CN118490423A - Medial and lateral femoral unicompartmental prostheses and femoral trochlear prostheses - Google Patents

Abstract

A medial femoral unicondylar prosthesis (201) and lateral femoral unicondylar prosthesis (301) and trochlear femoral prosthesis (401) are disclosed. The medial femoral unicondylar prosthesis comprises: a articular surface, which is the surface that contacts the medial patella and the medial tibial plateau during knee joint movement, that appears as an arc (203) on a first ellipse (38) in the sagittal position and as an arc (95) on a first circle (94) in the coronal position; and an inner surface, which is a portion adjacent to the bone-cutting surface and bone cement of the femoral condyle after the prosthesis is inserted, and which is a portion of the inner surface that is a portion of the posterior condyle in a straight-line section (202), and a distal portion of the inner surface (209) that is coincident with the articular surface arc section (203). The prosthesis utilizing the embodiment of the disclosure can be closer to the geometrical form of the femoral condyle of a normal human body, and design parameter values of various types of femoral prostheses are simplified.

Description

Medial and lateral femoral unicompartmental prostheses and femoral trochlear prostheses

This application is a divisional application of the Chinese invention patent application "Medial and lateral unicondylar femoral prosthesis and femoral trochlear prosthesis" with an application date of March 31, 2016 and application number 201610196679.5.

Technical Field

The present invention relates to an artificial knee joint prosthesis, in particular to a single compartment replacement prosthesis for early-stage knee joint medial compartment, lateral compartment and patellofemoral joint osteoarthritis.

Background Art

The knee joint is divided into three compartments, namely the medial compartment, lateral compartment and patellofemoral compartment. Early knee osteoarthritis (OA) can affect any compartment, but the medial compartment is the most common. At this time, the force line of the knee joint shifts medially (varus deformity), resulting in excessive wear of the medial compartment, causing thinning and exfoliation of the medial femoral condyle and the corresponding medial tibial plateau cartilage surface. The typical symptoms of medial compartment OA are varus deformity, pain with joint chords, osteophyte formation and collateral ligament laxity. Conservative treatment or non-surgical treatment measures (such as non-steroidal anti-inflammatory analgesics, articular cartilage nutrition and protection drugs, intra-articular injection of hyaluronic acid, knee braces, etc.) are only effective for patients with mild OA. When conservative treatment is ineffective, medial compartment unicompartmental knee arthroplasty (UKA) is the ultimate treatment. Medial compartment UKA of the knee refers to the surgical removal of the medial tibiofemoral articular surface of the knee joint, that is, the part of the articular cartilage surface that directly contacts the medial tibial plateau during flexion and extension of the medial femur distal end, as well as the corresponding articular cartilage surface of the tibial plateau. The purpose of the operation is to preserve the normal joint structure as much as possible with minimal surgical trauma, ultimately achieving better functional recovery, while retaining sufficient residual bone volume and room for operation for possible total knee replacement in the future. Moreover, with the improvement of implant materials and processing technology, more appropriate selection of case indications, and improvement of surgical skills, the efficacy of medial compartment UKA has been increasingly recognized. The incidence of OA in the lateral compartment and patellofemoral compartment is significantly lower than that in the medial compartment, but the treatment principles are the same as those for medial compartment OA, and UKA prosthesis replacement is also required when necessary.

The UKA prosthesis of the medial and lateral compartment can be divided into the UKA prosthesis on the tibial side (the UKA prosthesis of the medial and lateral tibial plateau) and the UKA prosthesis on the femoral side (the UKA prosthesis of the medial and lateral femoral condyle); the UKA prosthesis of the patellofemoral compartment is divided into the UKA prosthesis of the trochlea (part) and the patellar prosthesis. Compared with the UKA prosthesis on the tibial side, the design of the UKA prosthesis on the femoral side is more important because it directly affects the postoperative knee joint function. At present, it is generally believed at home and abroad that the UKA prosthesis on the femoral side that is closest to the geometric characteristics of the medial and lateral femoral condyles of the normal human body can provide the closest movement feeling to the normal knee joint. However, the geometric characteristics of the medial and lateral femoral condyles are extremely complex and have not been unanimously recognized. People initially believed that the medial and lateral femoral condyles of the femur were circular and rotated around a fixed axis1. Later, some scholars believed that the medial and lateral femoral condyles of the femur were spiral, and the rotation axis was not fixed, but there was an instantaneous rotation center2. In the 1990s, scholars once again supported the view that the medial and lateral condyles of the femur are circular and have a fixed axis of rotation3-5. In particular, the application of sagittal magnetic resonance imaging has made these researchers more convinced that the medial and lateral condyles of the femur are composed of two circles in the sagittal plane6-9. These different theories have led to different biomechanical and kinematic experimental results, and have directly affected the design of UKA prostheses for the medial and lateral condyles of the femur. For example, the Oxford unicompartmental prosthesis was designed based on the theory that the femoral condyle is a single curvature circle; the Miler-Galante prosthesis was designed based on the theory that the femoral condyle is composed of two or more circles, and so on. However, the current UKA prostheses for the medial and lateral condyles of the femur all have more or less shortcomings. For example, the Oxford Unicompartmental prosthesis (Oxford UKA): Although the long-term follow-up results are good, the shape of the prosthesis does not match the femoral condyle, resulting in a deep groove worn away between the prosthesis and the femoral condyle; and due to its single curvature circular design, the Oxford Unicompartmental prosthesis cannot restore the patient's lower limb force line that has already been varus deformed. The shapes of other types of UKA prostheses are mostly mismatched with the medial and lateral condyles of the femur during surgery, which leads to collision between the patella and the prosthesis during knee flexion, which can easily cause pain and surgical failure. The geometry of the femoral trochlea is the basis for manufacturing the femoral trochlea UKA prosthesis, but the geometric characteristics of the femoral trochlea are more complex and difficult to explain, so people simplify the design of the trochlea UKA prosthesis to have a valgus groove and correspondingly replace the patellar surface with a convex shape.

The femoral medial and lateral condyle UKA prostheses and femoral trochlea UKA prostheses produced by the prior art do not have a good morphological match with the femoral medial and lateral condyles and femoral trochlea. This morphological mismatch leads to collision between the patella and the prosthesis during knee flexion, causing knee flexion pain, prosthesis loosening, and ultimately surgical failure. Even though the Oxford unicompartmental prosthesis has a slightly lower chance of collision, it is designed based on the circular design of the medial condyle of the femur with a single curvature. The result of this is that a deeper groove exists between the front of the UKA prosthesis and the remaining bone of the medial condyle of the femur. Although there is no clinical evidence that this groove has an impact on the kinematics of the knee joint or the service life of the prosthesis, in fact, this groove is located at the farthest end of the femur, and its height cannot be restored, resulting in the inability to correct the varus deformity of the knee joint. If the prosthesis must be placed higher to correct the varus deformity, this will lead to collision between the patella and the prosthesis during flexion. The method of not releasing the medial collateral ligament in the Oxford unicompartmental surgery technique is also intended to prevent dislocation of the sliding gasket.

Summary of the invention

In view of one or more problems in the prior art, a unicompartmental knee prosthesis and a pulley prosthesis are proposed.

According to one aspect of the present disclosure, a medial femoral unicompartmental prosthesis is proposed, comprising: an articular surface, which is the surface in contact with the medial side of the patella and the medial side of the tibial plateau during knee joint movement, and which appears as an arc segment on a first ellipse in the sagittal plane and as an arc segment on a first circle in the coronal plane; and a medial side surface, which is the portion adjacent to the osteotomy surface and bone cement of the femoral condyle after the prosthesis is implanted, and which appears as a posterior condyle of the medial side surface in a straight cross-section, and a distal portion of the medial side surface consistent with the arc segment of the articular surface.

According to some embodiments, the medial femoral unicompartmental prosthesis further includes: a first column, disposed on the inner side surface, corresponding to the center of the first ellipse; and a second column, disposed on the inner side surface, corresponding to the focus of the first ellipse.

According to some embodiments, a locking screw hole is formed at the front end of the medial femoral unicompartmental prosthesis, and the locking screw hole is formed so that the direction of the locking screw inserted therein is different from the directions of the first column and the second column.

According to some embodiments, the major axis of the first ellipse is perpendicular to the femoral mechanical axis and its center corresponds to the medial collateral ligament attachment point of the medial femoral condyle.

According to some embodiments, the corresponding first ellipses on each level in the sagittal plane are gathered in three-dimensional space, and they constitute the shape of a complete medial femoral unicompartmental prosthesis. Their centers coincide in the sagittal plane, and the major and minor axis directions are consistent. The line connecting all the centers coincides with the transcondylar line (TEA) and is perpendicular to the Whiteside line.

According to some embodiments, in the axial perspective, the prosthesis is placed in a direction parallel to the Whiteside line and perpendicular to the transepicondylar line (TEA), and the outside of the prosthesis has a straight edge parallel to the Whiteside line and perpendicular to the TEA, while the medial arc edge is arc-shaped to adapt to the distal shape of the medial femoral condyle, the curvature of the front arc edge corresponds to the parameters of the mold circle, and the bottom is the curvature of the first circle in the coronal position.

According to some embodiments, the angle range of the arc segment on the first ellipse is 150 degrees to 200 degrees, and the angle range of the arc segment on the first circle is 50 degrees to 90 degrees.

According to another aspect of the present disclosure, a lateral femoral unicompartmental prosthesis is proposed, comprising: an articular surface, which is the surface that contacts the lateral side of the patella and the lateral side of the tibial plateau during the movement of the knee joint, and which appears as an arc segment on the second ellipse in the sagittal plane and as an arc segment on the third ellipse in the coronal plane; and a medial surface, which is the part adjacent to the osteotomy surface and bone cement of the femoral condyle after the prosthesis is implanted, and appears as the posterior condyle of the medial surface in a straight cross-section, and the distal end of the medial surface consistent with the arc segment of the articular surface.

According to some embodiments, the lateral femoral unicompartmental prosthesis further includes: a third column, disposed on the inner side surface, corresponding to the focus of the second ellipse.

According to some embodiments, a locking screw hole is formed at the distal end of the lateral femoral unicompartmental prosthesis, and the locking screw hole is formed so that the direction of the locking screw inserted therein is different from the direction of the third column.

According to some embodiments, the corresponding second ellipses (78) at each level in the sagittal plane are assembled in three-dimensional space, and they constitute the shape of a complete lateral femoral unicompartmental prosthesis. Their centers coincide with each other in the sagittal plane, and the major and minor axes are in the same direction. The line connecting all the centers coincides with the transcondylar line (TEA) and is perpendicular to the Whiteside line.

According to some embodiments, in the axial perspective, the prosthesis is placed in a direction parallel to the Whiteside line and perpendicular to the transepicondylar line (TEA), and the inner side of the prosthesis has a straight edge parallel to the Whiteside line and perpendicular to the TEA, while the outer arc edge is arc-shaped to adapt to the distal shape of the lateral femoral condyle, the curvature of the front arc edge corresponds to the curvature parameter of the circle, and the bottom is the curvature of the arc segment of the third ellipse in the coronal position.

According to some embodiments, the angle range of the arc segment on the second ellipse is 120 degrees to 160 degrees, and the angle range of the arc segment on the third ellipse is 50 degrees to 90 degrees.

According to another aspect of the present disclosure, a femoral trochlear prosthesis is proposed, comprising: an articular surface, which is the surface in contact with the patellar articular surface during knee joint movement, and which appears in the sagittal plane as a spatial collection of an arc segment on a fourth ellipse or circle and an arc segment on a fifth ellipse or circle; and an inner side surface, which is the portion adjacent to the osteotomy surface and bone cement of the femoral trochlear part after the prosthesis is implanted, and appears as an inner side surface consistent with the morphology of the femoral trochlear articular surface.

According to some embodiments, the fourth ellipse or circle and the fifth ellipse or circle are arranged concentrically, with the concentric axes spatially parallel to the TEA and perpendicular to the Whiteside line.

According to some embodiments, the femoral trochlear prosthesis has a column at the center and four locking screw holes around it for accommodating locking screws.

The prosthesis according to the above embodiment of the present disclosure can be closer to the geometric shape of the normal human femoral condyle and simplify the design parameter values of various models of femoral prostheses.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the drawings required for use in the embodiments or the prior art description are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

FIG1A is a sagittal cross-sectional view of the medial condyle of the knee joint of a prosthesis according to an embodiment of the present disclosure, illustrating the elliptical principle and characteristics of the medial condyle of the femur;

1B is a sagittal cross-sectional view of the medial trochlea of the knee joint of the prosthesis according to an embodiment of the present disclosure, illustrating the principle and characteristics of the ellipse of the medial femoral trochlea and its relationship with the ellipse of the medial femoral condyle;

FIG2 is a sagittal cross-sectional view of the most concave part of the femoral trochlea of the knee joint of the prosthesis according to an embodiment of the present disclosure, illustrating the circular feature of the part;

3 is a sagittal cross-sectional view of the lateral femoral condyle and femoral trochlea of the knee joint prosthesis according to an embodiment of the present disclosure, illustrating the principle and characteristics of the elliptical lateral femoral condyle and its relationship with the circular shape of the femoral trochlea;

4 is a schematic diagram of overlapping elliptical and circular structures of the femoral condyle of the prosthesis in the sagittal plane of the knee joint according to an embodiment of the present disclosure, illustrating that the femoral condyle is composed of an ellipse and a circle and its characteristics;

FIG5 is a coronal view of a knee joint of a prosthesis according to an embodiment of the present disclosure, illustrating that the medial and lateral condyles of the femur are composed of a circle and an ellipse and their characteristics;

FIG6 shows a sagittal view of a medial femoral condyle UKA prosthesis according to an embodiment of the present disclosure;

FIG7 shows a coronal view of a medial femoral condyle UKA prosthesis according to an embodiment of the present disclosure;

FIG8 shows an axial view of a medial femoral condyle UKA prosthesis according to an embodiment of the present disclosure;

9 is a perspective view of a UKA prosthesis of the medial femoral condyle depicting an embodiment of the present disclosure;

10A is a schematic diagram describing the operation of implanting a UKA prosthesis of the medial femoral condyle and the use of corresponding instruments according to an embodiment of the present disclosure;

10B is a schematic diagram describing the operation of implanting the medial femoral condyle UKA prosthesis and the use of corresponding instruments according to an embodiment of the present disclosure;

FIG11 is a sagittal view of a lateral femoral condyle UKA prosthesis according to an embodiment of the present disclosure;

12 is a coronal view of a UKA prosthesis of the lateral femoral condyle according to an embodiment of the present disclosure;

13 is a perspective view illustrating a lateral femoral condyle UKA prosthesis according to an embodiment of the present disclosure;

FIG. 14 is a perspective view illustrating the construction principle of a femoral trochlea UKA prosthesis according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

The specific embodiments of the present disclosure will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present disclosure. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it is obvious to those of ordinary skill in the art that these specific details do not have to be adopted to implement the present disclosure. In other examples, in order to avoid confusing the present disclosure, known materials or methods are not specifically described.

The UKA prosthesis according to the embodiment of the present disclosure (including the medial femoral condyle, the lateral femoral condyle and the femoral trochlear articular surface) has an outer shape that is closest to the geometric features of the femoral condyle and trochlear portion of a normal human body. The following one or more embodiments detail the elliptical principle and the design method applied to UKA. One or more embodiments will be presented in the form of diagrams. However, these diagrams and descriptions do not limit the innovative content that the present disclosure application intends to protect. Each diagram and description will be associated with other diagrams.

According to one or more embodiments, the UKA prosthesis element provided by the present disclosure includes: a medial femoral condyle, a lateral femoral condyle and a femoral trochlea replacement component. They can be used alone in specific cases of unicompartmental osteoarthritis, or in combination in cases of osteoarthritis of two or three compartments. Specifically, the medial femoral condyle UKA prosthesis element refers to the part that is articulated with the medial tibial compartment during knee joint movement; the lateral femoral condyle UKA prosthesis element refers to the part that is articulated with the lateral tibial compartment during knee joint movement; and the femoral trochlea UKA prosthesis element refers to the part corresponding to the patella during knee joint movement. Any UKA prosthesis element includes a prosthesis articular surface and a prosthesis inner surface. It should be noted that the "front" used here refers to the ventral side of the human body; "back" refers to the dorsal side of the human body; "inside" refers to the middle axis of the human body trunk; "outside" refers to the part away from the middle axis of the human body trunk; "near" refers to the head side of the human body; "far" refers to the tail side of the human body, and so on. Similarly, the descriptions of "sagittal", "coronal" and "axial" are the same as the definitions of anatomical planes. The "horizontal axis" points in the "anterior" and "posterior" directions and is parallel to the ground; the "vertical axis" points in the "distal" and "proximal" directions and is perpendicular to the ground. Generally speaking, the "most distal point" of a UKA prosthetic component refers to the farthest contact point with the corresponding tibial support component when the knee joint is fully extended; the "most posterior point" of a UKA prosthetic component refers to the point of maximum posterior eccentricity of the UKA prosthesis perpendicular to the "most distal point". The "anterior most point" of a UKA prosthetic component refers to the point of maximum anterior eccentricity of the UKA prosthesis opposite to the "most posterior point".

The embodiment described in the present disclosure is shown as a left-side femoral UKA prosthesis component. The right-side femoral UKA prosthesis component and the left-side femoral UKA prosthesis component are sagittal mirror images. Therefore, we declare that the characteristic principles of the femoral UKA prosthesis described here are equally applicable to left or right knee configurations. It should be noted that the femoral trochlear UKA prosthesis design disclosed in the present disclosure includes prostheses for both "patellar articular surface replacement" and "patellar articular surface non-replacement". Among them, the femoral trochlear UKA prosthesis of "patellar articular surface replacement" is designed with a trochlear groove and angle corresponding to the patella relative to the "patellar articular surface non-replacement" prosthesis.

According to one or more embodiments of the present disclosure, in the sagittal plane, the outer shape of the medial and lateral condyle articular surfaces of the femur is composed of an ellipse, and the outer shape of the medial and lateral trochlear articular surfaces is composed of an ellipse and/or a circle; in the coronal plane, the outer shape of the medial and lateral condyle articular surfaces of the femur is composed of an ellipse and a circle.

For example, the UKA prosthesis of the medial femoral condyle is designed and constructed based on the principle of sagittal ellipse and coronal circle. In the sagittal plane, each layer of the articular surface of the medial femoral condyle is a collection of ellipses, which form the complete shape of the medial femoral condyle in three-dimensional space. The direction of the articular cartilage surface of the medial femoral condyle is a concentric elliptical structure perpendicular to the transcondylar line (TEA) and parallel to the Whiteside line. In the coronal plane, the articular surface of the medial femoral condyle appears as an arc of a circle.

For another example, the UKA prosthesis of the lateral femoral condyle is designed and constructed based on the principles of sagittal ellipse and coronal ellipse. In the sagittal plane, each layer of the articular surface of the lateral femoral condyle is a collection of ellipses, which form a complete shape of the lateral femoral condyle in three-dimensional space. The ellipse of the lateral femoral condyle is slightly smaller than the ellipse of the medial femoral condyle, and its long axis direction is clockwise rotated at a certain angle with reference to the ellipse of the medial femoral condyle. The direction of the articular cartilage surface of the lateral femoral condyle is a concentric elliptical structure perpendicular to the transcondylar line (TEA) and parallel to the Whiteside line. In the coronal plane, the articular surface of the lateral femoral condyle appears as an arc of an ellipse.

According to the embodiments of the present disclosure, the femoral prosthesis trochlea UKA prosthesis is designed and constructed based on the principles of ellipse and circle. In the sagittal plane, all layers of the femoral trochlea can be expressed in ellipse or circle. They constitute a complete femoral trochlea structure in three-dimensional space. The sagittal plane of the medial femoral trochlea articular cartilage surface is a collection of ellipses, and the major and minor axes of these ellipses are in the same direction, and the center of each ellipse is arranged in concentric circles. However, the eccentricity of each ellipse is different. The sizes of these ellipses are arranged in the Fibonacci sequence, for example. All layers of the lateral femoral trochlea are expressed in circles. Although the radius of each lateral trochlea circle is different, the projections of their centers of circle coincide. This straight line connecting the femoral trochlea ellipse and the center of the circle is perpendicular to the transcondylar line (TEA) and parallel to the Whiteside line. The parameters of the medial femoral condyle ellipse and the circle of the most concave layer of the femoral trochlea determine the shape and major and minor diameter parameters of the entire prosthesis.

For example, the best or most correct position mode of the sagittal scanning of the knee joint by nuclear magnetic resonance (MRI) is: when the scanned knee joint is in the straight position of 0 degrees, the axial positioning phase of the knee joint is set to the direction along the line connecting the highest points of the medial and lateral femoral condyles, and the coronal positioning phase of the knee joint is set to the direction along the tangent tibial plateau articular surface. The geometric characteristics of the medial femoral condyle can be represented by an ellipse, which belongs to an arc on this ellipse. In one embodiment, we select the sagittal plane where the maximum value of the eccentricity (offset) of the rearmost point of the medial femoral condyle is located, that is, the middle plane of the medial femoral condyle, and the relationship between the medial femoral condyle and the ellipse is shown in Figure 1A. Starting from the anterior notch recess 34 formed on the articular cartilage surface 36 of the medial femoral condyle 42 when the anterior horn 33 of the medial meniscus is straightened, to the posterior notch recess 35 formed on the medial femoral condyle 42 when the posterior horn 43 of the medial meniscus is in the high flexion position, the articular cartilage surface 36 of the medial femoral condyle 42 of this section completely overlaps with an ellipse 38. The major axis of the ellipse 38 is perpendicular to the mechanical axis of the femur, and the center 39 thereof corresponds to the attachment point 123 of the medial collateral ligament of the medial condyle of the femur on the MRI axial scan. In one embodiment, the semi-major axis of the ellipse 38 is 31 mm, the semi-minor axis is 25 mm, and the eccentricity is 0.591. In another embodiment, the semi-major axis of the ellipse is 27 mm, the semi-minor axis is 22 mm, and the eccentricity is 0.58. In multiple embodiments, the semi-major axis is between 20 mm and 35 mm, the semi-minor axis is between 16 mm and 30 mm, and the eccentricity is between 0.5 and 0.7. At the same time, by measuring the angle α between the center 39 of the ellipse and the line connecting the anterior and posterior notches 34 and 35; the angle β between the center 39 of the ellipse and the line connecting the posterior notch 35 and the major axis of the ellipse 38, the shape and length of this section of the articular cartilage surface 36 can be accurately described. In one example, the angle α is 180 degrees, and the angle β is 35 degrees. In another embodiment, the angle α is 190 degrees, and the angle β is 40 degrees. In multiple embodiments, the angle α is between 170 degrees and 195 degrees, and the angle β is between 20 degrees and 45 degrees. In most cases, there is no medial femoral trochlear articular surface in front of the middle level of the medial femoral condyle, that is, the ellipse 38 at the middle level of the medial femoral condyle does not correspond to the level of the maximum value of the eccentricity (offset) of the most anterior point of the medial femoral trochlear, and the ellipses of these two levels are not consistent. Therefore, we project this medial femoral condyle ellipse 38 along the MRI sagittal scanning direction to the level of the maximum value of the eccentricity (offset) of the most anterior point of the medial femoral trochlear, as shown in Figure 1B. Starting from the anterior notch recess 46 formed on the articular cartilage surface 36 of the medial femoral condyle 42 when the anterior angle 45 of the medial meniscus is in the straight position at this level, it ends forward and upward to the medial femoral trochlear articular cartilage surface 37 at this level. This section of the trochlear articular cartilage surface 37 can be represented by an arc of an ellipse 40. Although this section of the articular surface of some subjects appears circular, it appears elliptical in most subjects. The major axis of the ellipse 40 of the medial femoral trochlea articular cartilage surface is perpendicular to the major axis of the ellipse 38 of the middle plane of the medial femoral condyle. This ellipse 40 is made based on the circle 70 on the most concave plane of the femoral trochlea (Figure 2), so the center 41 of this ellipse 40 and the center 41 of the circle 70 on the most concave plane of the femoral trochlea (Figure 2) completely overlap in the projection of the sagittal scan. In one embodiment, the semi-major axis of this ellipse 40 is 29mm, the semi-minor axis is 27mm, and the eccentricity is 0.365. In multiple embodiments, the semi-major axis of this ellipse 40 is between 20mm and 35mm, and the semi-minor axis is between 20mm and 30mm. Generally speaking, the difference between the semi-major axis and the semi-minor axis of this ellipse 40 is not large, for example 1mm, 2mm, or 3mm. At the same time, by measuring the angle γ between the center 41 and the line connecting the anterior notch 46 and the end point of the trochlear cartilage surface, and the angle γ' between the line connecting the center 41 to the end point of the trochlear cartilage surface and the semi-minor axis of the ellipse 40, the arc 37 of this section of the trochlear articular cartilage surface can be accurately described. In many embodiments, the angle γ is between 40 degrees and 80 degrees, and the angle γ' is between -5 degrees and 40 degrees.

According to some embodiments, the positional relationship between the center 39 of the medial femoral condyle ellipse 38 and the center 41 of the medial femoral trochlear ellipse 40 determines the spatial positional relationship between the entire femoral condyle and the femoral trochlear portion, and determines the parameter value of the outer diameter and inner diameter of the femoral prosthesis. The relationship between the medial femoral condyle ellipse 38 and the medial femoral trochlear ellipse 40 can be expressed by a rectangle 50 formed by the intersection of the major and minor axes of the medial femoral condyle ellipse 38 and the medial femoral trochlear ellipse 40. In one embodiment, the length 107 of the rectangle 50 is 13 mm and the width 109 is 9 mm. In another embodiment, the length 107 of the rectangle 50 is 12 mm and the width 109 is 7 mm. In multiple embodiments, the length 107 of the rectangle 50 is between 8 mm and 16 mm, and the width 109 is between 4 mm and 12 mm. The angle between the line connecting the centers 39, 41 of the two ellipses 38, 40 and the major axis of the medial femoral condyle ellipse 38 is θ. In one embodiment, θ is 32 degrees. In another embodiment, θ is 35 degrees. In various embodiments, the angle θ ranges from 25 degrees to 35 degrees.

The most concave plane 62 of the femoral trochlea is the plane where the Whiteside line is clinically located, as shown in Figure 2. This plane 62 is an important basis for determining the geometric morphology of the femoral medial and lateral trochlea articular surfaces. There is only one circle 70 that can best overlap with the articular cartilage surface 64 of this trochlea plane 62, and at the same time, can still best overlap with the subchondral bone surface 65 of this plane 62 after being proportionally reduced. The center 41 of this circle 70 completely overlaps with the center of the medial femoral trochlea ellipse 40 and the center of the lateral femoral trochlea circle 80 in the MRI sagittal scan projection, so both are represented by the center 41. The clinical Blumensaat line 63 is included in this circle 70. Similar to the previous description, the trochlea articular cartilage surface 64 of this plane 62 is an arc of the circle 70, and can be represented by the radius and angle of the circle 70. The angle between the center of the circle 41 and the line connecting the anterior and posterior boundaries of the trochlear articular cartilage surface 64 is ψ; the angle between the line connecting the center of the circle 41 and the anterior boundary of the articular cartilage surface 64 and the horizontal axis is ε. In one embodiment, the radius of this circle 70 is 24 mm, ψ is 100 degrees, and ε is 0 degrees. In another embodiment, the radius of this circle 70 is 25 mm, ψ is 105 degrees, and ε is 5 degrees. In multiple embodiments, the radius of this circle 70 is 16 mm to 30 mm, ψ ranges from 90 degrees to 125 degrees, and ε ranges from -20 degrees to 10 degrees. And the radius of this circle 70 is in a specific ratio to the semi-major axis length of the medial femoral condyle ellipse 38, such as 2/5, 3/5 or 3/4.

According to the embodiment of the present disclosure, the geometric shape of the lateral condyle of the femur can be represented by an ellipse, which is an arc of this ellipse. In one embodiment, we select the sagittal plane where the maximum value of the eccentricity (offset) of the rearmost point of the lateral condyle of the femur is located, that is, the middle plane of the lateral condyle of the femur. This plane is also the plane with the maximum value of the eccentricity (offset) of the most anterior point of the lateral trochlea of the femur in the sagittal plane, and the relationships shown are shown in Figure 3. Starting from the anterior notch recess 74 formed on the articular cartilage surface 76 of the lateral condyle of the femur 82 when the anterior angle 73 of the lateral meniscus is in the straight position, to the posterior notch recess 75 formed on the lateral condyle of the femur 82 when the posterior angle 83 of the lateral meniscus is in the high flexion position, the articular cartilage surface 76 of the lateral condyle of the femur 82 in this section completely overlaps with an ellipse 78. The major axis of the ellipse 78 is rotated clockwise at a certain angle Ω relative to the major axis of the femoral medial condyle ellipse 38, for example, 12 degrees in one embodiment, 18 degrees in another embodiment, and in multiple embodiments, Ω is rotated between 5 and 25 degrees on average. Its center 79 completely coincides with the center 39 of the femoral medial condyle ellipse 38 in sagittal projection; it corresponds to the lateral collateral ligament attachment point 122 of the femoral lateral condyle in the MRI axis. In one embodiment, the semi-major axis of the ellipse 78 is 30 mm, and the semi-minor axis is 26 mm; in another embodiment, the semi-major axis of the ellipse 78 is 26 mm, and the semi-minor axis is 23 mm. In multiple embodiments, the semi-major axis of the ellipse 78 is between 21 mm and 33 mm, the semi-minor axis is between 16 mm and 30 mm, and the eccentricity is between 0.5 and 0.7. At the same time, by measuring the angle φ between the center 79 and the line connecting the anterior and posterior notches 74 and 75, and the angle ζ between the line connecting the center 79 and the posterior notch 75 and the major axis of the lateral condylar ellipse 78, the arc of this section of the articular surface 76 can be accurately described. In one embodiment, φ is 130 degrees and ξ is 40 degrees. In multiple embodiments, the angle φ is between 120 degrees and 160 degrees, and the angle ζ is between 30 degrees and 70 degrees.

At this level, the section 77 from the anterior notch recess 74 to the end of the lateral femoral trochlear articular cartilage surface 77 can be represented by a circle 80. Although some subjects showed an ellipse, most subjects still showed a circle. The center 41 of the circle 80 of this lateral femoral trochlear level 72 completely coincides with the center of the medial femoral trochlear ellipse 40 and the center of the most concave level 62 of the femoral trochlear in the MRI sagittal plane. The radius of this circle 80 is between 25 mm and 35 mm, for example, 28 mm, or 26 mm. The angle between the line connecting the center 41 of the circle 80 and the intersection point below the ellipse 78 of the circle 80 and the line connecting the center 41 of the circle 80 and the end point of the lateral femoral trochlear articular cartilage surface is ρ; the angle between the line connecting the center 41 of the circle 80 and the end point of the lateral femoral trochlear cartilage surface and the horizontal axis is ρ'. The angle ρ is between 80 degrees and 120 degrees, such as 90 degrees, 100 degrees or 110 degrees; the angle ρ' is between -30 degrees and 20 degrees, such as -10 degrees, 0 degrees, or 10 degrees.

According to the embodiments of the present disclosure, in the sagittal scanning direction of the femoral condyle, the articular cartilage surfaces of the medial and lateral femoral condyles can almost all be represented by an ellipse, the articular cartilage surfaces of the medial and lateral femoral trochleas can almost all be represented by an ellipse and/or a circle, and the most concave part of the femoral trochlea (i.e., the center of the trochlear groove) is represented by a circle, as shown in FIG4 .

Each sagittal plane of the articular cartilage surface of the medial femoral condyle is a collection of concentric ellipses 92, in which each ellipse has a different size, the long and short axes are consistent and overlap, and each ellipse has an approximate eccentricity, as shown in Figure 4. This means that the direction of the lateral femoral condyle prosthesis is the same as the sagittal direction. Therefore, the true direction of the articular cartilage surface of the medial femoral condyle is parallel to the Whiteside line and perpendicular to the transcondylar line TEA. Each sagittal plane of the articular cartilage surface of the lateral femoral condyle is a collection of ellipses 93, as shown in Figure 4. Each ellipse has a different size, the long and short axes are consistent and overlap approximately, that is, the center of each ellipse is approximately overlapped and arranged in concentric circles. This means that the direction of the lateral femoral condyle prosthesis is the same as the sagittal direction. Therefore, the true direction of the articular cartilage surface of the lateral femoral condyle is parallel to the Whiteside line and perpendicular to the transcondylar line (TEA). The sagittal plane of the medial femoral trochlear articular cartilage surface is a collection of ellipses (Figure 4), and the major and minor axes of these ellipses are in the same direction, and the center of each ellipse is arranged in concentric circles. However, the eccentricity of each ellipse is different. The sizes of these ellipses are arranged in the Fibonacci sequence. In the sagittal MRI scan of the femoral condyle, all the lateral femoral trochlear planes are circular. Although the radius of each lateral trochlear circle is different, the projection of the center 41 coincides (Figure 4).

On the coronal plane passing through the center of the femoral medial condyle ellipse 39 and the center of the femoral lateral condyle ellipse 79, the coronal articular surfaces 95 and 97 of the femoral medial condyle can be represented by a circle and an ellipse, as shown in FIG5. With the center of the femoral medial condyle ellipse 39 as the center, a circle 94 can be well overlapped with the coronal articular surface 95 of the femoral medial condyle, and its radius is equal to the semi-minor axis of the femoral medial condyle ellipse 38. The arc of this section of the articular surface can be represented by an angle λ. The vertical line λ is divided into λ1 and λ2, wherein λ1 and λ2 can be equal or unequal. In one embodiment, the λ angle is 65 degrees; in another embodiment, the λ angle is 70 degrees. With the center of the femoral lateral condyle ellipse 79 as the center, an ellipse 96 is rotated clockwise by δ1 degrees, and is just tangent to the inner circle 94 and overlaps with the coronal articular surface 97 of the femoral lateral condyle. The eccentricity of the ellipse 96 is equal to 0.618, i.e., a perfect ellipse. The curvature of this section of the articular surface can be represented by an angle δ. The vertical line δ is divided into δ1 and δ2, wherein δ1 and δ2 are not equal. In one embodiment, the δ angle is 70 degrees; in another embodiment, the δ angle is 75 degrees.

According to the embodiment of the present disclosure, the UKA prosthesis of the medial femoral condyle has an elliptical geometry in the sagittal plane and a circular geometry in the coronal plane. According to the above embodiment, it is known that the medial femoral condyle is a collection of concentric ellipses, and the planes of these ellipses are spatially parallel to the Whiteside line of the pulley. The centers of these ellipses correspond to the attachment points of the medial collateral ligaments of the medial femoral condyle. Therefore, the geometric shape of the UKA prosthesis of the medial femoral condyle is: it is composed of concentric ellipses in the sagittal plane, as shown in Figure 6; it is composed of circles in the coronal plane, as shown in Figure 7. The UKA prosthesis 201 of the medial femoral condyle disclosed in the present disclosure is divided into an articular surface part, that is, the outer peripheral surface of the prosthesis that contacts the medial side of the patella and the medial side of the tibial plateau during the movement of the knee joint; and an inner side part, that is, the part adjacent to the osteotomy surface and bone cement of the femoral condyle after the UKA prosthesis 201 of the medial femoral condyle is placed, which is manifested as the posterior condyle of the inner side of the straight cross section, and the distal end of the inner side consistent with the arc segment of the articular surface.

In the sagittal plane, the medial femoral condyle UKA prosthesis 201 is an arc 203 of an ellipse 38, as shown in FIG6 . The front and rear points of this arc 203 correspond to the meniscus notch recess, forming an arc range, for example, 150 degrees to 200 degrees, wherein this arc range is 175 degrees in one embodiment, 185 degrees in another embodiment, and 180 degrees in another embodiment. It can be specifically expressed as an angle β between a straight line connecting the anterior and posterior meniscus notches recess 207, 208 and passing through the center of the ellipse 39 and the major axis of the ellipse. This angle β is 30 degrees in one embodiment, 35 degrees in another embodiment, and 40 degrees in another embodiment. The posterior condyle 202 of the inner side of the medial femoral condyle UKA prosthesis is the vertical line of the posterior meniscus notch recess 208 perpendicular to the major axis of the ellipse, which is also the location of the posterior condyle osteotomy. This position changes with the change of the prosthesis parameters. The distal end 203 of the medial femoral condyle UKA prosthesis 201 is in an elliptical arc shape. There are two columns on its inner side, namely a central column 204 corresponding to the center 39 of the ellipse; and a rear column 205 corresponding to the focus of the ellipse. At the end of the distal part 203 of this UKA prosthesis, there is also a nail hole 206 for a locking screw, corresponding to a locking screw 206'. This position contacts the meniscus in a normal human body, but does not contact the tibial plateau articular surface; and at the same time, it does not contact the patella, so screw fixation at this position does not affect the contact of the articular surface. Moreover, the direction of the locking screw 206' is different from that of the central column and the rear column, which can enhance the stability of the prosthesis. It can be understood that technicians in this field can set more columns as needed.

In the coronal plane, according to FIG5, we know that the coronal plane articular surface of the medial femoral condyle can be represented by an arc 95 of a circle 94, whose arc is λ, for example, the range of the arc is 50 degrees to 90 degrees, so the coronal plane shape of the medial condyle UKA prosthesis 201 is shown in FIG7. The arc segment 203 in the sagittal plane can be regarded as approximately coinciding with a circle 221, and the radius of the circle 221 is larger than the radius of the coronal plane circle 94 of the UKA prosthesis 201. The curvature and parameters of the circle 221 are used as mold parameters to prepare the bone bed surface.

From the axial perspective, the articular surface of the medial femoral condyle UKA prosthesis 201 is asymmetric, as shown in Figure 8. The prosthesis is placed in a direction parallel to the Whiteside line and perpendicular to the transcondylar line TEA. The inner and outer sides of the prosthesis each have a straight edge 243, 245, which are parallel to the Whiteside line and perpendicular to TEA. The medial arc edge 241 is in the shape of an arc to adapt to the shape of the distal end of the medial femoral condyle; the curvature of the front arc edge 242 corresponds to the parameters of the mold circle 221; the bottom 244 has the curvature of the coronal circle 94. Therefore, a three-dimensional diagram of the medial femoral condyle UKA prosthesis 201 is shown in Figure 9. In addition to the various positions mentioned above, the inner side of the prosthesis has corresponding recessed grooves to accommodate bone cement.

With the previously described MRI scanning direction of the femoral condyle, the optimal prosthesis size and position can be planned on the preoperative MRI image. Specific surgical operation: After exposure, the Whiteside line of the trochlear groove must be determined first, and the prosthesis direction line parallel to the Whiteside line must be marked on the medial condyle surface with an electric knife. An elliptical measuring mold 251 that best fits the ellipse of the medial femoral condyle is well fitted to the joint surface, as shown in FIG10A. The front end of the measuring mold 251 has a catch 254 structure that can hold the medial posterior condyle well. There are two nail holes 255 at the end of the measuring mold 251, which are fixed with short nails to achieve greater stability. It must be ensured that the hollow armrest 257 of the measuring mold corresponds to the direction of the attachment point of the medial collateral ligament, that is, the direction of the ellipse center 39. This hollow armrest 257 can be placed with a drill bit to drill a hole 258 on the medial femoral condyle to facilitate the next step of placing the drill center fixation pile. There is an osteotomy groove 256 at the lower end of the measuring grinder 251, which corresponds to the osteotomy line 202 of the posterior femoral condyle. Then remove the measuring grinder 251, place a fixed post 259 on the central channel 258, and use a hollow drill 271, whose radius is equal to the circle 221 mentioned above. The depth of the grinding is limited by the fixed post 259, and the depth is constantly compared with the prosthesis trial mold during the process.

According to the embodiment of the present disclosure, the UKA prosthesis of the lateral femoral condyle has an elliptical geometry in both the sagittal and coronal planes. According to the above embodiments, it is known that the lateral femoral condyle is a collection of concentric ellipses, and the planes of these ellipses are spatially parallel to the Whiteside line of the pulley. The centers of these ellipses correspond to the attachment points of the lateral collateral ligaments of the lateral femoral condyle. Therefore, the geometric shape of the UKA prosthesis of the lateral femoral condyle is: composed of concentric ellipses in the sagittal plane; composed of ellipses in the coronal plane, as shown in Figure 6. The UKA prosthesis 201 of the medial femoral condyle of the present disclosure is divided into an articular surface part, that is, the outer peripheral surface of the prosthesis that contacts the medial side of the patella and the medial side of the tibial plateau during the movement of the knee joint; and an inner side part, that is, the part of the medial femoral condyle UKA prosthesis 201 adjacent to the osteotomy surface of the femoral condyle and the bone cement after insertion, which is manifested as the posterior condyle of the inner side of the straight cross section, and the distal end of the inner side consistent with the arc segment of the articular surface.

In the sagittal plane, the femoral lateral condyle UKA prosthesis 301 is an arc of an ellipse 78, as shown in FIG11. The front and rear points of this arc correspond to the meniscus notches recess 307, 308, which form an angle range, for example, the arc range is 120 degrees to 160 degrees. In one embodiment, this angle is 145 degrees, and in another embodiment, it is 150 degrees. It can be specifically expressed as the angle α formed by the front and rear meniscus notches recess 307, 308 and the center of the ellipse 79. The line connecting the center 79 and the posterior meniscus notch 308 forms an angle β with the horizontal axis, and this angle β is 35 degrees in one embodiment, 40 degrees in another embodiment, and 35 degrees on average in multiple embodiments. The osteotomy direction 302 of the posterior condyle of the inner side of the femoral lateral condyle UKA prosthesis 301 is perpendicular to the horizontal axis. This position changes with the change of the ellipse parameters. The distal end 303 of the femoral lateral condyle UKA prosthesis 301 is in an elliptical arc structure. There is a column on the inner side, which is the rear column 305 corresponding to the focus of the ellipse. At the end of the distal part 303 of the UKA prosthesis, there is also a locking screw hole 306, corresponding to a locking screw 306'. This position contacts the meniscus in a normal human body, but does not contact the tibial plateau articular surface; at the same time, the position of this screw hole is biased to the outside and does not contact the patella, so screw fixation at this position does not affect the contact of the articular surface. Moreover, the direction of the locking screw 306' is different from that of the rear column, which can enhance the stability of the prosthesis.

In the coronal position, according to FIG. 5 , we know that the coronal articular surface of the femoral lateral condyle passing through the center 79 is represented by an arc 97 that conforms to an ellipse 96, and its arc is δ. For example, the range of this arc is 50 degrees to 90 degrees. Therefore, the coronal shape of the lateral condyle UKA prosthesis 301 is shown in FIG. 12 , and the corresponding coronal shape of the tibial side prosthesis articular surface is a concave shape 325 that adapts to this ellipse. This arc 97 can approximately overlap with a circle 321 that does not pass through the center 79, and its center position is 322. Its radius can be regarded as the semi-minor axis length of the ellipse 96. The direction axis 323 is not only the direction of the rear column 305, but also the direction of the grinding file drill and the fixing pile. Its angle with the vertical axis is 15 degrees. The curvature and parameters of this circle 321 are used as the parameters of the grinding tool to prepare the bone bed surface. In the coronal position, the direction of the locking nail hole and the locking screw 306 is at an angle of 15 degrees to the vertical axis. Therefore, the locking screw 306 is at an angle of 30 degrees to the rear post 305 to achieve maximum stability of the prosthesis.

From the axial perspective, the articular surface of the lateral femoral condyle UKA prosthesis 301 is asymmetric, as shown in Figure 8. The prosthesis is placed in a direction parallel to the Whiteside line and perpendicular to the transcondylar line TEA. The inner and outer condyles of the prosthesis each have a straight edge 343, 345, parallel to the Whiteside line and perpendicular to TEA. The outer arc edge 341 is in the shape of an arc to adapt to the distal shape of the lateral femoral condyle; the curvature of the front arc edge 342 corresponds to the curvature parameter of the circle 321; the bottom 344 is the curvature of the coronal ellipse 96. Therefore, the three-dimensional diagram of the medial femoral condyle UKA prosthesis 201 is shown in Figure 13. In addition to the various positions mentioned above, the inner side of the prosthesis has corresponding recessed grooves to accommodate bone cement.

The operating steps for placing the lateral femoral condyle UKA prosthesis are the same as those for placing the medial femoral condyle UKA prosthesis. There are corresponding special molds for the outer shape, which will not be repeated here.

According to the embodiment of the present disclosure, the femoral trochlear UKA prosthesis has a geometric shape of an elliptical or circular medial trochlear and a circular or elliptical lateral trochlear in the sagittal plane, and is suitable for non-patellar replacement and patellar replacement. For example, the femoral trochlear prosthesis 401 includes: an articular surface, which is a surface that contacts the patellar articular surface during the movement of the knee joint, and is represented in the sagittal plane as a spatial collection of arc segments 37 on the ellipse or circle 40 and arc segments 77 on the ellipse or circle 80; and an inner side surface, which is a portion adjacent to the osteotomy surface and bone cement of the femoral trochlear portion after the prosthesis is implanted, and is represented as an inner side surface 409 consistent with the morphology of the femoral trochlear articular surface. According to the above embodiment, the inner and outer trochleae of the femur are respectively composed of an elliptical and circular arc segment arranged concentrically, as shown in Figure 4. Therefore, the femoral trochlear UKA prosthesis 401 disclosed in the present disclosure is designed to be composed of the elliptical medial trochlear and circular lateral trochlear geometric shapes, which are arranged concentrically. The concentric axis 41' is parallel to the TEA in space and perpendicular to the Whiteside line. As shown in FIG14A, it is shown as a concentric ellipse and a circle of the inner and outer pulley parts, and the center circle 70 is the most concave circle of the pulley passing through the Whiteside line. There is a column 402 at the center of the femoral pulley UKA prosthesis 401, and there are four locking screw holes 403, 404, 405, 406 around it to place the locking screws, as shown in FIG14B.

In the above-mentioned embodiment, the design of the UKA prosthesis of the lateral femoral condyle is formed based on the elliptical structure of the lateral femoral condyle, and the ellipse of the lateral femoral condyle is designed according to the shape of the articular cartilage surface of the lateral posterior femoral condyle of the normal human knee joint. The ellipse of the lateral femoral condyle is slightly smaller than the ellipse of the medial femoral condyle. Its long axis direction is clockwise rotated at a certain angle with reference to the ellipse of the medial femoral condyle. At the same time, the center of the ellipse of the lateral femoral condyle and the medial femoral condyle is overlapped in the sagittal plane of the femoral prosthesis. The alternative scheme can simplify the ellipse of the lateral femoral condyle to be consistent with the ellipse of the medial femoral condyle in the long and short axis directions, and cancel the step of clockwise rotation, which can further simplify the process of designing and making the femoral prosthesis. Although the changed appearance is not consistent with the shape of the articular cartilage surface of the lateral posterior femoral condyle of the normal human shoulder joint, it is also acceptable. With the help of a matching tibial plateau side prosthesis gasket, a good joint kinematic effect can also be achieved.

In addition, in the design of the pulley UKA prosthesis, the medial and lateral pulleys of the femur are described as being composed of an ellipse or a circle. This scheme is the result of the final statistical analysis. Although the medial femoral condyle in most embodiments is an ellipse, there are also a few embodiments in which the medial femoral condyle is a circle; although the lateral femoral condyle in most embodiments is a circle, there are also a few embodiments in which the lateral femoral condyle is an ellipse. And our specific implementation plan is based on the analysis of the normal knee joint structure of the Chinese, and does not exclude differences caused by different races. If the medial femoral condyle is described as a circle and the lateral femoral condyle is described as an ellipse; or if both the medial and lateral femoral condyles are described as a circle or an ellipse, supplemented by a matching patellar replacement prosthesis, good joint kinematic effects can also be achieved.

It should be noted that the prosthesis proposed in the present disclosure will also be protected by this patent when it is not mass-produced, such as a customized individualized three-dimensional (3D) printed knee prosthesis.

Thus, the elliptical and circular prostheses proposed in the embodiments of the present disclosure are more in line with the normal human knee joint morphology and structure. This elliptical and circular principle simplifies the complex and uninterpretable knee joint structure into a simple and effectively repeatable elliptical and circular spatial structure.

In addition, the parameters of the femoral prosthesis made according to the elliptical and circular principles proposed in the embodiments of the present disclosure can be embodied in the form of elliptical and circular important angle parameters, and the parameters change accordingly with the changes in the parameters, thereby achieving accurate production of prostheses of different models. Moreover, each individual UKA prosthesis can be used alone or in combination. The correction of joint force line can be achieved.

Although the present disclosure has been described with reference to several typical embodiments, it should be understood that the terms used are illustrative and exemplary, rather than restrictive. Since the present disclosure can be embodied in a variety of forms without departing from the spirit or substance of the disclosure, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims (6)

1. A lateral femoral unicondylar prosthesis (301), comprising: An articular surface, the articular surface being the surface in contact with the outer side of the patella and the outer side of the tibial plateau during the movement of the knee joint, which is represented by an arc segment (303) on the second ellipse (78) in the sagittal plane and an arc segment (97) on the third ellipse (96) in the coronal plane; and The inner side is the portion adjacent to the osteotomy surface of the femoral condyle and the bone cement after the prosthesis is implanted, and is represented by the posterior condyle (302) of the inner side in a straight cross section, and the distal end (309) of the inner side consistent with the articular surface arc segment (303). 2. The lateral femoral unicondylar prosthesis (301) according to claim 1, further comprising: The third column (305) is arranged on the inner side surface and corresponds to the focus of the second ellipse (78). 3. The lateral femoral unicompartmental prosthesis (301) as described in claim 2, wherein a locking screw hole (306) is formed at the distal end of the lateral femoral unicompartmental prosthesis (301), and the locking screw hole is formed so that the direction of the locking screw (306') inserted therein is different from the direction of the third column (305). 4. The lateral femoral unicondylar prosthesis (301) as described in claim 1, wherein the corresponding second ellipses (78) on each level in the sagittal plane are gathered in three-dimensional space, and they constitute the shape of a complete lateral femoral unicondylar prosthesis, their centers coincide in the sagittal plane, and the major and minor axis directions are consistent, and the line connecting all the centers coincides with the transcondylar line (TEA) and is perpendicular to the Whiteside line. 5. The lateral femoral unicompartmental prosthesis (301) as described in claim 1, wherein in the axial perspective, the placement direction of the prosthesis (301) is parallel to the Whiteside line and perpendicular to the transepicondylar line (TEA), and the inner side of the prosthesis (301) has a straight edge (343) parallel to the Whiteside line and perpendicular to the TEA, and the lateral arc edge (341) is arc-shaped to adapt to the distal shape of the lateral femoral condyle, the curvature of the front arc edge (342) corresponds to the curvature parameter of the circle (321), and the bottom (344) is the curvature of the arc segment (97) of the third ellipse (96) in the coronal position. 6. The lateral femoral unicompartmental prosthesis (301) as described in claim 1, wherein the angle range of the arc segment (303) on the second ellipse (78) is 120 degrees to 160 degrees, and the angle range of the arc segment (97) on the third ellipse (96) is 50 degrees to 90 degrees.