Artificial knee joint, and beam member, insert member, and base plate used therein

Abstract

An artificial knee 1 is provided with: an insert member 2 that is buried in a portion of the joint surface of the medial condyle MC or lateral condyle LC of the tibia T; and a bridge member 3 that is placed underneath the insert member 2 and that has a length that allows anchoring of both ends of the bridge member to the cortical bone of the tibia T.

Description

[Technical field]

[0001] The present invention relates to an artificial knee joint, and a beam member, an insert member, and a base plate used therein. [Background technology]

[0002] The knee joint is a joint formed by the femur, tibia, and patella. The knee joint can move smoothly thanks to the articular cartilage at the distal end of the femur and the proximal end of the tibia and the meniscus between them acting as a cushion.

[0003] However, if the knee cartilage wears down due to obesity or aging, and the meniscus is damaged, not only will the cushioning between the distal end of the femur and the proximal end of the tibia be lost, but the knee joint will also deform and progress over time. In addition, the knee joint can also become deformed if a person develops rheumatoid arthritis or is injured in the knee. When the knee joint becomes deformed (osteoarthritis), the knee joint cannot move smoothly, and the patient feels severe pain when walking, and may even have difficulty walking.

[0004] Total knee arthroplasty (TKA) is used as a treatment for such knee osteoarthritis. Total knee arthroplasty is a technique in which the distal end of the femur and the proximal end of the tibia are resected and replaced with an artificial knee joint. Currently, many patients have undergone total knee arthroplasty, which has the effect of eliminating pain and enabling normal walking, and has a high degree of patient satisfaction. Many artificial knee joints for use in total knee arthroplasty have also been developed (see Patent Documents 1 and 2).

[0005] In recent years, unicondylar knee arthroplasty (UKA), in which only a part of the knee joint is replaced with an artificial knee joint, has also been adopted. Patent Document 3 below discloses a partial unicondylar system for unicondylar knee arthroplasty. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2013-172992 A [Patent Document 2] JP 2001-120583 A [Patent Document 3] Special Publication No. 2018-502651 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the current total knee arthroplasty and unicondylar knee arthroplasty, the meniscus cannot be preserved as a rule. In addition, in total knee arthroplasty, the entire joint surface is removed and replaced with an artificial knee joint, making it difficult to reproduce the original height of the joint surface. As the original joint surface height changes, there have been many reports of unexpected pain and limited range of motion after surgery, limiting patient satisfaction.

[0008] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an artificial knee joint that can obtain characteristics similar to those of a normal knee joint, as well as a beam member, an insert member, and a base plate used therein. [Means for solving the problem]

[0009] The artificial knee joint of the present invention comprises an insert member embedded in a part of the articular surface of the medial condyle or the lateral condyle of the tibia; and a beam member disposed below the insert member and having a length such that both ends are fixed to the cortical bone of the tibia.

[0010] According to this configuration, by embedding the insert member only in a part of the joint surface, the surface of the insert member can be made to match the remaining joint surface around it, so it is possible to reproduce the original height of the joint surface. In addition, by reproducing the original height of the joint surface, it is possible to preserve the meniscus. As a result, the artificial knee joint of the present invention can obtain characteristics close to those of a normal knee joint. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing an artificial knee joint in use. [Diagram 2] 4A and 4B are a perspective view and a cross-sectional view showing an insert member. [Diagram 3] FIG. [Figure 4A] FIG. [Figure 4B] 13A and 13B are a perspective view and a cross-sectional view showing a state in which a base plate according to another embodiment is used. [Figure 4C] 13A and 13B are a plan view and a side view of a base plate according to another embodiment. [Figure 4D] FIG. [Figure 4E] FIG. 13 is a plan view of a base plate according to another embodiment. [Figure 4F] FIG. 13 is a plan view of a base plate according to another embodiment. [Figure 4G] FIG. 13 is a plan view of a base plate according to another embodiment. [Figure 4H] FIG. 13 is a plan view of a base plate according to another embodiment. [Figure 4I] FIG. 13 is a plan view of a base plate according to another embodiment. [Figure 4J] FIG. 13 is a side view of a base plate according to another embodiment. [Figure 4K] 13A and 13B are a plan view and a side view of a base plate according to another embodiment. [Figure 4L] 13A and 13B are a plan view and a side view of a base plate according to another embodiment. [Diagram 5] 1A and 1B are perspective and plan views showing a surgical procedure. [Figure 6A] 13A and 13B are a plan view and a front view showing a state in which an artificial knee joint according to another embodiment is used. [Figure 6B] 13A and 13B are a plan view and a front view showing a state in which an artificial knee joint according to another embodiment is used. [Figure 6C]13A and 13B are a plan view and a front view showing a state in which an artificial knee joint according to another embodiment is used. [Figure 6D] 13A and 13B are a plan view and a front view showing a state in which an artificial knee joint according to another embodiment is used. [Figure 6E] 13A and 13B are a plan view and a front view showing a state in which an artificial knee joint according to another embodiment is used. [Figure 6F] 13A and 13B are a plan view and a front view showing a state in which an artificial knee joint according to another embodiment is used. [Figure 6G] 13A and 13B are a plan view and a front view showing a state in which an artificial knee joint according to another embodiment is used. [Figure 6H] 13A and 13B are a plan view and a front view showing a state in which an artificial knee joint according to another embodiment is used. [Figure 7] 13A and 13B are a plan view and a side view of an insert member according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an artificial knee joint according to one embodiment of the present invention will be described with reference to the drawings. The artificial knee joint of the present invention is an artificial knee joint used in artificial knee joint replacement surgery for treating osteoarthritis of the knee, rheumatoid arthritis, etc., and is characterized by its structure that can preserve the meniscus and ligaments.

[0013] [Artificial knee joint] Fig. 1 shows the artificial knee joint 1 in use. Figs. 2 to 4 show components of the artificial knee joint 1. In the following description of the artificial knee joint 1, the direction in which the tibia T extends is referred to as the up-down direction, and the front-back and left-right directions of the patient at the tibia T are referred to as the front-back direction and left-right direction, respectively.

[0014] The artificial knee joint 1 includes an insert member 2 embedded in a portion of the articular surface of the medial condyle MC or lateral condyle LC of the tibia T, and a beam member 3 disposed below the insert member 2. The artificial knee joint 1 may further include a base plate 4 disposed between the insert member 2 and the beam member 3. In FIG. 1, the insert member 2 is embedded in a portion of the articular surface of the lateral condyle LC.

[0015] The insert member 2 is embedded by removing a part of the articular surface of the medial condyle MC or lateral condyle LC of the tibia T, specifically a damaged part (worn part) of the articular surface. The insert member 2 is embedded with its height and surface shape adjusted so that its surface smoothly connects with the surrounding original articular surface.

[0016] It is preferable to prepare a plurality of types of insert members 2, and insert members 2a to 2c having different shapes are shown in Fig. 2. Fig. 2 shows a perspective view and a cross-sectional view of the insert members 2a to 2c.

[0017] The insert members 2a to 2c are generally disk-shaped. The insert member 2a is embedded in the medial condyle MC of the tibia T, and has a concave curved surface. The insert member 2b is embedded in the lateral condyle LC of the tibia T, and has a convex curved surface. The insert member 2c has a flat surface.

[0018] The lower surfaces of the insert members 2a to 2c are formed with a concentric stepped portion 20 into which the upper end portion of the cylindrical base plate 4 is fitted. If the base plate 4 is not provided, the stepped portion 20 is not formed.

[0019] The diameter of the insert members 2a to 2c is, for example, 15 to 25 mm, and preferably 17 to 22 mm. In practice, a plurality of insert members 2a to 2c with different diameters are prepared, and the insert member 2a to 2c of the optimum size is selected while referring to an MRI or other image of the patient.

[0020] The thickness of the insert members 2a-2c is, for example, 4 mm or more. A plurality of insert members 2a-2c with different thicknesses are prepared, and the insert member 2a-2c with the optimum thickness is selected while referring to an image such as an MRI of the patient. This allows the height of the surface of the insert members 2a-2c to be matched to the height of the original joint surface.

[0021] The recess of the insert member 2a embedded in the medial condyle MC is, for example, 1 to 2 mm, and the bulge of the insert member 2b embedded in the lateral condyle LC is, for example, 1 to 2 mm. The surfaces of the insert members 2a to 2c are formed so as to smoothly connect with the original joint surface around the embedded portion.

[0022] The insert members 2a to 2c are made of a material that is highly slippery and wear-resistant (such as high molecular weight polyethylene).

[0023] The beam member 3 is disposed below the insert member 2 in a substantially horizontal direction, and serves to support the insert member 2 from below. Such a beam member 3 having a raft function is sometimes called a raft pin. Note that the beam member 3 does not necessarily need to contact the lower surface of the insert member 2. In other words, the beam member 3 may support the insert member 2 via the cancellous bone in the tibia T, without contacting the lower surface of the insert member 2.

[0024] The shape of the beam member 3 is not particularly limited, and beam members 3a to 3c having different shapes are shown in Fig. 3. Fig. 3 shows a perspective view of the beam members 3a to 3c.

[0025] The beam members 3a to 3c are rod-shaped members, and have a length such that both ends in the longitudinal direction are fixed to the cortical bone of the tibia T. As a result, the beam members 3a to 3c become double-fixed beams, both ends of which are fixed to hard cortical bone. The length of the beam members 3a to 3c is, for example, 30 to 80 mm. In practice, a plurality of beam members 3a to 3c with different lengths are prepared, and the depth of the hole into which the beam members 3a to 3c are inserted during surgery is measured with a depth gauge to select the beam member 3a to 3c with the optimal length. The beam members 3a to 3c are prepared at a pitch of, for example, 2 mm, preferably 1 mm. The width of the beam members 3a to 3c is, for example, 2 to 8 mm.

[0026] There is no particular limitation on the cross-sectional shape of the beam member 3. The cross section of the beam member 3a is circular. However, the cross section of the beam member 3a may be elliptical.

[0027] The cross section of the beam member 3b is triangular. In the used state, the beam member 3b may be arranged so that the apex of the triangle faces upward as shown in Fig. 3, but may also be arranged so that the base of the triangle faces upward to form an inverted triangular cross section. By arranging the beam member 3b so that the base of the triangle faces upward, the function of supporting the insert member 2 is improved.

[0028] The cross section of the beam member 3c is quadrilateral. Here, the term "quadrilateral" is a concept that includes not only the rectangle shown in FIG. 3, but also a square, a trapezoid, a rhombus, and the like.

[0029] Although the beam member 3a having a circular cross section has a simple shape, in consideration of strength, the beam member 3b having a triangular cross section and the beam member 3c having a rectangular cross section are preferable. Also, the beam member 3b and the beam member 3c may be driven into a circular through hole made by a drill or the like.

[0030] The beam members 3a to 3c are made of a material that is highly biocompatible and has high rigidity (for example, titanium, stainless steel, etc.).

[0031] The base plate 4 is disposed between the insert member 2 and the beam member 3. The base plate 4 is cylindrical, and is fitted into a step 20 formed on the lower surface of the insert member 2 to support the outer edge of the insert member 2 from below. The cylindrical base plate 4 has a wall thickness of, for example, 1 mm.

[0032] A plurality of base plates 4 with different heights may be prepared. This allows the height of the insert member 2 to be adjusted by the base plate 4 rather than the insert member 2 itself. Also, a height adjustment plate (not shown) may be separately disposed between the base plate 4 and the beam member 3.

[0033] The base plate 4 does not necessarily have to be in contact with the beam member 3. In other words, the base plate 4 may not be in contact with the beam member 3, and the cancellous bone of the tibia T may be interposed between them.

[0034] The shape of the base plate 4 is not particularly limited, and Fig. 4A shows base plates 4a to 4d having different shapes. Fig. 4A shows a perspective view of the base plates 4a to 4d. Fig. 4B shows a perspective view and a cross-sectional view showing the use of the base plate 4d.

[0035] The base plate 4a has a cylindrical portion 40 formed with fitting holes 41 and fitting grooves 42 into which two beam members 3c having a rectangular cross section are fitted. The two beam members 3c are arranged in a cross shape. By combining the base plate 4a with the beam member 3c, the base plate 4a and the beam member 3c are integrated, thereby improving the function of supporting the insert member 2.

[0036] The base plate 4b has a cylindrical shape with a bottom, which has a cylindrical portion 40 and a bottom portion 43. This configuration can prevent the insert member 2 from sinking when a large load is applied.

[0037] The base plate 4c has a lattice-like mesh portion 44 formed at the lower opening of the cylindrical portion 40. With this configuration, the mesh portion 44 prevents the base plate 4c from sinking and reinforces the cylindrical portion 40 to maintain the cylindrical shape. In addition, the mesh portion 44 increases the installation area, thereby improving the function of supporting the base plate 4c when installed with cement.

[0038] The base plate 4d is configured such that the upper end surface of the cylindrical portion 40 is inclined with respect to a plane perpendicular to the cylindrical axis. On the other hand, the lower end surface of the cylindrical portion 40 is parallel to the plane perpendicular to the cylindrical axis. That is, the upper end surface of the base plate 4d is formed at an angle with respect to the lower end surface. The base plate 4d is used in combination with the insert member 2d shown in FIG. 4B. The upper surface of the insert member 2d is formed so as to be inclined with respect to a plane perpendicular to the cylindrical axis of the base plate 4d, similar to the upper end surface of the base plate 4d. In addition, the step portion 20 of the insert member 2d is parallel to the upper surface. According to this configuration, the height of the insert member 2d can be adjusted to match the height and shape of the actual joint surface of the tibia T by rotating the base plate 4d around the cylindrical axis. At this time, in order to prevent the insert member 2d from rotating relative to the base plate 4d, a protrusion and a groove that fits into this protrusion may be provided on the contact surfaces of the step portion 20 of the insert member 2d and the upper end surface of the base plate 4d. The shape and number of the protrusions are not particularly limited, and may be, for example, at least one point-like protrusion, or a plurality of linear protrusions extending radially from the cylindrical axis.

[0039] 4C to 4L show a base plate 4 according to another embodiment. The base plate 4 may include a cylindrical portion 40 (an example of a tubular portion) and a protruding portion that protrudes outward from the outer circumferential surface of the cylindrical portion 40. By providing the protruding portion on the outer circumferential surface of the cylindrical portion 40, it is possible to prevent the base plate 4 from sinking.

[0040] Fig. 4C shows a plan view and a side view of the base plate 4e, and Fig. 4D shows a perspective view of the fin 45. The base plate 4e has fins 45 provided on the cylindrical portion 40. Four fins 45 are provided in the circumferential direction of the cylindrical portion 40. The fins 45 are plate-shaped members made of the same material as the cylindrical portion 40. The fin 45 has a rectangular portion 45a and a triangular portion 45b. A part of the triangular portion 45b protrudes outward from the outer circumferential surface of the cylindrical portion 40. The triangular portion 45b has a sharp tip to easily penetrate cancellous bone.

[0041] The cylindrical portion 40 has an opening 40a that connects the inside of the cylinder to the outside of the cylinder. The width of the opening 40a is slightly wider than the width of the rectangular portion 45a of the fin 45. This allows the fin 45 to protrude from the inside of the cylinder to the outside of the cylinder through the opening 40a. The fin 45 may also have a stopper 45c that restricts the amount of protrusion from the outer circumferential surface of the cylindrical portion 40. The stopper 45c restricts the movement of the fin 45 by contacting the inner circumferential surface of the cylindrical portion 40.

[0042] 4E, the shape of each fin 45 may be made different to change the amount of protrusion of triangular portion 45b protruding from the outer circumferential surface of cylindrical portion 40. For example, the amount of protrusion of triangular portion 45b may be made smaller in a location closer to the cortical bone and larger in a location farther from the cortical bone.

[0043] 4F shows a plan view of the base plate 4f. The base plate 4f has four fins 46 provided on the cylindrical portion 40. The fins 46 have a rectangular portion 46a and a semicircular portion 46b. A part of the semicircular portion 46b protrudes from the outer circumferential surface of the cylindrical portion 40.

[0044] 4G shows a plan view of the base plate 4g. The base plate 4g has eight fins 45 provided on the cylindrical portion 40. The number of fins 45 is not particularly limited, but it is preferable to provide three or more fins.

[0045] 4H shows a plan view of the base plate 4h. The base plate 4h has four fins 47 provided on the cylindrical portion 40. The fins 47 extend in a direction inclined in the circumferential direction with respect to the normal direction to the outer circumferential surface of the cylindrical portion 40.

[0046] Fig. 4I shows a plan view of a base plate 4i, in which fins 47 extend in a direction different from that of the base plate 4h shown in Fig. 4H.

[0047] 4J shows a side view of the base plate 4j. The base plate 4j has fins 48 extending obliquely downward from the outer circumferential surface of the cylindrical portion 40.

[0048] The base plate 4k shown in FIG. 4K has threads 49 provided on the outer circumferential surface of the cylindrical portion 40. The threads 49 are provided intermittently in the circumferential direction along the outer circumferential surface of the cylindrical portion 40. The threads 49 are provided in multiple rows in the vertical direction. The threads 49 may be provided intermittently in the circumferential direction along the outer circumferential surface of the cylindrical portion 40, or may be provided over the entire outer circumferential surface of the cylindrical portion 40. The lower surface of the threads 49 preferably slopes upward toward the tip so that the base plate 4k can be easily hammered into the tibia (see the enlarged view).

[0049] The base plate 4m shown in FIG. 4L has recesses 50 provided on the outer peripheral surface of the cylindrical portion 40. The recesses 50 are provided intermittently in the circumferential direction along the outer peripheral surface of the cylindrical portion 40. The recesses 50 are provided in multiple rows in the vertical direction. Over time, cancellous bone enters the recesses 50, suppressing sinking of the base plate 4m. The recesses 50 may be provided intermittently in the circumferential direction along the outer peripheral surface of the cylindrical portion 40, or may be provided over the entire outer peripheral surface of the cylindrical portion 40.

[0050] The cylindrical portion 40 shown in Figures 4C to 4L is cylindrical with open top and bottom, but may have a bottom portion 43 as shown in Figure 4A(b), or may have a lattice-like mesh portion 44 as shown in Figure 4A(c).

[0051] [Surgical procedure] FIG. 5 shows an example of a surgical procedure. The articular surface of the lateral condyle LC of the tibia T shown in FIG. 5(a) is worn down. First, a through hole extending along the anterior-posterior direction is formed below the articular surface of the lateral condyle LC using a drill or the like. Two through holes are formed side by side in the lateral direction. Next, as shown in FIG. 5(b), a beam member 3 is driven into the through hole. Next, a round hole having a diameter corresponding to the diameter of the insert member 2 is formed in the lateral condyle LC above the beam member 3. Next, as shown in FIG. 5(c), a base plate 4 is inserted into the round hole formed above the beam member 3. Finally, as shown in FIG. 5(d), the insert member 2 is fitted to the upper end of the base plate 4.

[0052] As described above, the artificial knee joint 1 of this embodiment includes the insert member 2 embedded in a part of the articular surface of the medial condyle MC or the lateral condyle LC of the tibia T, and a beam member 3 that is disposed below the insert member 2 and has a length such that both ends are fixed to the cortical bone of the tibia T.

[0053] According to the artificial knee joint 1 of this embodiment, by embedding the insert member 2 only in a part of the joint surface, the surface of the insert member 2 can be made to match the height and shape of the remaining surrounding joint surface, so it is possible to reproduce the original height of the joint surface. Also, by reproducing the original height of the joint surface, it is possible to preserve the meniscus.

[0054] In addition, since the artificial knee joint 1 of this embodiment replaces only a part of the joint, the surgery is easy, the surgical invasion is minimal, and the risk of bleeding is reduced. It is possible to preserve the anterior cruciate ligament (ACL), and if the anterior cruciate ligament is damaged, it is also possible to reconstruct it at the same time. In addition to the meniscus, all ligaments can be preserved, and it is particularly possible to preserve the deep medial collateral ligament (dMCL), which was previously difficult to do.

[0055] The insert member 2 may be in contact with the beam member 3. According to this configuration, the insert member 2 is reliably supported by the beam member 3 from below.

[0056] The insert member 2 may be out of contact with the beam member 3. According to this configuration, a certain degree of play can be provided between the insert member 2 and the beam member 3, so that damage when a large load is applied can be suppressed.

[0057] It is preferable that the outer edge portion of the insert member 2 adjacent to the meniscus is formed in an arc shape. With this configuration, interference with the meniscus can be prevented, and the meniscus can be preserved.

[0058] The beam member 3 may be disposed only along the front-back direction. If the beam member 3 is disposed along the left-right direction, when a large load is applied to either the medial condyle MC or the lateral condyle LC, the other of the medial condyle MC and the lateral condyle LC may be adversely affected via the beam member 3.

[0059] The artificial knee joint 1 of this embodiment may further include a cylindrical base plate 4 that is disposed between the insert member 2 and the beam member 3 and supports the outer edge of the insert member 2. With this configuration, the insert member 2 is reliably supported from below by the base plate 4 and the beam member 3.

[0060] The base plate 4 may be in contact with the beam member 3. According to this configuration, the base plate 4 is reliably supported by the beam member 3 from below.

[0061] The base plate 4 may be out of contact with the beam member 3. With this configuration, a certain degree of play can be provided between the base plate 4 and the beam member 3, so that the base plate 4 can sink and the height of the insert member 2 can be appropriately adjusted.

[0062] The upper part of the base plate 4 may have an inclined surface that is inclined with respect to a plane perpendicular to the cylindrical axis. According to this configuration, the height of the insert member 2 can be adjusted to match the height and shape of the actual joint surface of the tibia T by rotating the base plate 4 around the cylindrical axis.

[0063] The surface of the insert member 2a embedded in the medial condyle MC of the tibia T is preferably formed into a concave curved surface. Normally, the original articular surface of the medial condyle MC is a concave curved surface, so with this configuration, the surface of the insert member 2a smoothly connects with the surrounding original articular surface.

[0064] The surface of the insert member 2b embedded in the lateral condyle LC of the tibia T is preferably formed into a convex curved surface. Normally, the original articular surface of the lateral condyle LC is a convex curved surface, so with this configuration, the surface of the insert member 2b smoothly connects with the surrounding original articular surface.

[0065] The artificial knee joint 1 is not limited to the configurations of the above-mentioned embodiments, and is not limited to the above-mentioned functions and effects. Of course, various modifications can be made to the artificial knee joint 1 without departing from the spirit of the present invention. For example, the configurations and methods of the above-mentioned embodiments may be arbitrarily adopted and combined, and one or more of the configurations and methods of the various modified examples described below may be arbitrarily selected and adopted in the configurations and methods of the above-mentioned embodiments.

[0066] For example, Fig. 6A shows an example in which the insert members 2 are embedded in parts of the articular surfaces of the medial condyle MC and the lateral condyle LC. In this figure, the base plate 4 is not shown, but the base plate 4 may be provided, and the same applies to the following figures.

[0067] Fig. 6B is an example where the insert member 2 is D-shaped in plan view, Fig. 6C is an example where the insert member 2 is semicircular in plan view, and Fig. 6D is an example where the insert member 2 is elliptical in plan view.

[0068] FIG. 6E shows an example in which beam members 3 extending in the left-right direction are arranged in addition to beam members 3 extending in the front-rear direction.

[0069] Fig. 6F is an example in which one beam member 3 extending along the front-rear direction and one beam member 3 extending along the left-right direction are arranged for each insert member 2. Fig. 6G is an example in which one beam member 3 extending along the front-rear direction and two beam members 3 extending along the left-right direction are arranged for each insert member 2. Fig. 6H is an example in which only three beam members 3 extending along the left-right direction are arranged.

[0070] 7 is a plan view and a side view of an insert member 2e according to another embodiment. The insert member 2e is supported from below by the beam member 3 without the base plate 4. Therefore, the insert member 2e is disk-shaped without a step 20. The disk-shaped insert member 2e has protrusions 21 on its outer peripheral surface. The protrusions 21 are provided intermittently in the circumferential direction along the outer peripheral surface of the insert member 2e. The protrusions 21 are provided in a plurality of rows in the vertical direction. It is preferable that the lower surface of the protrusions 21 is inclined upward toward the tip so that the insert member 2e can be easily driven into the tibia (see the enlarged view).

[0071] Furthermore, a unicondylar knee arthroplasty (UKA) may be adopted for the medial condyle MC, and a knee prosthesis 1 may be adopted for only the lateral condyle LC. [Explanation of symbols]

[0072] 1. Artificial knee joint 2 Insert material 2a Insert member 2b Insert material 2c Insert material 2d Insert material 3 Beam members 3a Beam member 3b Beam member 3c Beam member 4 Base plate 4a Base plate 4b Base plate 4c Base plate 4d base plate 4e Base plate 4f Base plate 4g base plate 4h Baseplate 4i Baseplate 4j Base plate 4k base plate 4m base plate 40 Cylindrical part 40a opening 43 Bottom 44 Mesh section 45 Finn 46 Finn 47 Finn 48 Finn 49 Threads 50 Recess T tibia MC medial condyle LC lateral condyle

Claims

1. An insert member embedded in a hole formed in a part of the articular surface of the medial condyle or the lateral condyle of the tibia; An artificial knee joint comprising: a beam member arranged below the insert member, having a length such that both ends are fixed to the cortical bone of the tibia, and supporting the insert member from below.

2. The knee prosthesis of claim 1 , wherein the insert member is in contact with the beam member.

3. The knee joint prosthesis of claim 1 , wherein the insert member is out of contact with the beam member.

4. The knee prosthesis of claim 1 , wherein the beam members are disposed only along the anterior-posterior direction.

5. The knee prosthesis of claim 1 , further comprising a cylindrical base plate disposed between the insert member and the beam member and supporting an outer edge of the insert member.

6. The knee prosthesis of claim 5 , wherein the base plate is in contact with the beam member.

7. The knee prosthesis of claim 5 , wherein the base plate is not in contact with the beam members.

8. The artificial knee joint according to claim 5 , wherein an upper portion of the base plate has an inclined surface that is inclined with respect to a plane perpendicular to the cylindrical axis.

9. The artificial knee joint according to claim 1 , wherein the surface of the insert member is formed as a concave curved surface, a convex curved surface, or a flat surface.

10. The artificial knee joint according to claim 1 , wherein the insert member is circular, elliptical, or semicircular in plan view.

11. The artificial knee joint according to claim 1 , wherein the insert member has a height and a shape adjusted so that a surface of the insert member smoothly connects with the surrounding natural joint surface.

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