Abstract
A tibial component placement guide for use in a knee arthroplasty procedure involving a knee joint comprising a tibia, a patella, and a femur, the tibial component placement guide comprising an overlay configured to be overlaid a resected tibia that typifies at least one of a shape and an outline of the resected tibia, the overlay including at least one of an indicia and an opening indicative of at least one of an orientation and a position of a presurgical kinematic axis of at least one of the femur and the patella.
Claims
1. A tibial component placement guide for use in a knee arthroplasty procedure involving a knee joint comprising a tibia, a patella, and a femur, the tibial component placement guide comprising: an overlay configured to be overlaid a resected tibia that typifies at least one of a shape and an outline of the resected tibia, the overlay including at least one of an indicia and an opening indicative of at least one of an orientation and a position of a presurgical kinematic axis of at least one of the femur and the patella.
2. The tibial component placement guide of claim 1, wherein the overlay includes an opening indicative of an orientation of a first presurgical axis of the femur and the second presurgical kinematic axis of the femur.
3. The tibial component placement guide of claim 2, wherein the opening comprises a through hole.
4. The tibial component placement guide of claim 3, wherein: the through hole outlines a T-shape; a horizontal aspect of the T-shape is indicative of the orientation of the first presurgical axis of the femur; and, a vertical aspect of the T-shape is indicative of the orientation of the second presurgical axis of the femur.
5. The tibial component placement guide of claim 3, wherein: the through hole outlines a + shape; a horizontal aspect of the + shape is indicative of the orientation of the first presurgical axis of the femur; and, a vertical aspect of the + shape is indicative of the orientation of the second presurgical axis of the femur.
6. The tibial component placement guide of claim 2, wherein: the opening comprises a first through hole and a second through hole; the first through hole is indicative of the orientation of the first presurgical axis of the femur; and, the second through hole is indicative of the orientation of the second presurgical axis of the femur.
7. The tibial component placement guide of claim 2, wherein: the opening comprises a first cutout and a second cutout; the first cutout is indicative of the position of the first presurgical axis of the femur; and, the second cutout is indicative of the position of the second presurgical axis of the femur.
8. The tibial component placement guide of claim 1, wherein the presurgical kinematic axis of the femur comprises a posterior condylar axis of the femur.
9. The tibial component placement guide of claim 1, wherein the presurgical kinematic axis of the femur comprises a helical axis of the femur.
10. The tibial component placement guide of claim 1, wherein the overlay includes the outline of the resected tibia.
11. The tibial component placement guide of claim 10, wherein the outline is patient-specific.
12. The tibial component placement guide of claim 1, further comprising at least one of an indicia and an opening indicative of at least two of a medial guide, a lateral guide, a size of the tibial component placement guide, and a particular patient.
13. The tibial component placement guide of claim 1, wherein the tibial component placement guide is fabricated from at least one of titanium, a titanium alloy, stainless steel, and a stainless steel alloy.
14. The tibial component placement guide of any of the foregoing claims, wherein the tibial component placement guide includes a through aperture configured to align a through fastener mounted to the resected tibia.
15. The tibial component placement guide of claim 14, wherein the through fastener comprises a pin.
16. The tibial component placement guide of claim 15, wherein: the through aperture comprises a plurality of through apertures; and, each of the plurality of apertures is configured to receive a pin.
17. The tibial component placement guide of any of the foregoing claims, wherein the overlay comprises a base plate.
18. The tibial component placement guide of claim 17, wherein the base plate includes a flange along a periphery of the base plate.
19. The tibial component placement guide of any of the foregoing claims, further comprising at least one of an indicia and an opening indicative of the orientation of a third axis of the femur, the third axis being parallel to the first axis.
20. The tibial component placement guide of claim 1, wherein the overlay includes an opening indicative of the orientation of the first presurgical axis of the patella.
21. The tibial component placement guide of claim 20, wherein the opening comprises a through hole.
22. A kinematic femoral component for use in a knee arthroplasty procedure involving a knee joint comprising a tibia, a patella, and a femur, the kinematic femoral component comprising: a femoral component replicating a presurgical trochlear groove angle of a femur that is parallel to a sagittal femoral kinematic plane.
23. The kinematic femoral component of claim 22, wherein a lateral aspect of the kinematic femoral component includes an anterior flange extending proximally, with the respect to a femur, between 10 to 45 millimeters beyond a femoral knee center of the femur.
24. The kinematic femoral component of claim 22, wherein a medial aspect of the kinematic femoral component includes an anterior flange extending proximally, the respect to a femur, between 10 to 25 millimeters beyond a femoral knee center of the femur.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] FIGS. 1A-1C are anatomical frontal, anatomical profile, and skeletal section views depicting the femoral and tibial mechanical axis.
[0051] FIG. 2A is a software user interface of an exemplary software system in accordance with the instant disclosure showing hip, knee, and ankle (HKA) axes.
[0052] FIG. 2B is a graphical depiction of a gap balance technique used during a knee arthroplasty procedure.
[0053] FIGS. 3A and 3B are X-ray fluoroscopic images of a knee joint bent approximately 90 degrees, as well as a compilation image showing the position of the femoral head and femoral condyles across a range of motion.
[0054] FIGS. 4A-4D are helical axes of motion corresponding to nine steps of knee flexion from 0 to 120 degrees, shown in an sagittal plane, an anteroposterior view of axes projected on the frontal plane. The geometrical center of the femur rotating around the screw/helical axis shown in a sagittal and an anteroposterior view of the geometrical centers of the femur projected on the frontal plane.
[0055] FIGS. 5A-5D include a frontal view of the knee joint showing the minimum points on the femoral condyles projected on the tibial plateau. A sagittal view of the knee joint showing 3 flexion angles and their corresponding lowest points projected on the tibial plateau. An anteroposterior view of the knee joint showing the three lowest points on the femur projected on the frontal plane. An axial view of the minimum points projected on the tibial plateau. Finally, a top view of the tibial plateau showing a plane going through the geometrical center of the tibia of knee joint.
[0056] FIG. 6 is a top view of the tibial plateau showing a plane going through the geometrical center of the tibia of knee joint.
[0057] FIG. 7 is a graphical representation of the top of a tibia and the average normal subjects' medial and lateral condyle contact positions during a deep knee bend activity.
[0058] FIG. 8 is a plot of anteroposterior translations of the contact points between the femur and the tibia during knee flexion.
[0059] FIG. 9 is a plot of axial rotation of the femur during knee flexion for normal subjects.
[0060] FIGS. 10A-10E are axial, top views of the minimum points projected on the tibial plateau of five subject knees showing clear medial pivoting motion of the femur relative to the tibia.
[0061] FIGS. 11A-11D depict helical axis of the normal knees showing the axis does not stay fixed in space during an entire movement through the available range of motion across four subject knees.
[0062] FIG. 12 is a graphical depiction of ligament attachment sites tracked during fluoroscopy of a knee joint.
[0063] FIG. 13 is a series of views of a virtual knee joint model showing ligaments reconstructed using ligament attachment sites.
[0064] FIG. 14 is a plot depicting average lengths in millimeters for the anterior cruciate ligament and the posterior collateral ligament at each increment of flexion during a deep knee bend.
[0065] FIG. 15 is a table detailing subjects lengths in millimeters for the anterior cruciate ligament and the posterior collateral ligament at each increment of flexion during deep knee bend.
[0066] FIGS. 16A and 16B are distal and posterior views of a posterior end of a femur.
[0067] FIGS. 17A and 17B are projections of tracked areas from the femur onto the tibia from zero degrees to 140 degrees projected on the tibia left A1/A2 and right A3/A4 from FIGS. 16A, 16B.
[0068] FIGS. 18A-18D include medial, lateral, and posterior views of a femur, along with associated curves depicting the curvature differences along the length of the medial and lateral condyles.
[0069] FIG. 19 is an elevated perspective view of a virtual femur model showing a series of surface points placed on the lateral and medial condyles on the posterior aspect.
[0070] FIG. 20 is an end view of a virtual femur model having a sphere fit to each of the medial and lateral condyles using the surface points in FIG. 19 in accordance with the present disclosure.
[0071] FIG. 21 is an end view of a virtual femur model having a cylinder fit to each of the medial and lateral condyles using the surface points in FIG. 19 in accordance with the present disclosure.
[0072] FIG. 22 is a graphical representation of a distal femur and comparison of the surgical transepicondylar axis, the clinical transepicondylar axis, the spherical axis, and the cylindrical axis.
[0073] FIG. 23 is a range of motion view showing how the femur moves with respect to the tibia and how the position of the femoral helical axis changes with this motion.
[0074] FIG. 24 is a graphical depiction showing how the femoral cylindrical axis changes across a range of motion between full extension (zero degrees) and a deep knee bend (152 degrees).
[0075] FIG. 25 is a graphical depiction showing how the femoral spherical axis changes across a range of motion between full extension (zero degrees) and a deep knee bend (152 degrees).
[0076] FIG. 26 is a graphical depiction showing how the femoral transepicondylar axis changes across a range of motion between full extension (zero degrees) and a deep knee bend (152 degrees).
[0077] FIG. 27 is a graphical depiction of the clinical and surgical transepicondylar axis of the femur.
[0078] FIG. 28 is an overlay compilation of the graphical depictions from FIGS. 24-26.
[0079] FIGS. 29A and 29B includes a range of motion view of the femur with respect to the tibia and an overhead view of the tibia showing how the helical/transverse axis of the femur changes with this range of motion.
[0080] FIG. 30 is a graphical representation showing the cylindrical axis of the femur is not normal with respect to the tibial mechanical axis.
[0081] FIG. 31 is a graphical representation of the distal femur showing the posterior condylar axis and the cylindrical axis are almost consistently parallel.
[0082] FIGS. 32A-32D are multiple views of a femur showing patella motion and tracking this motion in accordance with the instant disclosure via the intersection with the sagittal kinematic plane.
[0083] FIGS. 33A-33F are a series of images depicting how the motion of the patella is tracked with respect to the sagittal kinematic plane.
[0084] FIG. 34 is a graphical depiction of a patella virtual model constructed from surface points across four quadrants.
[0085] FIGS. 35A and 35B are medial and lateral views of a femur showing the natural motion of the patella contact surfaces with respect to the femoral trochlear groove.
[0086] FIGS. 36A-36D are various views showing how the contact surfaces of the patella embodies roughly the same curvature as the trochlear groove.
[0087] FIG. 37 depicts graphically the angular differences between the sagittal kinematic plane, the patella loci plane, and the femoral implant plane.
[0088] FIGS. 38A-38C are graphical depictions of motion of the patella before and after TKA and showing that post TKA the patella no longer replicates its natural kinematic motion.
[0089] FIG. 39 is an end view of a TKA femoral component constructed in accordance with the instant disclosure that includes a trochlear groove that is kinematically aligned.
[0090] FIG. 40 is an end view of a distal femur showing how present day implants trochlear groove is considerably different from the trochlear groove of the kinematic femoral component fabricated in accordance with the instant disclosure.
[0091] FIGS. 41A-41C depict initially the femoral postcondylar axis (PCA) and the intersection of a plane normal to the PCA, and then depict the intersection of a plane normal to the PCA with a plane normal to the tibial mechanical axis, and finally depicting the a plane normal to the PCA imposed onto the proximal tibia.
[0092] FIG. 42 is a graphical representation of the proximal tibia having calculated traditional tibia landmarks that include the medial eminence, lateral eminence, and AP1/3 Tubercle posterior cruciate ligament.
[0093] FIGS. 43A and 43B are graphical representations showing how the Cobb axis is determined using peripheral points on the medial and lateral condyles and circles approximating the curvature of the condyles.
[0094] FIGS. 44A-44C comprises multiple views of positions of the femur with respect to the tibia across a range of motion that are either load bearing (red) or non-load bearing (blue).
[0095] FIG. 45 is an overhead view of a proximal tibia showing the orientation of various axes.
[0096] FIG. 46 is a comparison overhead view showing mechanical alignment versus kinematic alignment of a commercially available tibial tray on a proximal tibia.
[0097] FIG. 47 is an overhead view showing mechanical alignment of a commercially available tibial tray on a proximal tibia.
[0098] FIG. 48 is an overhead view showing kinematic alignment of a commercially available tibial tray on a proximal tibia.
[0099] FIG. 49 is an overhead view showing kinematic alignment of a smaller commercially available tibial tray on a proximal tibia.
[0100] FIGS. 50A and 50B are comparison views showing femoral component alignment when aligned with the femoral PCA.
[0101] FIGS. 51A and 51B are comparison views showing femoral component alignment when aligned with the femoral PCA plus three degrees of offset.
[0102] FIG. 52 shows femoral component rotational alignment.
[0103] FIGS. 53A and 53B show multiple views of kinematic alignment between femoral and tibial components of a TKA.
[0104] FIGS. 54A and 54B show multiple views of a femoral component with respect to a tibial component using mechanical alignment and kinematic alignment (PPNP).
[0105] FIG. 55 is a process flow diagram depicting an exemplary process for generating an optimal implant placement.
[0106] FIGS. 56A and 56B are graphical depictions of initial tibial placement pursuant to the process flow diagram of FIG. 55.
[0107] FIGS. 57A and 57B are outline comparisons of the resected tibia and a commercially available tibial tray implant.
[0108] FIGS. 58A and 58B are graphical depictions showing the difference in tibial tray placement on a resected tibia in accordance with the process of FIG. 55, where the initial alignment is refined to the weighted match.
[0109] FIG. 59 comprises a series of commercially available tibial tray implants grouped according to alignment technique.
[0110] FIG. 60 is an overhead view of a tibia superimposed with the images of four commercially available tibial trays positioned via mechanical alignment.
[0111] FIG. 61 is an overhead view of a tibia superimposed with the images of four commercially available tibial trays positioned via kinematic alignment in accordance with the instant disclosure.
[0112] FIG. 62 is an overhead view of a tibia superimposed with the images of four commercially available tibial trays positioned via refined mechanical alignment.
[0113] FIG. 63 includes a series of overhead views of a tibia having mounted thereto the first and fourth commercially available tibial tray in accordance with mechanical alignment (AAP), in accordance with kinematic alignment (PPNP), and in accordance with a refined mechanical alignment (TechMah).
[0114] FIG. 64 includes a series of overhead views of a tibia having mounted thereto the second and third commercially available tibial tray in accordance with mechanical alignment (AAP), in accordance with kinematic alignment (PPNP), and in accordance with a refined mechanical alignment (TechMah).
[0115] FIG. 65 is an exemplary process diagram for calculating a posterior tibial axis using a statistical atlas.
[0116] FIG. 66 is an elevated perspective view of a tibia and femur, along with an MM image, confirming that the PCA for femur and tibia seldom lie along an image plane.
[0117] FIGS. 67A-67E includes overhead views of a tibia and of a femur on a tibia and how the PCA vary between the tibia and femur during rotation, along with a data set correlating the femoral PCA and Cobb axis.
[0118] FIGS. 68A-68C include graphical depictions of clusters and groupings that result from clustering data, as well as how the AP and ML dimensions are calculated/measured.
[0119] FIGS. 69A-69C include graphical depictions resection plane height variances and an average resection plane outline for a resected tibia.
[0120] FIGS. 70A-70C include graphical depictions resection plane varus and valgus variances and an average resection plane outline for a resected tibia.
[0121] FIGS. 71A-71C include graphical depictions resection plane posterior slope variances and an average resection plane outline for a resected tibia.
[0122] FIGS. 72A-72B include graphical depictions showing how an asymmetric tibial tray covers the resected tibia well, but is rotated incorrectly with respect to the projected femoral PCA.
[0123] FIGS. 73A and 73B are multiple views of a first exemplary tibial tray trial fabricated in accordance with the instant disclosure.
[0124] FIGS. 74A-74C are multiple views of a second exemplary tibial tray trial fabricated in accordance with the instant disclosure.
[0125] FIG. 75 is a graphical depiction of a process flow for patient specific kinematic guide fabrication.
[0126] FIG. 76 is an image of a resected tibia showing consistency between measured and calculated kinematic axes.
[0127] FIG. 77 is an overhead view of a mass customized kinematic alignment guide for a resected tibia fabricated in accordance with the instant disclosure.
[0128] FIGS. 78A and 78B are multiple views of the mass customized kinematic alignment guide of FIG. 77 that account for retention of the posterior cruciate ligament during TKA.
[0129] FIGS. 79A and 79B are multiple views, one showing the outline of a resected tibia and using the statistical atlas to determine the location of the posterior cruciate ligament, as well as a second showing a possible design for a kinematic friendly tibial tray that does not impinge upon the posterior cruciate ligament.
[0130] FIG. 80 is a graph showing high variability of setting tibial rotation using present day method (non-kinematic methods).
[0131] FIG. 81 is a graph showing placement error of kinematic placements using a guide in accordance with the instant disclosure, as validated through a software study.
[0132] FIG. 82 is a screen capture during the software validation study graphically depicted in FIG. 81.
[0133] FIG. 83 is a picture of a plurality of mass-customized tibial component kinematic placement guides fabricated in accordance with the instant disclosure, in various sizes.
[0134] FIG. 84 is an overhead view of a first exemplary mass-customized tibial component kinematic placement guide fabricated in accordance with the instant disclosure.
[0135] FIG. 85 is a picture of a distal femur showing the location of various measurements and landmarks.
[0136] FIG. 86 is a picture of a profile view of a femur showing the location of various axes and landmarks.
[0137] FIG. 87 is a picture of a distal femur showing the location of various axes, landmarks, and planes.
[0138] FIG. 88 is a picture of a proximal femur showing the location of various axes, landmarks, and planes.
[0139] FIG. 89 is a picture of a profile view of a femur showing the natural longitudinal curvature.
[0140] FIG. 90 is a picture of a proximal tibia showing the location of various axes, landmarks, and planes.
[0141] FIG. 91 is a picture of a profile view of a proximal tibia showing the location of various landmarks.
[0142] FIG. 92 is a picture of a profile tibia showing the mechanical axis of the tibia.
[0143] FIG. 93 is a picture of a distal tibia showing the location of the ankle center.
[0144] FIGS. 94A-94D are pictures of various distal femurs showing the location of the meniscal axis.
[0145] FIGS. 95A and 95B are images of the distal end of a femoral model showing how rotational changes with respect to the interface between the tibia and femur effect the shape of the trochlear groove.
[0146] FIG. 96 is a plot showing how quadriceps force changes as a function of knee flexion.
[0147] FIG. 97 is a picture of a distal femur tangible model marked up to show the medial boss as a blue line.
[0148] FIGS. 98A-98D are a series of views comparing the position of the femoral component of a TKA using mechanical alignment and kinematic alignment and how the patella cannot track the femoral component properly using mechanical alignment.
[0149] FIGS. 99A and 99B are comparative frontal views of femoral components placed via mechanical alignment (99A) and via kinematic alignment (99B).
[0150] FIGS. 100A and 100B are frontal and overhead views showing how current femoral components should be modified to account for correct kinematic alignment.
[0151] FIG. 101 is an image of a commercially available tibial tray properly aligned via kinematic alignment, yet continuing to show posterior cruciate ligament impingement, thus necessitating a revised design implant to avoid impingement and be properly kinematically aligned when mounted to the resected tibia.
[0152] FIG. 102 is a similar image to FIG. 101 showing posterior cruciate ligament impingement using a present day implant when kinematically aligned, with the posterior cruciate ligament represented by its most likely locations from the statistical atlas.
[0153] FIGS. 103A-103C are a series of images highlighting the differences in shape between the current day femoral component (FIG. 103A) and a femoral component designed in accordance with the instant disclosure (FIG. 103B) and how the design shapes compare to one another near the end of the trochlear groove (FIG. 103C).
[0154] FIG. 104 is a graphical process flow diagram illustrating an exemplary process sequence for creation of a mass customized kinematic alignment guide or trial in accordance with the instant disclosure.
[0155] FIG. 105 is an overhead view of a first exemplary patient-specific kinematic alignment guide for use with a resected tibia.
[0156] FIGS. 106A and 106B are various views of a second exemplary patient-specific kinematic alignment guide for use with a resected tibia showing the placement of the guide with respect to the tibia and with respect to the posterior cruciate ligament.
DETAILED DESCRIPTION
[0157] The exemplary embodiments of the present disclosure are described and illustrated below to encompass devices, methods, and techniques relating to knee arthroplasty. Of course, it will be apparent to those of ordinary skill in the art that the embodiments discussed below are exemplary in nature and may be reconfigured without departing from the scope and spirit of the present disclosure. It is also to be understood that variations of the exemplary embodiments contemplated by one of ordinary skill in the art shall concurrently comprise part of the instant disclosure. However, for clarity and precision, the exemplary embodiments as discussed below may include optional steps, methods, and features that one of ordinary skill should recognize as not being a requisite to fall within the scope of the present disclosure.
[0158] Referring to FIGS. 85-89, as used herein, the following are mechanical neutral anatomic landmark definitions for the femur: (1) Transepicondylar Axis (TEA): The axis joining the most medial prominence of the medial epicondyle and the most lateral prominence of the lateral epicondyle; (2) Posterior Condyle Axis (PCA): The axis joining the most posterior points on the medial and lateral condyles of the distal femur; (3) Distal Anatomical Axis (DAA): The distal anatomical axis is defined by locating the shaft centroids at the distal one-third and distal one-fifth of the overall femur length; (4) Central AP Axis (CAP): Axis defined with termini at the posterior aspect of the intercondylar notch and the most anterior portion of the intercondylar groove; (5) Femoral Saddle Point: A landmark located at the most distal extension of the intercondylar groove; (6) Knee Center: Using the two endpoints of the CAP measurement and the femoral saddle point, a plane is defined which bisects the femur into medial and lateral sides. The intersection of this plane with the TEA is the knee center, which forms the distal endpoint of the mechanical axis (MA) of the femur; (7) Distal Mechanical Entry Point of the Femur: The distal entry of the medullary canal. This landmark is estimated to be at the intersection of the anatomical axis of the femur with its intercondylar notch; (8) Mechanical axis (MA): Axis defined by the femoral head center and knee center; (9) AP Direction: Using the MA and the TEA, a mutually perpendicular vector with its origin at the knee center is used to define the antero-posterior (AP) direction, resulting in a direction similar to Whiteside's line; (10) Femoral AP Axis (FAA): Axis defined as the cross-product of the mechanical axis of the femur with the PCA; (11) Mediolateral Axis of the Femur (MLA): The cross-product of the femoral mechanical axis with its anteroposterior axis; (12) Femoral Head Center (FHC): Center of the sphere approximating femoral head; (13) Anterior Medio-lateral Width (AML): The AP direction is used to locate the two most anterior landmarks on the medial and lateral condyles of the distal femur. Connecting the two most anterior points gives a measurement of anterior medio-lateral width (AML) along the trochlear line; (14) Posterior Medio-lateral Width (PML): The AP direction is used to locate the two most posterior points on the medial and lateral condyles of the distal femur. Connecting the two most posterior points gives a measure of posterior medio-lateral width (PML) measured along the posterior condylar axis (PCA); (15) AP Length of Medial Condyle (MAP): Connecting the pairs of medial vertices defined above, respectively, gives the AP length of the medial condyle; (16) AP Length of Lateral Condyle (LAP): Connecting the pairs of lateral vertices defined above, respectively, gives the AP length of the lateral condyle (LAP); (17) Overall AP Length: The minimum distance between the prominences of the lateral anterior condyle and the posterior plane; (18) AP Angle: The angle of the AML vector relative to the posterior plane; (19) Distal Medial-lateral Length (DML): The most distal aspects of the medial and lateral condyles are recorded using MA as a reference direction. The distance between these two landmarks is denoted as DML; (20) Posterior Angle (PA): The angle between the vector connecting the DML length and the mean axis of the femur; (21) Condylar Twist Angle (CTA): The angle between the TEA and PCA; (22) Patellar Groove Height (GH): Calculated between the posterior aspect of the intercondylar notch and the midpoint between the two DML axis points; (23) Femoral Axis (FA): Line from the center of the femoral head to the center of the shaft at the level of the lesser trochanter. Anteversion (+) is ventral, retroversion (−) is dorsal; (24) Femoral Version: Angle comparing the femoral axis to the transepicondylar axis; (25) Femoral Shaft Curvature (SC): The radius of curvature of the femoral mean axis; (26) Femoral implant flexion/extension: Rotation about the mediolateral axis of the femur. From a lateral perspective, clockwise rotation is called extension for a right femur and flexion for a left femur; (27) Femoral implant varus/valgus angle: Rotation about the AP axis of the femur. From an anterior perspective in the frontal plane, clockwise rotation is called varus for a right femur and valgus for a left femur; (28) Femoral internal/external rotation of the femoral implant: Rotation about the mechanical axis of the femur. From a distal perspective in the axial plane, clockwise rotation is called internal rotation on a right femur and external rotation on a left femur. The system gives the operator the option of expressing internal/external rotation relative to the TEA or the PCA; (29) Femoral distal resection levels (medial and lateral): The distance between the distal cut plane and the most distal condyle points, following the mechanical axis; (30) Femoral distal resection level: A level on the side with the most distal condyle point; (31) Femoral posterior resection levels (medial and lateral): The distances between the posterior cut plane and the most posterior points on the medial and lateral condyles.
[0159] Referencing FIGS. 90-93, as used herein, the following are mechanical neutral anatomic landmark definitions for the tibia: (1) Mechanical axis (MA): the axis between the ankle joint center and the proximal entry of the medullary canal; (2) Proximal Entry of the Tibial Mechanical Axis: The proximal entry medullary canal. This landmark is estimated to be at 33% anterior in the AP direction and at 50% of the transtibial axis, prolonged in medial and lateral to the bone surfaces; (3) Intercondylar Eminence Points: The two highest projecting points on the medial and lateral intercondylar eminences; (4) Eminence Midpoint: The midpoint between the lateral and medial intercondylar eminence points; (5) Tibial Tuberosity: The most anteriorly protruding point on the tibial tuberosity; (6) ML: Maximum width of the tibia plateau in the medial-lateral direction; (7) ML Axis of the Tibia: The cross-product of its AP direction with its mechanical axis; (8) AP: Length of the tibial plateau in the anterior-posterior (AP) direction and passing through the midpoint of the tibial intercondylar eminence (i.e. eminence midpoint); (9) AP Direction: The axis that joins the center of the attachment area of the posterior cruciate ligament (PCL) and a point on the medial third of the tibial tuberosity; (10) AP Axis of the Tibia: The cross-product of the tibia mechanical axis with its ML axis; (11) Eminence Width (EW): Distance between medial and lateral intercondylar eminence points; (12) Tibial Twist Angle (TTA): Angle between the AP direction and a line connecting the intercondylar eminence midpoint and tibial tuberosity; (13) Lateral Plateau Height (LPH): Length of the lateral tibial plateau in the AP direction; (14) Lateral Plateau Width (LPW): Length of the lateral tibial plateau in the ML direction; (15) Medial Plateau Height (MPH): Length of the medial tibial plateau in the AP direction; (16) Medial Plateau Width (MPW): Length of the medial tibial plateau in the ML direction; (17) Eminence ML Ratio (EMLR): Ratio of MPW (i.e. medial plateau width) over ML; (18) Maximum Length: Length of the tibia from the medial malleolus to the intercondylar eminence; (19) Posterior Tibial Axis (PTA): Line connecting the most posterior surfaces of medial and lateral tibial plateau; (20) Transtibial Axis: Line connecting the anterior posterior midpoints of the medial and lateral tibial plateaus; (21) Tibial Center: Exact midpoint of the transtibial axis; (22) Tibial Tuberosity Angle (TTA): Angle formed by a line from the center point of the tibial tuberosity to the tibial center compared to the anterior tibial axis; (23) Ankle Center: Midpoint of the proximal talus articular surface, about 45% lateral to the most medial prominence of the transmalleolar axis; (24) Ankle Joint Center: The midpoint of the axis joining the most lateral point of the lateral malleoli and the most medial point of the medial malleoli; (25) Transmalleolar Axis: Line connecting the prominence of the medial and lateral malleoli (or tips of the malleoli); (26) Slope of the Tibial Implant: Rotation about the ML axis of the tibial. From a lateral side perspective, clockwise rotation is called anterior slope of extension for a right tibia and called posterior slope or flexion for a left tibia; (27) Varus/valgus Angle of the Tibial Implant: Rotation about the AP axis of the tibia. From an anterior perspective in the frontal plane, clockwise rotation is called valgus for a right tibia and varus for a left tibia; (28) Internal/external Rotation of the Tibial Implant: Rotation about the mechanical axis of the tibia. From a proximal perspective in the axial plane, clockwise rotation is called external rotation on a right tibia and internal rotation on a left tibia. The system gives the user the option of expression tibial rotation relative to the AP axis or the PTA; (29) Medial Resection Level of the Tibia: The distance between the cut plane and the most distal point on the medial plateau, following the mechanical axis. Therefore, augmenting or diminishing the resection level will translate the cut plane along the mechanical axis; (30) Lateral Resection Level of the Tibia: The distance between the cut plane and the most distal point on the lateral plateau, following the mechanical axis. Therefore, augmenting or diminishing the resection level will translate the cut plane along the mechanical axis.
[0160] Referring back to FIGS. 85-89, as used herein, the following are kinematic alignment definitions for the femur: (1) Projected Plane Normal to PCA (PPNP): Intersection of plane normal to PCA with plane normal to tibia MA. The PPNP axis depends on the orientation of the femur relative to the tibia; (2) Meniscal Axis: The axis extending through the contact centers of the medial condyle and the lateral condyle when in contact with the tibia in extension.
[0161] Referring back to FIGS. 90-93, as used herein, the following are kinematic alignment definitions for the tibia: (1) Posterior Tibial Axis (PTA): Line connecting the most posterior surfaces of the medial and lateral tibial plateau.
[0162] The instant disclosure relates to guides and trials for use with total or partial knee replacement surgeries as well as femoral and tibial orthopedic implants. As will be discussed in more detail hereafter, the exemplary embodiments of the instant disclosure include tibial and femoral placement guides to facilitate placement of the tibial and femoral implant components, as well as methods of fabricating these placement guides, in addition to method of using the placement guides, as well as methods of fabricating and placing novel prosthetic apparatuses that more closely approximate the natural kinematics of the knee in comparison to present day knee prosthetic components.
[0163] As discussed previously, present day placement of prosthetic knee components is premised solely upon mechanical alignment. In particular, the center of the femoral head and center of the ankle (see FIG. 1), which are used by conventional, computer assisted surgery and personal cutting instruments to align TKA mechanically, have no bearing on the kinematics of the knee. And this mechanical alignment sacrifices kinematics as the mechanical references used for alignment are inconsistent with kinematic references, thereby leading to kinematics that are abnormal, patient discomfort, and premature joint failure. Instead, the present disclosure is premised upon taking a novel approach premised upon kinematic alignment of prosthetic components.
[0164] Kinematic alignment of the knee is based on the normal kinematics of the knee. Kinematics in this context refers to the relative relationship of the femur, patella and tibia at any angle of flexion without load bearing force applied to the knee. The knee joint surface, menisci, and ligament structures determine the normal kinematic relationship among the femur, patella, and tibia. The following is a discussion of populating a statistical atlas that will be described in more detail hereafter as part of generating mass-customized guides and orthopedic implants in accordance with the instant disclosure.
[0165] A premise supporting kinematic alignment of the knee is accounting for and replicating three axes that govern the movement of the patella and tibia with respect to the femur. The primary axis of these three axes is a first transverse axis (i.e., helical axis) in the femur about which the tibia flexes and extends. In order to determine this first transverse axis of a knee joint, the instant disclosure makes use of X-ray fluoroscopy to image the knee joint. More specifically, a knee joint is imaged at distinct points throughout its range of motion (e.g., between full extension and 160 degrees flexion). These fluoroscopic images are registered to 3D models of the knee joint, as discussed previously, which are specific to that knee joint (i.e., patient and knee side specific). After registering the 3D model to the fluoroscopic images, a first transverse axis fitting process is conducted.
[0166] The first transverse axis fitting process involves fitting a sphere or cylinder to each joint condyle and, using this shape fitting information, calculating the transverse axis. Specifically, a circular or cylindrical shape is fit to the articular surfaces of the femoral and tibial condyles ranging between 10 to 160 degrees of flexion (see FIGS. 19-21). The hypothesis behind using the spherical or cylindrical axes is to approximate the true axis of rotation of the femur on the tibia. In order to determine the circular or cylindrical shape dimensions, for a given three dimensional model replicating the morphology of the bones of the knee joint (tibia, fibula, femur), a point cloud is generated by a computer software program from the 3D knee joint model, where each point in the cloud represents a surface point on the articular surface in question (with two articular surfaces for the distal femur and two articular surfaces for the proximal tibia). Each point cloud is then best fit to either a sphere or cylinder with known dimensions, after which the transverse axis extending through both spheres/cylinders is calculated by the software program (see FIG. 22). The first transverse axis is calculated across the range of motion captured by the 3D knee model, thus indicating how the transverse axis changes throughout the range of motion of the knee joint. In contrast to this kinematic alignment approach, conventional wisdom suggests that the TEA (clinical or surgical) mechanical axis is the axis of rotation of the femur on the tibia (see FIGS. 26 and 27). But the TEA mechanical alignment results in little to no rotation between the femur and tibia (see FIG. 26), which is by no means consistent with normal knee kinematics.
[0167] An ancillary axis to the first transverse axis for kinematic alignment is the PCA. The PCA is approximately parallel to the transverse axis and may be used in aligning the femur (see FIG. 31). After knowing the first transverse axis, the PCA is calculated by determining the most posterior points on the medial and lateral condyles of the distal femur.
[0168] There is a second transverse axis, which is a second of the three kinematic axes, in the femur about which the patella flexes and extends (see FIGS. 32A-32D). This second transverse axis is parallel, proximal, and anterior to the first transverse axis in the femur about which the tibia flexes and extends. However, it is not easily reproduced or approximated by a known biomechanical (or clinical) axis.
[0169] In order to determine the second transverse axis about which the patella flexes or extends, the center of mass of the patella (Loci) is tracked with respect to the femur using X-Ray fluoroscopy (see FIGS. 32A-33F). In particular, as discussed above, a knee joint is imaged at distinct points throughout its range of motion (e.g., between full extension and 160 degrees flexion). These fluoroscopic images (including femur, patella, fibula, and tibia) are registered to 3D models of the knee joint, as discussed previously, which are specific to that knee joint (i.e., patient and knee side specific). After registering the 3D model to the fluoroscopic images, a second transverse axis fitting process is conducted.
[0170] This second transverse axis fitting process involves determining the position of the patella loci (i.e., centroid) for each fluoroscopic image. In exemplary form, a software package determines the loci for each fluoroscopic image with respect to the femur. Each loci is then plotted as a point with respect to the 3D femur model, which creates a series of points—one for each fluoroscopy image—in 3D space with respect to the femur 3D model. The software then conducts a planar regression on the loci points to establish a best fit plane, which is either parallel or almost parallel with the sagittal kinematic plane extending through the femur. Likewise, the fitting process involves fitting a sphere or cylinder to each patella loci and, using this shape fitting information, calculating the second transverse axis. Specifically, a circular or cylindrical shape is fit to the loci across a knee range of motion, for example, between 10 to 160 degrees of flexion. It should be note that the loci points in 3D space essentially replicate a curve, and it is this curve that is fit to the curvature of the sphere or cylinder. The hypothesis behind using the spherical or cylindrical axes is to approximate the true axis of rotation of the patella about the femur. In sum, the software best fits either a sphere or cylinder with known dimensions to the loci points, after which the second transverse axis extending through the sphere/cylinder is calculated by the software program to be perpendicular to the sagittal kinematic plane. In contrast to this kinematic alignment approach, conventional orthopedic implants the patella groove angle is not parallel to or closely approximates a parallel orientation with respect to the sagittal plane. Moreover, quadriceps length is not restored by current implant designs (see FIGS. 38-40).
[0171] The third of the three axes is a longitudinal axis in the tibia about which the tibia internally and externally rotates on the femur. This longitudinal axis is perpendicular to each of the first and second transverse axes in the femur. This longitudinal axis is parallel to the sagittal kinematic plane, which is perpendicular to the posterior PCA of the femur (see FIG. 41).
[0172] As part of the instant technique, the Projected Plane Normal to PCA (PPNP) (i.e., sagittal kinematic plane) was compared to traditional landmarks (see FIGS. 42 and 43A, 43B). In addition, the sagittal kinematic plane was compared in both supine and weight bearing positions for the same subjects/patients (See FIGS. 44A, 44B and 45), with no significant differences being observed. What this means is that weight bearing images are not necessary as part of the instant process to create kinematic guides in accordance with the instant disclosure.
[0173] However, as part of the instant technique, a large angular rotation was observed between the PPNP and the ⅓ Tubercle-PCL of approximately 14 degrees (see FIGS. 46-53B). Accordingly, the inventor concluded that a different tibial plate design for the kinematic alignment was needed.
[0174] Referring to FIG. 55, a flow diagram is illustrated for an exemplary process in accordance with the instant disclosure. In particular, the flow diagram presents an exemplary process for determining the best position/pose for a given orthopedic implant. As will be discussed in more detail hereafter, the output of the flow diagram is the position the orthopedic implant should occupy when mounted to bone or another orthopedic component. In order to utilize this best pose information, the instant disclosure makes use of novel alignment guides that includes references thereon to ensure proper alignment of the implanted orthopedic component.
[0175] The process flow diagram is carried out electronically as part of a software package that automatically calculates position of a given orthopedic implant with respect to a template bone model or a patient specific bone model. For purposes of explanation, it is presumed that the example refers to a patient specific case. Nevertheless, those skilled in the art will readily understand the applicability of the exemplary process flow in cases involving non-patient specific implants and bone models (e.g., mass customized orthopedic implants and template bone models).
[0176] As an initial matter, the patient's bone 3D bone model is virtually cut in accordance with protocols from the manufacturer of the orthopedic implant in question. Using this virtual bone cut (VBC), an initial placement of a virtual model of the intended orthopedic implant (VM) is positioned in accordance with the anterior-posterior axis (see FIG. 56A). This initial placement of the VM is transformed into a 2D footprint that overlaps the VBC, where the position of the footprint is evaluated (see FIG. 56B). In particular, this evaluation includes determining the axes of the 2D footprint and comparing these axes to the one or more of the transverse axes and the longitudinal axis discussed previously. Post evaluation, calculations are made of the 2D footprint of the VM with respect to the VBC to determine and to what extent overhang and underhang areas are present. This evaluation makes use of the outline of the VBC and the 2D footprint of the VM (see FIGS. 57A and 57B). In other words, if the 2D footprint of the VM leaves exposed portions of the VBC, these areas are referred to as underhang areas, whereas aspects of the 2D footprint of the VM extending beyond (i.e., overhangs) the VBC are referred to as overhang areas. The calculations concerning overhang and underhang areas, in addition to calculations showing deviation between the axes of the 2D footprint of the VBC and one or more of the transverse axes and the longitudinal axis, are directed to a threshold sequence to discern whether or not the deviations are within a predetermined tolerance.
[0177] If the answer is “yes,” the pose information is visually made available via a user graphical interface to allow for human intervention and further error minimization. Presuming the human operator is satisfied with the pose (see FIG. 58B), the pose becomes final and an implant guide based upon this pose is fabricated. Conversely, if the human operator is unsatisfied with the pose (see FIG. 58A), a new pose is selected by the software (or manually by the operator) taking into account certain transformation bounds. This newly selected pose step is also the result if the threshold sequence determines that the deviations calculated were not within acceptable tolerances. Presuming a new pose is selected/generated, the software generates a 2D footprint of the selected orthopedic implant in question for this revised pose, then evaluates the revised pose, and calculates overhang and underhang areas. The calculations for the revised pose are evaluated by the threshold sequence, where downstream subprocesses are repeated as necessary until reaching the final pose for the orthopedic implant. At the time the final pose is confirmed, the software also generates instructions sufficient to select or fabricate the correct implant guide.
[0178] Referring to FIGS. 59-64, a series of commercially available tibial trays are depicted via overhead views. In particular, in FIG. 59, these four commercially available tibial trays are identified as Existing #1, Existing #2, Existing #3, and Existing #4 and duplicated pictorially into three separate rows. The first row, identified as AAP, corresponds to the current mechanical alignment techniques utilized to align the tibial tray with respect to the femur and femoral component as shown in FIGS. 60, 63, and 64. The current mechanical alignment technique for all four existing tibial trays is depicted graphically in FIG. 60 with respect to a resected tibia. As can be seen in FIG. 60, using mechanical keys for alignment results in the implants being rotated toward the lateral side (beyond 12 o'clock in the clockwise direction). Conversely, the second row, identified as PPNP, corresponds to the same four commercially available tibial trays, but this time having the tibial trays implanted and aligned kinematically in accordance with the instant disclosure as shown in FIGS. 61, 63, and 64. As can be seen in FIG. 61, proper kinematic alignment of present day tibial trays results in the trays being rotated toward the medial side (beyond 12 o'clock in the counterclockwise direction). What is also apparent in FIG. 61 is that none of these four commercially available tibial trays are designed structurally to optimize kinematic alignment. Specifically, it can be seen that the current tibial trays, when kinematically aligned, result in significant overlap for the lateral anterior portion and posterior medial portion, whereas significant underlap is present in the posterior lateral portion and the anterior medial portion. Finally, the third row also corresponds to a mechanical alignment technique that attempts have the contour of the implant most closely approximate the contour of the resected tibia with an emphasis on anterior edge alignment, which is shown in FIGS. 62-64.
[0179] FIGS. 63 and 64 show individually the four exemplary current tibial trays) being aligned on a resected tibia, two using prior art techniques (AAP, TechMah) and the third (PPNP) using the techniques disclosed herein for kinematic alignment. These figures simply supplement FIGS. 60-62 that show the four current tibial trays superimposed onto the same resected tibia for illustrative purposes and further confirm that none of these four commercially available tibial trays is optimized for kinematic alignment given the overlap and underlap present when kinematically aligned.
[0180] Turning to FIG. 65, an exemplary process flow diagram is depicted for calculating the posterior condylar axis using a statistical atlas for a tibia. As an initial starting point, in step (A), a generic bone model of the tibia is propagated with the most posterior medial and lateral point on the surface of the tibia using the data from the statistical atlas. Afterwards, in step (B), a planar regression is performed on the propagated points to generate two planes, a first for the medial points and a second for the lateral points. Using each plane and the points, in step (C), a pair of axes are generated, one for the medial side and a second for the lateral side, that are normal to a respective plane at the center of the points. In step (D), a line is generated between the most posterior points on the medial and lateral side using the location of the axes generated in step (C). Thereafter, in step (E), the cross product of the line in step (D) and the axes generated in step (C) generates a new axis corresponding to the true posterior direction. Using this true posterior direction, the statistical atlas is searched for only the two most posterior points in this true posterior direction, which are then used to generate the posterior condylar axis for the tibia. This same process is applicable to calculating the posterior condylar axis for the femur. FIG. 66 simply confirms that 2D imaging slices are less accurate for determining the posterior condylar axis for the femur and tibia given that the axes are most often not parallel to the plane the image slice is taken from. And FIG. 67 confirms that the femoral posterior condylar axis reliably sets the rotation relative to the tibia.
[0181] In view of the foregoing explanation, the following is an explanation of the process for generating a tibial, mass customized kinematic alignment guide. As depicted in FIG. 104, In exemplary form, a statistical atlas is utilized to calculate and extract various data that will be utilized as part of generating the mass customized kinematic alignment guide. This statistical atlas may be preexisting or may be newly generated. For purposes of explanation, construction of the statistical atlas follows.
[0182] The exemplary statistical atlas comprises a compilation of data from multiple subjects that involves the knee joint. By way of example, the statistical atlas may include various images and associated data derived from human knees such as, without limitation, X-ray images, CT images, MRI images, or other imaging technology. In the case of MRI images, the statistical atlas may include images of the soft tissue (e.g., cartilage) of the knee joint. By way of further example, it is presumed that the exemplary statistical atlas has been created from 100 MRI images and 66 CT images. These 166 images were then segmented to create 166 virtual joint models, which are also part of the statistical atlas.
[0183] Referring to FIGS. 69A-71C, the tibia from each virtual joint model within the statistical atlas is subjected to a resection process. As part of this resection process, each tibia has a plane applied thereto that simulates the bone cut a surgeon would make during a total knee arthroplasty (TKA) procedure to remove the proximal end of the tibia, thereby leaving a planar tibial end. As those skilled in the art are aware, the tibial bone cut carried out during a TKA is preferably made perpendicular to the sagittal plane. But absolute precision is not always possible, leading to tibial bone cuts that may be angled ±5 degrees from proximal to distal and ±5 degrees from medial to lateral, as well as having different heights ±1 millimeter from proximal to distal along the longitudinal length. Consequently, the resection process is carried out upon each tibia model taking into account a perfect bone cut (±0 degrees from proximal to distal, and ±0 degrees from medial to lateral) in order to make a resection cut, within 1 degree increments, for each combination between the ±15 degree deviation.
[0184] Post resection, the contour (i.e., outline shape) of each resected tibia is determined to identify the outermost bounds. After the outermost bounds (i.e., outline shape) of the resected tibia have been determined, a number of calculations are undertaken with respect to these bounds to measure various aspect of the resected tibia. By way of example, and not limitation, the following eight measurements were computed for each resection: (1) M_ML, width of medial plateau; (2) M_AP, height of medial plateau; (3) L_ML, width of lateral plateau; (4) L_AP, height of lateral plateau; (5) BB_AP, overall anterior-posterior height; (6) BB_ML, overall medial-lateral width; (7) LLMLR, ratio of widths between the lateral and medial plateaus; and, (8) MLAPR, ratio of heights between the lateral and medial plateaus. In other words, each resected tibia included shape/outline data, as well as eight sets of measurement data. Referencing FIGS. 68A-68C, using this shape/outline data and the measurement data, a clustering operation was undertaken to establish size groupings across the population of the statistical atlas. For each size grouping, in this case six groupings, the average outline of the resected tibia was computed and utilized to form the shape outline of a tibial kinematic guide.
[0185] Referring to FIGS. 72A-74C, it should be noted that this shape outline may be further refined by using data from the statistical atlas to account for ligament retention. By way of example, where the posterior cruciate ligament is retained, the eventual orthopedic tibial implant should not impinge or obstruct the ligament. In order to account for one or more retained ligaments, the statistical atlas may include soft tissue data reflecting the placement of one or more ligaments with respect to the bones of the knee joint. By knowing the attachment locations on the bones of the knee joint where ligaments attach, the shape outline of the tibial kinematic guide can be altered to ensure the outline does not overlap or otherwise impinge upon one or more locations where a ligament will be retained as part of a TKA. The most common of these alterations is a sweeping curved notch cut into the shape outline to allow for retention of the posterior cruciate ligament.
[0186] In addition to utilizing the shape outline of the resected tibias from the statistical atlas, the statistical atlas is also utilized to calculate the kinematic axes for each joint model. These kinematic axes, as discussed previously, are transformed into data that accompanies each tibial bone model and the resulting bone model having been resected. The kinematic axes data for each resected bone model within a given size population are averaged and superimposed onto the shape outline of the average tibia for each size group. In particular, the sagittal kinematic axis of the femur from anterior to posterior is superimposed onto the tibial outline, in addition to the first transverse axis of the femur. Other axes may likewise be superimposed on to the average tibial shape outline for each size group. This superimposition is eventually utilized to form structural signs informing the surgeon as to the position of certain kinematic axes with respect to the kinematic guide that, when positioned correctly to align its outline with that of the actual resected tibia during TKA, indicates the position of certain kinematic axes with respect to the actual resected tibia.
[0187] Using the shape outline data and the superimposition data, a tibial guide may be constructed. A first exemplary mass customized kinematic guide for a tibial implant is shown in FIGS. 73A, 73B. This tibial guide is utilized by a surgeon to provide markings onto the resected tibia that will guide the surgeon to correctly place the tibial orthopedic implant. As can be seen, the guide includes a shape that closely approximates the outline of the resected tibia. In this fashion, the surgeon would position the guide on top of the resected tibia to most closely match the contour/outline of the guide with the outline of the resected femur, which denotes the proper position of the guide. The interior area of the guide includes a single through opening. This through opening includes a pair of three-sided rectangular cutouts extending in the posterior and anterior directions, that are near the middle from medial to lateral, that are longitudinally aligned with one another on opposing edges of the cutouts. These cutouts correspond to the femoral sagittal kinematic plane. It is envisioned that a surgeon would use a hammer and corresponding rectangular drive bit, where the drive bit was sized to fit within the bounds of the cutouts, to force the drive bit into the resected tibia and make a mark corresponding to the femoral sagittal plane. Alternatively, the surgeon may use a marker to denote the locations of the cutouts. In either instance, the guide may be thereafter removed to leave behind an indication of the location of the femoral sagittal kinematic plane.
[0188] This first exemplary mass customized kinematic guide also includes a contour on the posterior side to account for retention of the posterior cruciate ligament (PCL). In addition, the posterior portion of the guide includes a series of projections that lie on opposing sides of the PCL contour. These projections represent the location of the tibial PCA, which should be aligned with the most posterior points of the medial and lateral condyles. The surgeon may utilize these projections to ensure the guide is properly positioned with respect to the tibia.
[0189] As shown in FIGS. 74A-74C, a first alternate exemplary mass customized kinematic guide for a tibial implant is identical to the first exemplary mass customized kinematic guide for a tibial implant, with the exception of the posterior projections. Instead of projections, the first alternate exemplary mass customized kinematic guide for a tibial implant includes a pair of rectangular recesses on opposing sides of the PCL contour. These recesses are sized to accept a corresponding style that extends posteriorly and distally from the guide. When inserted in to a corresponding recess, the styles cooperate to establish a posterior stop against which posterior portion of the resected tibia contacts to inhibit further anterior repositioning of the guide during the initial guide placement. In exemplary form, when the styles are inserted in to a corresponding recess, the surgeon uses the styles along with the outline shape of the guide to correctly position the guide with respect to the resected femur. Once correctly positioned, the surgeon may utilize the guide to make marks or attach fasteners to the top of the resected tibia to provide an indication of the placement of one or more axes of the femur.
[0190] Referring to FIG. 84, again using the shape outline data and the superimposition data, a tibial guide may be constructed. This second exemplary mass customized kinematic guide for a tibial implant is also intended to be utilized by a surgeon to provide markings (and/or attach pins or other fasteners) onto the resected tibia that will guide the surgeon to correctly place the tibial orthopedic implant. As can be seen, the guide includes a shape that closely approximates the outline of the resected tibia. In this fashion, the surgeon would position the guide on top of the resected tibia to most closely match the contour/outline of the guide with the outline of the resected femur, which denotes the proper position of the guide. The interior area of the guide includes T-shaped through opening along with four circular openings, two on opposing sides of the T-shaped opening. This T-shaped through opening includes an elongated media to lateral section (top, horizontal portion of the T), as well as an elongated posterior to anterior section (vertical portion of the T). The elongated medial to lateral section of the T-shaped opening corresponds to an axis in parallel with the femur PCA, while the elongated posterior to anterior section of the T-shaped opening corresponds to the femoral sagittal kinematic plane. The four circular openings are sized to receive pins or other fasteners that are mounted to the resected tibia and retained after the tibial guide is removed from the resected tibia.
[0191] In addition to the openings formed through this second exemplary mass customized kinematic guide, the guide also includes various indicia. In particular, the face of the guide opposite the resected tibia includes a “MED” indicia indicating to a surgeon that this side of the guide should be aligned with the medial portion of the tibia. In order for the surgeon to quickly know whether the guide is for the right tibia or the left tibia, the face includes a “R” indicia indicating that this guide is for use with the right tibia. In cases where the guide is fabricated to correspond to the left tibia, this “R” would be replaced with an “L.” Finally, the face of the guide also includes a size indicia, in this case a “4” indicating to the surgeon that this guide is a size four. Should the initial selection of the guide be too large or small, the surgeon can quickly request a smaller or larger size guide and operating room assistants can quickly discern the size of the guide using this size reference indicia. And similar to the first exemplary mass customized kinematic guide, this second exemplary mass customized kinematic guide also includes a contour on the posterior side to account for retention of the posterior cruciate ligament (PCL).
[0192] Referring to FIGS. 77, 78A, 78B, and 83, again using the shape outline data and the superimposition data, a further tibial guide may be constructed. This third exemplary mass customized kinematic guide for a tibial implant is also intended to be utilized by a surgeon to provide markings (and/or attach pins or other fasteners) onto the resected tibia that will guide the surgeon to correctly place the tibial orthopedic implant. As can be seen, the guide includes a shape that closely approximates the outline of the resected tibia. In this fashion, the surgeon would position the guide on top of the resected tibia to most closely match the contour/outline of the guide with the outline of the resected femur, which denotes the proper position of the guide. The interior area of the guide includes single through opening along with along with a pair of cutouts. The single through opening includes an enlarged anterior opening to accommodate tibial broach throughput. Extending off of this enlarged opening is a first pair of cutouts extending in the medial and lateral directions, terminating in circular openings. The circular openings are sized and configured to receive pins or other fasteners that are mounted to the resected tibia and retained after the guide is removed from the resected tibia. The dominant length of these first cutouts are delineated by parallel walls that cooperate to establish an axis that is parallel with the femoral PCA. A second set of cutouts extends in the posterior and anterior directions. These cutouts are representative of the location of the femoral sagittal kinematic plane. Finally, extending posteriorly and in the medial and lateral directions are a third set of cutouts that provide an area for larger fasteners or larger markings to be made onto the resected tibia.
[0193] Similar to the first and second exemplary mass customized kinematic guides, this third exemplary mass customized kinematic guide also includes a contour on the posterior side to account for retention of the posterior cruciate ligament (PCL). A fourth set of cutouts is formed on opposing sides of this posterior contour. These fourth cutouts extend in the medial and lateral directions, terminating in circular openings. The circular openings are sized and configured to receive pins or other fasteners that are mounted to the resected tibia and retained after the guide is removed from the resected tibia. The dominant length of these fourth cutouts are delineated by parallel walls that cooperate to establish an axis that is parallel with the femoral PCA.
[0194] In addition to the openings formed through this third exemplary mass customized kinematic guide, the guide also includes various indicia. In particular, the face of the guide opposite the resected tibia includes a “MED” indicia indicating to a surgeon that this side of the guide should be aligned with the medial portion of the tibia. In order for the surgeon to quickly know whether the guide is for the right tibia or the left tibia, the face includes a “R” indicia indicating that this guide is for use with the right tibia. In cases where the guide is fabricated to correspond to the left tibia, this “R” would be replaced with an “L.” Finally, the face of the guide also includes a size indicia, in this case a “4” indicating to the surgeon that this guide is a size four. Should the initial selection of the guide be too large or small, the surgeon can quickly request a smaller or larger size guide and operating room assistants can quickly discern the size of the guide using this size reference indicia.
[0195] While the foregoing explanation has been directed to processes and generation of mass customized tibial kinematic guides, it should be noted that patient-specific guides can be fabricated in accordance with the instant disclosure. Consequently, the following is an exemplary explanation of the process and resulting fabrication of a patient specific tibial kinematic guide.
[0196] Referring to FIG. 75, the following is an explanation of the process for generating a tibial, patient-specific kinematic alignment guide. In exemplary form, images of the patient knee joint are taken from one or more imaging modalities including, without limitation, X-ray images, CT images, ultrasound, and MRI images. In the case of MRI images, the patient knee joint images may include images of the soft tissue (e.g., cartilage) of the knee joint. These patient images are then segmented to create a patient-specific virtual joint model using a software program. Those skilled in the art are familiar with segmentation and utilizing 2D images to form a virtual 3D model.
[0197] The tibia from the patient-specific virtual joint model is subjected to a resection process using a software resection algorithm. As part of this resection process, the tibia has a plane applied thereto that simulates the bone cut a surgeon would make during a total knee arthroplasty (TKA) procedure to remove the proximal end of the tibia, thereby leaving a planar tibial end. As those skilled in the art are aware, the tibial bone cut carried out during a TKA is preferably made perpendicular to the sagittal plane. But absolute precision is not always possible, leading to tibial bone cuts that may be angled ±5 degrees from proximal to distal and ±5 degrees from medial to lateral, as well as having different heights ±1 millimeter from proximal to distal along the longitudinal length. Consequently, the resection process is carried out upon the tibia model taking into account a perfect bone cut (±0 degrees from proximal to distal, and ±0 degrees from medial to lateral) in order to make a resection cut, within 1 degree increments, for each combination between the ±5 degree deviation.
[0198] Post resection, the contour (i.e., outline shape) of the resected tibia is determined to identify the outermost bounds using a software contour algorithm. After the outermost bounds (i.e., outline shape) of the resected tibia have been determined, a number of calculations are undertaken with respect to these bounds to measure various aspect of the resected tibia. By way of example, and not limitation, the following eight measurements were computed for each resection: (1) M_ML, width of medial plateau; (2) M_AP, height of medial plateau; (3) L_ML, width of lateral plateau; (4) L_AP, height of lateral plateau; (5) BB_AP, overall anterior-posterior height; (6) BB_ML, overall medial-lateral width; (7) LLMLR, ratio of widths between the lateral and medial plateaus; and, (8) MLAPR, ratio of heights between the lateral and medial plateaus. In other words, each resected tibia includes shape/outline data, as well as eight sets of measurement data. Using this shape/outline data and the measurement data, the size and outline of the resected tibia is computed and utilized to form the shape outline of the patient-specific tibial kinematic guide.
[0199] It should be noted that this shape outline may be further refined by using data from the patient-specific images to account for ligament retention. By way of example, where the posterior cruciate ligament is retained, the orthopedic tibial implant should not impinge or obstruct the ligament. In order to account for one or more retained ligaments, the patient-specific virtual model of the knee joint includes one or more ligaments with respect to the bones of the knee joint. By knowing the attachment locations on the bones of the knee joint where ligaments attach, the shape outline of the patient-specific tibial kinematic guide can be altered to ensure the outline does not overlap or otherwise impinge upon one or more locations where a ligament will be retained as part of a TKA. The most common of these alterations is a sweeping curved notch cut into the shape outline to allow for retention of the posterior cruciate ligament.
[0200] In addition to generating the shape and size of the patient-specific kinematic guide, the computer program also calculates the kinematic axes for the patient-specific joint model using one or more axis/axes algorithms. These calculated kinematic axes, as discussed previously, are transformed into data that accompanies the tibial bone model and the resulting tibial bone model post resection. The kinematic axes data for the resected tibial bone model is superimposed onto the shape outline of the bone model. In particular, the sagittal kinematic axis of the femur from anterior to posterior is superimposed onto the shape outline, in addition to the first transverse axis of the femur. Other axes may likewise be superimposed onto the tibial shape outline for. This superimposition is eventually utilized to form structural signs informing the surgeon as to the position of certain kinematic axes with respect to the kinematic guide that, when positioned correctly to align its outline with that of the actual resected tibia during TKA, indicates the position of certain kinematic axes with respect to the actual resected tibia.
[0201] Using the shape outline data and the superimposition data, a patient-specific tibial guide may be constructed. A first exemplary patient-specific kinematic guide for a tibial implant is shown in FIGS. 105, 106A, and 106B. This tibial guide is utilized by a surgeon to provide markings onto the resected tibia that will guide the surgeon to correctly place the tibial orthopedic implant. As can be seen, the guide includes a shape that precisely mirrors the outline of the resected tibia. In this fashion, the surgeon would position the guide on top of the resected tibia to most closely match the contour/outline of the guide with the outline of the resected femur, which denotes the proper position of the guide. The interior area of the guide includes a single through opening. This through opening includes a pair of three-sided rectangular cutouts extending in the posterior and anterior directions, that are near the middle from medial to lateral, that are longitudinally aligned with one another on opposing edges of the cutouts. These cutouts correspond to the femoral sagittal kinematic plane. It is envisioned that a surgeon would use a hammer and corresponding rectangular drive bit, where the drive bit was sized to fit within the bounds of the cutouts, to force the drive bit into the resected tibia and make a mark corresponding to the femoral sagittal plane. Alternatively, the surgeon may use a marker to denote the locations of the cutouts. In either instance, the guide may be thereafter removed to leave behind an indication of the location of the femoral sagittal kinematic plane.
[0202] This first exemplary patient-specific kinematic guide also includes a contour on the posterior side to account for retention of the posterior cruciate ligament (PCL). In addition, the posterior portion of the guide includes a series of projections that lie on opposing sides of the PCL contour. These projections represent the location of the tibial PCA, which should be aligned with the most posterior points of the medial and lateral condyles. The surgeon may utilize these projections to ensure the guide is properly positioned with respect to the tibia.
[0203] As shown in FIG. 74, a first alternate exemplary patient-specific kinematic guide for a tibial implant is identical to the first exemplary patient-specific kinematic guide for a tibial implant, with the exception of the posterior projections. Instead of projections, the first alternate exemplary patient-specific kinematic guide for a tibial implant includes a pair of rectangular recesses on opposing sides of the PCL contour. These recesses are sized to accept a corresponding style that extends posteriorly and distally from the guide. When inserted in to a corresponding recess, the styles cooperate to establish a posterior stop against which posterior portion of the resected tibia contacts to inhibit further anterior repositioning of the guide during the initial guide placement. In exemplary form, when the styles are inserted in to a corresponding recess, the surgeon uses the styles along with the outline shape of the guide to correctly position the guide with respect to the resected femur. Once correctly positioned, the surgeon may utilize the guide to make marks or attach fasteners to the top of the resected tibia to provide an indication of the placement of one or more axes of the femur.
[0204] Referring to FIG. 84, again using the shape outline data and the superimposition data, a tibial guide may be constructed. This second exemplary patient-specific kinematic guide for a tibial implant is also intended to be utilized by a surgeon to provide markings (and/or attach pins or other fasteners) onto the resected tibia that will guide the surgeon to correctly place the tibial orthopedic implant. As can be seen, the guide includes a shape that mirrors the outline of the resected tibia. In this fashion, the surgeon would position the guide on top of the resected tibia to most closely match the contour/outline of the guide with the outline of the resected femur, which denotes the proper position of the guide. The interior area of the guide includes T-shaped through opening along with four circular openings, two on opposing sides of the T-shaped opening. This T-shaped through opening includes an elongated media to lateral section (top, horizontal portion of the T), as well as an elongated posterior to anterior section (vertical portion of the T). The elongated medial to lateral section of the T-shaped opening corresponds to an axis in parallel with the femur PCA, while the elongated posterior to anterior section of the T-shaped opening corresponds to the femoral sagittal kinematic plane. The four circular openings are sized to receive pins or other fasteners that are mounted to the resected tibia and retained after the tibial guide is removed from the resected tibia.
[0205] In addition to the openings formed through this second exemplary patient-specific kinematic guide, the guide also includes various indicia. In particular, the face of the guide opposite the resected tibia includes a “MED” indicia indicating to a surgeon that this side of the guide should be aligned with the medial portion of the tibia. In order for the surgeon to quickly know whether the guide is for the right tibia or the left tibia, the face includes a “R” indicia indicating that this guide is for use with the right tibia. In cases where the guide is fabricated to correspond to the left tibia, this “R” would be replaced with an “L.” Finally, the face of the guide also includes a size indicia, in this case a “4” indicating to the surgeon that this guide is a size four. Should the initial selection of the guide be too large or small, the surgeon can quickly request a smaller or larger size guide and operating room assistants can quickly discern the size of the guide using this size reference indicia. And similar to the first exemplary patient-specific kinematic guide, this second exemplary patient-specific kinematic guide also includes a contour on the posterior side to account for retention of the posterior cruciate ligament (PCL).
[0206] Referring to FIGS. 77, 78A, 78B, and 83, again using the shape outline data and the superimposition data, a further tibial guide may be constructed. This third exemplary patient-specific kinematic guide for a tibial implant is also intended to be utilized by a surgeon to provide markings (and/or attach pins or other fasteners) onto the resected tibia that will guide the surgeon to correctly place the tibial orthopedic implant. As can be seen, the guide includes a shape that closely approximates the outline of the resected tibia. In this fashion, the surgeon would position the guide on top of the resected tibia to most closely match the contour/outline of the guide with the outline of the resected femur, which denotes the proper position of the guide. The interior area of the guide includes single through opening along with along with a pair of cutouts. The single through opening includes an enlarged anterior opening to accommodate tibial broach throughput. Extending off of this enlarged opening is a first pair of cutouts extending in the medial and lateral directions, terminating in circular openings. The circular openings are sized and configured to receive pins or other fasteners that are mounted to the resected tibia and retained after the guide is removed from the resected tibia. The dominant length of these first cutouts are delineated by parallel walls that cooperate to establish an axis that is parallel with the femoral PCA. A second set of cutouts extends in the posterior and anterior directions. These cutouts are representative of the location of the femoral sagittal kinematic plane. Finally, extending posteriorly and in the medial and lateral directions are a third set of cutouts that provide an area for larger fasteners or larger markings to be made onto the resected tibia.
[0207] Similar to the first and second exemplary patient-specific kinematic guides, this third exemplary patient-specific kinematic guide also includes a contour on the posterior side to account for retention of the posterior cruciate ligament (PCL). A fourth set of cutouts is formed on opposing sides of this posterior contour. These fourth cutouts extend in the medial and lateral directions, terminating in circular openings. The circular openings are sized and configured to receive pins or other fasteners that are mounted to the resected tibia and retained after the guide is removed from the resected tibia. The dominant length of these fourth cutouts are delineated by parallel walls that cooperate to establish an axis that is parallel with the femoral PCA.
[0208] In addition to the openings formed through this third exemplary patient-specific kinematic guide, the guide also includes various indicia. In particular, the face of the guide opposite the resected tibia includes a “MED” indicia indicating to a surgeon that this side of the guide should be aligned with the medial portion of the tibia. In order for the surgeon to quickly know whether the guide is for the right tibia or the left tibia, the face includes a “R” indicia indicating that this guide is for use with the right tibia. In cases where the guide is fabricated to correspond to the left tibia, this “R” would be replaced with an “L.” Finally, the face of the guide also includes a patient indicia, in this case a last name or abbreviated name indicating to the surgeon that this guide is for a particular patient in order to distinguish one patient-specific guide from another patient-specific guide.
[0209] In addition to tibial guides, the present disclosure also provides for tibial orthopedic trials that are mass customized and patient-specific. FIGS. 73 and 74 show exemplary tibial orthopedic trials. It should be understood that the foregoing guides may be modified to include a flange around the periphery of the footprint that would operate to transform the guide into a tibial tray trial. In this fashion, the trial would be shaped to accept a tibial tray trial insert in order to test fit the size and location of the trial orthopedic before the final orthopedic implants are permanently implanted. It should further be noted that the peripheral flange is only one modification that may be make to differentiate a guide from a trial. In certain circumstances, the guides disclosed herein may be utilized as trials without having any structural changes in that the tibial tray inserts are configured to engage the guides for test fitting, thereby allowing the guides to function as trials too.
[0210] An exemplary sequence will now be described for use of the exemplary tibial guides and trials. In particular, those skilled in the art are familiar with total knee arthroplasty. Accordingly, a detailed discussion of all procedures performed is unnecessary and certain procedures have been omitted in furtherance of brevity. In order to prepare the tibia for implantation of an orthopedic component, the surgeon resects the tibia to remove the proximal end of the tibia to leave a relatively planar surface to which the eventual tibial tray implant will sit. After the tibia has been resected, the surgeon obtains a medial or lateral guide and places the guide on the resected surface. In the case of a mass-customized guide, the surgeon will choose a guide size and orient the guide so that the outer periphery of the guide best matches or aligns with the outline of the resected tibia. While this positioning is not as precise as a patient specific approach, it nonetheless provides greater accuracy to replicate natural kinematics that using mechanical alignment techniques. In the context of a patient-specific guide, the surgeon will orient the guide to precisely overlay and align the guide so that the outer contours of the guide match or align themselves with the same contours of the resected tibia.
[0211] In either instance, after positioning the guide on top of the resected tibia and aligning the guide, the surgeon can than make a mark, indicia, or other visual representation onto the surface of the resected tibia by using one of the openings of the guide. By way of example, one of the through openings in the guide may be oriented in parallel to the femoral post condylar axis. If the surgeon wishes to align the tibial tray component with respect to this reference axis, the surgeon may use a punch and drive it through the opening in the guide in order to make an indentation into the surface of the resected femur. In addition or alternatively, the surgeon may use a biologically acceptable marker and draw the reference axis onto the resected tibia using the guide to orient the mark.
[0212] As discussed previously, the guides in accordance with the instant disclosure may provide openings that allow for one or more reference axes or planes to be carried over to the resected tibia from the femur. The surgeon, depending upon his preference, may use one or more of these openings to make marks or other visually perceptible notations upon the resected tibia that will remain as one or more points of reference. After making one or more marks, the guide may be removed from the tibia.
[0213] In an instance where the guide doubles as a trial tibial tray, post markings, the surgeon may retain the guide/trial on top of the resected tibia and mount to it one or more tibial tray insert trials that allow the surgeon to test the size and orientation of the ultimate tibial tray and tray insert. When using the guide that doubles as a trial, the surgeon may nonetheless make any markings desired onto the resected tibia and thereafter remove the tibia guide/trial to carry out further procedures to prepare the resected tibia to receive the final tibial tray implant. But it should be note that, for example, it is within the scope of the disclosure for the guide/trial to include a large enough opening to accommodate through put of a broach or other reaming instrument while retaining the guide/trial in position on top of the resected tibia.
[0214] In addition to tibial guides, the present disclosure also provides for tibial tray orthopedic implants that are mass customized and patient-specific. The orthopedic components may be fabricated precisely as discussed above with respect to the guides and trials in terms of the shape of the tibial tray and, in addition, include a tibial stem adapter on the underside of the plate that receives a tibial tray stem. Accordingly, a detailed description that is redundant process of creating one or more bone models, calculating relevant landmarks for the bones of the model, performing a virtual tibia resection along with accounting for expected cut deviations, creation of plate contours that account for soft tissue and thereafter aligning various axes and planes with respect to the resected tibia, and in the case of a mass customize implant, extracting the contour features and clustering the contour features to establish one or more shapes and sizes that account for soft tissue retention (e.g., the posterior cruciate ligament), with respect to the creation of tibial tray plates has been omitted in furtherance of brevity. Nevertheless, to the extent necessary for basis in claiming a mass customized or patient-specific tibial tray orthopedic implant, the prior disclosure directed to fabricating guides and trials is incorporated herein by reference.
[0215] While the foregoing disclosure has been directed to the tibial side of a knee arthroplasty procedure, many of the foregoing processes and techniques are applicable to the femur and alignment of the femoral orthopedic implant component. By way of introduction, when the knee is in significant flexion, a large component of quadriceps force compresses the patella against the femur (see FIG. 96). The resultant joint stress is dictated by the size of the patellofemoral contact area, and patellofemoral cartilage congruity determines that surface area. Conversely, when the knee is at or near full extension, the quadriceps generates predominantly tibiofemoral compression in addition to the ground reaction generated by both the head, arm and trunk (HAT) and the limb in swing phase. Therefore, joint stress in the extended knee is dictated primarily by tibiofemoral cartilage congruity. Moreover, this curve explains why patients with patellofemoral joint derangements are able to perform physical exercise against resistance with less pain if the knee flexion is kept lower than 20 degrees.
[0216] The adult human knee is thus a complex interaction product of its habitual motion pattern as produced by the interactions of condylar form and ligamentous restraint, dictated by positional information, and cartilage/fibrous tissue modeling throughout ontogeny. As a consequence, when both processes ceased development at adulthood, the myriad fiber lengths within its restraint systems have remained congruent with the joint's condylar surface geometry, and in the adult will continue to work together, maintaining a normal stereotyped motion pattern such that the velocity vectors of the two rigid bodies are uniformly tangent to their points of contact throughout the joint's normal range of motion (See FIG. 104).
[0217] Such modeling provides an explanation for a unique feature of the human knee, its medial condylar boss (see FIG. 97). This structure is obviously present in both dissections and dry specimens and truly reflects its contact throughout development, to the medial meniscus. It is never seen in the distal femur of other primates or mammals, and is a distinct, spiral, surface swelling of the medial condylar surface immediately distal to its meniscal groove (i.e., the “medial oblique groove” of the femur).
[0218] As mentioned previously, the combination of cartilage modeling and the habitual contact of the distal femoral surface with the anterior portion of the medial and lateral menisci leaves small corresponding grooves on the dry femur, the medial and lateral meniscal grooves. A line connecting these grooves, the meniscal axis (see FIG. 97, blue line), thus defines the position of the tibial plateau during full extension of the joint. This axis can be used to functionally orient the femur for further anatomical observation (see FIGS. 94A-94D).
[0219] As seen in FIGS. 95A, 95B, 98A-98D, 99A, and 99B, kinematically aligned components will have different patellofemoral forces than mechanical alignment in both extension and flexion. From published clinical results and visible in FIGS. 98A-98D, during flexion the location of trochlear groove is close to the normal anatomy in kinematically aligned knees—indicating potentially improved patellofemoral function during flexion. In extension, however, current implants lateralize the patella in mechanically neutral alignment, reducing patellofemoral forces in extension. When existing components are placed in kinematic alignment, there are increased patellofemoral forces in extension.
[0220] Previous systems must strike a balance between performance in flexion and performance in extension.
[0221] Using the meniscal axis in FIG. 97, the femoral surface can be functionally divided into flexion (red in FIG. 97) and extension surfaces (orange in FIG. 97). The extension surface for use in kinematic alignment can be optimized in a way that reduces risk of subluxation in multiple ways. First, if it is desirable to keep the natural trochlear groove Q angle, the lateral aspect of the anterior flange must be raised to resist the increased patellofemoral forces (relative to current designs). This raised aspect is seen in FIG. 103C. An alternative is to widen, or lateralize the patellar groove in extension, reducing Q angle and thus reducing patellofemoral forces. A suggested widening of the groove and increase in lateral surface area are seen in FIGS. 100A, 100B. FIGS. 99A and 99B show reduction in lateral anterior surface area for a kinematically aligned femoral component (left) versus the mechanically aligned femoral component (right).
[0222] The tibial footprint of existing systems also can benefit from optimization for kinematic alignment. FIGS. 101 and 102 provide overlays of existing system and kinematic alignment plate design, highlighting potential issues with current designs that often require undersizing of the component due to anterior overhang or impingement with the posterior cruciate ligament. Using process outlined in FIG. 104, the footprint of the tibial implant can be matched to the anatomy when in kinematic alignment.
[0223] Following from the above description and invention summaries, it should be apparent to those of ordinary skill in the art that, while the methods and apparatuses herein described constitute exemplary embodiments of the present invention, it is to be understood that the inventions contained herein are not limited to the above precise embodiment and that changes may be made without departing from the scope of the invention as defined by the following proposed points of novelty. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of the invention, since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.
