Customized orthopaedic implants and related methods

The present disclosure relates to orthopedic implants, and more specifically to methods and devices used in the design of orthopedic implants and orthopedic jigs used in joint replacement and revision surgery.

(Cross-reference of related applications) This application is filed on February 25, 2009, with its respective disclosures incorporated herein by reference, in US Provisional Patent Application No. 61 / 208,509, entitled "DEFORMABLE ARTICULATING TEMPLATE", and July 2009. Claims priority under US Provisional Patent Application No. 61 / 222,560 named "CUSTOMIZED ORTHOPAEDIC IMPLANTS AND RELATED METHODS" filed on 2nd.

Analyzing the unique shape differences of the knee joint between different ethnic groups to develop implantable orthopedic devices is a major concern for the knee prosthetic industry. Therefore, the research presented has three aspects. That is, by developing a new automated feature detection algorithm, it is possible to determine a set of automated measurements based on highly morphologically deformed regions, which in turn can be used for different groups of knee joints. Enables a statistical framework for analyzing differences.

Ethnic differences in lower limb morphology focus on differences between Asian and Western populations, as variation between Asian and Western populations is important in implant design. I'm matching. For example, the Chinese femur is more anteriorly curved and outwardly rotated than the Caucasian femur, and is intermedullary. canal) is smaller, and the distal condyle is also smaller. Similarly, the Caucasian femur is larger than the Japanese femur in terms of length and dimensions of the distal condyle. There are also ethnic differences between black and white Americans in the bone mineral content (BMD) of the proximal femur and the axial length of the hip joint. Black women have a lower prevalence of osteoporotic fractures than white women because of the synergistic effect of higher BMD, shorter hip length, and shorter intertrochanteric width. If there is, there is an explanation. Similarly, older Asian and black men have been found to have thicker cortex and higher BMD than white and Hispanic men, a factor in the high bone strength in these ethnic groups. May be contributing. In general, blacks have a thicker cortical bone, a narrower endosteal diameter, and a larger BMD than whites. Interestingly, however, these traits are most pronounced in African blacks compared to American blacks.

The following analysis considers quantitative and geometric morphometric variations in the lower extremities of modern American blacks, whites, and East Asians. Three-dimensional statistical bone atlases are used to facilitate rapid and accurate data collection in the form of automated measurements, as well as measurements used in biomedical research and some newly devised measurements. .. Shape analysis is performed by statistical processing that combines principal component analysis (PCA) and multiple discriminant analysis. Quantitative analysis uses t-test, power test, and linear discriminant analysis, and is co-pending with the name "IMPLANT DESIGN ANALYSIS SUITE" whose disclosure is incorporated herein by reference to the Implant Design and Analysis Suite. (See US Patent Application No. 12 / 673,640) in. As outlined in the rest of this disclosure, the results of these analyzes add to the existing knowledge of morphological variation in the knee joint and are useful to extract for knee prosthetic design. Provide information.

The innovation of this approach is in part due to the use of computed tomography (CT) scans for data acquisition, combined with the computational power and accuracy provided by the statistical bone atlas. An exemplary dataset containing 943 men and women (81.5% American Caucasian, 9% American Black, 9.5% East Asian, overall male / female ratio 65/35%), Scanned using CT scan. This study included only normal femur and tibia. Femurs and tibias with severe osteophytes and other abnormalities were specifically excluded. Only one femur and tibia was selected from each individual and did not prioritize either the right side or the left side.

Bone was CT scanned using a 0.625 mm x 0.625 mm x 0.625 mm cubic voxel. The result is a high resolution 3D radiograph in the form of DICOM image slices. Next, the stacked image data was segmented to generate a surface model. This process has been found to be reliable with negligible intra-observer and inter-observer errors. These models were then added to the ethnic-specific statistical bone atlas.

Briefly, a bone atlas is an average or template mesh that captures major bone shape variations and allows comparison of global shape differences between groups or populations. The bone atlas was originally developed for automatic medical image segmentation, but it can also be used as a means of digitally reproducing bone and performing statistical shape analysis. In addition, bone atlases are useful in biological anthropology as a means of studying sexual dimorphism and for reconstructing native fossils and making shape comparisons between fossil species. Has been proven.

For the analysis of ethnic differences, we used a new method of technology previously developed to create statistical representations of bone shape. Statistics of three independent femurs, one atlas containing only the American white femur, one atlas containing only the American black femur, and one atlas containing only the East Asian femur Edited the physiologic atlas. Similarly, for the tibia, we created three similarly classified independent atlases (ie, American Caucasian, American Black, and East Asian tibia). The process of creating these statistical atlases and adding bone to them is outlined below.

First, all bone models in the dataset were compared and a bone model with average shape characteristics that served as a template mesh was selected. The points in the template mesh were then matched against the corresponding points in all other training models. This ensures that all bones have the same number of vertices and the same degree of triangular connectivity. A series of overlay and distortion techniques were then used to select the corresponding points on all other bone models in the training set. This process of picking out new model point correspondences to be added to the atlas is "non-trivial." The matching algorithms described below use some well-known computer vision techniques, as well as new contributions for final surface alignment.

During the first step of the matching algorithm, the center of gravity of the template mesh and the center of gravity of the new mesh were aligned and the template mesh was prescaled to match the dimensions of the new mesh's bounding box. .. Second, the template mesh is rigid to the new mesh using the standard Vertex-Vertex Iterative Closest Point (ICP) algorithm. alignment) was performed. Third, after solid alignment, general affine deformation was performed without repetition. This method was applied to align the template mesh to the new mesh with 12 degrees of freedom (including rotation, translation, scaling, and misalignment). After the affine transformation step, the template and the new model have reached the limits of the linear transformation, but the local parts of the model still remain significantly separated. The goal of the final surface-surface matching is to create new points on the surface of the new model that have local spatial characteristics similar to those of the template model, so new to reduce misalignment. We have developed a nonlinear iterative distortion method.

With reference to Figure 1, in order to achieve point correspondence, the iterative algorithm for finding the closest vertex-vertex correspondence from the template to the new model is used as before, but this time, the template from the new model Correspondence to the model is also found. With both of these point correspondences, points on the template mesh are moved towards new mesh positions using the asymmetric weighting of the corresponding vectors. Next, a subroutine consisting of an iterative smoothing algorithm is applied to the template mesh transformed this time. This smoothing algorithm attempts to average the size of adjacent triangles on the template mesh and thereby eliminate discontinuities. In the early days of the distortion algorithm, the smoothing algorithm uses the actual area of the surrounding triangles to define the smoothing vector applied to each point, which effectively excludes outliers with large triangles. Help to do. As a result, early in the process, the template mesh takes large steps and requires greater smoothing. However, towards the end of the process, the smoothing vector is normalized by the total area of the surrounding triangles, which allows the template mesh to be expanded to a region of high curvature. After this procedure is completed for all femurs and tibias within each atlas, the atlas is ready for morphological shape analysis and automated metric comparison.

Innovative statistical processing was used to analyze the overall shape difference between the two groups. This method uses the power of PCA (linear and non-linear) as both a means of variable reduction and a global shape descriptor. This method finds a discriminating point between different genders and / or different ethnic groups when normalized to the first principal component (PC) considered first for scaling. It is designed. This procedure highlights areas on the model that will be highly discriminating, without using any other information. The landmarks identified by this algorithm provide reasonable discriminating power between ethnic groups without the use of any other landmarks. This feature-finding algorithm is used to examine femoral and tibial shape differences between American Caucasians, Blacks, and East Asians that are independent of size differences.

Extensive comparisons were made using specific measurements at landmarks defined on ethnic-specific statistical atlases. These landmarks were selected based on their surgical importance, clinical relevance, and historical measurements. Since the atlas consists of homologous points on each femur or tibial model, it provides a wealth of information to automate this process. Also, each bone model in the atlas is aligned with respect to the same coordinate frame. A total of 99 femur and 23 tibia measurements, angles, and indices were calculated. Furthermore, for the sake of brevity, only the most significant metric properties will be discussed in the results section. Unless otherwise specified, the measurements outlined below represent the three-dimensional (3D) Euclidean distance between a pair of landmarks, and the angle is measured as a 3D rotation between the vectors. In some examples, these measurements were projected onto a plane for comparison with previous studies in the field. A subset of these measurements is shown in Figure 2-Figure 4. The landmarks that define the endpoints of the measurements are first calculated and then defined for the surgical and anatomical axes.

Related surgery to identify ethnic differences in the distal femur and proximal tibia on a global scale, discover areas that are likely to provide discriminative information, and assist in the design of implantable prostheses New methods for measuring target and anatomical features are presented. Various studies have attempted to identify ethnic differences in the femur and tibia using measurement techniques that lack accuracy and accuracy. Unfortunately, with these methods it was not possible to find features of lesser importance.

The ordered sequence of methods used in accordance with this disclosure proves significant global differences between genders and ethnic groups, which continue to use trait-finding methods to simply identify areas that can be highly different. It allows for separation and, ultimately, the coding of algorithms for exploring and measuring surgically relevant anatomical features with a high degree of accuracy and reproducibility. Bones with different scales were considered to have the potential for size-dependent shape changes. This method excluded the correlation between the measured variables and their magnitudes in order to reveal the distinct ethnic differences in shape.

Using the above analysis, the inventor determined that black Americans had longer, straighter femurs and narrower knees than white Americans. In addition, this analysis revealed differences in the dimensions and orientation of the lateral condyles that resulted in differences in the overall shape of the distal femur. That is, black Americans have trapezoidal knees, and white Americans have more square knees. For each group, differences in the distal femur were also reflected in the adjacent tibia, with black Americans having a longer lateral tibial condyle. The average medial-lateral length of the tibial plateau was slightly longer in blacks than in whites, but this difference was not overly significant given the sample dimensions. However, black Americans have significantly longer and stronger tibias. In this study, major morphological differences were found between East Asian populations and both American whites and American blacks.

It is not clear to what extent genetic differences contribute to lower limb morphology, and mixed-race individuals pose a challenge. In fact, blood group data show that since their arrival in the United States, black Americans have approached white Americans and are moving away from their ancestral West African populations.

Racial differences in lower limb morphology are apparent and have been shown to be statistically significant, but there is more statistical noise in the American black sample vs. the American Caucasian sample. May exist. This noise may be the result of the combined effects of genetic mixing since arrival in the United States and selective mitigation in a milder environment. However, as discussed above, the effects of mixed races have not eliminated the distinctive morphological differences between these subgroups of the American population.

To understand the kinematics of a normal knee joint, it is first necessary to understand the anatomy of the articular surface of the knee joint. The knee joint is the joint between the femur and tibia, the two largest bones in the human leg. The articular surface at the knee joint consists of a curved surface that forms the lateral and medial condyles of the distal portion of the femur and is in contact with the lateral and medial tibial plateaus of the proximal portion of the tibia.

The femoral condyle leads to the anterior groove, the pulley, which is the joint to the patella or kneecap. The tibial plateau is separated by an intercondylar ridge that acts as an attachment point for the anterior cruciate ligament and meniscus. The tibial plateau is also asymmetric, with the smaller of the two being the lateral plateau. Anatomical studies of the femoral tibial joint have shown that the medial area has a larger contact area than the lateral area.

The fibula is attached to the outside of the tibia by a dense membrane along its length and at the ends by ligament-supported cartilage joints. This bone-to-bone connection allows very little relative movement. The proximal tibial joint is below the horizontal plane of the tibial-femoral joint, while the distal ends of the two bones form the proximal end of the ankle joint.

In a normal knee, posterior femoral rollback occurs routinely during increased flexion. A larger amount of posterior femoral rollback has been observed during movements that require greater tortuosity, such as deep knee bending. Posterior rollback is substantially greater at the femoral tibial joint lateral than medial, thus creating a medial swivel axial rotation pattern in which the tibia rotates inward with respect to the femur as flexion increases. Numerous kinematic evaluations have found posterior femoral rollbacks of similar pattern and scale during deep flexion movements. This is somewhat different from the axial rotation pattern observed after total knee arthroplasty (TKA), in which case the magnitude of the axial rotation is smaller and sometimes lateral rotation and reverse screw home rotation (increased flexion). As the tibia rotates outward with respect to the femur, it shows a pathological rotation pattern.

Also, the anterior translation of the femur on the tibia observed after TKA has many potentially unfavorable consequences. First, as a result of the anterior femoral translation, the flexion axis is more anterior and the maximum knee flexion is smaller. Second, the quadriceps moment arm is reduced, resulting in reduced efficiency of the quadriceps. Third, there is a risk that anterior sliding of the femoral component on the polyethylene (PE) surface of the tibia will accelerate PE wear.

The main purpose of TKA should be to reproduce normal knee movements. Currently, this purpose is largely overlooked. Numerous fluoroscopic analyzes in vivo under weight show that it is difficult to obtain normal knee movement after TKA with existing orthopedic implants. Multiple dyskinesias (reduced posterior femoral rollback, bizarre anterior femoral translation, reverse axial rotation pattern, and lift-off of the femoral condyle) are usually present. Better to understand these kinetic variations work in a direction that reduces and eliminates, or at least adapts to, these kinetic abnormalities without creating adverse conditions that limit implant performance or longevity. It supported the design of TKA implants. Most knee implants are off-the-shelf knee systems designed for average movements rather than patient-specific movements. Therefore, individual patient customization should be used for knee TKA movements and movements that are indistinguishable from normal knees. Customization is currently a daunting task, but this disclosure addresses this customization, in part, by providing the deformable joint template (DAT) methodology described below.

For the purposes of the present disclosure, the radius of curvature is the radius of a circle having a circumferential curvature that approximates the curvature of a rounded object. For example, the radius of curvature is infinite for a straight line, and as the curvature increases, the radius decreases from infinity. As can be seen in FIG. 5, the radius of curvature of the small circle is smaller than the radius of curvature of the large circle because the curvature of the small circle is greater than the curvature of the large circle. Simply put, the smaller the radius of curvature, the greater the curvature.

With reference to FIGS. 6 and 7, the inventor maps and simulates the curvature of the innate knee condyle by applying two or more radii of curvature from anterior to posterior along the cam surface. I found that I could do it. In particular, for the Caucasian population, five different radii of curvature (identified as r1-r5) were found to faithfully follow the curvature of the cam surface from anterior to posterior to the condyle. Furthermore, it was found that the asymmetry in the radius of curvature of the condyle was responsible for the internal rotation of the tibia with respect to the femur during flexion. When the flexion exceeds 20 °, sliding motion begins on both condyles.

Extension of the knee joint results in a combined external rotation of the tibia with respect to the femur. This rotation is described as a "screw home" movement of the knee. This screw home movement is due to the presence of a larger area of seating surface above the medial condyle than above the lateral condyle. When the entire articular surface of the lateral condyle is exhausted, the femur rotates around the tibial spine until the joint is screw-homed, that is, close-packed in the extended state. As the knee osteoarthritis flexes and extends, this rotation causes the tibia to move on the femur in a vortex or spiral that results from the anatomical construction of the medial femur. When the tibia slides over the femur from a fully extended position, it descends and ascends the curvature of the medial femur and simultaneously externally rotates. This movement is reversed when the tibia returns to its fully flexed position. The screw home mechanism provides the knee with higher stability in any position than would be possible if the femoral tibial joint had a pure hinge structure.

Referring to FIG. 8, the meniscal cartilage (meniscus) between the femoral condyle and the tibial articular surface serves to deepen the tibial articular surface to accommodate the femoral condyle, two meniscal fibrocartilage structures. The body. Looking at the cross section, the meniscus has a wedge-shaped appearance. The meniscus (1) transfers loads through the joints, (2) enhances joint compatibility, (3) distributes synovial fluid across the joint surface, and (4) prevents bone collisions during joint movement. Performs several important functions, including. In the presence of the meniscus, the load-bearing area for each condyle is approximately 6 cm²However, if the meniscus is damaged or severely deteriorated, this area is approximately 2 cm.²Decrease to. Therefore, as the effective load-bearing area increases, the stress transmitted to the cartilage decreases and vice versa.

With reference to FIGS. 9 and 10, a normal knee joint is inherently equipped with an anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) located inside the joint in the intercondylar space. These ligaments control anterior-posterior and axial rotational movements in the joint. The anterior cruciate ligament provides the primary constraint on the anterior movement of the tibia with respect to the femur, while the posterior cruciate ligament provides the primary constraint on the posterior movement of the tibia, accounting for more than 90% of total resistance to this movement. FIG. 10 shows the changes in ACL and PCL lengths at different flexion angles of the knee joint. A detailed description of the effects of ACL and PCL constraints on the design of posteriorly stabilized knee implants is discussed in more detail below.

The morphological shape of the distal femur should determine the shape, orientation, and kinematics of the prosthetic substitution used in TKA. The traditional prosthetic design is centered on the trochlear groove and incorporates a symmetrical femoral condyle. Conventional surgical techniques place the femoral component in the center of the distal femur and position it relative to the variable bone landmark. However, demonstrated patterns of insufficiency and kinematic studies have shown that conventional design and surgical techniques neglect the tracking of the patella and its distal femur, as well as the morphology and kinematics of the distal femur. It proves to reflect a poor understanding of the kinematics of the knee joint.

The pulley is designed to guide and hold the patella. Patella tracking is affected by many different factors: the geometry of the trochlear groove, the geometry of the posterior side of the patella, the soft tissue extensor mechanism, and the orientation of the tibia. Normal movement of the patella on the femur during flexion is an intercondylar along the central sulcus of the femoral patellar surface. It is a vertical displacement that descends (notch). The trochlear groove and the posterior geometry of the patella constrain patella tracking, especially at high flexion angles. The patella is centrally held by the fit of the small articular surface to the groove of the femur and the patellofemoral ligament. These ligaments represent the conformation of the capsule into the thickened structure medial and lateral to the patella. These ligaments are located above and below both sides and extend posteriorly from the anterior surface of the patella towards the sides of each femoral condyle. These ligaments also constrain the movement of the patella, but may be overturned by groove restraints or external forces. In a normal knee, it is permissible to estimate that patella tracking will be fairly similar to the orientation of the pulleys. As a result, in order to reproduce this innate patella track, the orientation of the trochlear groove of the knee prosthesis should be similar to the orientation of the innate trochlear.

In summary, the knee joint is an example of a very well-balanced system. Small changes within this system affect the entire system. Changes within the patello-femoral joint can have a fairly long-term effect due to the relatively high force transmitted within this part of the knee joint. TKA easily induces changes within the patello-femoral joint. At present, the orientation of the pulley grooves of the simulated TKA component does not match the orientation of the natural pulley. Therefore, the groove orientation of future femoral components should incorporate a trochlear groove that simulates the natural orientation of the natural femoral trochlear groove.

<figref num="1">It is a flowchart which outlines the process of making an atlas.</figref><figref num="2">Screenshots and associated images showing the automatic calculation of landmarks using IDAS software.</figref><figref num="3">FIG. 5 is a diagram of the distal end of the femur showing the axes, landmarks, and measurements taken.</figref><figref num="4">FIG. 3 is a front view of the femur of FIG. 3 showing specific axes, landmarks, and measurements taken.</figref><figref num="5">It is an exemplary diagram showing how the curvature on the surface of a bone can be approximated using circles with different radii.</figref><figref num="6">FIG. 5 is a side view of the lateral condyle of a human knee joint with five radii of curvature applied to approximate the curvature of the cam surface from anterior to posterior.</figref><figref num="7">FIG. 5 is a side view of the medial condyle of the human knee joint with five radii of curvature applied to approximate the curvature of the cam surface from anterior to posterior.</figref><figref num="8">FIG. 5 is a plan view of the proximal end of the human tibia, including the cartilage that forms part of the human knee joint.</figref><figref num="9">It is a front view of the knee joint which shows the anterior cruciate ligament and the posterior cruciate ligament while the knee is partially flexed.</figref><figref num="10">Includes a series of frontal views of the knee joint at various angles of knee flexion showing the location of the anterior and posterior cruciate ligaments.</figref><figref num="11">FIG. 6 is an overall schematic of an exemplary process for designing an orthopedic implant that includes a patient-customized orthopedic template or one of a series of templates for the general population.</figref><figref num="12">Bottom view of several electronic 3D distal femur models generated from medical imaging instruments, corresponding to the actual innate femur from a human patient.</figref><figref num="13">An electronic model of a human knee joint, including cartilage and ligaments, based on data from an actual human knee joint medical imaging device showing the joint in flexion position.</figref><figref num="14">An electronic model of a human knee joint, including cartilage and ligaments, based on medical imaging instrument data of a real human knee joint showing a joint close to full extension.</figref><figref num="15">A series of 2D vertical slice representations of the knee joint showing interactions between the tibia, femur, and patella that are close to full extension.</figref><figref num="16">A 3D representation of the 2D slice of Figure 15 added to the other vertical slices, showing where the slices were taken and the relative positions of the tibia, femur, and patella near full extension.</figref><figref num="17">It is a distal view of the femur showing the most anterior, distal, and posterior points along the medial and lateral cam trajectories.</figref><figref num="18">FIG. 5 is an edited view of the medial and lateral condyles of the distal femur with trajectories that approximate the outermost portion of the cam surface of each condyle over the entire range of motion of each condyle.</figref><figref num="19">A 3D representation showing the orbit of the outermost part of the cam surface of each condyle for an exemplary distal femur, as well as the tibia and patella with respect to the innermost surface of the glider groove associated with the distal femur. It is a rear elevation view.</figref><figref num="20">In addition to showing the distal femur with imaginary lines, it is a lateral side view of the knee joint showing the tibia and patella of FIG. 18, as well as the cam trajectory and trochlear groove trajectory.</figref><figref num="21">FIG. 6 is an exemplary chart showing a series of radius of curvature measurements for both male and female human femurs, as well as where the measurements were taken.</figref><figref num="22">It is a lateral side view of the knee joint showing the tibia and patella with respect to the position and dimension of the corresponding radius of curvature for the lateral and medial condyle outermost cam plane trajectories.</figref><figref num="23">FIG. 5 is a front view showing the usual differences between the shapes of the distal femurs between Asians, American Caucasians, and American Blacks.</figref><figref num="24">FIG. 5 is a side view showing the usual differences between the shapes of the medial femoral condyles between Asians, American Caucasians, and American Blacks.</figref><figref num="25">FIG. 5 is a side view showing the usual differences between the shapes of the lateral femoral condyles between Asians, American Caucasians, and American Blacks.</figref><figref num="26">It is an exemplary longitudinal section of an exemplary lateral condyle prosthesis showing how the measurements of c1-c4 are transformed into the curvature of the prosthetic device made according to the present disclosure.</figref><figref num="27">3D showing lateral and medial condyles and arched profiling of the trochlear groove, as well as the outermost cam surface trajectory of the lateral and medial condyles for an exemplary distal femur, and the innermost trajectory of the trochlear groove. It is an expression.</figref><figref num="28">It is a 3D representation of Fig. 22 superimposed on a 3D bone model of the natural femur.</figref><figref num="29">FIG. 23 is an enlarged view of FIG. 23 showing the distal portion of the femur and the superimposed 3D representation.</figref><figref num="30">FIG. 3 is a perspective view of the distal portion of the femur, including an exemplary 3D representation of the surface.</figref><figref num="31">It is a mathematical representation of the curvature shown in FIG.</figref><figref num="32A">It is a graph which plotted the ratio of the medial condyle and the lateral condyle to each other for 0-30 degrees.</figref><figref num="32B">It is a graph which plotted the ratio of the medial condyle and the lateral condyle to each other for 40-70 degrees.</figref><figref num="32C">It is a graph which plotted the ratio of the medial condyle and the lateral condyle to each other for 80-110 degrees.</figref><figref num="32D">It is a graph which plotted the ratio of the medial condyle and the lateral condyle to each other for 120-150 degrees.</figref><figref num="33">The proximal end of the tibia, showing the axes, landmarks, and measurements obtained in accordance with the present disclosure.</figref><figref num="34A">FIG. 5 is an end view of the distal femur showing a typical Asian pulley trajectory.</figref><figref num="34B">FIG. 3 is an end view of the distal femur showing a typical American Caucasian pulley trajectory.</figref><figref num="34C">It is an end view of the distal femur showing the pulley trajectory of a typical American black man.</figref><figref num="35">It is a composite diagram showing pulley trajectories for typical Asians, American Caucasians, and American Blacks.</figref><figref num="36">It is a composite side view showing the shape of the pulley track for a typical Asian, American Caucasian, and American Black.</figref><figref num="37">It is a distal view of the femur showing the area with the greatest difference between Asians and Caucasians of American descent.</figref><figref num="38">It is a distal view of the femur showing the area where the difference between American Caucasians and American Blacks is greatest.</figref><figref num="39">An elevational perspective view of the tibia showing the area with the greatest difference between American Caucasians and American Blacks.</figref><figref num="40">Proximal view of the tibia showing the area with the greatest difference between Asians and Caucasians of American descent.</figref><figref num="41">FIG. 5 illustrates an exemplary process of repairing a deformed or missing anatomy using a C1 / C2 ratio according to the present disclosure.</figref><figref num="42">It is an exemplary plot of AP height vs. ML width.</figref><figref num="43">It is a plot for determining the optimum number of clusters using the Dunn index and the modified Dunn index.</figref><figref num="44">The alternative Dunn exponential equation (ADI).</figref><figref num="45">A collection of diagrams showing an exemplary approximation of the tibial plateau, using a series of contours perpendicular to the main axis of the medial and lateral plateaus.</figref><figref num="46">It is an exemplary plot of AP height vs. ML width.</figref><figref num="47">It is a perspective view of an exemplary polyethylene implant.</figref><figref num="48">It is a series of perspective views of an exemplary implant.</figref><figref num="49">It is a perspective view of an exemplary implant.</figref><figref num="50">FIG. 6 is a cross-sectional view of an exemplary implant.</figref><figref num="51">It is a perspective view of an exemplary implant.</figref><figref num="52">FIG. 3 is an anterior view of an exemplary femoral and tibial component for a cross-holding implant made to accommodate the anatomical shape of a patient's knee.</figref><figref num="53">FIG. 6 is a cross-sectional view of the lateral condyle and condyle receiver for an exemplary femoral and tibial component for a cross-holding implant made to accommodate the anatomical shape of the patient's knee.</figref><figref num="54">FIG. 6 is a cross-sectional view of the medial condyle and condyle receiver for an exemplary femoral and tibial component for a cross-holding implant made to accommodate the anatomical shape of the patient's knee.</figref><figref num="55">A comparison showing the differences between anatomical implants and existing functional implants.</figref><figref num="56">It is a comparison showing the difference in restoring the correct ratio of the medial and lateral anterior parts of the knee.</figref><figref num="57">Shows the profile of a number of functional implants.</figref><figref num="58">Shows the profile of a number of functional implants.</figref><figref num="59">An exemplary shaded map showing variability between African-American and Caucasian populations, with lighter shadows corresponding to larger differences and darker shadows corresponding to fewer differences.</figref><figref num="60">It is an exemplary flow chart for generating a patient-specific implant from a 3D bone model.</figref><figref num="61">It is a diagram depicting a point cloud used to represent the surface of a patient's bone and to calculate the contour of a cross section of the bone.</figref><figref num="62">It is a diagram depicting the updating of parameterized implant constraints with patient-specific contours in the early stages of patient-specific implant creation.</figref><figref num="63">It is a figure which shows that the contour is swept to generate the smooth joint implant surface which is specific to a patient by this disclosure.</figref><figref num="64">An exemplary process flow diagram for updating an existing legacy implant system with an anatomically suitable template.</figref><figref num="65">It depicts an updated existing legacy implant system that incorporates a more anatomically accurate patellar groove.</figref><figref num="66">An exemplary list of parameters used to describe an exemplary femoral component designed in accordance with the present disclosure.</figref><figref num="67">An exemplary flowchart illustrating the process of automatically updating template parameters and generating implant CAD.</figref><figref num="68">The distal femur, shown with the corresponding area of contact highlighted.</figref><figref num="69">Proximal tibia, shown with corresponding contact area highlighted for knee flexion between 0-40 degrees.</figref><figref num="70">Proximal tibia, shown with corresponding contact area highlighted for knee flexion between 60-140 degrees.</figref><figref num="71">Top view of a tibial tray insert modified or redesigned to simulate or approximate normal knee kinematics.</figref><figref num="72">A conventional PS knee implant with limited rotation around the axis.</figref><figref num="73">FIG. 3 is an elevational perspective view of an exemplary knee prosthesis designed by the present disclosure that provides retention of the anterior cruciate ligament.</figref><figref num="74">FIG. 3 is a front view of an exemplary knee prosthesis designed by the present disclosure for use after anterior cruciate ligament revision surgery.</figref>

An exemplary embodiment of the invention is a method and device for designing a prosthesis knee implant, more specifically a device and device for designing a knee implant that more faithfully follows the biodynamics of the natural knee. , As well as the resulting implant itself, are described and illustrated below. Of course, it will be apparent to those skilled in the art that the preferred embodiments discussed below are exemplary in nature and can be reconstructed without departing from the scope and intent of the invention. However, for clarity and accuracy, any steps, methods, such that those skilled in the art will recognize that the exemplary embodiments discussed below are not a requirement to fall within the scope of the present invention. And may include features.

Below are definitions of axes, landmarks, and measurements for the distal femur (see Figure 2-Figure 4). These definitions also serve as a basis for the correct interpretation of these terms used in this disclosure.

"Epicondyle Transverse Axis (TEA)"-This measurement is known in the anthropological literature as the width between the two epicondyles. To calculate the clinical epicondyle transverse axis (TEA), a rough set of vertices is placed on the outermost ridge of the lateral epicondyle on the average femur and on the innermost ridge of the medial epicondyle. Determined manually. This step was performed only once because the vertices within the femoral atlas are homologous. A rough set of these points was used to define a search area with a radius of 10 mm from the center of gravity of the rough set of vertices, both outside and inside. Then, by defining a vector from each of these centroids, we give a rough direction for TEA. By maximizing the distance in this rough direction, a pair of points is selected and these selected points form the endpoints of the TEA measurement (see Figure 2). "Distal anatomical axis"-The distal anatomical axis was defined by positioning the center of gravity of the diaphysis at the distal third and distal fifth of the total length of the femur. Central AP Axis (CAP)-The distal anatomical axis and TEA were used to define a reciprocal orthogonal axis with terminations on the posterior surface of the intercondylar notch and the most anterior portion of the intercondylar groove. The length of this axis is recorded as a CAP (Figure 3). This axis is similar to the "height of the intercondylar notch". "Femoral saddle point"-A landmark located in the most distal extension of the intercondylar groove. The two endpoints of the "center of the knee" (K) -CAP measurement and the saddle point of the femur are used to determine the plane that bisects the femur medial and lateral. The intersection of this plane with the TEA is the center of the knee, which forms the distal end of the mechanical axis (MA) of the femur. The proximal end of the MA is the center of the femoral head (see Proximal Femoral Measurements below). "AP direction"-When MA and TEA are used, the anteroposterior (AP) direction is determined using a mutual orthogonal vector with the knee center as the origin, and a direction similar to the Whiteside line is obtained. "Anterior medial-lateral width (AML) and posterior medial-lateral width (PML)"-using the AP orientation, four landmarks are the most anterior and posterior points of the medial and lateral condyles of the distal femur. Be positioned. Connecting the two most anterior points gives an anterior medial-lateral width (AML) measurement along the lane, and connecting the two most posterior points measures along the posterior condyle axis (PCA). A measure of the posterior medial-lateral width (PML) is obtained (see Figure 2). "AP length of medial and lateral condyles (LAP and MAP)"-AP length of lateral condyle (LAP) and AP length of medial condyle (MAP) when paired with each of the lateral and medial vertices defined above ) Is obtained (see Figure 3). "Back plane"-The back plane was defined using a unique plane that contained the endpoints of the PML measurement and was also parallel to the ML. "Total AP length"-Minimum distance between the ridge of the lateral anterior condyle and the posterior plane (see Figure 3). AP Angle-The angle of the AML vector with respect to the back plane (see Figure 3). "Distal medial-lateral length (DML)"-MA was used in the reference direction to record the most distal planes of the medial and lateral condyles. The distance between these two landmarks was named DML. "Posterior angle (PA)"-The angle between the vector connecting the DML lengths and the mean axis of the femur (see Figure 4). "Condyle Twist Angle (CTA)"-The angle between TEA and PCA. "Knee groove height (GH)"-calculated between the posterior surface of the intercondylar notch and the midpoint between the two DML axes (see Figure 4). Femoral diaphyseal curvature (SC)-Radius of curvature of the average femoral axis.<u style="single">End of definition description</u><u style="single">Explanation of the table at the end of the text</u> "Table 1" Lists the results of important femoral measurements-mean, standard deviation, t-test, and power test for typical Asians, typical American Caucasians, and typical American Blacks. "Table 2" Lists important tibial measurements-mean, standard deviation, t-test, and power test results for typical Asians, typical American Caucasians, and typical American Blacks. Table 3 The percentages of changes in the length of the anterior cruciate ligament and posterior cruciate ligament are listed with respect to the knee flexion angle.

With reference to FIG. 11, a schematic overview of the exemplary knee design process 100 involves obtaining one or more electronic three-dimensional (3D) bone representations 102 stored in an electronic database. For the purpose of designing a total knee joint implant that will replace the distal part of the femur, the proximal part of the tibia, the cartilage between them, and at least part of the patella in the case of total patella plasty. Has a 3D bone representation of the distal femur, proximal tibia, and patella, as well as a 3D jig representation used to prepare the femur, tibia, and patella to accept TKA orthopedic components. Is useful. To generate these 3D bone and 3D jig representations, the patient or corpse can be subjected to a CT scan, a series of x-rays, MRI, and / or ultrasound imaging. Using images of bone and soft tissue obtained from these tests and, if possible, an interpolated aspect of bone or soft tissue, one or more 3D bone representations and one or more. Build a 3D jig representation of.

The images obtained from the above tests are loaded into a computer for data analysis. As is known to those of skill in the art, MRI creates a series of 2D "slices" of relevant parts of human anatomy. These 2D slices can then be segmented and stacked on top of each other to create a 3D model or representation of human anatomy. As long as MRI is used to construct the slices, the accuracy of the 3D model depends, in part, on how "thick" the slices obtained from the MRI are. For CT scans, X-rays, and ultrasound, a similar process is used to take 2D images from different points and use them to build a 3D model of the anatomical feature in question, for illustration purposes only. As the anatomical features of this problem are explained in the context of the human knee joint.

This same process for acquiring 2D images and using these images to create 3D models is applicable to the generation of 3D models of any human joint or bone. This same process can be applied to living or dead humans to generate multiple bone or joint models for further analysis. These same 2D images, in order to more accurately depict the anatomy of each human feature (bones, joints, etc.), between bones, in exemplary morphology, between the femur and tibia. It should be understood that it is also useful for constructing a 3D model of cartilage that can be selectively inserted between them. As discussed below, a 3D model of cartilage can be useful in building a 3D jig model.

Reference to FIG. 12 shows a series of 3D distal femoral representations. As discussed in more detail below, the exemplary knee design process 100 can be utilized to design and build customized knee implants that are unique to each patient's anatomy. In addition, an exemplary knee design process 100 can be utilized to approximate the anatomical structure of a larger population when customization costs are not commercially feasible or desirable, one or more. More general purpose implants can be designed and constructed.

Seeing FIG. 11 again, after modeling one or more bones so that the 3D representation is generated in electronic form, the 3D representation correlates additional data with this 3D representation in database 104. Stored in. In an exemplary form, Database 104 includes, but is not limited to, the age, gender, race, and height of the original human whose bones, joints, etc. were scanned to classify these expressions, each 3D. It also includes representation-specific data. At the same time, each 3D representation can include a grade or rating for the condition of bones, joints, etc. In an exemplary form, identify classifications for cartilage wear, bone degeneration, and osteophyte development when storing 3D depictions of knee joints (at least proximal tibia and distal femur) in database 104. can do.

With reference to FIGS. 13 and 14, following the generation of each individual bone model, the exemplary process 100 involves the generation of a 3D model of the knee joint 300. This 3D model 300 of the knee joint comprises orienting the distal femur 302, the proximal tibia 304, and the patella 306 in the orientation each takes when the joint is fully extended. The computer software can then behave to reposition the bones of the 3D model to create a virtual range of motion until the knee joint is fully flexed. At the same time, the 3D model 300 is a cartilage inserted between bones 302, 304, 306 to represent the innate cartilage that cooperates with the proximal end of tibia 304 to form a receiver for the medial and lateral condyles. (Not shown) can be included.

With reference to FIGS. 15 and 16, the 3D joint model 300 generates a 2D contact profile or "slice" that shows how the orientation of each slice changes as the knee joint moves through its range of motion. It is useful for. In particular, these 2D representations are useful in understanding that prosthetic implants can be thought of as a series of slices that coalesce and work together to form the entire joint, just like a natural knee. As a result, by assessing and understanding the geometry of each slice, a unique contour unique to each patient can be imagined or generalized across a more comprehensive population. Note that the 3D joint model 300 can incorporate different local anatomical structures (topograhy) depending on ethnicity, gender, and / or age. These various local anatomical structures result in different slices.

With reference to Figures 17-20, after each 3D model 300 is generated and saved, a series of radius of curvature measurements is obtained for both the medial and lateral condyles 308, 310 associated with each 3D model. .. In an exemplary form, the distal femoral 3D model includes the corresponding medial and lateral condyles 308, 310 separated by trochlear grooves 312. The medial and lateral condyles 308 and 310 each include a cam surface, which has a point along the cam surface that is farthest from the center of the bone as the femur rotates through the range of motion. The medial anterior point (the most anterior point in the medial condyle), the medial distal point (the most distal point on the medial condyle), and the medial posterior point (the most posterior point in the medial condyle) to calculate the medial profile. ) And the plane defined by) intersects the distal femur, resulting in contours corresponding to the most protruding points on the surface of the medial condyle, using this same method, FIGS. 17, 19, And the outer profile as shown in FIG. 20 is calculated. These 3D orbitals are then transformed into a single best-fit orbital in one plane for each condyle.

For the calculation of the groove profile, a set of contours is extracted by crossing the distal femur with a series of planes that rotate about the epicondyle transverse axis by 10 degrees. Groove points are then defined using the lowest points on these contours, as shown in FIG.

A similar procedure is used to generate a set of points along the 3D trajectory of the trochlear groove, using the points along the surface that are closest to the center of the bone as the femur rotates through its range of motion. These recent contacts (ie, the lowest part of the trough) are shown in FIGS. 19 and 20. This 3D orbital is then transformed into a single best fit orbital in one plane (as shown in FIGS. 19 and 20).

With reference to FIGS. 21 and 22, the inventor of the present invention attempts to design a prosthetic femoral component that closely resembles the natural shape of the distal femur, with support surfaces for both the medial and lateral condyles. We found that the shape of the 2D orbit for and the 2D orbit for the pulley groove are important. To determine specific dimensions and curvature measurements to generate the femoral component, the inventor applied four radii of curvature to each femoral condyle to accurately address the curvature of the innate femoral condyle. I found that I would follow.

23-Refer to FIG. 25, FIG. 23 is a composite view of the lateral and medial femoral condyles of whites, blacks, and Asians, while FIG. 24 is of the medial femoral condyles of whites, blacks, and Asians. Showing the medial profile, FIG. 25 shows the lateral profile of the lateral femoral condyle of Caucasians, blacks, and Asians.

Again, with reference to FIGS. 6, 21 and 26, each trajectory for the outermost cam surface of the medial condyle and the outermost cam surface of the lateral condyle is segmented into four zones. It was confirmed by the inventor that the curvature of each of these zones can be approximated by the curvature of a circle. In other words, each zone approximates a constant arc of a circle. For example, the first zone has a radius of curvature identified as c1. Simply put, the value of this c1 is the radius of the circle that most faithfully approximates the curvature of this part of the orbit, which is the rearmost part of the 2D orbit on the cam surface. The second zone, which is directly adjacent to the first zone, has a radius of curvature c2. Again, this value of c2 is the radius of the circle that most faithfully approximates the curvature of this second zone. The third zone follows the second zone and also contains the radius of curvature c3. Finally, the fourth zone, which approximates the contour of each anterior portion of each condyle, has a radius of curvature c4.

For situations where a series of knee joints are electronically modeled from X-rays, CT scans, MRI, etc., a comparison is made to identify how the radius of curvature varies within each zone and across all zones. It can be performed. The chart in Figure 21 is derived from a real 3D bone model derived from human X-rays, CT scans, and / or ultrasound. This chart contains the average radius of curvature (in centimeters) expressed in meters for each zone, based on gender. In addition to showing the mean radius of curvature for each zone, this table also shows the standard deviation for each zone so that quick comparisons between zones can be made for the lateral and medial condyles.

With reference to FIGS. 22 and 26 again, the lateral view of the human knee joint removes the distal part of the femur and the radius of curvature of each of the four zones for both the medial and lateral condyles (c1-c4). Replace it with the circle corresponding to. This figure gives a representation of what the radius of curvature represents with respect to the anatomical features of the adjacent distal femur, with the relative magnitude of the arc and the circle. As discussed below, these circles relate to attempts to approximate the curvature of the natural distal femur in prosthetic implants. The position of the center of the circle can be used inside the exemplary model. These can be calculated using the linear square fitting of a circle that gives the radius and center of the circle that most closely approximates the curve at each set of points on the curve.

With reference to FIGS. 27-32, as discussed above, trace the outermost cam points throughout the range of motion of the medial and lateral condyles, and the innermost points throughout the range of motion of the trochlear groove. , 3D orbital is created. The local anatomy of both the condyle and the trochlear groove is mathematically mapped using the trajectory of each outermost cam with the trajectory for the trochlear groove. The curvature of the inner, outer and groove profiles is then calculated by finding the best number of passing circles that accurately approximate the curve as shown in FIG. To capture the curvature of the condyle surface, the curves previously created by crossing the femur with the plane around the TEA are trimmed medially, laterally, and around the groove profile, and then these trimmings. The circle of curvature for each of the contours made is calculated as shown in FIG.

In addition to the trough trajectories, each of the outermost cam trajectories of the condyle is divided in variable angle increments along the range of motion in which the distal femur rotates with respect to the tibia. In the images presented, an increment of 10 degrees was used, but other increments are also within the scope of the present disclosure (in some exemplary embodiments, for example, an increment of 5-15 degrees may be used. it can). The length of each orbit is divided by 10 degrees, and one curve is applied to the boundary of each increment. A separate medial-lateral curve is applied to each condyle and lateral portion of the trochlear groove (medial to lateral) in increments of 10 degrees. The arcs of each individual inner-outer curve are selected to best approximate the inner-outer curvature at each point along their respective trajectories. The radius of curvature is then determined for each inner-outer curve.

With reference to FIG. 33, the following landmarks and measurements were automatically identified for the distal femur. 1) Intercondylar ridge-the two highest protruding points on the ridge of the medial and lateral condyles. 2) Midpoint of ridge-Midpoint between the lateral intercondylar ridge and the medial intercondylar ridge. 3) Tibial rough surface-the most anterior protruding point on the tibial rough surface. 4) ML-Maximum width of tibial plateau in the medial-lateral direction. 5) The length of the tibial plateau in the anterior-posterior (AP) direction through the midpoint of the AP-tibial intercondylar ridge (ie, the midpoint of the ridge). 6) Rise Width (EW)-Distance between the medial intercondylar ridge and the lateral intercondylar ridge. 7) Tibial twist angle (TTA)-The angle between the AP direction and the line connecting the midpoint of the intercondylar ridge to the rough tibial surface. 8) Lateral Plateau Height (LPH)-The length of the lateral tibial plateau in the AP direction. 9) Lateral Plateau Width (LPW)-The length of the lateral tibial plateau in the ML direction. 10) Medial Plateau Height (MPH)-The length of the medial tibial plateau in the AP direction. 11) Medial Plateau Width (MPW)-The length of the medial tibial plateau in the ML direction. 12) Rise ML ratio (EMLR)-Ratio of MPW (ie inner plateau width) to ML. 13) Maximum length-the length from the medial malleolus of the tibia to the intercondylar ridge.

With reference to FIGS. 34A-36, it can be seen that pulley grooves of different ethnicities have different shapes and trajectories. Figure 34A represents a typical Asian trochlear track, Figure 34B represents a typical American Caucasian pulley track, and Figure 34C represents a typical American black pulley track. In addition, Figure 35 shows a composite diagram of pulley trajectories for typical Asians, typical American Caucasians, and typical American Blacks. Finally, FIG. 36 shows a side view showing how the shape of the trochlear groove varies between Asians, American Caucasians, and American Blacks as well. The results obtained from the feature-finding shape analysis tools as described above highlight the shape differences in the femoral trunk, lateral condyle, and greater trochanter, in addition to the distal femur.

With reference to Table 1 and Figures 37-40, the results are obtained from the t-test and power test for automatically measured values. In American blacks, the lateral condyle had a higher AP height (p &lt;0.01), whereas the medial condyle height was not significant, making it more square than in American Caucasians. As a result, the AP condyle angle was larger in black Americans, as more trapezoidal knees were formed compared to shaped knees. On the other hand, our analysis of the distal femur of the East Asian population identified clear patterns in AP and ML, which were of East Asian descent compared to both Caucasian and African American populations. AP and ML measurements were small in the population (p &lt;0.01). In general, Asian populations are more trapezoidal in shape than Caucasian and African American populations (p &lt;0.01). In addition, East Asian populations also have a narrower anterior width (p &lt;0.01).

Analyzing the curvatures of both the outer and inner profiles, these profiles are accurate with four different radii of curvature for American Blacks and Caucasians and three different radii of curvature for East Asians. It was found that it could be approximated (see Figure 6). These four radii were coherent between the two ethnic groups (Black American and White American), but their radius values were different for each ethnic group, as shown in Figures 23-25.

The results of the feature discovery for the tibia show that the ethnic differences between black Americans and white Americans are greater around the rough tibial area, whereas the medial and lateral plateau areas. Shows that it is not significant. Except for minor differences in the proximal tibialis anterior, the only area that was significant was the tip of the medial malleolus (see Figures 39 and 40). However, significant morphological differences were found between East Asian populations and both American whites and American blacks (Figs. 23-35). The results obtained from the t-test and the power test also emphasize these findings. The most significant variables are scale-related variables, including maximum length, a measure of diaphyseal robustness, and some measurements of the tibial plateau. Briefly, the tibia of black Americans has a longer and more robust tibia and a slightly wider tibial plateau.

Table 2 shows autometric measurements for the tibia, with lateral plateau height being the most significant measurement (p &lt;0.05), which correlates with significant differences in lateral femoral condyle height.

With reference to FIG. 31 again, the radius of curvature for the medial-lateral curve was determined in increments of 10 degrees from posterior to anterior for both the medial and lateral condyles. The first row consists of 10 degrees increments along the outermost cam surface trajectories for both the medial and lateral condyles. The second and third columns show the radius of curvature of the medial and lateral condyles at each angle increment. The last two columns are the ratios corresponding to the curvature of the inner-outer radius of curvature divided by the radius of curvature for each cam surface trajectory. In other words, this ratio is the denominator of the radius of curvature of each condyle end-to-end radius of curvature and the radius of curvature of the zone along the orbit of the outermost cam surface of each condyle (with the same number per zone). There is) and. This ratio is then plotted zone by zone for various planes taken at a particular angle with respect to the mechanical axis (MA).

With reference to FIG. 41, the C1 / C2 (see FIG. 29) ratio can be used to repair deformed anatomy to produce a smooth articular surface for patient-specific implants. The process can be started by calculating the lateral and medial profiles and curves of the condylar surface on a patient-by-patient basis, as outlined in the previous issue, and then these contours have the curvature of the curve in each compartment. Evaluated to verify that it is within the normal anatomical range. The deformed compartments are then highlighted, the C1 / C2 ratios are calculated for the anatomically correct compartments, and then the ratios for the deformed compartments are interpolated using these compartments, and when this process is complete, the patient's correct compartments. A smooth implant joint curvature that mimics the anatomy is produced.

If there is an abnormality in the bone, the above result is used to approximate the radius of curvature C2 along the condyle. For the medial and lateral condyles, the relationship between the ratios of C1 and C2 has been identified and can be used to calculate the radius of curvature C2 for a particular position along either condyle.

Radius of curvature for the outermost cam surface trajectory for the medial and lateral condyles, as well as curvature mapping for the medial-lateral arc, can be used to create new patient-specific prosthetic implants. At each angle increment, a smooth curve is generated using the radius of curvature and three points along the medial condyle, trochlear groove, and lateral condyle (see Figure 29). The surface that sweeps these smooth curves is then used to approximate the articular surface of the implant.

With reference to FIGS. 41 and 26, four different radii of curvature were identified for the outermost cam surfaces of the lateral and medial condyles.

With reference to Figures 42-44, the dimensions of the cutting box were identified by analyzing the aspect ratio between the anteroposterior height and the ML width. AP height is defined as the distance between the sizing point on the femur and the most posterior point, while ML width is defined as the medial and lateral femur dimensions. This aspect ratio is then calculated for the entire population, but not limited to the features highlighted in Table 1, and then used as a multidimensional feature vector for clustering the population, how compact the cluster is. The best number of clusters is determined using both the Dunn index and the modified Dunn index, which are used to identify whether they are well separated (see Figures 43 and 44). In an exemplary form, 12 clusters were found that best represented the American Caucasian population, divided into 6 clusters for men and 6 clusters for women.

With reference to FIG. 45, the tibial plateau is approximated using a series of contours perpendicular to the main axis of the medial and lateral plateaus. These contours are used to parameterize the polyethylene surface for tibial implants.

With reference to FIG. 46, the dimensions of the six tibial plates were identified by measuring the anterior-posterior length of the tibial surface and measuring the length of the tibia in the medial-lateral direction. The ratio between these two measurements was then clustered using fuzzy c-means to identify the six dimensions that best fit this population.

With reference to FIGS. 47-51, the polyethylene component reflects the anatomical shape of the tibial plateau for cross-holding implants (see Figure 47) and double-cross implants (see Figures 48-51). The polyethylene component can be modular and can include medial and lateral polyethylene inserts that preserve the tibial ridge. A connector is used to ensure the correct installation of the insert (Figure 39). Once secured, the connector is removed, leaving only the medial and lateral polyethylene inserts and tibial trays in place (Figure 51).

See FIGS. 52-54 for the femoral and tibial parts of the implant that correspond to the anatomical shape of the knee, showing matching curvatures between the radii of the two parts.

With reference to Figures 55-58, the comparison shows the difference between an anatomical implant and an existing functional implant. FIG. 55 shows the difference when restoring the correct ratio between the medial and lateral anterior parts of the knee. Existing functional implants (blue) do not properly restore this ratio, resulting in stronger tension along the quadriceps, which can alter knee movement and subluxation of the patella. It can cause dislocation. Figures 56-58 show the curvature of the medial and lateral profiles of the anatomical implant in comparison to existing functional implants. FIG. 56 shows a direct comparison with a typical implant, while FIGS. 57 and 58 show profiles of a number of functional implants.

With reference to Figure 59, the colormap shows the variation between the African-American population and the Caucasian population. Light colors show a greater difference than dark colors. The lateral condyle shows a slight difference, but there is little variation at the distal end of the femur.

An exemplary process of selecting the template that best fits the patient's anatomy can be described as follows. First, the patient's knee is imaged to generate a 3D surface of the patient's femur and tibia. The femur is then analyzed and the medial and lateral cam trajectories are calculated. The inner and outer sagittal curves are then calculated. The anterior-posterior and medial-lateral dimensions of the femur are also calculated. The curvature of the cam trajectory along the sagittal curve, AP dimensions, and / or medial and lateral widths can be used to find the template that best fits the patient. For patients whose implant template does not fit their anatomy, a custom implant is generated as shown by the right branch in Figure 11.

With reference to FIG. 60, an exemplary process for generating patient-specific implants from any of the imaging modalities involves generating three-dimensional patient-specific models, which are then described above. (DAT) Added to the statistical atlas, point correspondence and normalization are achieved, and when this process is complete, the associated surgical landmarks are automatically calculated (TEA, MA, PCA, ... etc.) ).

With reference to Figures 61-63, the contour of the bone cross section is then calculated using a plane that rotates around the TEA (see Figure 61), and then another set of contours perpendicular to the MA is calculated. (See Figure 62). The set of these two contours is then used to automatically update the constraints of the parameterized implant template, and when these constraints are updated, the implant articular surface is then swept. A smooth continuous surface is generated (see Figure 63). In addition, the template cutting box is updated with measurements of anterior-posterior height and medial-lateral width obtained from the patient's bone. The box is then combined with a smooth articular surface to generate a CAD model of the patient-specific implant. The 3D CAD model of this implant is then evaluated against a patient-specific 3D model of bone, the placement is verified, and the range of motion is simulated using the 3D implant model and the 3D bone model. When the verification process is complete, a 3D implant model is output from the computer to the manufacturing facility to manufacture the implant. In an exemplary form, the computer output of the 3D implant model can be in the form of G-code for a CNC machine.

With reference to Figure 64, the exemplary flow chart also uses implant templates generated from clusters that best fit the population to update existing legacy systems to ensure compatibility with the patient's anatomical tendencies. Outline the method. This process involves importing a CAD model of an existing implant system and transforming it into the same parameter display space as the anatomical template. This process involves producing a collection of three-dimensional contours around the central axis of the implant. These contours are used to generate a set of constraints in a manner similar to an anatomical template. When the implant is parameterized as in the template, the parameter values in the template are used to update the characteristics of the parameterized implant. Features of these parameterized implants include, but are not limited to, patellar groove curvature, condyle curvature, AP height, and ML width.

Figure 65 shows how an anatomically suitable template can be used to update an existing implant family to create an implant that mimics the anatomical patellar groove.

With reference to FIGS. 66 and 67, the femur CAD model, represented by exemplary parameters, consists of more than 300 parameters. The CAD model is defined by a 10 degree increment cross section around the TEA axis. The parameters define specific points and curvatures in each cross section. The patello-femoral compartment of the implant is defined by three points from the medial, lateral, and groove curvatures, along with three radii, as discussed above. For the cross section of the condyle, the medial and lateral sides are defined by two points and one radius. Molding information is unique within the cross section in order to automatically create a complete implant CAD model.

With reference to Figures 68-70, the total range of motion of the femur with respect to the tibia should be fully characterized in order to design a functional implant that most faithfully mimics normal knee movement. To achieve this goal, a collection of anatomical areas is localized on the femur and projected onto the tibia over the entire range of motion. First, the most distal area on the medial side of the femur, which is the area of contact between the femur and tibia when fully extended, was localized (A1) (see Figure 69). The second area is the most distal area of the lateral condyle (A2), while the third area is the most posterior area of the medial condyle (A3) and the fourth area is the most posterior of the lateral condyle. Area (A4) (see Figure 70). Over the entire range of motion, each area on the femur was projected onto the tibia to characterize the movement of these areas with respect to the tibial plateau surface. A clear pattern of movement was observed on the medial side where area A1 moved anteriorly until 40 degree flexion, after which it was out of contact with the tibial surface. At the same time, after 40 degrees, area A3 begins to move forward with axial rotational tracking. On the outside, area A2 moves forward smaller than A1 up to a 40 degree bend, where it is out of contact like A1. At the same time, area A4 comes into contact and moves forward in a smaller area than area A3.

With reference to Figures 68-72, in order to achieve a normal movement pattern with a functional PS implant, both the curvature of the femoral implant and the design of the polyethylene component were designed to provide more natural movement. Should be fixed. In addition, the cam position on the polyethylene component is modified to constrain the movement of the femur and allow further rotation around the axis (see Figure 71). None of the existing functional implants can be actuated to give as much rotation as the rotation around the axis observed in a normal knee. A PS implant (see, eg, Figure 72) was implanted, and then X-ray fluorescence fluoroscopy was performed to observe the position of the femoral component with respect to the cam. As a result, the cam position was found to be inside the femoral implant. Observed, this implied that this cam position did not allow sufficient rotation around the axis. In order to improve the rotation of the implant joint around the axis, the cam position was modified to tilt outward according to the position on the medial side. This modification allows for a better range of rotation around the axis that more closely approximates the normal range of motion of the innate knee joint.

As can be seen in FIGS. 69 and 70, the outside of the tibia has two different sites. The outer curvature of PS polyethylene in FIG. 71 is designed to adapt to such unique conditions. During bending from 0 to 40 degrees, the front of the polyethylene part is defined by four sets of curvatures. This geometry is further angled to prevent the femoral component from sliding excessively anteriorly between these flexion angles. The posterior part of the polyethylene part is also defined by four sets of curvatures, which engage the lateral condyle during flexion from 60 degrees to 140 degrees. This portion is designed to be flatter to provide smoother movement and prevent collisions. The inside has a set of curvatures shaped in the shape of a deep dish for rolling motion during bending from 60 degrees to 140 degrees. The second set of curvatures introduces a unique track that first follows the position of the bend from 60 degrees to 120 degrees and then leads to the position of the bend from 0 degrees to 40 degrees. Allows smooth transitions between tracks at position.

With reference to Figures 73-74 and Table 3, to design anatomically suitable posterior cruciate, ACL, and PCL implants, study the location of the PCL and ACL when the knee joint is moved through its range of motion. Must. A statistical atlas was used to localize and propagate ACL and PCL insertion locations throughout the population. Both ACL and PCL were deformed by moving the knee joint through range of motion to map changes in ligament shape and length across range of motion. Table 3 emphasizes the difference in length between ACL and PCL as a percentage of ACL length. This data can be used to design implants that adapt to retention of either PCL or ACL, or both ACL and PCL.

According to the above description and the outline of the invention, the methods and devices described herein constitute exemplary embodiments of the invention, but the inventions contained herein are limited to these embodiments. Instead, it should be apparent to those skilled in the art that changes can be made to such embodiments without departing from the scope of the invention as defined by the claims. Furthermore, the invention is defined by the claims, and any limitation or element that describes the exemplary embodiments presented herein is unless such limitation or element is explicitly stated. It should be understood that it is not intended to be incorporated into the interpretation of the elements of any claim. Similarly, the invention is defined by the claims, and there may be potential and / or unforeseen advantages of the invention, even if not explicitly discussed herein. It should be understood that it is not always necessary to meet any or all of the identified advantages or objectives of the invention disclosed herein in order to be within the scope of the claims. The present invention is defined as follows. (1) A method of producing patient-specific prosthetic implants The human anatomy incorporates dimension and curvature features that mimic the dimensions and contour features of the human anatomical features using at least one medical scan of unique patient-derived human anatomical features. The stage of generating a three-dimensional electronic representation of a feature, The stage of obtaining multiple prosthetic implant templates representing the same human anatomical features from a human population, and To construct the patient-specific prosthesis implant, the 3D electronic representation of the human anatomical feature is used to represent the dimensional and curvature features represented by the 3D electronic representation of the human anatomical feature. The three-dimensional electronic representation of the unique patient is compared with the plurality of prosthesis implant templates, and the prosthesis that best corresponds to the three-dimensional electronic representation among the plurality of prosthesis implant templates. The step of selecting at least one of the plurality of prosthesis implant templates by a method including obtaining an implant template, and The human anatomy specific to the unique patient, having a cam surface formed by combining a plurality of radii of curvature close to the plurality of radii of curvature in the unique patient's innate anatomical features. The step of customizing the selected prosthetic implant template to form the patient-specific prosthetic implant that mimics the features of the dimensions and curvature of the features, and A step of virtually test-fitting the customized prosthetic implant using the three-dimensional electronic representation of the human anatomical features. A method characterized by including. (2) Obtaining multiple prosthetic implant templates Group multiple models in the database For each of the plurality of models in the database, associate at least one of age, ethnicity, and gender. The plurality of prosthetic implant templates, each of the plurality of prosthetic implant templates, are common to at least a portion of the human population seeking to create a three-dimensional model, and the plurality of prosthetic implant templates. At least 5 of the templates generate different shapes for at least one of the contours and dimensions The method according to (1), which comprises the step of forming the implant. (3) At least one of the dimensions and contours in which the implant forming step approximates at least one of the average dimensions and contours of at least a portion of the human population from which the three-dimensional model was generated. The method according to (2), which comprises incorporating the above. (4) Local anatomical structure of the medial condyle cam surface, local anatomical structure of the lateral condyle cam surface, and local anatomical structure of the trochlear groove for at least two of the plurality of electronic three-dimensional models. The method according to any one of (1) to (3), further comprising the step of measuring at least one of. (Five) The step of selecting at least one of the plurality of prosthetic implant templates is the lowest of any of the plurality of prosthetic implant templates for the three-dimensional electronic representation of the human anatomical features. The method according to any one of (1) to (4), which comprises a step of evaluating whether or not it has a deviation rate. (6) The three-dimensional electronic representation of the human anatomical feature includes a model of the line of contact, the model contains a plurality of radii of curvature, and each of the radii of curvature is part of the line of contact. The method according to (1), characterized in that it is associated. (7) The act of selection compares the radius of curvature associated with the model of the line of contact with the corresponding radius of curvature associated with at least one of the plurality of prosthetic implant templates. The method according to (6), which further comprises. (8) The method according to (1), wherein the step of generating a three-dimensional electronic representation of the human anatomical feature includes a step of forming a plurality of bone models of the human population. .. (9) A femoral shell is generated from bone mapping, a profile / point generated from the shell is generated by sweeping around the bone every 10 degrees, a curve is generated from the profile / point, and the curve is formed. The method according to (8), characterized in that at least four radii are matched. (10) The stage of forming the multiple bone models is In the step of identifying a plurality of points associated with the contact surface of the bone, A step of dividing the plurality of points associated with the contact surface into a plurality of zones, each of which includes some of the plurality of points. The step of approximating the plurality of points in each zone using the first curve determined by the radius of curvature, and The stage of creating a model of the contact surface by combining each of the first curves, and The method according to (8), which comprises. (11) A step of identifying a plurality of separated positions of the contact surface along the model, and A step of approximating the shape of the bone in the vicinity of the separated position using a second curve defined by the radius of curvature and arranged so as to be substantially orthogonal to the model of the contact surface. The method according to (10), which further comprises. (12) The step of identifying the plurality of separated positions identifies the plurality of separated positions by dividing the model of the contact surface into a plurality of portions having substantially the same angle. The method according to (11), which comprises: (13) The method according to (12), wherein the substantially equal portion is between about 5 degrees and about 15 degrees. (14) The method according to (12), wherein the portion having substantially the same angle is about 10 degrees. (15) Includes a patient-specific human joint component implant that mimics the dimensions and curvature of the innate anatomical part to replace the patient's innate anatomical part. A patient-specific prosthetic implant, wherein the human joint component implant incorporates a cam surface made by associating a plurality of radii of curvature that approximate the plurality of radii of curvature of the innate anatomical portion. (16) The human joint part is a femur part of the knee joint. The femoral component comprises a medial condyle having the cam surface. The patient according to (15), wherein the cam surface comprises an anterior-distal-posterior surface incorporating at least three radii of curvature that are oblique with respect to the medial and lateral directions of the femoral component. Specific prosthetic implant. (17) The human joint part is a femur part of the knee joint. The femoral component comprises the lateral condyle with the cam surface. The patient according to (15), wherein the cam surface comprises an anterior-distal-posterior surface incorporating at least three radii of curvature that are oblique with respect to the medial and lateral directions of the femoral component. Specific prosthetic implant. (18) The human joint part is a femur part of the knee joint. The femoral component includes lateral and medial condyles, each condyle having its own cam surface. The cam surface for the lateral condyle includes an anterior-distal-posterior surface incorporating at least three radii of curvature that are oblique with respect to the medial-lateral direction of the femoral component. The cam surface for the medial condyle includes an anterior-distal-posterior surface incorporating at least three radii of curvature that are oblique with respect to the medial-lateral direction of the femoral component. The patient-specific prosthetic implant according to (15), wherein the at least three radii of curvature for the lateral condyle are not identical to the at least three radii of curvature for the medial condyle. (19) The human joint part is a femur part of the knee joint. The femoral component comprises a medial condyle having the cam surface. The patient-specific prosthetic implant according to (15), wherein the cam surface comprises an medial-lateral surface that incorporates at least three radii of curvature that are generally parallel to the medial and lateral directions of the femoral component. (20) The human joint part is a femur part of the knee joint. The femoral component comprises the lateral condyle with the cam surface. The patient-specific prosthetic implant according to (15), wherein the cam surface comprises an medial-lateral surface that incorporates at least three radii of curvature that are generally parallel to the medial and lateral directions of the femoral component. (21) The human joint part is a femur part of the knee joint. The femoral component includes lateral and medial condyles, each condyle having its own cam surface. The cam surface for the lateral condyle comprises a medial-lateral surface incorporating at least three radii of curvature that are generally parallel to the medial-lateral direction of the femoral component. The cam surface for the medial condyle includes a medial-lateral surface that incorporates at least three radii of curvature that are generally parallel to the medial-lateral direction of the femoral component. The patient-specific prosthetic implant according to (15), wherein the at least three radii of curvature for the lateral condyle are not identical to the at least three radii of curvature for the medial condyle. (22) The human joint part is a femur part of the knee joint. The femur component includes a trochlear groove surface. The patient-specific according to (15), wherein the trochlear groove surface includes an anterior-distal surface incorporating at least two radii of curvature that are oblique with respect to the medial and lateral directions of the femoral component. Prosthetic implant. (23) The human joint part is a femur part of the knee joint. The femur component includes a trochlear groove surface. The patient-specific prosthetic implant according to (15), wherein the trochlear groove surface includes an inner-outer surface that incorporates at least two radii of curvature that are generally parallel to the medial and lateral directions of the femoral component. .. (24) The femur component includes a pulley groove surface.(18) or (21), wherein the pulley groove surface comprises an anterior-distal surface incorporating at least two radii of curvature that are oblique with respect to the medial and lateral directions of the femoral component. The patient-specific prosthetic implants described. (25) The femur component includes a pulley groove surface. The patient according to (18) or (21), wherein the pulley groove surface includes an inner-outer surface incorporating at least two radii of curvature that are generally parallel to the medial-lateral direction of the femoral component. Specific prosthetic implant. (26) A method of producing a patient-specific prosthetic implant. Using at least one medical scan of a unique patient-derived human anatomical feature to generate a three-dimensional electronic representation of the human anatomical feature, and A step of automatically marking a plurality of surgical markers on the three-dimensional electronic representation of the human anatomical feature, and<u style="single">Epicondyle transverse axis (TEA)</u>A step of rotating a two-dimensional plane around the to create a slice of the three-dimensional electronic representation of the human anatomical feature, resulting in a bone cross-section contour. The step of associating the obtained bone cross-sectional contour with the virtual implant template, The stage of generating a patient-specific prosthetic implant using the virtual implant template, and A method characterized by including. (27) The method according to (26), further comprising the step of sweeping the virtual implant template to create a smooth articular surface template after associating the obtained bone cross-sectional contours. .. (28) The method according to (27), further comprising generating a virtual template cutting guide representing a cut portion to be made in human bone to accept the patient-specific prosthetic implant. (29) The patient-specific prosthetic implant uses the patient-specific virtual model to further include the step of merging the virtual template cutting guide with the smooth articular surface template to generate a patient-specific virtual model. The method according to (28), characterized in that it is generated. (30) The step of generating the virtual template cutting guide comprises automatically measuring the anterior-posterior height and the medial-exterior width of the three-dimensional electronic representation of the human anatomical feature. The method described in 28). (31) The step of generating the virtual template cutting guide comprises automatically measuring the anterior-posterior height and the medial-exterior width of the three-dimensional electronic representation of the human anatomical feature. The method described in 28). (32) The patient-specific prosthetic implant uses the patient-specific virtual model to further include the step of merging the virtual template cutting guide with the smooth articular surface template to generate a patient-specific virtual model. The method according to (31), characterized in that it is generated. (33) The step of generating the virtual template cutting guide includes a step of automatically measuring the anteroposterior height and the medial / lateral width of the three-dimensional electronic representation of the human anatomical feature. The method described in 31).

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