenge with traditional intraoperative registration systems and methods is that the model generated from these systems and methods may not lend itself to independent measurement and / or registration of cartilage and / or bone wear. While traditional processes may be sufficient to generate a basic model, the model does not indicate how much wear is present at the relevant locations along the femur and / or tibia, which may limit the value, usefulness and / or application of these traditional systems and methods in surgical resection planning. For example, the amount of wear may need to be known at various locations in order to calculate or otherwise determine a desired and / or proper location of one or more resection(s) to be performed as part of the TKA.

[0034] In some embodiments, intraoperative registration 104 may include using a wand or probe 403 to register points and / or locations of wear on the cartilage 401 and / or bone(s) 402 of the patient’s femur and / or tibia, as shown in FIGS. 4A-4B. This method of probing or “depth gauging” may be performed independently of other registration processes to create a model of the patient’s bone(s) that includes and / or accounts for tibial and / or femoral wear. Alternatively, depth gauging may be performed after, or in conjunction with, traditional processes (e.g., the painting of the bone(s)) to generate a digital model as described above, but which accounts for wear. In the former example, depth gauging is used to generate the model and inform the model regarding the presence of cartilage and / or bone wear. In the latter example, the depth gauging is used to update a basic model of the patient’s bone(s) to account for how much cartilage and / or bone wear is present. In both examples, a model is generated which accounts for cartilage and / or bone wear, providing advantages to the user when planning resections, such as for a TKA.6361.005AWO Page 8 of 38

[0035] Informing wear may allow for a computer to automatically and / or algorithmically calculate aspects of the resection plan, such as one or more resection(s) which can be performed to resurface the femur and / or tibia to their pre- arthritic state(s). This automatic function may increase efficiency during surgery, for example, by reducing the amount of time invested to plan one or more surgical resection(s), by reducing the number of necessary personnel in an operating room, and / or by decreasing intra-operative cognitive load and inefficiencies, among other advantages. As described herein, information regarding the thickness(es) of implant components to be inserted into the knee joint and / or other information may be used in calculating the RGs (e.g., resections to achieve a desired HKA) to assist in aspects of the resection planning.

[0036] Referring again to FIGS. 4A-4B, in embodiments, the user (e.g., a surgeon) may touch a tip of the probe 403 to one or more locations of wear along the femur and / or tibia in order to register relevant locations of wear for or on a computer model. In FIG. 4A, the probe 403 is shown contacting an unworn surface of the patient’s cartilage 401 corresponding to point A, which represents 0 mm of wear (no wear). Once the probe 403 has contacted the cartilage 401, the location may be registered on the model. The user may then manually input the amount of wear (here, 0 mm), for example, by using a digital interface (e.g., a computer interface) to inform the model regarding wear at that location by interacting with a graphical user interface element such as a button, radio selection, input field, or other element. In some embodiments, the user may press one or more buttons of a set of buttons 404 to inform the model regarding wear at the probed location. In some embodiments, the user may use another input method such as moving a slider (e.g., on a computer interface) to inform the model regarding wear. In some embodiments, the computer may default the values of probed locations to 0 mm of wear, which are then manually adjusted by the surgeon. In such embodiments, where no wear is present, the user may not need to manually input the amount of wear at the registered location and may instead proceed to register other relevant locations of wear. Relevant locations of wear to be registered may include, for example, FDMW, FDLW, FPMW, FPLW, TLW, and / or TMW.

[0037] In FIG. 4B, the probe 403 is shown contacting a worn surface of the patient’s cartilage 401 corresponding to point B, which represents 1 mm of wear to6361.005AWO Page 9 of 38the patient’s cartilage 401. Once the probe 403 has contacted the cartilage 401 at point B, the user may manually input the amount of wear (here, 1 mm) in a similar manner to above using a digital interface (e.g., a computer interface) to inform the model regarding wear at that location. For example, the user may press one or more buttons of the set of buttons 404 to inform the model regarding wear at the probed location(s).

[0038] In some embodiments, intraoperative registration 104 may further include obtaining measurements regarding the alignment of the tibia and femur relative to each other, and / or the alignment of the knee, hip and ankle relative to each other (the “hip-knee-ankle” angle or HKA). Specifically, there may be a desire to record a patient’s “arthritic” HKA (A-HKA) representing the pre-operative HKA of the patient. Additionally, there may be a desire to record and / or store a “correctable” HKA (C-HKA) representing the desired HKA (e.g., target HKA) of the patient following treatment of the knee joint (e.g., following a TKA). When stress is applied to the leg during surgery, but before any resections are performed, it may be possible to record and / or store both the A-HKA and the C-HKA of a patient. The resections may thus be planned to result in a post-operative HKA that matches to a target, such as the C-HKA (or to within a threshold thereof), following surgery (e.g., following a TKA), as described in more detail below. Measurements regarding the patient’s HKA (e.g., A-HKA or C-HKA) may be collected and used as part of the process absent any data regarding surrounding soft tissues (e.g., soft tissue balance).

[0039] Referring back to FIG. 1, in various embodiments, intraoperative evaluation 102 may be combined with intraoperative registration 104. For example, in some embodiments, the user may perform intraoperative registration 104 while performing intraoperative evaluation 102 of wear. In some embodiments where intraoperative registration 104 includes both brushing (e.g., “painting”) the femur and / or tibia and depth gauging (e.g., via the probe 403), the user may first intraoperatively register 104 the relevant anatomy by sweeping the patient’s anatomy to generate a basic model that does not account for wear. In such an embodiment, the user may then intraoperatively evaluate 102 the anatomy for wear, and then return to intraoperatively registering 104 that wear using depth gauging. Intraoperative evaluation 102 and intraoperative registration 104 may thus occur in different orders relative to each other, or simultaneously, depending on the embodiment.6361.005AWO Page 10 of 38

[0040] As depicted in FIG. 1, the process may further include planning 106 one or more femoral resections and / or planning 108 one or more tibial resections. In an example, the one or more femoral resection(s) may be planned 106 before the one or more tibial resection(s) are planned 108. In other embodiments, the one or more tibial resection(s) may be planned 108 before the one or more femoral resection(s) are planned 106. The detailed description will proceed below to discuss an example in which the femoral resection(s) are planned 106 before the tibial resection(s) are planned 108, but it should be understood that the example is for illustrative purposes only, and the order of planning 106 the femoral resection(s) and the planning 108 the tibial resection(s) may occur in any order relative to each other. Additionally, there is no requirement to record, or if recorded no requirement to use, data related to soft tissue as part of the workflow of FIGS. 1, 2 or 3, such as data which may be collected with the use of a tensioner, nor is there a requirement to record, or if recorded to use, a soft tissue balance graph.

[0041] Aspects of the workflow(s) are discussed herein primarily in the context of a TKA for a patient with mild varus knee for illustrative purposes. However, it should be understood that the workflow(s) may be useful in a variety of procedures to be performed on the knee for a variety of deformities.

[0042] FIG. 2 depicts an example workflow for planning 106 the femoral resection(s) in accordance with aspects described herein. Aspects of FIG. 2 may be performed automatically (e.g., by a computer employing an algorithm), manually (e.g., by a user and / or surgeon), or a combination of both. Planning 106 the femoral resection(s) may include adjusting 202 femoral varus / valgus to determine a slope of one or more cut(s) or resection(s) to be made to the distal medial femur and the distal lateral femur. Relevant anatomic parameters for adjusting 202 the femoral varus / valgus may include FDMW and FDLW. In the example, the patient exhibits (and intraoperative registration identifies) 2 mm FDMW and 0 mm FDLW.

[0043] Initially, adjusting 202 the femoral varus / valgus may include determining a femoral distal difference (FDD), i.e., the difference in wear between the distal medial and distal lateral sides of the femur. The FDD may inform whether the patient exhibits a varus or valgus condition. If FDD = FDLW - FDMW, then a positive FDD reflects a valgus condition and a negative FDD reflects a varus condition (FDD = 06361.005AWO Page 11 of 38reflects a neutral alignment). As noted above, the example patient here exhibits 2 mm FDMW and 0 mm FDLW. Thus, in the example patient, FDD = 0 - 2 mm = -2 mm, verifying that the patient exhibits a varus condition.

[0044] Alternatively, FDD may be defined as FDD = FDMW - FDLW, in which case a negative FDD reflects a valgus condition and a positive FDD reflects a varus condition. Thus, in the example, FDD = 2 mm - 0 mm = 2 mm, again verifying that the patient exhibits a varus condition. Whether the calculation is performed using FDD = FLDW - FDMW or FDD = FDMW - FLDW is a matter of preference. Aspects are described below as if FDD = FDLW - FDMW, however, it should be understood by one skilled in the art that embodiments of the systems and methods described herein may use either calculation.

[0045] The planned distal femoral resection(s) can account for any varus / valgus condition, for instance by adjusting so that the difference between the planned femoral distal medial resection on the medial femur and the planned femoral distal lateral resection on the lateral femur is the same as the FDD (-2 mm, in this example), meaning a greater amount of femoral wear will result in a lesser amount of resected bone at that location. In other words, software can automatically adjust the varus / valgus alignment until FDMW - FDLW = FDD. In this example, and continuing with the example values above, the FDD of -2 mm informs that the distal femoral resection(s) should be -2 mm medially than laterally. Said differently, the distal femoral resection(s) should be sloped and / or angled such that 2 mm less bone is resected from the distal medial femur as compared to the distal lateral femur.

[0046] In one particular example, after adjusting 202 the femoral varus / valgus to determine the slope of the resection(s) as described above, the software may proceed to adjust 204 the planned distal femoral resection(s) proximally or distally (while maintaining the slope). Relevant parameters for adjusting 204 the resection(s) proximally or distally include the desired and / or actual distal thickness of the relevant implant component, here being the femoral component. The thickness of the femoral component may be set / selected by a surgeon or could be set / determined automatically, if desired, and may be upsized or downsized during resection planning depending on aspects of the process. By way of non-limiting example, the desired distal femoral component thickness for the example patient is 9 mm (a common6361.005AWO Page 12 of 38thickness for such a component). In other examples, a different femoral component having a different thickness may be used. In any case, the femoral component may be subject to modification during the process.

[0047] Another relevant parameter to adjusting 204 the planned distal femoral resection(s) proximally or distally may be the RGs, specifically, the FDMR and the FDLR. The FDMR and FDLR may be defined as the difference between the femoral component distal thickness and either FDMW or FDLW, respectively. Thus, femoral component distal medial thickness - FDMW = FDMR, and femoral component distal lateral thickness - FDLW = FDLR. Said another way, FDMR + FDMW = femoral component distal medial thickness, and FDLR + FDLW = femoral component distal lateral thickness. However, in some embodiments, because the slope of the planned distal femoral resection(s) has already been determined, the process could perform only one of these two calculations to determine the proximal / distal adjustment to be made to the distal femoral resection(s). The software may simply adjust 204 one of the FDMR or the FDLR proximally or distally using whichever equation relates to the chosen parameter, and, by maintaining the slope determined by adjusting 202 the femoral varus / valgus, the other of the FDMR or the FDLR is automatically adjusted.

[0048] As noted above, an example femoral component thickness of 9 mm is used in planning 106 the femoral resection(s) for the example patient. Thus, in an example, the proximal / distal adjustment to the distal femoral resection(s) may be determined by calculating 9 mm - 0 mm = 9 mm, and thus FDLR = 9 mm. The planned distal femoral resection may thus be adjusted 9 mm proximally, and 9 mm total is to be resected from the lateral distal femur in order to accommodate the femoral component. Because it was earlier determined that there is a -2 mm difference in the amount of wear between the FDLW and FDMW, the FDMR may thus automatically be calculated by the software. For example, the FDMR may automatically be calculated by adding the FDLR and the FDD in order to determine FDMR while also maintaining the slope of the planned distal femoral resection(s). In the example, 9 mm + (-2 mm) = 7 mm, and thus FDMR = 7 mm.

[0049] Upon determining the values for FDMR and FDLR, the software may perform an additional calculation to confirm those values are correct. For example, the software may run a calculation to confirm that FDMR - FDLR = FDLW -6361.005AWO Page 13 of 38FDMW, i.e., that the amount to be resected from the distal medial femur and the distal lateral femur is equal to the amount of wear on the distal lateral femur minus the amount of wear on the distal medial femur. In the example, 7 mm - 9 mm = 0 mm - 2 mm = -2mm, and thus the condition is met, and the software may confirm the amounts to be resected from the distal medial femur and the distal lateral femur, respectively. Thus, in the example, the software confirms that FDMR = 7 mm and FDLR = 9 mm.

[0050] In some embodiments, where a distal thickness of the femoral component is known, adjusting 202 the femoral varus / valgus and adjusting 204 the distal femoral resection(s) proximally or distally may be performed in any order relative to each other. Thus, while an embodiment of the process is described above in which the femoral varus / valgus is adjusted 202 and then the resection(s) are adjusted 204 proximally or distally, there may be other embodiments in which the resection(s) are adjusted 204 proximally or distally and then the femoral varus / valgus is adjusted 202 to determine the slope of the resection(s). However, adjusting 202 the femoral varus / valgus and adjusting 204 the resection(s) proximally or distally are to be performed before or after planning resection(s) to the posterior femur, as described below.

[0051] Planning 106 the femoral resection(s) may further include adjusting 208 femoral intemal / extemal rotation to determine the slope of one or more cut(s) or resection(s) to be made to the posterior medial femur and the posterior lateral femur. Relevant anatomic parameters for adjusting 208 the femoral internal / extemal rotation may include FPMW and FPLW. In the example, the patient exhibits (and intraoperative registration identifies) 2mm FPMW and 0mm FPLW. Adjusting 208 femoral intemal / extemal rotation may refer more specifically to a modification to influence the rotational alignment of the femoral component as it is received thereon, which may influence the post-operative angular relationship between the femur and the tibia of the knee joint as it transitions between flexion and extension.

[0052] Initially, adjusting 208 the femoral internal / extemal rotation may include determining a femoral posterior difference (FPD), i.e., the difference in wear between the posterior medial and posterior lateral sides of the femur. The FPD may further inform whether the patient exhibits an internally or externally rotated position. If FPD6361.005AWO Page 14 of 38= FPLW - FPMW, then a positive FPD reflects an externally rotated condition and a negative FPD reflects an internally rotated condition (FPD = 0 reflects a neutral alignment). As noted above, the example patient here exhibits 2 mm FPMW and 0 mm FPLW. Thus, in the example patient, FPD = 0 - 2 mm = -2 mm, verifying that the patient exhibits an internally rotated condition.

[0053] Alternatively, FPD may be defined as FPD = FPMW - FPLW, in which case a negative FPD reflects an externally rotated condition and a positive FPD reflects an internally rotated condition. Thus, in the example, FPD = 2 mm - 0 mm = 2 mm, again verifying that the patient exhibits an internally rotated condition. Whether the calculation is performed using FPD = FPLW - FPMW or FPD = FPMW - FPLW is a matter of preference. Aspects are described below as if FPD = FPLW - FPMW, however, it should be understood by one skilled in the art that embodiments of the systems and methods described herein may use either calculation.

[0054] The planned posterior femoral resection(s) can account for the impact of any varus / valgus condition on the intemal / extemal rotation of the femur, for instance by adjusting so that the difference between the planned femoral posterior medial resection on the medial femur and the planned femoral posterior lateral resection on the lateral femur is the same as FPD (-2 mm, in this example), meaning a greater amount of femoral wear will result in a lesser amount of resected bone at that location. In other words, software can automatically adjust the internal / external rotation of the femur until FPMW - FPLW = FPD. In this example, and continuing with the example values above, the FPD of -2 mm informs that the posterior femoral resection(s) should be sloped and / or angled such that 2 mm less bone is resected from the posterior medial femur as compared to the posterior lateral femur.

[0055] In one particular example, after adjusting 208 the femoral internal / external rotation to determine the slope of the resection(s) as described above, the software may proceed to adjust 210 femoral flexion and extension (flex / extend the planned femoral component) until the corresponding amount of bone to be resected from the posterior medial femoral condyle equals the femoral component thickness of the posterior medial femoral condyle minus the amount of wear in that anatomic location (i.e., minus FPMW). One relevant parameter here may therefore be the desired and / or actual posterior thickness of the femoral implant component. The posterior thickness6361.005AWO Page 15 of 38of the femoral component may be set / selected by a surgeon or could be set / determined automatically, if desired, and therefore may be upsized or downsized depending on aspects of the process. By way of non-limiting example, the desired posterior femoral component thickness for the example patient is 9 mm (a common thickness for such a component). In other examples, a different femoral component having a different posterior thickness may be used if needed, for instance if flexion or extension of the component pursuant to 210 is needed beyond set threshold(s) as explained further below. In any case, the femoral component may be subject to modification during the process.

[0056] Another relevant parameter to adjusting 210 the planned femoral resection(s) to account for the internal / external rotation of the femur may be the RGs, specifically the FPMR and the FPLR. The FPMR and FPLR may be defined as the difference between the femoral component posterior thickness and either FPMW or FPLW, respectively. Thus, femoral posterior medial component thickness - FPMW = FPMR, and femoral posterior lateral component thickness - FPLW = FPLR. Said another way, FPMR + FPMW = femoral component posterior medial thickness, and FPLR + FPLW = femoral component posterior lateral thickness. However, because the slope of the planned posterior femoral resection has already been determined, the process could perform only one of these two calculations to determine the adjustment to be made to femoral flexion and extension. The software may simply adjust 210 one of the FPMR or the FPLR using whichever equation relates to the chosen parameter, and by maintaining the slope determined by adjusting the femoral flexion and extension, the other of FPMR and FPLR is automatically adjusted.

[0057] As noted above, an example femoral component posterior thickness of 9 mm is used in planning 106 the femoral resection(s) for the example patient. Thus, in an example, the adjustment to the femoral flexion and extension may be determined by calculating FPLR as 9 mm - 0 mm = 9 mm, and thus FPLR = 9 mm. The planned posterior femoral resection may thus be adjusted 9 mm (e.g., proximally), and 9 mm total is to be resected from the lateral posterior femur in order to accommodate the femoral component. Because the software earlier determined there to be a -2 mm difference in the amount of wear between the FPLW and FPMW, the FPMR may thus automatically be calculated by the software. For example, the FPMR may automatically be calculated by adding the FPLR and the FPD in order to determine6361.005AWO Page 16 of 38FPMR while also maintaining the slope of the planned posterior femoral resection(s).In the example, 9 mm + (-2 mm) = 7 mm, and thus FPMR = 7 mm.

[0058] In some embodiments, where a posterior thickness of the femoral component is known, adjusting 208 femoral intemal / external rotation and adjusting 210 femoral component flexion and extension may be performed in any order relative to each other. Additionally, or alternatively, anterior or posterior translation may be used to position the femoral component and accomplish the same intend as the adjusting 210 femoral component flexion and extension. Thus, while an embodiment of the process is described above in which the femoral intemal / external rotation is adjusted 208 and then the femoral flexion and extension are adjusted 210, there may be other embodiments in which the femoral flexion and extension are adjusted 210 and then the femoral internal / external rotation is adjusted 208 to determine the slope of the resection(s). However, adjusting 208 the femoral internal / extemal rotation and adjusting 210 the femoral component flexion and extension are to be performed before or after planning resection(s) to the distal femur as described above. Thus, the adjusting 202, 204 may be performed before or after the adjusting 208, 210.

[0059] Upon determining the values for FPMR and FPLR, the software may perform a calculation to confirm those values are correct. For example, the software may run a calculation to confirm that FPMR - FPLR = FPLW - FPMW, i.e., that the amount to be resected from the posterior medial femur and the posterior lateral femur is equal to the amount of wear on the posterior lateral femur minus the amount of wear on the posterior medial femur. In the example, 7 mm - 9 mm = 0 mm - 2 mm = -2 mm, and thus the condition is met, and the software may confirm the amounts to be resected from the posterior medial femur and the posterior lateral femur, respectively. Thus, in the example, the software confirms that FPMR = 7 mm and FPLR = 9 mm.

[0060] Once all femoral RGs (e g., FDMR, FDLR, FPMR, FPLR) are known, the software may perform an additional check 212 of the planned resections to confirm that the resections (in conjunction with the component assumed for use) properly resurface the femur to its prearthritic state. In some examples, this check may be useful as confirmation that the plan remains consistent with the goal, as sometimes component shapes can vary in a non-spherical or asymmetrical way such that adjustment(s) to one component position can impact another component position.6361.005AWO Page 17 of 38Asymmetric components can change resection(s) at other location(s) when changing the position of the asymmetric component. If it is determined that the planned resections (when coupled with the planned component) do not properly resurface the femur to its prearthritic state, the process of planning 106 the femoral resection(s) may require returning to the beginning of the planning 106 and re-calculating and / or re-performing each calculation already performed. In the example embodiment, in which the femoral varus / valgus was adjusted 202 first, the process may return to adjusting 202 the femoral varus / valgus. In other embodiments, the process may return first to adjusting 204 the planned distal femoral resection(s) proximally or distally, adjusting 208 femoral intemal / external rotation, or adjusting 210 femoral flexion and extension, depending on the order in which those actions were performed. Once each calculation has been re-performed, the process again determines 212 whether the planned resections properly resurface the femur to its prearthritic state. The process will loop in this way until it is determined 212 that the planned resections will properly resurface the femur to its prearthritic state.

[0061] The process may further include checking or otherwise determining 214 whether the planned femoral resections violate any custom rule(s) set by the surgeon. For example, rules could be built into the system based on femoral component type. For instance, a cruciate retaining implant may be flexed (i.e., at 210) up to 9 degrees before function of that implant is negatively impacted. At 9 degrees of flexion, the software may calculate / determine that a femoral upsizing is necessary. Anterior femoral anchoring may be needed for femoral flexion / extension adjustments described herein, in other words in order for the femoral flexion and extension to happen correctly. The increasing in size of the femoral component increases the anterior / posterior dimension of the femoral component such that less flexion is required to appropriately restore posterior femoral condyles to their prearthritic state.

[0062] Alternatively, a femoral downsizing event may occur if extension (i.e., at 210) reaches some threshold, for instance 0 degrees, and FPMR does not yet equal the femoral component posterior thickness minus the FPMW. In this event, the femoral component may be downsized (decreasing the anterior / posterior thickness of the component).6361.005AWO Page 18 of 38

[0063] When a femoral upsizing event is triggered (e.g., by obtaining 9 degrees of flexion, as described above), the planned femoral component, which has been upsized, may then be adjusted for use through the entire algorithm, and thus the process of planning 106 the femoral resection(s) returns to 202 and proceeds with the upsized component. Similarly, when a femoral downsizing event is triggered (e.g., by obtaining 0 degrees of flexion before the appropriate conditions are met), the planned femoral component, which has been downsized, may then be adjusted for use through the entire algorithm, and thus the process of planning 106 the femoral resection(s) returns to 202 and proceeds with the downsized component. Thus, if it is determined 214 that one or more custom rule(s) are violated by any of the planned resections, the process may again return to the beginning of planning 106 the femoral resection(s) (e.g., to whichever adjustment 202, 204, 208, 210 was performed first) and proceed through the process of FIG. 2 using parameters of the resized component. The process will loop in this way until it is determined 214 that no custom rule is violated. In some embodiments, once it is determined 214 that no custom rule is violated, and / or that all custom rules are met, the process may proceed to planning 108 the tibial resection(s) (FIG. 1). In other embodiments where the planning 108 the tibial resection(s) has already occurred, the process may proceed to perform 216 the femoral resection(s) following a determination 214 that no custom rule is violated.

[0064] Different femoral components may have different optimal amounts of flexion, and surgeons may have preferences with regard to how many degrees of flexion they will tolerate before a femoral component upsizing or downsizing is desired. For example, a posterior stabilized implant may want to trigger a femoral upsizing event at 5 degrees of flexion. The foregoing are examples of custom rules meant to be illustrative and non-limiting, and the surgeon may wish to implement custom rules in other regards. As another example, a surgeon may add boundaries regarding a maximum tolerable varus or valgus of the patient’s HKA.

[0065] The software may be configured such that the user may input custom rules using a computer interface. For example, the user may interact with graphic user interface elements on a computer display such as buttons, input fields, or other elements to set custom rules. The software may be configured to notify and / or alert the surgeon when a boundary and / or rule is violated. For example, indications of a violated rule may be provided to the user by highlighting areas of the model, such as6361.005AWO Page 19 of 38by changing colors, employing flashing graphical elements, or other means (e.g., on a computer display), or by using sounds to draw the surgeon’s attention to the violated rules. The surgeon may then have the opportunity to adjust the planned resection(s) such that the rule is no longer violated.

[0066] In an example, a surgeon may set a custom rule (e.g., using computer interface elements) that the planned femoral resection(s) should not result in more than 5 degrees of varus. If the software performs the various calculations and returns a resection plan with 7 degree of varus, that boundary may be highlighted (e.g., made red, yellow, or some other color), flash, or in some way be visually modified on a computer display to alert and / or notify the surgeon of the violation. In some embodiments, sound (e.g., an audible alarm) may be used to alert the surgeon to a violation of a custom rule, either as an alternative to or in combination with visual indications. The surgeon may then adjust the solution by removing varus from the femur or the tibia as a compromise to appease their boundary. In some embodiments, the surgeon may adjust one or more planned resections by inputting the desired modifications to any of the planned femoral resections or tibial resections into the software by interacting with graphical user interface elements as described above. The software may then automatically adjust the resection plan (e.g., recalculate one or more of the planned resections) to achieve a solution which satisfies the custom rule(s). The software may default to an unbounded, and the surgeon may be required to affirmatively input custom rules, for example, using a computer interface.

[0067] Returning to FIG. 1, the process may further include planning 108 the tibial resection(s). FIG. 3 depicts an example workflow for planning 108 the tibial resection(s) in accordance with aspects described herein. Aspects of FIG. 3 may be performed automatically (e.g., by a computer employing an algorithm), manually (e.g., by a user and / or surgeon), or a combination of both. In some embodiments, planning 108 the tibial resection(s) may occur before planning 106 the femoral resection(s). In other embodiments, planning 108 the tibial resection(s) may occur after planning 106 the femoral resection(s).

[0068] As shown in FIG. 3, planning 108 the tibial resection(s) may include adjusting 302 tibial varus / valgus to determine a slope of one or more cut(s) and / or resection(s) to be made to the medial tibia and lateral tibia. Relevant anatomic6361.005AWO Page 20 of 38parameters for adjusting 302 the tibial varus / valgus may include TMW and TLW. In the example, the patient exhibits (and intraoperative registration identifies) 2 mm TMW and 0 mm TLW.

[0069] Initially, adjusting 302 the tibial varus / valgus may include determining a tibial difference (TD), i.e., the difference in wear between the medial side and the lateral side of the tibia. The TD may inform whether the patient exhibits a varus or valgus condition. If TD = TLW - TMW, then a positive TD reflects a valgus condition and a negative TD reflects a varus condition (TD = 0 mm represents a neutral alignment). As noted above, the example patient here exhibits 2 mm TMW and 0 mm TLW. Thus, in the example patient, TD = 0 mm - 2 mm = -2 mm, verifying the patient exhibits a varus condition.

[0070] Alternatively, TD may be defined as TD = TMW - TLW, in which case a negative TD reflects a valgus condition, and a positive TD reflects a varus condition. Thus, in the example, TD = 2 mm - 0 mm = 2 mm, again verifying that the patient exhibits a varus condition. Whether the calculation is performed using TD = TLW - TMW or TD = TMW - TLW is a matter of preference. Aspects are described below as if TD = TLW - TMW, however, it should be understood by one skilled in the art that embodiments of the systems and methods described herein may use either calculation.

[0071] The planned tibial resection(s) can account for any varus / valgus condition, for instance by adjusting so that the difference between the amount of bone to be resected from the medial tibial and the amount of bone to be resected from the lateral tibia is the same as the TD (-2 mm, in this example), meaning a greater amount of tibial wear will result in a lesser amount of resected bone at that location. In other words, software can automatically adjust the varus / valgus alignment until TLW - TMW = TD. Continuing with the example values above, the TD of -2 mm informs that the medial tibial resection(s) should be -2 mm medially than laterally. Said differently, the tibial resection(s) should be sloped and / or angled such that 2 mm less bone is resected from the medial tibia as compared to the lateral tibia.

[0072] In one particular example, after adjusting 302 the tibial varus / valgus to determine the slope of the resection(s) as described above, the software may proceed to adjust 304 the planned tibial resection(s) proximally or distally (while maintaining6361.005AWO Page 21 of 38the slope). Relevant parameters to adjusting 304 the resection(s) proximally or distally include the desired and / or actual thicknesses of implant components (e.g., tibial components) to be inserted into the knee joint, such as of a tibial tray and of a polyethylene insert. The thickness of the tibial component(s) may be set / selected by a surgeon or could be set / determined automatically, if desired, and therefore may be downsized or upsized depending on aspects of the process. A common thickness of a tibial tray is 4 mm, and a common thickness of a polyethylene insert is 6 mm. By way of non-limiting example, a common tibial tray and a common polyethylene insert are to be used with the example patient, and therefore the example thickness of the tibial components is 10 mm. In other examples, different tibial components having different thicknesses may be used. In any case, any of the tibial components may be subject to surgeon modification during the process.

[0073] Another relevant parameter to adjusting 304 the tibial resections proximally or distally may be the RGs, specifically the TMR and TLR. The TMR and TLR may be defined as the difference between the tibial components thickness(es) and either TMW and TLW, respectively. Thus, tibial component medial thickness - TMW = TMR, and tibial component lateral thickness - TLW = TLR. Said another way, TMR + TMW = tibial component medial thickness, and TLR + TLW = tibial component lateral thickness. However, in some embodiments where the slope of the planned tibial resection(s) has already been determined, the process could perform only one of these two calculations to determine the proximal / distal adjustment to be made to the tibial resection(s). The software may simply adjust 304 one of the TMR or the TLR proximally or distally using whichever equation relates to the chosen parameter (e.g., TMW or TLW, respectively), and by maintaining the slope determined by adjusting 202 the tibial varus / valgus, the other of the TMR or the TLR is automatically determined.

[0074] As noted above, the example tibial components thickness of 10 mm is used in planning 108 the tibial resection(s) for the example patient. Thus, in the example, the proximal / distal adjustment to the tibial resection(s) may be determined by calculating 10 mm - 0 mm = 10 mm, and thus TLR = 10 mm. The planned tibial resection(s) may thus be adjusted 10 mm, and 10 mm total is to be resected from the lateral distal tibia in order to accommodate the tibial components. Because the software earlier determined there to be a -2 mm difference in the amount of wear6361.005AWO Page 22 of 38between TMW and TLW, the TMR may thus automatically be calculated by the software. For example, the FDMR may automatically be calculated by adding the TLR and the TD in order to determine TMR while also maintaining the slope of the planned tibial resection(s). In the example, 10 mm + (-2 mm) = 8 mm, and thus TMR = 8 mm.

[0075] Upon determining the values for TMR and TLR, the software may perform an additional calculation to confirm those values are correct. For example, the software may run a calculation to confirm that TMR - TLR = TLW - TMW, i.e., that the amount to be resected from the medial tibia minus the amount to be resected from the lateral tibia is equal to the amount of wear on the lateral tibia minus the amount of wear on the medial tibia. In the example, 8 mm - 10 mm = 0 mm - 2 mm = -2 mm, and thus the condition is met, and the software may confirm the amounts to be resected from the medial tibia and the lateral tibia. Thus, in the example, the software confirms that TMR = 8 mm and TLR = 10 mm.

[0076] In some embodiments, where the thickness(es) of the tibial components are known, adjusting 302 the tibial varus / valgus and adjusting 304 the tibial resection(s) proximally or distally may be performed in either order relative to each other. Thus, while an embodiment of the process is described above in which the tibial varus / valgus is adjusted 302 and then the resection(s) are adjusted 304 proximally or distally, there may be other embodiments in which the resection(s) are adjusted 304 proximally or distally and then the tibial varus / valgus is adjusted 302 to determine the slope of the resection(s). However, both adjustments 302, 304 are to be performed before proceeding to perform other aspects of the process.

[0077] Once the tibial RGs (e.g., TMR, TLR) are known, the software may perform an additional calculation to determine 306 whether the planned resection(s) resurface the tibia to its prearthritic state. If it is determined that the planned resections do not properly resurface the tibia to its prearthritic state, the process of planning 108 the tibial resection(s) may require returning to the beginning of the planning 108 and re-calculation and / or re-performing each calculation already performed. In the example embodiment, in which the tibial varus / valgus was adjusted 302 first, the process may return to adjusting 302 the tibial varus / valgus. In other embodiments, the process may return first to adjusting 304 the planned tibial6361.005AWO Page 23 of 38resection(s) proximally or distally, depending on which action was performed first. Once each calculation has been re-performed, the process again determines 306 whether the planned tibial resection(s) properly resurface the tibia to its prearthritic state. The process will loop in this way until it is determined 306 that the planned tibial resection(s) will properly resurface the tibia to its prearthritic state.

[0078] The process may further include checking or otherwise determining 308 whether the planned tibial resection(s) violate any custom rule(s) set by the surgeon. For example, rules could be built into the system based on tibial component type. For instance, varying types of implants might favor different target posterior slopes or acceptable ranges for the posterior slope. For example, a posterior stabilized implant may favor 2 degrees of posterior slope, whereas a cruciate retaining implant may favor 5-7 degrees of posterior slope. Thus, in some embodiments, custom rules may be set (e.g., by interacting with a computer interface) depending on the component(s) being used to alert the surgeon when more or less than the desired and / or preferred target, or range, such as degree of slope, is detected. Some surgeons may choose to set the slope to match the patient’s native slope or set the slope to optimize implant kinematics, among other reasons.

[0079] If it is determined 308 that one or more custom rule(s) are violated by the tibial resection(s), the process may again return to planning 108 the tibial resection(s) (e.g., to whichever adjustment 302, 304 was performed first) and reperform the aspects of FIG. 3 using the updated metrics. The process can, if necessary, loop in this way until it is determined 308 that no custom rule is violated. In some embodiments, once it is determined 308 that no custom rule is violated, and / or that the custom rules are met, the process may proceed to planning 106 the femoral resection(s) (FIG. 1). In other embodiments where the planning 106 the femoral resection(s) has already occurred, the process may proceed to perform 310 the tibial resection(s) following a determination 310 that no custom rule is violated.

[0080] As noted, different tibial components may have different optimal characteristics, such as the degree of posterior slope, and surgeons may have preferences regarding how much slope may be tolerated. The example of rules discussed above regarding posterior slope of a tibial component is meant to be illustrative and non-limiting, and a surgeon may wish to implement rules in other6361.005AWO Page 24 of 38regards. As another example, a surgeon may add boundaries regarding a maximum tolerable varus or valgus of the patient’s HKA. The software may be configured to alert or otherwise notify the surgeon when a boundary and / or rule is violated, such as by highlighting areas of the model to draw the surgeon’s attention to the violated rules. The surgeon may then have the opportunity to adjust and / or re-calculate the planned resection(s) such that the rule is no longer violated.

[0081] Once the femoral resections and the tibial resections have been planned (106, 108) as described above, the surgeon and / or computer may determine whether the patient’s final HKA following surgery matches the C-HKA recorded during intraoperative registration. In some embodiments, the surgeon may select an option to “match correctable HKA” at which time software could adjust the tibial coronal alignment planned resection until the planned tibial coronal alignment plus the planned femoral coronal alignment created a final HKA which matches the C-HKA. In such embodiments, the final HKA is to match the C-HKA, or match to within some specifiable different thereof. To accomplish this, tibial coronal alignment may be adjusted by adding in varus or valgus to the tibial resection (e.g., to the TMR and / or to the TLR), until the final HKA matches the C-HKA. The femoral coronal alignment may also be adjusted in varus or valgus until the HKA matches the C-HKA. Alternatively, a combination of tibial and femoral alignment correction could be chosen per surgeon preference.

[0082] For example, if the C-HKA of the example patient is 3 degrees varus, but the femoral and tibial resection planning calculated a solution with a planned HKA of 5 degrees, the surgeon could select the “match correctable HKA” option and the software could automatically remove 2 degrees of varus from the planned tibial resection(s) so the final anticipated HKA following execution of the resection plan matches the C-HKA. Alternatively, there could be automatic removal of 2 degrees of varus from the planned femoral resection or a combination of 1 degree removal from each the tibia and femur. No further iterations of prior aspects of the process are required when the surgeon selects the “match correctable HKA” option, as this may be provided as an algorithmic override based on HKA guardrails chosen by the surgeon.6361.005AWO Page 25 of 38

[0083] The process may further include performing 110 the planned resections. The performing 110 the planned resections may include performing 216 the planned femoral resection(s) and performing 310 the planned tibial resection(s). Following the performing 110 of the planned resection(s), the femur may be fitted with the femoral implant component, and the tibia may be fitted with the tibial implant components.

[0084] In an embodiment shown in FIG. 5, the process may include performing 502 a pre-operative assessment of patient anatomy (e.g., the patient’s knee joint). The process may further include recording 504 one or both of a pre-operative HKA and a target HKA to be achieved post-operatively. In the example, a target HKA is determined based on at least the pre-operative assessment. Additionally, or alternatively, a target HKA and / or a preoperative HKA may be determined intraoperatively as part of intraoperative registration of patient anatomy (e.g., via depth probing) of the knee joint, such as of the femur and tibia.

[0085] The process may further include setting 506 an initial resection plan for resurfacing the patient femur and resurfacing the patient tibia. Setting 506 the initial resection plan may include setting planned femoral resections to the patient femur to resurface the patient femur (e.g., in preparation of receiving an implant or component thereof) and setting at least one planned tibial resection to the patient tibia to resurface the patient tibia (e.g., in preparation of receiving an implant or component thereof). The setting the planned femoral resections and the setting the at least one planned tibial resection may be performed absent recording and / or use of data describing and / or relating to balance of soft tissue of the knee joint, such as a soft tissue graph.

[0086] Setting the planned femoral resections may include, based on evaluated femoral distal medial wear and femoral distal lateral wear, adjusting a femoral varus / valgus parameter for one or more planned distal femoral resections to be made to a distal portion of the patient femur and adjusting the one or more planned distal femoral resections proximally or distally based on a distal thickness of a femoral implant component. Setting the planned femoral resections may further include, based on evaluated femoral posterior medial wear and femoral posterior lateral wear, adjusting femoral implant component internal / external rotation to set a slope of one or more posterior femoral resections to be made to a posterior portion of the patient6361.005AWO Page 26 of 38femur and adjusting femoral implant positioning to a desired position based on a posterior thickness of the femoral implant component.

[0087] Setting the at least one planned tibial resection may include adjusting, based on evaluated tibial medial wear and tibial lateral wear, a tibial varus / valgus parameter for the planned at least one tibial resection to be made to the tibia, and adjusting the at least one planned tibial resection proximally or distally based on thickness of one or more tibial implant components.

[0088] Continuing with the example from FIG. 5, the process may determine 508 a planned post-operative HKA based on the initial resection plan. The planned postoperative HKA may represent the anticipated HKA of the patient post-operatively should the initial resection plan to be performed following the setting 506. The process may then proceed to selectively adjust the initial resection plan (set at 506) based on the target HKA and the planned post-operative HKA. In this aspect, the adjustment is done selectively meaning it may be performed as long as certain condition(s), and may not be performed if those conditions are not met. More specifically, the process of FIG. 5 includes a determination 510 whether the postoperative HKA is within or exceeds a threshold (e.g., a threshold degree or amount) of the target HKA. The selectively adjusting may thus include a determination of whether to adjust the initial resection plan based on whether a difference between the target HKA and the planned post-operative HKA exceeds the threshold. It should be noted that a threshold could be ascertained based on a provided or determined maximum or minimum acceptable number, in which case exceeding that number would prompt an adjustment as described below. Alternatively, the threshold could be ascertained based on a number provided that is the most extreme (least or greatest) unacceptable number, in which case the threshold for purposes of determination 510 could be exclusive of that number, meaning that a value equal to that provided number is considered to exceed the threshold for purposes of 510.

[0089] If the process determines at 510 that the planned post-operative HKA exceeds or is otherwise not within the threshold of the target HKA, the process may proceed to adjust 512 the planned post-operative tibial coronal alignment and / or the planned post-operative femoral coronal alignment. In some embodiments, this adjustment may adjust one or both of the planned post-operative tibial coronal6361.005AWO Page 27 of 38alignment and the planned post-operative femoral coronal alignment based on the difference between the planned post-operative HKA and the target HKA exceeding the threshold. In some embodiments, this adjustment may adjust one or both of the planned post-operative tibial coronal alignment and the planned post-operative femoral coronal alignment such that the adjusted planned post-operative HKA matches the target HKA or is otherwise within the threshold degree of the target HKA. In some embodiments, this adjustment may adjust the planned post-operative tibial coronal alignment to provide the adjusted resection plan with the adjusted planned post-operative HKA and maintain the planned post-operative femoral coronal alignment the same as under the initial resection plan.

[0090] Thus, in embodiments, the selectively adjusting may adjust one or both of (i) the planned post-operative tibial coronal alignment by adjusting a planned tibial resection of the at least one planned tibial resection, and (ii) the planned postoperative femoral coronal alignment by adjusting a planned femoral resection of the planned femoral resections. In embodiments, the selectively adjusting, by way of 512, may provide an adjusted resection plan with an adjusted planned post-operative HKA that is within the threshold of the target HKA.

[0091] Where the process instead determines at 510 that the planned postoperative HKA is within (e.g., does not exceed) the threshold degree of the target HKA, the process may determine as part of the selective adjustment that no adjustment is needed to the initial resection plan, in which case the process ends. In this manner, the selectively adjusting commenced after 508 includes determining that no adjustment is necessary, for example, because the planned post-operative HKA matches or is otherwise within the threshold of the target HKA. The initial resection plan may then be used in the performance of the surgical procedure (e.g., the TKA) to achieve an actual post-operative HKA that is within a threshold of the target HKA.

[0092] Where the process instead determines the planned post-operative HKA exceeds or is otherwise outside the threshold degree, the process may end following the generation of the adjusted resection plan as described above by way of 512. In such a scenario, the adjusted resection plan may then be used in the performance of the surgical procedure (e.g., the TKA) to achieve an actual post-operative HKA that is within a threshold of the target HKA. Alternatively, the selectively adjusting may6361.005AWO Page 28 of 38include determining that no adjustment is necessary, for example, because the planned post-operative HKA matches or is otherwise within the threshold of the target HKA.

[0093] Aspects described herein can be useful in clinical and educational settings. Software implementing features described herein can be integrated into robotic surgery applications for performing robotic surgeries in hospitals and ambulatory surgery center operating rooms.

[0094] Accordingly, aspects provide a goal-based and data-driven, targeted solution. In contrast, other approaches might place a heavy emphasis on variable patient data that includes pre-operative non-orthopedic factors (demographics, mental disposition), pre-operative orthopedic factors (BMI, deformity, imaging data), and post-operative data, and essentially captures any possible variables that can be considered, without emphasizing a data-driven target per se, and producing a ranked- order list of possible solutions based on varying surgeon preferences but with no predetermined optimal goal. This is distinguished from aspects described herein in which raw data and information is used to provide a definitive answer in terms of femoral component position and tibial component position to properly align a femur and / or tibia during a TKA. In other words, operator selection may be minimized in accordance with aspects herein, which provides simplicity, efficiency, and a removal of the need of resources as discussed. Automation provided by aspects described herein can also minimize or remove the need to train the company representative and surgeon on the intricacies of surgical robot operation to properly execute the surgical procedure (the learning curve of which may be steep). Such complexity can be a barrier of entry to adopting robotic technology as discussed above.

[0095] One or more embodiments described herein may be incorporated in, performed by, and / or used by one or more computer systems, such as one or more computer systems that are incorporated into and / or in communication with an orthopedic surgical robot system. Processes described herein, and / or aspects thereof, may be performed singly or collectively by one or more such computer systems. A computer system may also be referred to herein as a data processing device / system, computing device / system / node, or simply a computer. The computer system may be based on one or more of various system architectures and / or instruction set architectures.6361.005AWO Page 29 of 38

[0096] Software executing on a computer system can build and provide (e.g., for graphical display on a display device) a graphical user interface (GUI). The software could be software that performs processes described herein. A GUI includes graphical elements, such as fields, buttons, sliders, toggles, radio selections, images, text values, and others. Some such graphical elements may be interactive in the sense that a user, such as a surgeon or other user of the software, can interact with the elements to set, adjust, select, specify, define, indicate, or the like, desired settings, targets, goals, or any other parameters for processing described herein (e.g., the surgeon setting the desired degree of flexion at which a femoral component upsizing may occur). Examples of such parameters are those discussed herein related to knee arthroplasty or other joint replacement procedures. In some examples, each such attribute may have a corresponding graphical interface element with which the user might interact to set, adjust, select, specify, etc. a value for that attribute. In this manner, aspects can build, provide and / or display a GUI with elements corresponding to processing parameters, as well as elements to display or otherwise convey results of such processing, for instance values related to alignment of a knee joint or HKA, as examples, or other outputs of the processing.

[0097] FIG. 6 shows a computer system 600 in communication with external device(s) 612. Computer system 600 includes one or more processor(s) 602, for instance central processing unit(s) (CPUs). A processor can include functional components used in the execution of instructions, such as functional components to fetch program instructions from locations such as cache or main memory, decode program instructions, and execute program instructions, access memory for instruction execution, and write results of the executed instructions. A processor 602 can also include register(s) to be used by one or more of the functional components. Computer system 600 also includes memory 604, input / output (VO) devices 608, and VO interfaces 610, which may be coupled to processor(s) 602 and each other via one or more buses and / or other connections. Bus connections represent one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include the Industry Standard Architecture (ISA), the Micro Channel6361.005AWO Page 30 of 38Architecture (MCA), the Enhanced ISA (EISA), the Video Electronics StandardsAssociation (VESA) local bus, and the Peripheral Component Interconnect (PCI).

[0098] Memory 604 can be or include main or system memory (e.g., Random Access Memory) used in the execution of program instructions, storage device(s) such as hard drive(s), flash media, or optical media as examples, and / or cache memory, as examples. Memory 604 can include, for instance, a cache, such as a shared cache, which may be coupled to local caches (examples include LI cache, L2 cache, etc.) of processor(s) 602. Additionally, memory 604 may be or include at least one computer program product having a set (e.g., at least one) of program modules, instructions, code, or the like that is / are configured to carry out functions of embodiments described herein when executed by one or more processors.

[0099] Memory 604 can store an operating system 605 and other computer programs 606, such as one or more computer programs / applications that execute to perform aspects described herein. Specifically, programs / applications can include computer readable program instructions that may be configured to carry out functions of embodiments of aspects described herein.

[0100] Examples of EO devices 608 include but are not limited to microphones, speakers, Global Positioning System (GPS) devices, RGB, IR, spectral, and / or other forms of cameras, lights, accelerometers, gyroscopes, magnetometers, sensor devices configured to sense light, proximity, heart rate, body and / or ambient temperature, blood pressure, and / or skin resistance, registration probes, robotic tools, and activity monitors. An I / O device may be incorporated into the computer system as shown, though in some embodiments an EO device may be regarded as an external device (612) coupled to the computer system through one or more EO interfaces 610.

[0101] Computer system 600 may communicate with one or more external devices 612 via one or more EO interfaces 610. Example external devices include a keyboard, a pointing device, a display, and / or any other devices that enable a user to interact with computer system 600. Other example external devices include any device that enables computer system 600 to communicate with one or more other computing systems or peripheral devices such as a printer. A network interface / adapter is an example EO interface that enables computer system 600 to communicate with one or more networks, such as a local area network (LAN), a6361.005AWO Page 31 of 38general wide area network (WAN), and / or a public network (e.g., the Internet), providing communication with other computing devices or systems, storage devices, or the like. Ethernet-based (such as Wi-Fi) interfaces and Bluetooth® adapters are just examples of the currently available types of network adapters used in computer systems (BLUETOOTH is a registered trademark of Bluetooth SIG, Inc., Kirkland, Washington, U.S.A.).

[0102] The communication between I / O interfaces 610 and external devices 612 can occur across wired and / or wireless communications link(s) 611, such as Ethernetbased wired or wireless connections. Example wireless connections include cellular, Wi-Fi, Bluetooth®, proximity -based, near-field, or other types of wireless connections. More generally, communications link(s) 611 may be any appropriate wireless and / or wired communication link(s) for communicating data.

[0103] Particular external device(s) 612 may include one or more data storage devices, which may store one or more programs, one or more computer readable program instructions, and / or data, etc. Computer system 600 may include and / or be coupled to and in communication with (e.g., as an external device of the computer system) removable / non-removable, volatile / non-volatile computer system storage media. For example, it may include and / or be coupled to a non-removable, nonvolatile magnetic media (typically called a “hard drive”), a magnetic disk drive for reading from and writing to a removable, non-volatile magnetic disk (e.g., a “floppy disk”), and / or an optical disk drive for reading from or writing to a removable, nonvolatile optical disk, such as a CD-ROM, DVD-ROM or other optical media.

[0104] Computer system 600 may be operational with numerous other general purpose or special purpose computing system environments or configurations. Computer system 600 may take any of various forms, well-known examples of which include, but are not limited to, personal computer (PC) system(s), server computer system(s), such as messaging server(s), thin client(s), thick client(s), workstation(s), laptop(s), handheld device(s), mobile device(s) / computer(s) such as smartphone(s), tablet(s), and wearable device(s), multiprocessor system(s), microprocessor-based system(s), telephony device(s), network appliance(s) (such as edge appliance(s)), virtualization device(s), storage controller(s), set top box(es), programmable consumer electronic(s), network PC(s), minicomputer system(s), mainframe computer6361.005AWO Page 32 of 38system(s), and distributed cloud computing environment(s) that include any of the above systems or devices, and the like.

[0105] Aspects of the present invention may be a system, a method, and / or a computer program product, any of which may be configured to perform or facilitate aspects described herein.

[0106] In some embodiments, aspects of the present invention may take the form of a computer program product, which may be embodied as computer readable medium(s). A computer readable medium may be a tangible storage device / medium having computer readable program code / instructions stored thereon. Example computer readable medium(s) include, but are not limited to, electronic, magnetic, optical, or semiconductor storage devices or systems, or any combination of the foregoing. Example embodiments of a computer readable medium include a hard drive or other mass-storage device, an electrical connection having wires, random access memory (RAM), read-only memory (ROM), erasable-programmable read-only memory such as EPROM or flash memory, an optical fiber, a portable computer disk / diskette, such as a compact disc read-only memory (CD-ROM) or Digital Versatile Disc (DVD), an optical storage device, a magnetic storage device, or any combination of the foregoing. The computer readable medium may be readable by a processor, processing unit, or the like, to obtain data (e.g., instructions) from the medium for execution. In a particular example, a computer program product is or includes one or more computer readable media that includes / stores computer readable program code to provide and facilitate one or more aspects described herein.

[0107] As noted, program instruction contained or stored in / on a computer readable medium can be obtained and executed by any of various suitable components such as a processor of a computer system to cause the computer system to behave and function in a particular manner. Such program instructions for carrying out operations to perform, achieve, or facilitate aspects described herein may be written in, or compiled from code written in, any desired programming language. In some embodiments, such programming language includes object-oriented and / or procedural programming languages such as C, C++, C#, Java, etc.

[0108] Program code can include one or more program instructions obtained for execution by one or more processors. Computer program instructions may be6361.005AWO Page 33 of 38provided to one or more processors of, e.g., one or more computer systems, to produce a machine, such that the program instructions, when executed by the one or more processors, perform, achieve, or facilitate aspects of the present invention, such as actions or functions described in flowcharts and / or block diagrams described herein. Thus, each block, or combinations of blocks, of the flowchart illustrations and / or block diagrams depicted and described herein can be implemented, in some embodiments, by computer program instructions.

[0109] Although various embodiments are described above, these are only examples.

[0110] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0111] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below, if any, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of one or more embodiments has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain various aspects and the practical application, and to enable others of ordinary skill in the art to understand various embodiments with various modifications as are suited to the particular use contemplated.6361.005AWO Page 34 of 38

Claims

CLAIMS1. A computer-implemented method for planning a surgery to a knee joint of a patient, the knee joint including a patient femur and patient tibia, the method including: recording a target hip-knee-ankle angle (HKA) for the patient based on a preoperative assessment of the knee joint; based on an evaluation of wear of the knee joint, setting an initial resection plan for resurfacing the patient femur and resurfacing the patient tibia, the setting the initial resection plan including setting planned femoral resections to the patient femur to resurface the patient femur and setting at least one planned tibial resection to the patient tibia to resurface the patient tibia; determining a planned post-operative HKA of the patient based on the initial resection plan, wherein the planned post-operative HKA is a function of: a planned post-operative femoral coronal alignment of the patient provided by the planned femoral resections of the initial resection plan; and a planned post-operative tibial coronal alignment of the patient provided by the planned at least one tibial resection of the initial resection plan; and selectively adjusting the initial resection plan based on the target HKA and the planned post-operative HKA, wherein the selectively adjusting adjusts one or both of (i) the planned post-operative tibial coronal alignment by adjusting a planned tibial resection of the at least one planned tibial resection, and (ii) the planned post-operative femoral coronal alignment by adjusting a planned femoral resection of the planned femoral resections, and provides an adjusted resection plan with an adjusted planned post-operative HKA that is within a threshold of the target HKA.6361.005AWO Page 35 of 382. The method of claim 1 wherein the selectively adjusting adjusts the one or both of the planned post-operative tibial coronal alignment and the planned post-operative femoral coronal alignment such that the adjusted planned postoperative HKA matches the target HKA.

3. The method of claim 1 or 2, wherein the selectively adjusting adjusts the planned post-operative tibial coronal alignment to provide the adjusted resection plan with the adjusted planned post-operative HKA and maintains the planned postoperative femoral coronal alignment the same as under the initial resection plan.

4. The method of claim 1, wherein the target HKA is determined intraoperatively as part of intraoperative registration of patient anatomy of the knee joint.

5. The method of claim 1, wherein the selectively adjusting includes: determining whether to adjust the initial resection plan based on whether a difference between the target HKA and the planned post-operative HKA exceeds the threshold; and performing processing based on the determining whether to adjust.

6. The method of claim 5, wherein the selectively adjusting adjusts the one or both of the planned post-operative tibial coronal alignment and the planned post-operative femoral coronal alignment based on the difference exceeding the threshold.

7. The method of claim 1, wherein the setting the planned femoral resections includes: adjusting, based on evaluated femoral distal medial wear and femoral distal lateral wear, a femoral varus / valgus parameter for one or more planned distal femoral resections to be made to a distal portion of the patient femur; adjusting the one or more planned distal femoral resections proximally or distally based on a distal thickness of a femoral implant component;6361.005AWO Page 36 of 38adjusting, based on evaluated femoral posterior medial wear and femoral posterior later wear, femoral implant component internal / extemal rotation to set a slope of one or more posterior femoral resections to be made to a posterior portion of the patient femur; and adjusting femoral implant positioning to a desired position based on a posterior thickness of the femoral implant component and wherein the setting the at least one planned tibial resection includes: adjusting, based on evaluated tibial medial wear and tibial lateral wear, a tibial varus / valgus parameter for the planned at least one tibial resection to be made to the patient tibia; adjusting the at least one planned tibial resection proximally or distally based on thickness of one or more tibial implant components.

8. The method of any of claims 1, 2, 4, 5, 6, or 7, wherein the setting the planned femoral resections and the setting at least one planned tibial resection is performed absent use of data describing balance of soft tissue of the knee joint.

9. A computer system comprising: a memory; and a processing circuit in communication with the memory, wherein the computer system is configured to perform a method of any of claims 1-8.

10. A computer program product comprising: a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method of any of claims 1-8.6361.005AWO Page 37 of 38

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