CN111643230B - Tibial plateau, mobile plateau spacer, fixed plateau spacer and prosthesis system for primary total knee replacement - Google Patents

Abstract

The invention relates to a tibia platform, which is used for installing a platform gasket and can realize the switching of a fixed platform gasket and a movable platform gasket on the same tibia platform. Wherein the dovetail comprises a wedge-shaped fixing structure and a guiding structure, the wedge-shaped fixing structure can fixedly hold the fixed platform gasket on the tibial platform surface, and the side surface of the platform front fixing piece and the side surface of the wedge-shaped fixing structure of the dovetail positioned at the other side of the central hole are suitable for respectively and simultaneously playing a role of stopping the rotating movable platform gasket. The invention also relates to a fixed platform liner and a movable platform liner that mate with the tibial platform. The invention also relates to a prosthetic system for a primary total knee replacement comprising a femoral condyle, a tibial plateau and a fixed plateau pad or a mobile plateau pad, wherein the sagittal plane posterior arc of the femoral condyle and the mobile plateau pad has a high degree of conformity.

Description

Tibial plateau, mobile plateau spacer, fixed plateau spacer and prosthesis system for primary total knee replacement

Technical Field

The invention relates to a tibial plateau, in particular to a posterior cruciate ligament retaining tibial plateau. The invention also relates to a mobile platform liner and a stationary platform liner adapted to be mounted on the tibial plateau. The present invention also relates to a prosthetic system for a primary total knee replacement comprising a femoral condyle, a tibial plateau as described above, a mobile plateau pad, or a fixed plateau pad.

Background

The total knee arthroplasty is mainly suitable for diseases such as severe knee pain and knee dysfunction, can effectively solve the knee joint diseases of patients, relieves the pain of patients and recovers the knee joint functions of the patients to a certain extent. The process in which a knee prosthesis replaces a native knee is called primary total knee replacement.

Knee prostheses primarily include PS knee prostheses adapted to leave no Posterior Cruciate Ligament (PCL) and CR prostheses that leave PCL. The CR knee joint prosthesis can keep the femoral condyle rolling motion anatomically, and can better reduce the balance of knee joint cartilage tissue and the change of knee joint kinematics. However, if there is PCL injury, failure or operation due to anatomical characteristics of the posterior cruciate ligament, the operation such as bone cutting and ligament loosening in operation causes the functional problem of the posterior cruciate ligament, and a PS prosthesis is needed.

The primary purpose of Posterior Cruciate Ligament (PCL) preservation is to increase posterior stability of the artificial knee prosthesis and to achieve femoral rollback, resulting in greater flexion; traditional cruciate retaining type fixed bearing knee prosthesis replacement (i.e., CR-type prosthesis replacement) requires that the posterior cruciate ligament perform well; therefore, the patient with complete posterior cruciate ligament can use the fixed platform low-shape degree liner, and the patient can roll back through the posterior cruciate ligament of the human body, so that the clinical manifestation is better.

When the high-conformity arc-shaped pad is used on the basis of a CR type prosthesis (posterior cruciate ligament retaining type prosthesis), the abrasion of the platform pad can be reduced due to the improvement of the degree of conformity, and the knee instability caused by incomplete functions of the posterior cruciate ligament can be solved by the design of heightening the front and the back lips, but the design can lead the femoral condyle to be arranged at the center of the pad to reduce the front and the back sliding, so that a certain limitation is formed on the movement. During flexion, the high-conformity liner posterior is more stressed if the femoral condyles are designed with a fixed liner-platform design as they roll back on the platform liner. When a rotary-type gasket-platform design is employed, the large shear force due to the high degree of compliance is converted into a rotation of the platform-platform gasket, so that the restriction problem due to the high degree of compliance of the gasket can be avoided, and wear is minimized. Thus, if a patient with damage to the posterior cruciate ligament is to use a high-compliance rotary-type platform pad during total knee replacement, the prosthesis will have a higher lifetime.

However, it is difficult to accurately determine whether the posterior cruciate ligament is intact prior to surgery, and the integrity of the posterior cruciate ligament is not necessarily effectively ensured due to the specificity of the tibial lateral dead center position of the posterior cruciate ligament. In addition, there may be problems with posterior cruciate ligament function during surgery due to the anatomical features of the posterior cruciate ligament, during surgery osteotomies, ligament loosening, etc. Therefore, the PS prosthesis is required to replace the CR prosthesis according to the condition in operation, but the structural characteristics of the existing PS prosthesis and the CR prosthesis are greatly different, the prosthesis is required to be replaced again, the bone loss of a patient is caused, the operation time is prolonged, and the difficulty is increased. However, no product is currently available that can achieve an intraoperative instant switching between a low-form-factor fixed platform pad and a high-form-factor rotary platform pad on the same tibial plateau.

Most movable platform gaskets can improve the mobility, but the risk that the gaskets strike surrounding ligaments exists due to the fact that the gasket mobility is too large, and if the rotation limitation is not available, the risk of unscrewing is easily caused in the flexion and extension movement, so that the platform gaskets are separated. For the fixed platform prosthesis, the irrational locking mechanism between the liner and the platform is easy to cause fretting wear, dislocation and the like of the liner and the platform in the movement process of the prosthesis. Therefore, satisfying the low jog locking mechanism of the stationary platform and the moderate rotational restriction of the rotary platform are problems that need to be solved simultaneously while ensuring flexible switching between the movable platform pad and the stationary platform pad in the prosthetic operation.

CN101351172a discloses a prosthetic knee system, in which the surgeon can switch between a fixed bearing component and a movable bearing component depending on the specific circumstances in the operation. In this patent publication, the stem of the fixed bearing component has a non-circular cross-section along at least a portion of its length (see fig. 4 thereof), as well as the longitudinal bore of the base component has a non-circular cross-section along at least a portion of its length, which interact to prevent movement of the fixed bearing component (see fig. 7 thereof). Moreover, the longitudinal bore and a substantial portion of the base stem have a circular cross-section so that the same base component can be used with a mobile bearing component. The stem of the mobile bearing component has a circular cross-section along its entire axial length (see fig. 9 thereof). The portion of the mobile bearing component that is not received in the recess of the tibial base. Thus, the mobile bearing component is free to rotate about the central longitudinal axis of the stem when assembled with the tibial base component (see fig. 11 thereof). The mobile bearing component is free to rotate about the central longitudinal axis of the stem but lacks a locking means, so that there is a risk of the bearing component striking the surrounding ligament due to its too great a mobility, and a risk of unscrewing during the re-flexion and extension movements due to the lack of rotational limitation, resulting in a back-out. In this configuration, first, there is no projection above the flat upper surface of the tibial base component that limits possible rotation of the fixed bearing component or rotation of the mobile bearing component itself. The structure preventing rotation of the stem of the fixed bearing component is designed to be within the central bore below the flat upper surface of the tibial base component; there is no disclosure of rotational limitation of the movable socket part. Second, both the fixed and the movable bearing components require a stem. The fixed bearing part requires an anti-rotation structure to be arranged on the stem, while the movable bearing requires the stem to be inserted into the central hole as a rotation axis.

CN102133138B discloses a knee prosthesis system for total knee replacement surgery comprising a plurality of distinct femoral components, a plurality of distinct fixed tibial components, a plurality of distinct movable tibial components, a plurality of fixed inserts, and a plurality of movable inserts. These tibial, femoral, and fixation inserts form different combinations that are available. It is clear that this patent publication does not disclose that the same femoral component has both fixed and movable inserts that are suitable at the same time, and therefore it is not possible to temporarily decide whether to use a fixed or a movable insert during surgery. In addition, in this patent publication, only the tibial component for the fixation insert is provided with a projection arrangement for the fixation insert (for example, fig. 4 and the corresponding description part thereof) on the tibial plateau surface, while in all embodiments for the movable insert (for example, fig. 12 and the corresponding description part thereof) any projection arrangement on the tibial plateau surface is avoided.

The fit between the plateau pad and the femoral condyle is defined by the coronal and sagittal plane radius ratios of the femoral condyle to the plateau pad. The conformity defines the similarity of the joint surface radii of the prosthetic components. In short, the closer the radius ratio of the femoral condyle to the tibial plateau pad is to 1, the better the fit, the larger the contact area between the two components, and the stress of the femoral condyle on the tibial plateau pad can be reduced. However, the prior art does not specifically improve the fit between the plateau pad and the femoral condyle, particularly between the plateau pad and the sagittal posterior arc of the femoral condyle. In commercial products, the sagittal posterior arc radius ratio of the femoral condyle to the plateau pad is greater than 0.5 and less than 0.68.

Disclosure of Invention

Accordingly, the present invention is directed to an improved tibial plateau, a fixed plateau spacer, a movable plateau spacer, and a prosthetic system for primary total knee replacement including the above tibial plateau, fixed plateau spacer, and movable plateau spacer, wherein the tibial plateau enables switching of the fixed plateau spacer and the movable plateau spacer on the same tibial plateau, and is capable of effectively restricting rotational degrees of freedom and preventing the movable plateau spacer from coming out.

The present invention provides a prosthetic system suitable for use in a primary total knee replacement. The fixed platform gasket is CR type; the joint surface of the movable platform gasket and the femoral condyle have high fitting degree, so that the contact area can be increased, the contact stress can be reduced, the dislocation of the knee joint prosthesis can be effectively prevented, and the movable degree of freedom of the knee joint can be limited to a certain extent; the movable platform pad rotates on the tibia platform, so that the freedom degree of the knee joint can be improved. The prosthesis system composed of the femoral condyle, the movable platform liner and the tibia platform can replace a PS knee joint prosthesis, and is suitable for the condition that the Posterior Cruciate Ligament (PCL) is damaged, loosened or not reserved. The tibia platform is a universal platform which can be simultaneously applicable to fixed type and movable type platform gaskets, and after the knee joint is damaged in operation, the movable type platform gaskets can be directly replaced, so that the function of the PS knee joint prosthesis is realized.

Clinical experience proves that under the condition of normal knee joint force line, the rotation range of the platform liner is generally-5 degrees to 5 degrees in the movement processes of extending and bending the knee joint and the like. The maximum rotation range of the movable platform gasket is-15 degrees to 15 degrees, and the gasket can be ensured not to collide with the wedge-shaped fixing structures on the two sides of the front fixing piece and the dovetail part of the tibia platform under the normal knee joint force line. When the knee joint prosthesis force line is deviated due to the failure of the prosthesis and the like, the rotation range of the movable platform liner is-15 degrees to 15 degrees, so that the knee joint prosthesis is ensured not to be dislocated and other adverse events.

According to a first aspect of the present invention there is provided a tibial plateau adapted to cooperate with a plateau pad, wherein the plateau pad is a fixed plateau pad or a movable plateau pad, the fixed plateau pad having a planar lower surface and the movable plateau pad having a downwardly projecting central post on the planar lower surface in addition to the planar lower surface, wherein the upper side of the tibial plateau has a tibial plateau surface adapted to cooperate with the lower surface of the plateau pad, the tibial plateau surface having a plateau front anchor and a dovetail portion projecting upwardly from the tibial plateau surface at the front and rear of the tibial plateau surface respectively, a central aperture being provided in the centre of the tibial plateau surface, the lower side of the tibial plateau body having a downwardly projecting central stem; wherein the central hole penetrates the tibial plateau surface and extends into the central stem, and is adapted to guide the central post which receives and rotatably holds the movable plateau pad, wherein the dovetail comprises a centrally located guiding structure and two wedge-shaped fixing structures located on both sides, wherein the front platform fixing member comprises a front face opposite to the central guiding structure of the dovetail and side faces located on both ends, the front face of the front platform fixing member is provided with an arc-shaped clamping groove adapted to engage with a corresponding arc-shaped clamping hook of the front portion of the plateau pad, and the arc-shaped clamping hook and thus the fixed plateau pad are cooperatively limited by the arc-shaped clamping groove and the wedge-shaped fixing structures of the dovetail to move up and down and horizontally. Wherein the dovetail wedge-shaped securing structure is configured to fixedly retain the stationary platform liner on the tibial platform surface, wherein a side of the platform anterior securing member and a side surface of the dovetail wedge-shaped securing structure on the other side of the central aperture are configured to simultaneously act as stops for the rotating movable platform liner to prevent further rotation of the movable platform liner, respectively. Preferably, the fixed platform liner has a volumetric shape that fills the space between the anterior platform mount and the dovetail above the tibial plateau surface.

In this configuration, the fixed platform liner may be snapped by the platform front mount and the wedge-shaped mounting structure on both sides of the dovetail. The clamping hook at the front end of the fixed platform liner stretches into the clamping groove of the front fixing piece of the platform. The rear end of the fixed platform gasket is clamped into the wedge-shaped fixed structures at two sides of the dovetail part. The dovetail part wedge-shaped fixing structure is symmetrically distributed in an eight-shaped way, belongs to a triangle-like structure, and has a stable fixing effect on the fixed platform gasket. Meanwhile, the triangular-like structure has the best limiting and anti-impact abrasion effects on the movable platform gasket. Thus, the dovetail wedge-shaped securing structure cooperates with the anterior platform securing member to fixedly retain the stationary platform liner on the tibial plateau surface.

Furthermore, since the bottom side of the fixed platform liner has a flat plane and no protruding center post is provided, the fixation of the fixed platform liner on the tibial plateau is achieved by the wedge-shaped fixation structure of the anterior plateau fixation and the dovetail part above the tibial plateau surface. This way of fixation is compared to fixation by means of a recess and protrusion structure of non-circular cross-section only in the central bore. The fixation is also more stable because the moment arm against rotation is larger, the available contact area is larger.

And when the mobile platform liner is in use, the central post of the mobile platform liner is guided and received by the central aperture of the tibial plateau, thereby providing an axis of rotation. The rotation limit of the movable platform gasket is realized by simultaneously stopping the movable platform gasket through the side surface of the front fixing piece of the platform and the side surface of the wedge-shaped fixing structure of the dovetail part, which is positioned at the other side of the center hole. When the movable platform gasket rotates to a limit position on one side, for example, the movable platform gasket rotates around the central column by +/-15 degrees, one side surface of the front platform fixing piece of the movable platform gasket and the side surface of the dovetail part, which is positioned on the other side of the central hole, are simultaneously abutted against the outer circumferential surface of the movable platform gasket, so that a larger stop force arm and a larger stop area are formed, and the pressure intensity and the stress concentration between the contact parts are reduced.

Preferably, the body of the side wall of the central bore is cylindrical and has a ramp of widened dimension near the upper portion of the tibial plateau surface to facilitate insertion of the central post, and narrows away from the lower portion of the tibial plateau surface to stop the central post. Thus, the center post of the mobile tibial plateau pad can be easily inserted into the central bore of the tibial plateau along a slope having a widened dimension and down the cylindrical surface of the sidewall of the central bore until stopped at the narrowed portion. At this time, the lower surface of the movable platform liner is just placed on the tibial plateau surface.

According to a second aspect of the present invention there is provided a fixed platform liner, the underside of which is shaped to engage with the dovetail wedge-shaped fixation formations of the anterior platform mount (8) and the dovetail of the tibial plateau described above.

Preferably, the front portion of the fixed platform liner is provided with an arcuate hook adapted to engage with an arcuate slot in the front face of the front platform mount, the arcuate hook and thus the fixed platform liner being cooperatively restrained from up and down movement and horizontal rotational movement by a wedge-shaped securing structure of the arcuate slot and dovetail portion.

According to a third aspect of the present invention there is provided a mobile platform spacer having a central post on its underside adapted to be guided and received and rotatably retained in said central bore and having an outer peripheral surface adapted to simultaneously stop upon rotation against the side of the anterior platform mount of the tibial platform and the side surface of the dovetail section of the wedge-shaped fixation structure on the other side of the central bore.

Preferably, the volume of the space of the movable platform gasket accommodated between the platform front mount and the dovetail is shaped so as not to receive any stop during rotation of the movable platform gasket before the stop of the movable platform gasket against the side surface of the platform front mount and the side surface of the wedge-shaped fixing structure of the dovetail on the other side of the center hole.

The flexible and stable connection of the movable tibial plateau pad and the tibial plateau enables the femoral condyle and the movable tibial plateau pad to have a design with high fitting degree. According to an advantageous embodiment of the invention, the ratio of the radius of the femoral condyle coronal surface to the radius of the mobile tibial plateau pad coronal surface is from 0.96:1 to 0.98:1, and the ratio of the radius of the femoral condyle sagittal plane posterior arc to the mobile plateau pad sagittal plane posterior arc is from 0.80:1 to 0.94:1. As the radius ratio approaches 1, the fit increases, thereby optimizing the contact area between the femoral condyle and the mobile tibial plateau pad and reducing the pressure between the surfaces.

Preferably, the front part of the movable platform gasket is provided with an arc-shaped clamping hook which is suitable for being engaged with an arc-shaped clamping groove on the front surface of the front fixing piece of the platform, and the arc-shaped clamping hook is limited by the arc-shaped clamping groove to move up and down, but does not limit horizontal rotation. It should be noted that the width of the arcuate hooks of the movable platform liner are significantly different from the width of the arcuate hooks of the fixed platform liner. The latter fills the whole arc-shaped clamping groove on the front surface of the front fixing piece of the platform so as to strengthen the fixing effect. The arcuate hooks of the movable platen liner are allowed to move in the arcuate slots.

According to a fourth aspect of the present invention there is provided a prosthetic system for a primary total knee replacement comprising: femoral condyles; the tibial plateau described above; the stationary platform liner or the mobile platform liner disposed between the femoral condyle and the tibial plateau, wherein the underside of the stationary platform liner or the mobile platform liner rests on the tibial plateau.

Drawings

Fig. 1 schematically illustrates a perspective view of a prosthetic system for a primary total knee replacement with a tibial plateau, a plateau spacer, a femoral condyle assembled in place;

fig. 2 schematically illustrates a perspective view of a tibial plateau;

fig. 3 schematically illustrates a schematic cross-sectional view of a tibial plateau;

fig. 4 schematically illustrates another perspective view of the tibial plateau;

fig. 5 schematically illustrates a perspective view of a stationary platform liner;

fig. 6 schematically illustrates a cutaway assembly view of the stationary platform liner mounted on a tibial plateau;

FIG. 7 schematically illustrates a perspective view of a movable floor mat;

figures 8 and 9 schematically illustrate the installation of the mobile platform liner on the tibial plateau in an assembled vertical section;

fig. 10A-10C schematically illustrate the rotation of the mobile platform liner on the tibial platform in an assembled horizontal section.

Fig. 11A schematically illustrates the radius ratio of the femoral condyle coronal surface to the mobile tibial plateau pad coronal surface.

Fig. 11B schematically illustrates the radius ratio of the sagittal plane posterior arc of the femoral condyle to the sagittal plane posterior arc of the mobile platform liner.

Pressure finite element analysis of the fixed platen liner and the movable platen liner is shown in fig. 12A and 12B, respectively.

Fig. 13A to 13B show experimental verification with cadaveric bones, respectively.

Fig. 13C shows the cadaveric bone after removal of the posterior cruciate ligament.

Fig. 13D shows the tibial plateau of the present invention in a straightened position after the mobile platform liner has been mounted on the tibial plateau after posterior cruciate ligament resection.

Fig. 13E shows the tibial plateau of the present invention in a high flexion position after the mobile plateau spacer is installed on the tibial plateau after posterior cruciate ligament resection.

Detailed Description

Fig. 1 schematically shows a perspective view of a prosthetic system for a primary total knee replacement, wherein the tibial plateau 3, the plateau pad 4, and the femoral condyle 1 have been assembled in place. The platform liner 4 receives the femoral condyle 1 on its upper surface and the tibial platform 3 on its lower surface. Also shown is a central stem 310 extending downwardly from the lower surface of the tibial plateau. The center shank 310 may have delta wings on both sides for reinforcement.

Wherein the platform pad 4,5 is a fixed platform pad 4 or a movable platform pad 5, two different platform pads 4,5 may be mounted on the same tibial platform 3, which facilitates intra-operative selection.

Fig. 5 schematically shows a perspective view of the stationary platform liner 4. The stationary platen liner 4 the platen liner lower surface 430 is designed in a generally flat shape with a front portion having a platen liner front recess 420 and a rear portion having a dovetail recess 440. The anterior plateau pad recess 420 and the dovetail recess 440 are shaped to correspond to the anterior plateau mount 320 and the dovetail 340, respectively, of the upper side of the tibial plateau. Fig. 6 schematically illustrates a cutaway assembly view of the fixed platform liner mounted on a tibial platform. When mounted to tibial plateau 3, the plateau pad anterior recess 420 and dovetail recess 440 engage the plateau anterior mount 320 and dovetail 340, particularly the wedge-shaped mount 342 of dovetail 340, respectively, on the upper side of the tibial plateau.

Fig. 7 schematically shows a perspective view of the movable floor mat 5. The movable platform liner 5 has a center post 510 projecting downwardly from the platform liner lower surface 530 in addition to a lower generally flat platform liner lower surface 530, a front platform liner forward recess 520 in the front thereof, and a rear dovetail recess 540 in the rear thereof. The anterior plateau pad recess 520 and the dovetail recess 540 are shaped to correspond to the anterior plateau mount 320 and the dovetail 340, respectively, of the upper side of the tibial plateau. Figures 8 and 9 schematically illustrate the installation of the mobile platform liner on the tibial plateau in an assembled vertical section. When mounted to the tibial plateau 3, the central post 510 of the mobile plateau pad 5 is inserted into the central aperture 330 of the tibial plateau 3 in addition to the anterior plateau pad recess and dovetail recess respectively engaging the anterior plateau securing element and dovetail portion, particularly the dovetail portion wedge-shaped securing structure, of the upper side of the tibial plateau. As shown in fig. 8, the body of the sidewall of the central bore is cylindrical and has a ramp of widened dimension near the upper portion of the tibial plateau surface to facilitate insertion of the central post, while narrowing away from the lower portion of the tibial plateau surface to stop the central post. As shown in fig. 9, the center post of the mobile tibial plateau pad can be easily inserted into the central bore of the tibial plateau along a slope having a widened dimension and down the cylindrical surface of the sidewall of the central bore until stopped at the narrowed portion. At this time, the lower surface of the movable platform liner is just placed on the tibial plateau surface.

As shown in fig. 5 and 6, the front part of the fixed-type platform gasket 4 is provided with an arc-shaped hook 423 adapted to be engaged with an arc-shaped hook groove 323 of the front surface of the platform front fixing member 320, and the arc-shaped hook 423 is restricted from moving up and down and horizontally rotating by the arc-shaped hook groove 323; as shown in fig. 7 and 8, the front portion of the movable platform gasket 5 is provided with an arc-shaped hook 523 adapted to be engaged with an arc-shaped groove 323 of the front surface of the platform front fixing member 320, and the arc-shaped hook 523 is restricted from moving up and down by the arc-shaped groove 323, but is not restricted from horizontal rotation.

Fig. 2 and 4 schematically show perspective views of the tibial plateau 3. Fig. 3 schematically shows a schematic cross-sectional view of a tibial plateau. The upper side of the tibia platform 3 is provided with a tibia platform surface 300 which is suitable for being matched with the lower surfaces of the platform gaskets 4 and 5, the front part and the rear part of the tibia platform surface 300 are respectively provided with a platform front fixing piece 320 and a dovetail part 340 which are protruded upwards out of the tibia platform surface, the center of the tibia platform surface 300 is provided with a center hole 330, and the lower side of the tibia platform main body is provided with a center handle 310 which is protruded downwards; wherein the central hole penetrates the tibial plateau 300 and extends into the central stem 310, the central post 510 adapted to receive and rotatably retain the movable plateau pad 5, wherein the dovetail comprises a centrally located guide structure and two laterally located wedge-shaped securing structures, wherein the front plateau securing member comprises a front face 321 opposite the central dovetail guide structure and two laterally located side faces 322, the front plateau securing member face being provided with arcuate slots 323 adapted to engage corresponding arcuate catches 423 (shown in FIG. 6) of the front portion of the plateau pad to limit the up and down movement of the plateau pads 4,5, but not to limit the horizontal rotational movement, wherein the wedge-shaped securing of the dovetail 340

The fixed structure 342 is designed to be adapted to fixedly retain the stationary platform liner 4 on the tibial plateau surface, wherein the side 322 of the anterior platform mount and the side surface 343 of the dovetail on the other side of the central aperture of the wedge-shaped fixed structure 342 are designed to simultaneously act as stops for the rotating movable platform liner 5, respectively, to prevent further rotation of the movable platform liner 5.

Fig. 10A-10C schematically illustrate the rotation of the mobile platform liner on the tibial platform in an assembled horizontal section. The center post 510 of the underside of the movable platform liner 5 is adapted to be guided and received and rotatably retained within the center bore 330. The outer peripheral surface of the mobile platform insert 5 is adapted to simultaneously stop upon rotation against the side 322 of the anterior platform mount 320 of the tibial platform 3 and the side surface 343 of the dovetail portion of the wedge-shaped fixation structure 342 on the other side of the central aperture 330.

Fig. 10A shows the movable platform gasket 5 in a central angular position, where the movable platform gasket 5 is not in contact with the platform forward mount or dovetail. Fig. 10B shows the movable floor mat 5 in a limit angular position of clockwise rotation, in the figure approximately +15 degrees. At this time, the movable platform gasket 5 is in contact with the side 322 of the platform front mount on the left side and is also in contact with the side surface 343 of the wedge-shaped fixing structure of the dovetail 340 on the right side. Fig. 10C shows the movable floor mat 5 in a limit angular position of counterclockwise rotation, in the figure approximately-15 degrees. At this time, the movable platform gasket 5 contacts the side surface 343 of the wedge-shaped fixing structure of the dovetail 340 at the left side and contacts the side surface 322 of the platform front fixing member at the right side just as well.

In the prior art, no numerical limitation is made to the ratio of the coronal radius and the sagittal posterior arc radius of the femoral condyle to the mobile tibial plateau pad. However, in the present invention, the femoral condyle and the mobile tibial plateau pad are designed to have a high fit. As shown in FIG. 11A, the ratio of the radius of the femoral condyle coronal surface 101 to the radius of the mobile tibial plateau pad coronal surface 501 is 0.96:1 to 0.98:1. For ease of understanding, the imaginary circle at which the radii of the femoral condyle coronal surface 101 and the mobile tibial plateau pad coronal surface 501 lie is shown in phantom in fig. 11A. As shown in FIG. 11B, the radius ratio of the femoral condyle sagittal plane posterior arc 102 to the mobile platform liner sagittal plane posterior arc 502 is 0.80:1 to 0.94:1. As the radius ratio approaches 1, the fit increases, thereby optimizing the contact area between the femoral condyle and the mobile tibial plateau pad and reducing the pressure between the surfaces.

Those skilled in the art will appreciate that the distal radius of the femoral prosthesis when straightened is much greater than the posterior condylar radius when flexed, while the posterior surface of the tibial prosthesis has only one fixed radius. Therefore, the anastomosis of the artificial knee joint in the standing position is better than that in the knee bending position. Therefore, only the contact pressure and the contact area of the stationary platform lining and the movable platform lining in the standing position are compared below.

Table 1: contact pressure and contact area contrast of fixed platform liner and movable platform liner under standing position

	Contact pressure (Mpa)	Contact area (mm 2)
			Fixed platform gasket	16.8	187
Movable platform gasket	10.9	378

Wherein, the radius ratio of the femoral condyle (coronal surface) of the selected prosthesis to the radius of the coronal surface of the fixed platform pad or the movable platform pad is 0.966:1; the ratio of the radius of the femoral condyle to the radius of the posterior arc of the sagittal plane of the fixed platform pad (retroverted design) is nearly infinite and is 0.9:1.

Pressure finite element analysis of the fixed platen liner and the movable platen liner is shown in fig. 12A and 12B, respectively. In contrast, the contact area of the movable platform liner is significantly increased and the pressure is significantly reduced.

Fig. 13A to 13B show experimental verification with cadaveric bones, respectively. Wherein fig. 13A shows the situation where the posterior cruciate ligament is preserved. At this time, the tibial plateau of the present invention is fitted with a fixed plateau spacer, as shown in fig. 13B, with good knee joint motion. Fig. 13C shows the removal of the posterior cruciate ligament from the cadaveric bone, with the knee flexion gap enlarged and the prosthesis prone to dislocation. Fig. 13D and 13E show the tibial plateau of the present invention in the straightened position (fig. 13D) and in the flexed position (fig. 13E), respectively, after removal of the posterior cruciate ligament, with the mobile plateau spacer installed, with good knee motion.

The foregoing describes preferred embodiments of the invention, but the spirit and scope of the invention is not limited to the specific disclosure herein. Those skilled in the art can make any combination and extension of the above embodiments according to the teachings of the present invention to make further embodiments and applications within the spirit and scope of the present invention. The spirit and scope of the present invention are not limited by the specific embodiments, but by the appended claims.

List of reference numerals

1. Femoral condyle

3. Tibia plateau

4. Fixed platform gasket

5. Movable platform gasket

300. Tibia flat table top

310. Center handle

320. Front fixing piece of platform

321. Front face of front fixing piece of platform

322. Side of front fixing piece of platform

323. Arc-shaped clamping groove

330. Center hole

332. Side wall of central hole

340. Dovetail part

341. Guiding structure

342. Wedge-shaped fixing structure

343. Side surfaces of wedge-shaped fixing structure

510. Center column

420 Front recess of 520 platform liner

423 520 arc-shaped clamping hook

430 530 lower surface of platform liner

440 540 dovetail notch

101. Femoral condyle coronal surface

501. Movable platform liner coronal plane

102. Femoral condyle sagittal plane posterior arc

502. Sagittal plane posterior arc of mobile platform liner

Claims (10)

1. A tibial plateau (3) adapted to cooperate with a plateau pad, wherein the plateau pad (4, 5) is either a stationary plateau pad (4) or a mobile plateau pad (5), both the stationary plateau pad (4) and the mobile plateau pad (5) having a planar lower surface, and the mobile plateau pad (5) further being provided with a downwardly projecting central post (510) on the planar lower surface,

it is characterized in that the upper side of the tibia platform (3) is provided with a tibia platform surface (300) which is suitable for being matched with the lower surfaces of the platform gaskets (4, 5), the front part and the rear part of the tibia platform surface (300) are respectively provided with a platform front fixing piece (320) and a dovetail part (340) which are protruded upwards out of the tibia platform surface (300), the center of the tibia platform surface (300) is provided with a center hole (330), the lower side of the tibia platform main body is provided with a center handle (310) which is protruded downwards,

wherein the central hole (330) extends through the tibial plateau surface (300) and into the central stem (310), adapted to guide the central post (510) that receives and rotatably retains the mobile plateau pad (5),

wherein the dovetail (340) comprises a guiding structure (341) at the center and wedge-shaped fixing structures (342) at both sides,

wherein the front platform fixing part (320) comprises a front surface opposite to the guide structure (341) in the center of the dovetail part (340) and side surfaces at two ends, the front surface of the front platform fixing part (320) is provided with an arc clamping groove (323) which is suitable for being combined with a corresponding arc clamping hook (423) at the front part of the fixed platform gasket (4) to limit the up-down movement and the horizontal rotation movement of the fixed platform gasket (4) and is suitable for being combined with a corresponding arc clamping hook (523) at the front part of the movable platform gasket (5) to limit the up-down movement of the movable platform gasket (5) without limiting the horizontal rotation movement of the movable platform gasket (5),

wherein the dovetail wedge-shaped fixation structure (342) is designed to be adapted to cooperate with the anterior platform fixation (320) to fixedly retain the stationary platform liner (4) on the tibial plateau (300),

wherein the side surfaces (322) of the platform front mount (320) and the side surfaces (343) of the wedge-shaped mounting structure (342) of the dovetail on the other side of the central hole (330) are designed to simultaneously act as stops for the rotating movable platform pad (5) to prevent further rotation of the movable platform pad (5), respectively.

2. The tibial plateau (3) of claim 1, wherein,

the body of the side wall of the central hole (330) is cylindrical and has a slope of widened dimension near the upper portion of the tibial plateau (300) to facilitate the insertion of the central post (510), while the lower portion remote from the tibial plateau (300) narrows to stop the central post (510) from further descending.

3. A stationary platform liner (4) is characterized in that,

the underside of the stationary platform liner is shaped to engage with the wedge-shaped fixation structure (342) of the anterior platform mount (320) and the dovetail (340) of the tibial platform (3) according to claim 1 or 2.

4. A stationary platen liner (4) according to claim 3, characterized in that the front portion of the stationary platen liner (4) is provided with an arcuate hook (423) adapted to engage an arcuate slot (323) in the front face of the platen front mount (320), the arcuate hook (423) and thus the stationary platen liner (4) being cooperatively restrained from up and down movement and horizontal rotational movement by a wedge-shaped securing structure (342) of the arcuate slot (323) and the dovetail (340).

5. The stationary platen liner (4) of claim 3 or 4, having a volumetric shape that fills the space between the platen front mount (320) and the dovetail (340) above the tibial platen face (300).

6. A movable platform liner (5) is characterized in that,

the underside of the mobile platform pad has a central post (510) adapted to be guided and received and rotatably held in the central hole (330), and the outer peripheral surface of the mobile platform pad is adapted to simultaneously stop against the side surface (322) of the anterior platform mount (320) of the tibial platform (3) according to claim 1 or 2 and the side surface (343) of the dovetail part of the wedge-shaped fixation structure (342) located on the other side of the central hole (330) according to rotation.

7. The mobile platform liner (5) according to claim 6, wherein the radius ratio of the sagittal posterior arc (102) of the femoral condyle (1) to the sagittal posterior arc (102) of the mobile platform liner (5) is from 0.80:1 to 0.94:1.

8. The mobile platform gasket (5) according to claim 6 or 7, characterized in that the front part of the mobile platform gasket (5) is provided with an arc-shaped hook (523) adapted to engage with an arc-shaped slot (323) of the front face of the platform front mount (320), said arc-shaped hook being limited from moving up and down by the arc-shaped slot (323) but not from horizontal rotational movement.

9. The mobile platform pad (5) according to claim 6 or 7, characterized in that the volume of the space of the mobile platform pad (5) accommodated between the platform front mount (320) and the dovetail (340) is shaped so as not to be subject to any stop during rotation of the mobile platform pad (5) before stopping against the side face (322) of the platform front mount (320) and the side face (343) of the dovetail part of the wedge-shaped securing structure (342) located on the other side of the central hole (330).

10. A prosthetic system for a primary total knee replacement, comprising:

a femoral condyle (1),

the tibial plateau (3) of claim 1 or 2,

a stationary platform liner (4) according to any one of claims 3 to 5 or a mobile platform liner (5) according to any one of claims 6 to 9 arranged between a femoral condyle (1) and a tibial plateau (3),

wherein the underside of the fixed platform pad (4) or the movable platform pad (5) is placed on the tibial platform (3).