ANATOMIC KNEE PROSTHESIS AND DESIGNING METHOD
20230111847 · 2023-04-13
Inventors
Cpc classification
A61B2034/104
HUMAN NECESSITIES
A61F2002/4633
HUMAN NECESSITIES
A61B2034/108
HUMAN NECESSITIES
A61F2/3886
HUMAN NECESSITIES
A61F2002/30878
HUMAN NECESSITIES
A61B2034/105
HUMAN NECESSITIES
International classification
Abstract
A knee prosthesis and a method of selecting for a particular patient a knee prosthesis from an inventory of available knee prosthesis or from 3D knee prosthesis models is provided. The method includes the steps of (a) parameterizing a knee prosthesis according to well-defined and independent knee joint compartments, (b) generating a large number knee shapes in the form of 3D knee prosthesis models which reproduce the 3D shape asymmetries of each individual knee, thereby enabling the replication of the knee motion of essentially any patient by generating shapes which vary the shape parameters (surface and dimension) of at least one of those compartments and storing these 3D knee prosthesis models in a database, and (c) studying the patient’s pathology and developing pre -pathological knee prosthesis criteria matching the patient’s needs. Using a planning algorithm, a suitable knee prosthesis may be selected among an inventory of existing knee prostheses or the large number of knee shapes, the prosthesis or shape selected best meeting the patient’s needs as determined by the study.
Claims
1-69. (canceled)
70. A computer-assisted method of making a natural, personalized implant for a patient including the following steps: (a) measuring the patient’s preoperative condition including at least; (i) HKA alignment, (ii) relative movement of the femur vs tibia, namely sliding and rolling motion combination, (iii) femur and tibia contact surfaces and bone shape, and (iv) patella shape and position relative to the femur and tibia, and contact surfaces of the patella with the femur; (b) reproducing postoperative, 3D HKA realignment to pre-arthritic HKA if not outlier; (.sub.C) defining postoperative 3D HKA realignment to corrected pre-arthritic HKA HKA if outlier; (d) defining, target postoperative relative movement of the femur vs tibia (sliding and rolling motion combination) according to (b), (c) and (a)(ii); (e) defining the shape of femur and tibia prosthesis contact surfaces according to (b), (c) and (a)(iii); (f) defining the shape of femur and tibia prostheses attachment according to (e) and (a)(iii); (g) defining target postoperative patella position relative to the femur prosthesis and relative to the tibia prosthesis according to (b), (c), (d), (e), (a)(iv) and to patient’s anatomic history (if known); (h) defining the shape of the contact surfaces between femur prosthesis and patella according to (b), (c), (d), (e), (g), and (a)(iv) (Contact surface only between the femoral component and the patella component, not between the patella component and the tibia component); (i) making other measurements depending on the needs of the patient; and (J) fabricating the prosthesis according to the measurements and definitions.
71. The method of claim 70, further including the step of measuring the preoperative Antero-posterior dimension of the distal femur and reproducing the correct AP prosthetic femoral size, respecting that the implant cannot be rotated (or inclined or flexed) more than 10° in the sagittal plane.
72. The method of claim 70, further including the step of measuring the preoperative FMA distal, posterior and TMA (joint lines); reproducing postoperative FMA, IMA obliquities to pre-arthritic FMA, TMA obliquities, if not outlier, and reproducing the pre-arthritic femoral torsion, and defining postoperative FMA, TMA obliquities to corrected pre-arthritic FMA, TMA obliquities, if outlier, and adapting the femoral torsion according to the matrix of planning.
73. The method of claim 70, further including the step of measuring the preoperative TL obliquity as well as depth of the trochlea; and defining which part of the final obliquity has to be done on the bone, namely orientation of the resection, and which one has to be integrated into the implant, (condylar offset), following rules described in the matrix of planning.
74. The method of claim 70, further including the step of either reproducing postoperative TL obliquity to pre-arthritic TL obliquity (if not outlier) and reproducing the depth of the trochlea; or defining postoperative TL obliquity to corrected pre-arthritic TL obliquity, if outlier, and reproducing the depth of the trochlea by adding a lateral elevation on the trochlea.
75. The method of claim 70, further including the step of either reproducing postoperative condylar and trochlear JL curves to pre-arthritic JL curves, if not outlier or defining postoperative condylar and trochlear Joint Line curves to corrected pre-artritic JL curves, if outlier by correcting the JL curve of the lateral condyle in the case of hypoplasia or of both condyles in the case of sagittal deformities for instance recurvatum or large flessum.
76. The method of claim 70, further including the step of either reproducing postoperative condylar and trochlear Medio-Lateral curves to pre-arthritic ML (if not outlier) or defining postoperative condylar and trochlear ML curves to corrected pre-arthritic ML curves, if outlier by correcting the ML curve of the lateral condyle or of both condyles in the case of sagittal deformities for instance recurvatum or large flessum.
77. The method of claim 70, further including the step of measuring the distance between the axis of each condyle to the middle of the knee and reproducing the distance.
78. The method of claim 70, further including the step of defining the outside limits of the articular surface for both condyles and trochlea (contouring) in order to avoid prosthetic overhang or undersizing.
79. The method of claim 70, further including the step of measuring the preoperative posterior tibia slope; and either reproducing the postoperative posterior tibia slope (TPS) to corrected pre-arthritic TPS if not outlier or defining postoperative posterior tibia slope to be corrected to pre-arthritic posterior tibia slope if outlier.
80. The method of claim 70, further including the step of defining the rotation of the tibia component by measuring the angle to the anterior tibia tuberosity (TTA), which is the AP axis and by the axis going through the centers of the two circles describing the medial and lateral tibia surface geometry (ML axis).
81. The method of claim 70, further including the step of defining the AP & ML position of the tibia keel to obtain a well centered keel on the tibia metaphysis and / or diaphysis.
82. The method of claim 70, further including the step of defining the outside limits of the tibia components contouring (to the tibia rim) in order to avoid prosthetic overhang (risk of conflict with surrounding soft tissue leading to pain) or undersizing (risk of sinking leading to revision).
83. The method of claim 70, further including the step of measuring the distance between the distal femoral resection and the tibia proximal resection (gap in extension) in order to respect the global thickness of the implant.
84. A prosthesis made according to claim 70, wherein the tibial insert, the tibial tray and the keel, components of the prosthesis of the invention, are each made up of one or more parts which are adapted to be assembled before or during the surgery.
85. The prosthesis of the claim immediately above, wherein at least one of these components has (a) one element selected from one of the group of elements consisting of (i) the articulation surface of the tibial insert comprising the medial condyle corresponding surface. (ii) the trochlea corresponding surface, and (iii) the lateral condyle corresponding surface, (b) a bone facing surface of the tibial tray, and (c) the keel portion.
86. The prosthesis of the claim immediately above, wherein any desired orientation angle, offset or any combination thereof may be applied to the tibial insert, the tibial tray and the keel so as to best adapt to the need of the individual patient.
87. The prosthesis of claim 85, wherein the tibial insert, the tibial tray and the keel are each formed of one or more elements.
88. The prosthesis of claim 84, wherein the keel is formed so as not to be orthogonal to the bone facing surface, and is oriented at a selected angle so as to adapt to the need of the individual patient.
89. The prosthesis of claim 84, wherein the keel is not orthogonal to the bone facing surface, and is oriented at another angle, and the bone facing surface is oriented at an angle so as to adapt to the need of the individual patient.
90. The prosthesis of the claim immediately above, wherein the medial insert thickness is thin so as to favor the knee to be orientated in varus.
91. The prosthesis of claim 84, wherein the keel is not formed orthogonal to the bone facing surface, and is oriented at a selected angle, the bone facing surface is oriented at another selected angle, and the lateral condyle corresponding surface presents an offset, so as to adapt to the need of the individual patient.
92. The prosthesis of claim 84, wherein the keel is not orthogonal to the bone facing surface, and is oriented at a selected angle, the bone facing surface is oriented at a second selected angle, and the bicondyle distal tangent is oriented at a third selected angle, so as to adapt to the need of the individual patient.
93. The prosthesis of claim 84, wherein the offset is selected from within the range of from 0 to 10 mm, and the orientation angles of the offset angles are selected up to 12°.
94. The prosthesis of the claim immediately above wherein the offset is selected from within a range from -10° to + 10° in mediolateral or in anteroposterior dimensions, and is oriented at an angle of up to 12° around the longitudinal axis of the keel.
95. The prosthesis of claim 84, wherein the sagittal J-curve is adapted to fit with the corresponding surface of the femoral prosthesis, so that the functioning of the knee prosthesis of the invention fits the need of the individual patient.
96. The prosthesis of the claim immediately above wherein the sagittal J-curve is essentially a single radius.
97. The prosthesis of claim 95, wherein the sagittal J-curve is essentially a combination of two or more radii, which dimension falls in the range from 15 mm to 80 mm.
98. The prosthesis of claim 84, wherein, to fit with the tibia of the individual patient, in the sagittal plane, the keel of the tibial component of a knee prosthesis of the invention is placed at the center of the tibial component and optionally presents an offset towards the anterior part of the tibia or towards the posterior part of the tibia.
99. The prosthesis of the claim immediately above, wherein the offset is selected from a range of from 0 to 10 mm.
100. The prosthesis of claim 98, wherein the offset is selected from within the range of -10° to +10° in mediolateral or in anteroposterior dimensions, and is oriented at an angle selected within the range of up to 12° around the longitudinal axis of the keel.
101. The prosthesis of the claim immediately above, wherein, for the same purpose of fitting with the tibia of the individual patient, in the sagittal plane, the bone facing surface of the tibial component of a knee prosthesis of the invention is oriented at an angle selected from within a range which varies from 0° to 12°.
102. The prosthesis of claim 84, wherein the articulating surfaces of the patella component are made to fit to their respective corresponding surfaces of the femoral component, also taking into account the patient’s hip-knee-ankle (HKA) alignment, be it normal, varus or valgus.
103. The prosthesis of claim 84, wherein, in the case the femoral component has an offset between the distal lateral condyle and the distal medial condyle, the offset is reproduced in the patella component.
104. The prosthesis of the claim immediately above, wherein the patella component and the mediolateral surfaces can be symmetrical or asymmetrical between medial and lateral compartments, and the anteroposterior surfaces can be symmetrical or asymmetrical between the anterior and posterior compartment and selected, optionally using a planning algorithm, so as to match the needs of the individual patient.
105. The prosthesis of claim 84, wherein each of the medial, lateral, anterior, posterior compartments are formed so as to fall in the range from 8 mm to 30 mm in width and height, which values are independent of the patella thickness, which thickness is selected to be at least 6 mm or more.
106. The method of any of claim 70, the method including the step of applying curve/surface fitting and smoothing techniques between shapes that interact across adjacent bone compartments in order to meld elements of the prosthesis that correspond to a bone compartment thereby creating a composite knee prosthesis adapted to the needs of the patient.
107. A method for production of a partial or total knee prosthesis adapted to an individual patient’s constitutional anatomy, the method comprises a design step considering the current and the pre-pathology knee motion behavior of the patient, and further considering the patient’s individual Hip-Knee-Ankle (HKA) alignment, and using these inputs, re-creating a knee articulation model as it was naturally, wherein further, this re-created natural knee articulation model and not the pathological knee articulation model is used to create a prostheses that re-creates this natural knee articulation.
108. A femoral prosthesis for implantation on a femur of a patient’s knee, comprising: (a) two condylar portions comprising the medial and lateral condyles, having a bone-facing surface for abutting at least a portion of each condyle of the patient’s knee and an articular surface generally opposite each bone-facing surface, each articular surface having a curvature (J-curve) generally disposed in a first plane (sagittal plane) and ML curve generally disposed in a second and third plane (frontal plane for the distal condyles and transverse planes for the posterior condyles); each articular surfaces of the medial and lateral condyles may have a condylar offset in the second and third plane, which is optionally equivalent; (b) a trochlear portion, comprising the trochlear depth as well as the lateral and medial trochlear elevations, having a bone-facing surface for abutting at least a portion of the trochlea of the patient’s knee and an articular surface generally opposite the bone-facing surface; each articular surface having a curvature (J-curve) generally disposed in a first plane (sagittal plane) and ML curve generally disposed in a second and third plane (frontal plane and transverse planes); each articular surfaces of the medial and lateral elevations optionally having an offset and a depth to the trochlea in the second and third plane, which can be equivalent or not; (c) the articular surface orientation of the trochlea portion to the distal and posterior condylar portions of the distal and posterior condyles are not dependent and are parallel or obliquely oriented (convergent or divergent) in at least one of the planes; (d) an ML condylar offset is optionally integrated between the medial and lateral articular surfaces of the distal (::: distal condylar offset) and posterior (= posterior condylar offset) condylar portions of the distal and posterior condyles, this condylar offset being optionally equivalent between distal and posterior condylar portions; and (e) an ML trochlear offset is optionally integrated between the medial and lateral articular surfaces of the medial and lateral trochlear elevation, this trochlear offset optionally being the same as the condylar offset of the distal and posterior condyles.
109. The prosthesis of the claim immediately above, wherein the sagittal J-curve of at least one of the joint-surface from the distal and posterior condyles (medial, lateral) or the trochlea (elevation, trochlea depth) is defined by a single, double or multi-radius or is fitting with a patient-specific J-curve.
110. The prosthesis of claim 108, wherein the sagittal J-curve of at least one of the medial and lateral joint-surfaces from the distal and posterior condyles is optionally positioned at a fixed distance to the trochlea J-curves (medial and / or lateral elevation, trochlea depth), optionally symmetrically.
111. The prosthesis of one of claims 107, wherein the sagittal J-curve of at least one of the joint-surface from the distal and posterior condyles (medial, lateral = narrowing angle) or the trochlea (medial and / or lateral elevation, trochlea depth = sulcus axis in frontal plane, Whiteside line in the axial plane) is optionally obliquely oriented in at least one of the planes, mainly the frontal and the axial planes.
112. The prosthesis of claim 107, wherein at least one of the joint facing-surface of the condylar portion and / or of the trochlea portion has an articular geometry and dimensions corresponding (or close matching, or close fitting) to the patient’s knee articular surface, in terms of sizing (comprising at least AP sizing), shape (comprising at least condylar and trochlear offset, J-curves and ML curves) and contour (comprising at least AP/ML, sizing, narrowing angle, trochlear height, posterior condyles height).
113. The prosthesis of claim 107, wherein the tangent linking the medial and lateral most distal points of the bone- facing surfaces of the distal or the tangent linking the medial and lateral most posterior points of the bone-facing surfaces of the posterior condyles or the tangent linking the medial and lateral most anterior points of the bone-facing surfaces of trochlea portion are parallel or oblique with respect to one another.
114. The prosthesis of claim 108, wherein the bone-facing surfaces are defined with a single straight flat or oblique surface or with two staggered (offset) flat or oblique surfaces or with a staggered (offset) curved surface.
115. The prosthesis of claim 108, wherein the bone-facing surfaces are fixed to the bone with optionally with a cemented fixation.
116. The prosthesis of claim 108, wherein the prosthesis corresponds to different systems selected from one of the group of systems consisting of PS: Postero-Stabilized, UC: Ultra-Congruent, PCR: Posterior Cruciate Retaining, and BCR: Bi-Cruciate Retaining, and is adapted for mobile insert or fixed insert, for primary or revision knee (semi-constrained or constrained, hinged), optionally for cemented fixation, for monobloc or modular components, and for any material typically a material selected from one of the group of materials consisting of Ti, CrCo, and Ceramic.
117. A method of manufacturing a knee prosthesis from a 3D model selected after applying a method, the method including: (a) analysis of a patient’s current and pre-pathological knee motion behavior as well as the patient’s 3D HKA alignment, (b) optionally using a planning algorithm, selection of a suitable 3D model from a comprehensive database of 3D models of varying knee morphologies, each 3D model being adapted to a known morphology as well as production limitations and requirements, and (c) manufacturing of the selected 3D model which represents a producible and essentially custom knee prosthesis adapted to the individual patient’s 3D constitutional anatomy, thus making it possible to re-create the knee articulation as it was naturally.
118. A nontransient information storage medium having a knee prosthesis characterization and selection program that instructs a processor to implement the above method of claim 70 so as to accept inputs and produce outputs.
119. A nontransient information storage medium having a knee prosthesis characterization and selection program encoded thereon that, when executed, implements a method which instructs a processor to execute steps which aid a user in selecting a 3D knee prosthesis model for a particular patient, the method consisting of at least the steps of: (a) parameterizing a knee prosthesis according to well-defined and independent knee joint compartments, (b) generating a large number knee shapes in the form of 3D knee prosthesis models which reproduce the 3D shape asymmetries of a large number of individual knee samples including models that replicate the knee motion of essentially any patient by generating shapes which vary the shape parameters (surface and dimension) of at least one of the compartments and storing these 3D knee prosthesis models in association with each model’s shape parameters and asymmetries in a database allowing comparing of the asymmetries of the patient’s knee with those of the 3D knee prosthesis model, and (c) after studying the patient’s pathology and developing pre-pathological knee prosthesis criteria matching the patient’s needs, optionally using a planning algorithm, searching the database comparing the large number of knee shapes based on a best match of the asymmetries of each model to identify candidate matches: (d) providing a display of candidate matches and their attributes on an output device; (e) providing a means of selecting a best match among suitable candidate matches identified; and (f) optionally generating a production order if the selected knee prosthesis is not in inventory.
120. The medium of the claim immediately above, wherein the processor responds to inputs and outputs communicated by the program to and from a user.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The attached drawings represent, by way of example, different embodiments of the invention.
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[0098] Those skilled in the art will appreciate that elements in the Figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, dimensions may be exaggerated relative to other elements to help improve understanding of the invention and its embodiments. Furthermore, when the terms “first”, ‘second’, and the like are used herein, their use is intended for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. Moreover, relative terms like “front”, “back”, “top” and “bottom”, and the like in the Description and/or in the claims are not necessarily used for describing exclusive relative position. Those skilled in the art will therefore understand that such terms may be interchangeable with other terms, and that the embodiments described herein are capable of operating in other orientations than those explicitly illustrated or otherwise described.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0099] The following description is not intended to limit the scope of the invention in any way as it is exemplary in nature, serving to describe the best mode of the invention known to the inventors as of the filing date hereof. Consequently, changes may be made in the arrangement and/or function of any of the elements described in the exemplary embodiments disclosed herein without departing from the spirit and scope of the invention.
[0100] This invention makes it possible to re-create the knee articulation as it was naturally, as it considers not only the whole knee motion behavior of the patient (current and pre-pathology), but also his individual HKA (Hip-Knee-Ankle) alignment. The articulation of the patella may also be taken into account.
[0101] Referring to
[0102] Well-known prior art for knee prostheses considers only the anterior/posterior translation (120) and the flexion/extension (120) rotation, which results in a rather simple prostheses, but has the drawback that the surgeon implants non-anatomically a non-anatomic implant. Such prostheses of the prior art have been found satisfying in terms of life duration (+93% after 15 years) but low in customer satisfaction (70%). Due to this situation, a number of patients who would benefit from a prosthesis delay the operation, fearing the risk of discomfort or pain. When discomfort and pain prevent the patient from sleeping quietly, then the patient asks for a knee prosthesis. The subject tries to wait as long as possible with medication, but if he waits too long, this may render the operation more difficult, as the knee deviation and pathology may increase and impact ligaments tension and collateral joints. In some countries, where the costs play a role, patients visit the doctor very late and so must do bilateral knee replacements at the same time (due to the damage caused the healthier knee by the prolonged load on the unhealthy knee).
[0103] A more recent generation of prostheses still uses the same limitation to the anterior/posterior translation (120) and the flexion/extension (120) rotation, but considers that an inclination of the flexion/extension (120) rotation can be made to obtain a movement that is closer to the natural motion of the patient’s knee. Since these prostheses are only in use for a few years, lifetime and patient satisfaction are not yet known. Nevertheless, even in this case, the surgeon attempts to anatomically implant a non-anatomic prosthesis.
[0104] Referring now to
[0105] Current prior art considers that all patients should be brought to the normal alignment (
[0106] Referring now to
[0111] In a second step 3004, target postoperative HKA alignment is defined according to the substep (a) above and to patient’s anatomic history (if known).
[0112] In a third step 3006, the target postoperative relative movement of the femur vs tibia (sliding and rolling motion combination) is defined according to the second step and substep (b) above.
[0113] In a fourth step 3010, the shape of femur and tibia prostheses contact surfaces is defined according to the second and third steps as well as substep (c) above.
[0114] In a fifth step 3012, the shape of femur and tibia prostheses attachment is defined according to the fourth step and substep (c) above.
[0115] In a sixth step 3014, the target postoperative patella position relative to the femur prosthesis and relative to the tibia prosthesis is defined according to the second, third and fourth steps as well as substep (d) above and to patient’s anatomic history (if known).
[0116] In a seventh step 3016, the shape of the contact surfaces between the femur prosthesis and the patella is defined according to the second, third, fourth and sixth steps as well as substep (d) above (contact surface only between the femoral component and the patella component, not between the patella component and the tibia component).
[0117] In an eighth step 3020, the above definitions are merged to define an individually adapted knee prosthesis.
[0118] Referring now to
[0122] Referring now to
[0134] Referring now to
[0139] Some individuals with healthy knee joints have either: [0140] a constitutional varus alignment (O shape of the limb); [0141] a constitutional valgus alignment (X shape of the limb); or [0142] a constitutional neutral alignment (I shape of the limb).
[0143] The deviated limb alignment in those healthy knees (varus or valgus) is not considered as a misalignment, but simply as a deviated constitutional limb alignment.
[0144] Inside the knee joint, some parameters vary very widely, among the same population, thus for the same dimension of the knee, the shape itself may change significantly.
[0145] The main parameters, which act functionally on the joint are described below: [0146] Alpha (α): Angle between FMA and BCD [0147] DCA: Angle between TEA and BCD [0148] PCA: Angle between TEA and BCP [0149] ATA: Angle between TEA and TL [0150] SA: Sulcus Axis (links KC to TG) [0151] WL: Whiteside Line, links KC to TGL
[0152] All those parameters may vary with each other more than 15° (every angulated parameter can vary from its average value to 7.5° meaning that the range of variability of each parameter among the healthy population is estimated to 15° — a Gaussian curve).
[0153] Those variations may be due to genetics (hereditary), ontogenesis, posturology and / or activity and / or bodyweight during growth, before skeletal maturity, gender, morphotype (endomorphic, ectomorphic, mesomorphic) or ethnics (daily life activities linked to deep knee flexion).
[0154] There is for each knee, an intimate link between the geometry of the knee and the surrounding soft tissue envelope, especially with the cruciate, collateral and retinaculae ligaments. If the shape of the knee changes after implantation of a knee prosthesis, the relation between the insertion of the ligaments and the joint surface changes and this may not only create difficulty or even an inability to correctly balance the knee between the medial and lateral compartment, but also between the extension and the flexion as well as the midflexion.
[0155] Referring now to
[0156] Referring now to
[0171] Referring now to
[0182] Referring now to
Comparison With Standard (Off-the-shelf) Knee Prostheses and Limits of This System
[0183] Because the knee prosthesis or knee implant is non-anatomic (in that it only roughly matches the anatomical movement of a human knee) and has to be implanted in a manner that more or less matches the anatomy of the patient’s knee joint, many significantly simplifications and compromises have to be integrated into the design of knee prostheses.
[0184] Initially the goal was to mechanically optimize the implantation of the prosthesis in order to obtain high longevity or life expectancy of the prosthesis. These knee prostheses have been designed to always be implanted mechanically (90° cuts to mechanical axis in the coronal plane), with both a symmetrical condyle shape and thickness and for a neutral limb realignment.
[0185] Then dogmatic concepts were implemented in the range of sizes of the knee prostheses of different companies in a compromise of the shape, size and alignment to an average knee and limb morphotype, which concepts include: [0186] The number of sizes is typically limited to 10 sizes. However, this cannot realistically fulfil the wide variation in dimensions from small knees to very wide knees, because we know that the smallest sizes of the Caucasian population do not fit the corresponding sizes of the Asian population. Further, most companies increase sizes by adding a size in-between two sizes but not by increasing the extreme sizes. [0187] The Medio-Lateral /Antero-Posterior ratio has been considered fixed, but we know now that it changes significantly among the population, and prosthetic overhang or component undersizing have been well described. [0188] The sagittal shape of the condyles and / or trochlea (J-curve) has typically been simplified to a single or double or multiple radii, but we know now that some patients have a single or a multi-radii J-curve. [0189] The femoro-patellar joint has always typically been simplified with a fixed oriented sulcus axis, but we know now that if the distal femur is in varus or in valgus, the sulcus axis is not oriented equally in such a way. [0190] Fifth, the condylar offset is almost never considered except for Smith & Nephew’s Journey knee with a fixed offset of 2.5 mm for both the medial, the distal, and posterior condyles, but we know now, that the obliquity of the joint line changes significantly among the population and also between the distal and posterior condyles.
[0191] Today, clinical outcomes after 15 years of implantation demonstrate more than 93% of survivorship of the knee prosthesis. However, 30% of the population of patients complain of dissatisfaction after total knee replacement, either of pain, loss of mobility, or abnormal kinematics.
[0192] A further challenge today is also that the population requiring a total knee replacement is younger and still very active. Consequently, the function of the knee and global satisfaction is more and more important. The trend today is thus to do one’s best to install anatomically a non-anatomic knee prosthesis. The function will be improved but with a risk of a loss of longevity of the knee prosthesis, resulting in a higher risk of early component loosening.
Knee Implantation (Standard Knee Implantation, Patient-Specific or Personalized/Individualized or Customized Implantation) is Described as Below
[0193] Referring now to
[0194] An inner, bone-facing surface of the femoral component conforms to the corresponding surface of the femoral condyle. Alternatively, it can conform to one or more optimized bone cuts on the femoral condyle. However, the outer, articular surface of the component is enhanced to incorporate a smooth surface having a nearly constant radius in the coronal plane. The corresponding articular surface of the tibial tray (insert) has a surface contour in the coronal plane that is matched to the outer articular surface.
[0195] In certain embodiments, the articular surface of the component incorporates a sagittal curvature that positively-matches the patient’s existing or healthy sagittal radius.
[0196] Modern knee prosthesis: [0197] Symmetrical condyles; [0198] Same thickness between medial and lateral condyles for distal and posterior condyles, but can be different between distal and posterior; [0199] Tangent of the distal and posterior condyles parallel to knee prosthesis flexion axes; [0200] Elevation of the trochlea fixed and parallel to the tangent of the posterior condyle (axial plane); [0201] No condylar offset (excepted for S&N, 2.5 mm offset); [0202] Fixed sulcus axis oriented laterally at about 6° or eccentrically laterally;
[0203] The inventive activity of the invention also consists being able to vary the medial femoro-tibial joint to the lateral femoro-tibial joint to the femoro-patellar joint independently from each other. This can be defined as the variable parameters described below:
[0204] Personalized knee prosthesis: [0205] Offset in the distal condyles (not a fixed value) = alpha distal angle ad [0206] Offset in the posterior condyles (not a fixed value) = alpha posterior angle αp [0207] Offset in the trochlear elevation (not a fixed value) [0208] ad is equivalent or not to αp and is equivalent or not to the trochlear elevation angle (ATA) [0209] DCA can be equivalent or not to αd [0210] PCA can be equivalent or not to αp [0211] SA is not a fixed value (sulcus axis = γ1) [0212] WL is not a fixed value (Whiteside line = γ2)
Difference Between Standard (STD), Off the Shelf (OTS) Prosthesis and the Personalized Knee Prosthesis of the Invention
[0213] Referring now to
[0214] Referring in particular to
[0215] Referring now to
[0234] Referring in particular to
[0235] Similarly, the medial condylar axis 832 and the lateral condylar axis 834 as measured from the femoral mechanical axis (FMA) 836 can vary from one another by up to 10 mm.
[0236] Referring to
[0237] Referring now to
[0238] Referring now to
[0239] Referring now to
[0240] Referring now to
[0258] Referring now to
[0259] Referring now to
[0260] Referring now to
[0261] Referring now to
[0284] In a knee prosthesis according to the invention, the tibial insert component 1160 is made to match (“match” meaning for example via the application of known curve/surface fitting and smoothing techniques between shapes as mentioned, e.g., using “SOLIDWORKS”™ or the like, that interact across adjacent bone compartments) the femoral implant 1110, in other words the tibial insert component 1160 shares with the femoral implant 1110: [0285] the same or essentially the same mediolateral dimension 1120, [0286] the same or essentially the same medial condyle dimension from femoral mechanical axis 1122, [0287] the same or essentially the same lateral condyle dimension from femoral mechanical axis 1124, [0288] the same or essentially the same condyle interaxis 1130, [0289] the same or essentially the same medial condyle central axis from femoral mechanical axis 1132, [0290] the same or essentially the same lateral condyle central axis from femoral mechanical axis 1134, [0291] the same or essentially the same transepicondylar axis 1146, such that: [0292] the medial condyle surface of the femoral implant 1152 fits to the medial condyle corresponding surface of the tibial insert component 1162, [0293] the trochlea surface of the femoral implant 1153 fits to the trochlea corresponding surface of the tibial insert component 1163, [0294] the lateral condyle surface of the femoral implant 1154 fits to the lateral condyle corresponding surface of the tibial insert component 1164, and [0295] the bicondyle distal tangent of the tibial insert component 1166 fits to the bicondyle distal tangent of the tibial insert component 1166.
[0296] Referring now to
[0297] Referring in particular to
[0298] Referring now to
[0299] Referring now to
[0300] Referring now to
[0301] In a knee prosthesis of the invention, the offsets 1172, 1174 can vary from 0 to 10 mm, and the angles 1182, 1184 can vary from 0° to 15°.
[0302] Referring now to
[0307] In practice, the tibial insert, the tibial tray and the keel can be realized in one or more parts, and assembled by any of the appropriate techniques as well known in the industry, such assembly may be done before or during the surgery. For the purpose of the present explanation, these elements are presented as if made in one part with different sections: (i) the articulation surface of the tibial insert comprising the medial condyle corresponding surface 1262, the trochlea corresponding surface 1263 and the lateral condyle corresponding surface 1263, (ii) the bone facing surface of the tibial tray 1230 and (iii) the keel 1240. In a knee prosthesis of the invention, any orientation angle, any offset and any combination thereof applied to the tibial insert, the tibial tray and the keel so as to adapt to the need of the individual patient.
[0308] Referring now to
[0309] Referring now to
[0310] Referring now to
[0311] Referring now to
[0312] Typically, the offset can vary from -10° to +10° in mediolateral or in anteroposterior dimensions, and can be oriented up to 12° around the longitudinal axis of the keel.
[0313] Referring now to
[0314] The sagittal J-curve 1310 is adapted to fit with the corresponding surface of the femoral implant of the invention, so that the functioning of the knee prosthesis of the invention fits the need of the individual patient. To this end, the sagittal J-curve 1310 can be made of one radius but can also be made of a combination of two radii 1312, 1313 (
[0315] To fit with the tibia of the individual patient, in the sagittal plane the keel 1340 of the tibial component 1300 of a knee prosthesis of the invention can be placed at the center of the tibial component 1300 (
[0316] For the same purpose of fitting to the tibia of the individual patient, in the sagittal plane the bone facing surface 1332 of the tibial component 1300 of a knee prosthesis of the invention can be oriented at an angle 1344 (
[0317] The tibial component 1300 of a knee prosthesis of the invention can combine any and all the characteristics described in the present disclosure so as to better match the needs of the individual patient (
[0318] Typically, the offset can vary from -10° to +10° in mediolateral or in anteroposterior dimensions, and can be oriented up to 12° around the longitudinal axis of the keel.
[0319] Referring now to
[0335] In a knee prosthesis of the invention, all these parameters can be adapted to fit with the needs of the individual patient. In such prosthesis, the mediolateral dimension 1470 can vary from 40 mm to 150 mm, the mediolateral dimensions of the condyles 1472, 1474 can both and independently vary from 15 mm to 70 mm, and the anteroposterior dimensions of the condyles 1442, 1444 can both and independently vary from 30 mm to 70 mm. Referring now to
[0336] In the coronal plane, the bone facing surface 1532 can present a certain orientation angle 1534, and the surface where the tibial insert is attached can present a certain offset 1535 (
[0337] Referring now to
[0338] Referring now to
[0348] The geometry of the patella component of a knee prosthesis of the invention is adapted to fit the need of the individual patient. The articulating surfaces of the patella component 1862, 1863, 1864 are made to fit to their respective corresponding surfaces of the femoral component 1852, 1853, 1854, also taking into account the patient’s hip-knee-ankle (HKA) alignment, be it normal, varus or valgus. As an example, in the case the femoral component has an offset (1872 in
[0349] Referring now to
[0350] Referring now to
[0364] In a knee prosthesis of the invention, all these parameters can be adapted to fit with the needs of the individual patient. Each of the 4 compartments (medial, lateral, anterior, posterior) can be specified to fall in the range from 8 mm to 30 mm in width and height. The values are independent of the patella thickness, which should be at least 6 mm or more.
Main Features Around the Invention
[0365] The invention’s design specificities for the distal and posterior condyles to the trochlea part of the femoral component are personalizable features that, when put together, realign the pathologic limb as it was before the pathology and which reshape the joint surface as close as possible to the pre-arthritic shape and size of the knee joint.
[0366] The different types of correction: [0367] from the pathologic deviated limb alignment to the pre-arthritic limb alignment; [0368] from the pathologic knee joint surface to the pre-arthritic knee joint surface (the two condyles and the trochlea), which implicates the medio-lateral curves of the articular surface as well as the sagittal J-curves of both condyles and trochlea; [0369] from the pathologic femoral (distal, posterior and in-between), tibial proximal & trochlear joint lines to the corresponding pre-arthritic joint lines (=condylar offset, trochlear offset between medial and lateral compartments); [0370] from the pathologic distance between the depth of the trochlea to the medial and lateral trochlear elevation to the corresponding pre-arthritic distance; [0371] from the pathologic coronal distance between the sagittal axis of the condyles and the trochlea to the middle of the knee to the corresponding pre-arthritic distance;
[0372] Supplementary corrections (or rules that we internally use to avoid outliers in terms of alignment and shapes and whose range defines what is normality and abnormality for alignment and shape and thus indicate what is replicated or adjusted) from the native or pre-arthritic limb alignment and knee shape may be made: [0373] when the pre-arthritic limb alignment is considered as mechanically unstable (too deviated, if HKA postop more than 5° in varus or in valgus HKA <175° or HKA >185°, risk of loosening of the components because of an imbalance in load sharing because of excessive abduction or adduction moment), a correction of the limb alignment is applied to restrict the global alignment between 175° < HKA postop < 185°; [0374] when the pre-arthritic knee joint lines are considered as mechanically not stable (too oblique condyles, if FMA postop more than 5° FMA < 85° or FMA > 95°, TMA < 85° or TMA > 95°, risk of loosening of the components because of imbalance load sharing), a correction of the condylar offset is applied to restrict the obliquity of the condyles and proximal tibia to 5° (85° < FMA, TMA < 95°). This also happens when the medial or lateral condyle is under-developed (hypoplasia) or when the bone wear in a condyle is excessive; [0375] when the pre-arthritic limb alignment has to be corrected, this means that a restricted or hybrid alignment is targeted and the postop limb alignment is an in-between alignment between the anatomical deviated pre-arthritic and a neutral postop alignment (in this condition, a compromise is made with the FMA (femoral distal joint line obliquity). This compromise has to be moved back/reported posteriorly to the condyles to balance the correction during the whole flexion). [0376] when the pre-arthritic lateral elevation of the trochlea is too flat, this may lead to an unstable patella during flexion (patellar dislocation), thus a lateral wall will be built (at least 5 mm) to secure and correctly center the patella during the flexion; [0377] when the pre-arthritic tibia slope is too excessive or insufficient (excessive downslope or upslope), this may lead to a loss of mobility or contribute to an excess of extension (recurvatum) with associated knee joint laxity, and therefore a correction is systematically applied such that the posterior tibia slope falls within the range of 0° < TPS < 10°.
Method of Making the Personalized Prosthesis
[0378] Referring now to
[0403] Referring now to
[0413] Referring now to
[0414] Referring now to
[0415] As will be appreciated by skilled artisans, the present invention may be embodied as a system, a device, or a method. In one aspect, the invention is a computer-implemented method in which a task-specific program is encoded on a medium for selecting a suitable knee prosthesis for a particular patient. The computer includes a CPU/processor, memory, an input and an output device operably interconnected thereto which implements one or more of the method steps described herein.
[0416] It should be understood that in all embodiments described herein, in which a selection is made among a number of 3D knee prostheses, a parameterized model specific to each component of the knee prosthesis (femoral component, tibial component, tibial insert, patellar component) is constructed from sketches/representations in order to generate essentially all the shape configurations that represent the worldwide anatomical variability of the normal knee joint. The parameterized models are divided into compartments (for the femoral component for instances : medial distal condylar compartment, medial posterior condylar compartment, lateral distal condylar compartment, lateral posterior condylar compartment, medial trochlear compartment, lateral trochlear compartment). In each of those independent compartments, sketches/representations are defined to reproduce the shape and dimension of a corresponding part of the knee joint surfaces and prosthetic contours. These sketches/representations are defined in each plane (coronal, sagittal and transverse) and allow for the replication in the knee prosthesis, the shape and dimension of the knee joint, in each of these planes. Fixed values as well as parameterized values (mathematical functions) define each of those sketches/representations. The parameterized values are dynamically linked to calculation tables, which define the relationships between each independent compartment and describe also the 3D variability of each of those compartments. Each prosthetic component configuration (shape and dimension) generated by the parameterized model and the calculation tables replicate the anatomical variability of the normal knee joints.
[0417] It should also be understood that in each of the substeps of the methods described herein for selecting a 3D knee prosthesis model, a planning algorithm is used which allows for the selection for each patient, among this huge family of prosthetic configurations stored in the database, the unique patient-specific component configuration, where the prosthetic shape and size best match the pre-arthritic patient knee joint motion. In a first step, anatomical landmarks are identified in the hip, knee, ankle joint (but also on upper body), in order to define the patient pathologic leg and knee morphotype and phenotype. In a second step, a 3D planning algorithm, consisting in a matrix specific to each plane, defines the specific correction to bring to the leg alignment as well as to the pathologic knee shape, in order to replicate the pre-arthritic knee alignment and knee joint shape. Note that normality (average +/- 2 standard deviations for each parameter) in a knee prothesis selection is essentially always attainable using these inputs, but outliers are not allowed and abnormal (average with more than 2 standard deviations for at least one parameter) prosthetic knee shapes will not be produced. In a third step, the algorithm will then select among all knee configurations, the unique and patient-specific prosthetic knee size, which resurface and replicate the pre-arthritic knee joint (shape and dimension), by directly positioning the component at the correct 3D orientation and alignment.
[0418] In another embodiment, a nontransient information storage medium having a knee prosthesis characterization and selection program encoded thereon is provided. When the program is executed, it implements a method which instructs a processor to aid a user in selecting a 3D knee prosthesis model for a particular patient. The method encoded thereon includes the steps of: [0419] (a) using a parameterizing module, parameterizing a knee prosthesis according to well-defined and independent knee joint compartments, [0420] (b) using a model generator, generating a large number knee shapes in the form of 3D knee prosthesis models which reproduce the 3D shape asymmetries of a large number of individual knee samples and storing the same on a database, thereby enabling the good replication of the knee motion of essentially any patient by generating shapes which vary the shape parameters (surface and dimension) of at least one of the compartments and storing these 3D knee prosthesis models in association with each model’s shape parameters and asymmetries in a database allowing comparing of the asymmetries of the patient’s knee with those of the 3D knee prosthesis model, and [0421] (c) after studying the patient’s pathology and developing pre-pathological knee prosthesis criteria matching the patient’s needs, using a search module to search the database comparing the large number of knee shapes based on a best match of the asymmetries of each model to identify candidate matches: [0422] (d) providing a display of candidate matches and their attributes on an output device; [0423] (e) providing a means of selecting a best match among suitable candidate matches identified; [0424] (f) optionally generating a production order if the selected knee prosthesis is not in inventory.
[0425] Where ever processing is referred to in this application, artificial intelligence such as but not limited to neuronal networks and/or machine learning algorithms may be used to facilitate the analysis of a patient’s current anatomy, to calculate most probable pre-pathological anatomies for this patient, to help select an appropriate prosthesis in the database (e.g., applying pattern recognition and classification algorithms) and/or to help design a specific prosthesis for this patient.
[0426] Moreover, the system contemplates the use, sale and/or distribution of any goods, services or information having similar functionality described herein.
[0427] The specification and figures should be considered in an illustrative manner, rather than a restrictive one and all modifications described herein are intended to be included within the scope of the invention claimed. Accordingly, the scope of the invention should be determined by the appended claims (as they currently exist or as later amended or added, and their legal equivalents) rather than by merely the examples described above. Steps recited in any method or process claims, unless otherwise expressly stated, may be executed in any order and are not limited to the specific order presented in any claim. Further, the elements and/or components recited in apparatus claims may be assembled or otherwise functionally configured in a variety of permutations to produce substantially the same result as the present invention. Consequently, the invention should not be interpreted as being limited to the specific configuration recited in the claims.
[0428] Benefits, other advantages and solutions mentioned herein are not to be construed as critical, required or essential features or components of any or all the claims.
[0429] As used herein, the terms “comprises”, “comprising”, or variations thereof, are intended to refer to a non-exclusive listing of elements, such that any apparatus, process, method, article, or composition of the invention that comprises a list of elements, that does not include only those elements recited, but may also include other elements such as those described in the instant specification. Unless otherwise explicitly stated, the use of the term “consisting” or “consisting of” or “consisting essentially of” is not intended to limit the scope of the invention to the enumerated elements named thereafter, unless otherwise indicated. Other combinations and/or modifications of the above-described elements, materials or structures used in the practice of the present invention may be varied or adapted by the skilled artisan to other designs without departing from the general principles of the invention.
[0430] The patents and articles mentioned above are hereby incorporated by reference herein, unless otherwise noted, to the extent that the same are not inconsistent with this disclosure.
[0431] Other characteristics and modes of execution of the invention are described in the appended claims.
[0432] Further, the invention should be considered as comprising all possible combinations of every feature described in the instant specification, appended claims, and/or drawing figures which may be considered new, inventive and industrially applicable.
[0433] The invention may be characterized by the following feature sets: [0434] 1. A method of selecting a 3D knee prosthesis model for a particular patient, the method consisting of: [0435] (a) parameterizing a knee prosthesis according to well-defined and independent knee joint compartments, [0436] (b) generating a large number knee shapes in the form of 3D knee prosthesis models which reproduce the 3D shape asymmetries of each individual knee, thereby enabling the replication of the knee motion of essentially any patient by generating shapes which vary the shape parameters (surface and dimension) of at least one of those compartments and storing these 3D knee prosthesis models in association with each model’s shape parameters and asymmetries in a database allowing comparing of the asymmetries of the patient’s knee with those of the 3D knee prosthesis model, and [0437] (c) studying the patient’s pathology and developing pre-pathological knee prosthesis criteria matching the patient’s needs, [0438] wherein a suitable knee prosthesis best match of the patient’s needs may be selected among the large number of knee shapes based on a best match of the asymmetries of each model, the shape selected best meeting the patient’s criteria. [0439] 2. The method of feature set 1, wherein the method includes the further step of, optionallyusing a planning algorithm, selecting a suitable knee prosthesis from among the large number of knee shapes based on a best match of the asymmetries of each model, the shape selected best meeting the patient’s criteria. [0440] 3. The method of the above feature set, wherein the selected 3D knee prosthesis model is used to produce a suitable prosthesis for the patient. [0441] 4. The method of the above feature set, wherein the produced prosthesis is made available to the surgeon for implantation. [0442] 5. The method of feature set 1, wherein invention’s design specifications for distal and posterior condyles to the trochlea part of the femoral component are used to personalize features which when put together realign a pathologic limb as it was before the pathology and reshape the joint surface as close as possible to the pre-arthritic shape and size of the knee joint. [0443] 6. A method of preparing a database of 3D knee prosthesis models from which can be selected a 3D knee prosthesis model that matches a particular patient’s needs, the method comprising the steps of: [0444] (a) parameterizing a selected knee prosthesis design configuration into features which correspond to well defined and independent knee joint compartments; [0445] (b) generating a large number of the 3D knee prosthesis models corresponding to at least one of the compartments by varying shape parameters such as surface and dimension and which reproduce the 3D shape asymmetries of a sample population of individual knees; and [0446] (c) populating the database with the generated models, thereby producing the database of 3D knee prosthesis models with high variability; [0447] (d) studying, using 3D scans, the motion of a patient’s knee; [0448] (e) adjusting for pathologies and optionally soft tissue influences in order to create a hypothesized pre-pathological model of the motion of the patient’s knee; [0449] (f) optionally using a planning algorithm, selecting from an inventory of available knee prostheses or from the database of 3D knee prosthesis models the model or models which best replicate the hypothesized pre-pathological model or models of the patient’s knee motion defined by the 3D shape asymmetries of the patient’s knee; [0450] (g) fabricating the selected prosthesis model if a matching knee prosthesis is not available in inventory; and [0451] (h) making the prosthesis available for implantation. [0452] 7. A knee prosthesis is provided which is manufactured from a 3D model selected after applying a method including the steps of: [0453] (a) analysis of a patient’s current and pre-pathological knee motion behavior as well as the patient’s HKA alignment, [0454] (b) optionally using a planning algorithm, selection of a suitable 3D model from a comprehensive database of 3D models of varying knee morphologies, each 3D model being adapted to a known morphology as well as production limitations and requirements, and [0455] (c) manufacturing of the selected 3D model which represents a producible and essentially custom knee prosthesis adapted to the individual patient’s 3D constitutional anatomy, thus making it possible to re-create the knee articulation as it was naturally. [0456] 8. A method according to the invention consists of the following steps: [0457] (a) Using CT-san, X-ray, MRI, EOS, in loaded or unloaded conditions, monopodal, bipodal, under varus / valgus stress or any other measuring equipment and/or method as well-known in the field, measuring patient’s preoperative condition including at least: [0458] (i) HKA alignment, [0459] (ii) relative movement of the femur vs tibia (sliding and rolling motion combination), [0460] (iii)femur and tibia contact surfaces and bone shape, and [0461] (iv)patella shape and position relative to the femur and tibia, and contact surfaces of the patella with the femur; [0462] (b) defining target postoperative HKA alignment according to (ai) and to patient’s anatomic history (if known); [0463] (c) defining target postoperative relative movement of the femur vs tibia (sliding and rolling motion combination) according to (b) and (aii); [0464] (d) defining the shape of femur and tibia prostheses contact surfaces according to (b), (c) and (aiii); [0465] (e) defining the shape of femur and tibia prostheses attachment according to (d) and (aiii); [0466] (f) defining target postoperative patella position relative to the femur prosthesis and relative to the tibia prosthesis according to (b), (c), (d), (aiv) and to patient’s anatomic history (if known); [0467] (g) defining the shape of the contact surfaces between femur prosthesis and patella according to (b), (c), (d), (f) and (aiv) (Contact surface only between the femoral component and the patella component, not between the patella component and the tibia component); and [0468] (h) merging all the above definitions into an individually adapted knee prosthesis. [0469] 9. The method of one of feature sets 1 to 4 wherein the 3D scans are video scans of the patient’s knee in motion. [0470] 10. The method of one of feature sets 1 to 4, wherein the known joint compartments include at least one of the following compartments: extension compartment, flexion compartment; medial compartment; lateral compartment; femoro-tibia compartment; and femoro-patellar compartment. [0471] 11. The of one of feature sets 1 to 4, wherein the method includes consideration of the articulation of the patella in selecting a suitable 3D model. [0472] 12. A prosthesis made according of one of feature sets 1 to 4. [0473] 13. The method of one of feature sets 1 to 4, wherein the knee prosthesis of the invention is adapted in the case of constitutional femur varus such that the femoral prosthesis (1110) has the distal lateral condyle shorter than the distal medial condyle, generating an offset (1172) between the condyles, the same offset (1172) is reproduced in the tibial insert component (1160). [0474] 14. The method of one of feature sets 1 to 4, wherein the knee prosthesis of the invention is adapted for a case of constitutional femur valgus where the femoral prosthesis (1110) has the distal lateral condyle longer than the distal medial condyle generating an offset (1174) between the condyles, the same offset (1174) is reproduced in the tibial insert component (1160). [0475] 15. The method of one of feature sets 1 to 4, wherein the knee prosthesis of the invention is adapted for a case of constitutional femur varus where the femoral prosthesis (1110) has an angle (1182) opening from the distal lateral condyle to the distal medial condyle, the same angle (1182) is reproduced in the tibial insert component (1160). [0476] 16. The method of one of feature sets 1 to 4, wherein the knee prosthesis of the invention is adapted for a case of constitutional femur valgus where the femoral prosthesis (1110) has an angle (1184) opening from the distal medial condyle to the distal lateral condyle, the same angle (1184) is reproduced in the tibial insert component (1160). [0477] 17. The method of one of feature sets 1 to 4, wherein the knee prosthesis of the invention, the offsets (1172, 1174) vary from 0 to 10 mm, and the angles (1182, 1184) vary from 0° to 15°. [0478] 18. The method of one of feature sets 1 to 4, wherein, when sizing the prosthesis, the shape radius of the medial condyle surface in the coronal and transverse plane (962), the shape radius of the trochlea surface in the coronal plane (963) and the shape radius of the lateral condyle surface in the coronal and transverse plane (964) are adjusted independently from each other and independently from the prosthesis size and from the patient’s hip-knee-ankle (HKA) alignment, be it normal, varus or valgus. [0479] 19. The method of one of feature sets 1 to 4, wherein contouring (outside dimension of the prosthesis) is adjusted so as not to overhang or uncover the resected area to resurface. [0480] 20. The method of one of feature sets 1 to 4, wherein contouring angles (982, 984, 992, 994) for the anterior and posterior faces of the femoral prosthesis are adjusted independently from each other and independently from the prosthesis size and from the patient’s hip-knee-ankle (HKA) alignment, be it normal, varus or valgus. [0481] 21. The method of one of feature sets 1 to 4, wherein contouring angles (982, 984, 992, 994) for the anterior and posterior faces of the femoral prosthesis are varied from 0° to 50° in order to obtain the desired knee kinematics and to adapt to the patient’s size. [0482] 22. The method of one of feature sets 1 to 4, wherein the shape of the medial condyle surface in the sagittal plane (medial condyle J-curve) (972), the shape of the trochlea surface in the sagittal plane (trochlea J-curve) (973) and the shape of the lateral condyle surface in the sagittal plane (lateral condyle J-curve) (974) are adjusted independently from each other and independently from the prosthesis size and from the patient’s hip-knee-ankle (HKA) alignment, be it normal, varus or valgus. [0483] 23. The method of one of feature sets 1 to 4, wherein the shape of the medial condyle surface in the sagittal plane (medial condyle J-curve) (972), the shape of the trochlea surface in the sagittal plane (trochlea J-curve) (973) and the shape of the lateral condyle surface in the sagittal plane (lateral condyle J-curve) (974) can be made of one radius but can also be made of a combination of two or more radii, which dimension can vary from 15 mm to 65 mm. [0484] 24. The method of any of the above feature sets, wherein via use of a combination of radii, the transition from one radius to the next radius is smoothened by the use of a spline or any other appropriate curve. [0485] 25. The method of any of the above feature sets, wherein the femoral part of the knee prosthesis of the invention is adapted to any bony resections selected from one of the group of resections consisting of planar, inclined, curved, offset, and double-inclined adapted to the individual need of the patient. [0486] 26. The method of the above feature set, wherein the bone resection is sawed or milled so as to be adapted to the individual needs of the patient. [0487] 27. The method of making a natural, personalized implant including at least one or all of the following steps: [0488] (a) measuring the preoperative, 3D HKA Alignment of the knee; [0489] (b) reproducing postoperative, 3D HKA realignment to pre-arthritic HKA (if not outlier); [0490] (c) defining postoperative 3D HKA realignment to corrected pre-arthritic HKA (if outlier); [0491] (d) measuring the preoperative Antero-posterior dimension of the distal femur; [0492] (e) reproducing the correct AP prosthetic femoral size, respecting that the implant cannot be rotated (or inclined or flexed) more than 10° in the sagittal plane ; [0493] (f) measuring the preoperative FMA distal, posterior and TMA (joint lines); [0494] (g) reproducing postoperative FMA, TMA obliquities to pre-arthritic FMA, TMA obliquities (if not outlier) and reproduce the pre-arthritic femoral torsion; [0495] (h) defining postoperative FMA, TMA obliquities to corrected pre-arthritic FMA, TMA obliquities (if outlier) and adapt the femoral torsion according to the matrix of planning; [0496] (i) measuring the preoperative TL obliquity as well as depth of the trochlea; [0497] (j) defining which part of the final obliquity has to be done on the bone (orientation of the resection) and which one has to be integrated into the implant (condylar offset), following rules described in the matrix of planning; [0498] (k) reproducing postoperative TL obliquity to pre-arthritic TL obliquity (if not outlier) and reproduce the depth of the trochlea; [0499] (l) defining postoperative TL obliquity to corrected pre-arthritic TL obliquity (if outlier) and reproduce the depth of the trochlea by adding a lateral elevation on the trochlea; [0500] (m) reproducing postoperative condylar and trochlear JL curves to pre-arthritic JL curves (if not outlier); [0501] (n) defining postoperative condylar and trochlear Joint Line curves to corrected pre-arthritic JL curves (if outlier by correcting the JL curve of the lateral condyle in the case of hypoplasia or of both condyles in the case of sagittal deformities for instance recurvatum or large flessum); [0502] (o) reproducing postoperative condylar and trochlear Medio-Lateral curves to pre-arthritic ML (if not outlier); [0503] (p) defining postoperative condylar and trochlear ML curves to corrected pre-arthritic ML curves (if outlier by correcting the ML curve of the lateral condyle or of both condyles in the case of sagittal deformities for instance recurvatum or large flessum); [0504] (q) measuring the distance between the axis of each condyle to the middle of the knee and reproducing the distance; [0505] (r) defining the outside limits of the articular surface for both condyles and trochlea (contouring) in order to avoid prosthetic overhang or undersizing; [0506] (s) measuring the preoperative posterior tibia slope; [0507] (t) reproducing the postoperative posterior tibia slope (TPS) to corrected pre-arthritic TPS if outlier; [0508] (u) defining the rotation of the tibia component by measuring the angle to the anterior tibia tuberosity (TTA), which is the AP axis and by the axis going through the centers of the two circles describing the medial and lateral tibia surface geometry (ML axis);0 [0509] (v) defining the AP & ML position of the tibia keel to obtain a well centered keel on the tibia metaphysis and / or diaphysis; [0510] (w) defining the outside limits of the tibia component’s contouring (to the tibia rim) in order to avoid prosthetic overhang (risk of conflict with surrounding soft tissue leading to pain) or undersizing (risk of sinking leading to revision); and [0511] (x) measuring the distance between the distal femoral resection and the tibia proximal resection (gap in extension) in order to respect the global thickness of the implant. [0512] 28. A prosthesis made according of one of feature sets 1 to 4, wherein the tibial insert, the tibial tray and the keel, components of the prosthesis of the invention, are each made up of one or more parts and assembled before or during the surgery. [0513] 29. The prosthesis of the above feature set, wherein at least one of these components has [0514] (a) one element selected from one of the group of elements consisting of [0515] (i) the articulation surface of the tibial insert comprising the medial condyle corresponding surface (1262), [0516] (ii) the trochlea corresponding surface (1263), and [0517] (iii) the lateral condyle corresponding surface (1263), [0518] (b) a bone facing surface of the tibial tray (1230), and [0519] (c) the keel portion (1240). [0520] 30. The prosthesis of the above feature set, wherein any desired orientation angle, offset or any combination thereof may be applied to the tibial insert, the tibial tray and the keel so as to best adapt to the need of the individual patient. [0521] 31. The prosthesis of either of the above two feature sets, wherein the tibial insert, the tibial tray and the keel can each be formed of one or more elements. [0522] 32. The prosthesis of any of the above feature sets, wherein the keel (1240) is formed so as not to be orthogonal to the bone facing surface (1230), but is oriented at a selected angle (1242) so as to adapt to the need of the individual patient. [0523] 33. The prosthesis of any of the above feature sets, wherein the keel (1240) is not orthogonal to the bone facing surface (1230), but is oriented at an angle (1242), and the bone facing surface (1230) is oriented at an angle (1232) so as to adapt to the need of the individual patient. [0524] 34. The prosthesis of the above feature set, wherein the medial insert thickness is made thin so as to favor the knee to be orientated in varus. [0525] 35. The prosthesis of any of the above feature sets, wherein the keel (1240) is not formed orthogonal to the bone facing surface (1230), but is oriented at a selected angle (1242), the bone facing surface (1230) is oriented at another selected angle (1232), and the lateral condyle corresponding surface (1264) presents an offset (1265), so as to adapt to the need of the individual patient. [0526] 36. The prosthesis of any of the above feature sets, wherein the keel (1240) is not orthogonal to the bone facing surface (1230), but is oriented at a selected angle (1242), the bone facing surface (1230) is oriented at a second selected angle (1232), and the bicondyle distal tangent (1266) is oriented at a third selected angle (1267), so as to adapt to the need of the individual patient. [0527] 37. The prosthesis of any of the above feature sets, wherein the offset (1265) can vary from 0 to 10 mm, and the orientation angles (1232, 1242, 1267) can vary up to 12°. [0528] 38. The prosthesis of the above feature set wherein the offset can vary from -10° to +10° in mediolateral or in anteroposterior dimensions, and can be oriented up to 12° around the longitudinal axis of the keel. [0529] 39. The prosthesis of any of the above feature sets, wherein the sagittal J-curve (1310) is adapted to fit with the corresponding surface of the femoral prosthesis of the invention, so that the functioning of the knee prosthesis of the invention fits the need of the individual patient. [0530] 40. The prosthesis of the above feature set wherein the sagittal J-curve (1310) is essentially a single radius. [0531] 41. The prosthesis of the penultimate feature set, wherein the sagittal J-curve (1310) is essentially a combination of two or more radii (1312, 1313, 1314, 1315) , which dimension falls in the range from 15 mm to 80 mm. [0532] 42. The prosthesis of any of the above feature sets, wherein, to fit with the tibia of the individual patient, in the sagittal plane, the keel (1340) of the tibial component (1300) of a knee prosthesis of the invention is placed at the center of the tibial component (1300) and optionally presents an offset (1342 towards the anterior part of the tibia or towards the posterior part of the tibia. [0533] 43. The prosthesis of the above feature set, wherein the offset (1342) can vary from 0 to 10 mm. [0534] 44. The prosthesis of the penultimate feature set, wherein the offset varies from -10° to +10° in mediolateral or in anteroposterior dimensions, and is oriented up to 12° around the longitudinal axis of the keel. [0535] 45. The prosthesis of the above feature set, wherein, for the same purpose of fitting with the tibia of the individual patient, in the sagittal plane, the bone facing surface (1332) of the tibial component (1300) of a knee prosthesis of the invention can be oriented at a selected angle (1344) which may vary up to 12°. [0536] 46. The prosthesis of any of the above feature sets, wherein the articulating surfaces of the patella component (1862, 1863, 1864) are made to fit to their respective corresponding surfaces of the femoral component (1852, 1853, 1854), also taking into account the patient’s hip-knee-ankle (HKA) alignment, be it normal, varus or valgus. [0537] 47. The prosthesis of any of the above feature sets, wherein, in the case the femoral component has an offset (1872, 1874) between the distal lateral condyle and the distal medial condyle, the offset (1872, 1874) is reproduced in the patella component. [0538] 48. The prosthesis of the above feature set, wherein the patella component of a knee prosthesis of the invention, the mediolateral surfaces can be symmetrical or asymmetrical between medial and lateral compartment, and the anteroposterior surfaces can be symmetrical or asymmetrical between the anterior and posterior compartment and selected, optionally using a planning algorithm, so as to match the needs of the individual patient. [0539] 49. The prosthesis of any of the above feature sets, wherein each of the medial, lateral, anterior, posterior compartments are specified to fall in the range from 8 mm to 30 mm in width and height, which values are independent of the patella thickness, which should be at least 6 mm or more. [0540] 50. The method of any of the above feature sets wherein curve/surface fitting and smoothing techniques are applied between shapes that interact across adjacent bone compartments in order to meld elements of the prosthesis that correspond to a bone compartment in order to create a composite knee prosthesis adapted to the needs of the patient. [0541] 51. A partial or total knee prosthesis designed according to an individual patient’s constitutional anatomy, re-creating the knee articulation as it was naturally wherein its geometry is determined by varying independently to each other, the medial femoro-tibial joint to the lateral femoro-tibial joint to the femoro-patellar joint. [0542] 52. A method for production of a partial or total knee prosthesis adapted to an individual patient’s constitutional anatomy, the method comprises a design step considering the current and the pre-pathology knee motion behavior of the patient, and further considering his individual Hip-Knee-Ankle (HKA) alignment, and using these inputs, re-creating a knee articulation model as it was naturally, wherein further, this re-created natural knee articulation model and not the pathological knee articulation model is used to create a prostheses that re-creates this natural knee articulation. [0543] 53. A femoral prosthesis for implantation on a femur of a patient’s knee, comprising: [0544] two condylar portions comprising the medial and lateral condyles, having a bone-facing surface for abutting at least a portion of each condyle of the patient’s knee and an articular surface generally opposite each bone-facing surface; each articular surface having a curvature (J-curve) generally disposed in a first plane (sagittal plane) and ML curve generally disposed in a second and third plane (frontal plane for the distal condyles and transverse planes for the posterior condyles); each articular surfaces of the medial and lateral condyles may have a condylar offset in the second and third plane, which can be equivalent or not; [0545] a trochlear portion, comprising the trochlear depth as well as the lateral and medial trochlear elevations, having a bone-facing surface for abutting at least a portion of the trochlea of the patient’s knee and an articular surface generally opposite the bone-facing surface; each articular surface having a curvature (J-curve) generally disposed in a first plane (sagittal plane) and ML curve generally disposed in a second and third plane (frontal plane and transverse planes); each articular surfaces of the medial and lateral elevations may have an offset and a depth to the trochlea in the second and third plane, which can be equivalent or not; [0546] the articular surface orientation of the trochlea portion to the distal and posterior condylar portions of the distal and posterior condyles are not dependent and can be parallel or obliquely oriented (convergent or divergent) in at least one of the planes; [0547] an ML condylar offset can be integrated between the medial and lateral articular surfaces of the distal (= distal condylar offset) and posterior (= posterior condylar offset) condylar portions of the distal and posterior condyles, this condylar offset being equivalent or different between distal and posterior condylar portions; and [0548] an ML trochlear offset can be integrated between the medial and lateral articular surfaces of the medial and lateral trochlear elevation, this trochlear offset being equivalent or different than the condylar offset of the distal and posterior condyles. [0549] 54. The prosthesis of the above feature set, wherein the sagittal J-curve of at least one of the joint-surface from the distal and posterior condyles (medial, lateral) or the trochlea (elevation, trochlea depth) is defined by a single, double or multi-radius or is fitting with a patient-specific J-curve. [0550] 55. The prosthesis of one of the above two feature sets, wherein the sagittal J-curve of at least one of the medial and lateral joint-surfaces from the distal and posterior condyles is positioned at a fixed or variable distance to the trochlea J-curves (medial and / or lateral elevation, trochlea depth), symmetrically or asymmetrically. [0551] 56. The prosthesis of one of feature sets 51 or 52, wherein the sagittal J-curve of at least one of the joint-surface from the distal and posterior condyles (medial, lateral = narrowing angle) or the trochlea (medial and / or lateral elevation, trochlea depth = sulcus axis in frontal plane, Whiteside line in the axial plane) is parallel or obliquely oriented in at least one of the planes, mainly the frontal and the axial planes. [0552] 57. The prosthesis of feature sets 51 to 54, wherein at least one of the joint facing-surface of the condylar portion and / or of the trochlea portion has an articular geometry and dimensions corresponding (or close matching, or close fitting) to the patient’s knee articular surface, in terms of sizing (comprising at least AP sizing), shape (comprising at least condylar and trochlear offset, J-curves and ML curves) and contour (comprising at least AP/ML, sizing, narrowing angle, trochlear height, posterior condyles height). [0553] 58. The prosthesis of feature sets 51 to 55, wherein the tangent linking the medial and lateral most distal points of the bone-facing surfaces of the distal or the tangent linking the medial and lateral most posterior points of the bone-facing surfaces of the posterior condyles or the tangent linking the medial and lateral most anterior points of the bone-facing surfaces of trochlea portion are parallel or oblique between themselves. [0554] 59. The prosthesis of any of the above prosthesis feature sets, wherein the bone-facing surfaces are defined with a single straight flat or oblique surface or with two staggered (offset) flat or oblique surfaces or with a staggered (offset) curved surface. [0555] 60. The prosthesis of any of the above prosthesis feature sets, wherein the bone-facing surfaces can be fixed to the bone with a cemented or cementless fixation. [0556] 61. The prosthesis of any of the above prosthesis feature sets, wherein the prosthesis corresponds to different systems (PS: Postero-Stabilized, UC: Ultra-Congruent, PCR: Posterior Cruciate Retaining, BCR: Bi-Cruciate Retaining), for mobile insert or fixed insert, for primary or revision knee (semi-constrained or constrained, hinged), for cemented or cementless or any other type of fixation, for monobloc or modular components, for every material (Ti, CrCo, Ceramic, ...) [0557] 62. A method of manufacturing a knee prosthesis from a 3D model selected after applying a method, the method including: [0558] (a) analysis of a patient’s current and pre-pathological knee motion behavior as well as the patient’s 3D HKA alignment, [0559] (b) optionally using a planning algorithm, selection of a suitable 3D model from a comprehensive database of 3D models of varying knee morphologies, each 3D model being adapted to a known morphology as well as production limitations and requirements, [0560] (c) manufacturing of the selected 3D model which represents a producible and essentially custom knee prosthesis adapted to the individual patient’s 3D constitutional anatomy, thus making it possible to re-create the knee articulation as it was naturally. [0561] 63. A nontransient information storage medium having a knee prosthesis characterization and selection program that instructs a processor to implement one of any of the above methods so as to accept inputs and produce outputs. [0562] 64. A nontransient information storage medium having a knee prosthesis characterization and selection program encoded thereon that, when executed, implements a method which instructs a processor execute steps which aid a user in selecting a 3D knee prosthesis model for a particular patient, the method consisting of the steps of: [0563] (a) parameterizing a knee prosthesis according to well-defined and independent knee joint compartments, [0564] (b) generating a large number knee shapes in the form of 3D knee prosthesis models which reproduce the 3D shape asymmetries of a large number of individual knee samples including models that replicate the knee motion of essentially any patient by generating shapes which vary the shape parameters (surface and dimension) of at least one of the compartments and storing these 3D knee prosthesis models in association with each model’s shape parameters and asymmetries in a database allowing comparing of the asymmetries of the patient’s knee with those of the 3D knee prosthesis model, and [0565] (c) after studying the patient’s pathology and developing pre-pathological knee prosthesis criteria matching the patient’s needs, optionally using a planning algorithm, searching the database comparing the large number of knee shapes based on a best match of the asymmetries of each model to identify candidate matches: [0566] (d) providing a display of candidate matches and their attributes on an output device; [0567] (e) providing a means of selecting a best match among suitable candidate matches identified; [0568] (f) optionally generating a production order if the selected knee prosthesis is not in inventory. [0569] 65. The medium of the above feature set, wherein the processor is a computer processor connected to memory, wherein the processor responds to the program to access a database adapted to store 3D knee prosthesis models or inventoried knee prostheses. [0570] 66. The medium of the above feature set, wherein the processor responds to inputs and outputs communicated by the program to and from a user.
[0571] Additional features and functionality of the invention are described in the claims appended hereto and/or in the abstract. Such claims and/or abstract are hereby incorporated in their entirety by reference thereto in this specification and should be considered as part of the application as filed.
[0572] Multiple variations and modifications are possible in the embodiments of the invention described here. Although certain illustrative embodiments of the invention have been shown and described here, a wide range of changes, modifications, and substitutions is contemplated in the foregoing disclosure. While the above description contains many specific details, these should not be construed as limitations on the scope of the invention, but rather exemplify one or another preferred embodiment thereof. In some instances, some features of the present invention may be employed without a corresponding use of the other features. Accordingly, it is appropriate that the foregoing description be construed broadly and understood as being illustrative only, the spirit and scope of the invention being limited only by the claims which ultimately issue in this application.
Appendix
Definitions
[0573] Definitions of Knee anatomical points [0574] Definitions of Knee center [0575] Definitions of the Average Knee Flexion Axis [0576] Definitions of Knee Alignment [0577] Coronal or frontal Plane [0578] Axial or Transverse Plane
Observations
[0579] Comparison with Standard (Off-the-shelf) knee prostheses and limits of this system Description of Knee prosthesis
Description of the Invention
[0580] Difference between STD (Off-The Shelf) prosthesis and our Personalized knee prosthesis:
[0581] Definitions of Knee anatomical points: [0582] FHC (332): Femoral Head Center [0583] KC (330): Knee Center [0584] TC (334): Talus Center (not represented) [0585] ME (342): Medial Epicondyle [0586] LE (344): Lateral Epicondyle [0587] MDC (352): Medial Distal Condyle [0588] LDC (354): Lateral Distal Condyle [0589] MPC (362): Medial Posterior Condyle [0590] LPC (364): Lateral Posterior Condyle [0591] TGH (372): Trochlea Groove High [0592] TGL (374): Trochlea Groove Low [0593] LT (384): Lateral Elevation of the Trochlea [0594] MT (382): Medial Elevation of the Trochlea
[0595] Definitions of Knee center: [0596] KC (330): Top of the intercondylar notch [0597] TSE (3_): Top of the tibia eminencia (not represented) [0598] MTEA (3_): Middle of the TEA (346)
[0599] Definitions of the Average Knee Flexion Axis: [0600] TEAs (3464): Surgical Transepicondylar Axis (top of LE (344) to sulcus of ME (342)) [0601] TEAc (3462): Clinical Transepicondylar Axis (top of LE (344) to top of ME (342)) [0602] CA: Cylinder axis (Links the center of the two spheres of the posterior condyles) [0603] EFA: Extension Facet Axis (links the center of distal radius of the two condyles) [0604] FFA: Flexion Facet Axis (links the center of posterior radius of the two condyles) [0605] FHA: Femoral Helical Axis (combines flexion axis with axial rotation) [0606] With the mechanism of 4-bar linkages, the average knee flexion axis could also be at the intersection of the two cruciate ligaments in the sagittal plane, or at the intersection of both the cruciate and collateral ligaments. [0607] With Kinematics alignment, BCD and BCP are the instantaneous knee flexion axes.
[0608] Definitions of Knee Alignment: [0609] HKA: Mechanical Axis of the Limb [0610] (=load bearing axis) [0611] Links two lines, the first between FHC to KC with the line between KC and TC [0612] If the angle between the two line is 0 (HKA 180°), the alignment is neutral [0613] If the angle between the two line is > 0 (HKA > 180°), the alignment is valgus [0614] If the angle between the two line is < 0 (HKA < 180°), the alignment is varus
[0615] Coronal or frontal Plane: [0616] FAA (326): Femoral Anatomical Axis (links KC (330) to middle of diaphysis) [0617] FMA (336): Femoral Mechanical Axis (links FHC (332) to KC (330)) [0618] HKS (338): Angle between FAA (326) & FMA (336) [0619] Range is between 1° to 10° [0620] BCD (356): Bicondyle Distal Tangent (links LDC (354) to MDC (352)) [0621] Alpha (α, 358): Angle between FMA (336) and BCD (356) [0622] Also called FMA: femoral Mechanical Angle (although to an unskilled reader, there may be a risk of confusion between FMA= Femoral Mechanical Axis (336) and FMA=Femoral Mechanical Angle, a person of ordinary skill will know the difference from its context). [0623] Also called midface: mechanical Medial Distal Femoral Angle [0624] Can be orthogonal or not to FMA (336) [0625] Range is between 82° to 105° [0626] TEA (346): Transepicondylar Axis or Biepicondylar Axis [0627] Links ME (342) to LE (344) [0628] TEAs (3464): Surgical Transepicondylar Axis [0629] TEAc (3462): Clinical Transepicondylar Axis [0630] = Insertions of the two collateral ligaments [0631] Can be parallel or not to BCD (356) [0632] Can be orthogonal or not to FMA (336) [0633] DCA (358): Distal Condylar Angle [0634] Angle between TEA (346) and BCD (356) [0635] Range is between -5° to 10° [0636] SA (376): Sulcus Axis (links KC (330) to TGH (372)) [0637] SA can be between FMA (336) and FAA (326) or outside the range [0638] Can be orthogonal or not to TEA (346) and / or to BCD (356)
[0639] Axial or Transverse Plane: [0640] TL (386): Trochlear Line, links LT (382) to MT (384) [0641] TEA (346): Transepicondylar Axis or Biepicondylar Axis, links ME (342) to LE (344) [0642] BCP (366): Bicondyle Posterior Tangent (links LPC (364) to MPC (362)) [0643] PCA (368): Posterior Condylar Angle [0644] Angle between TEA (346) and BCP (366) [0645] Range is between -5° to 10° [0646] WL (377): Whiteside Line, links KC (330) to TGL (374) [0647] WL can be orthogonal or not to TEA and / or to BCP [0648] ATA (388): Anterior Trochlear Axis [0649] Angle between TEA (346) and TL (386) [0650] Range is between -5° to 10°