JP2003061991A - Artificial knee joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backward stable type artificial knee joint with a sufficient mechanical strength while keeping the excellent slidability of ceramics. SOLUTION: A first rib 14 continuing to a cam 13 and extending in the direction nearly perpendicular to the inner surface 3a of the femur member 3 is formed in the ridge part with the post engaging groove 12, and a second rib 15, continuous with the first rib 14, extends obliquely forward. The front end of the second rib 15 is apart from the corner part between the rear oblique wall 8 and the bottom wall 9 of the inner surface 3a by 3-10 mm to the front or to the rear (the distance w). In the structure, the front end 15a of the second rib 15 continues to the inner surface 3a of the femur member 3 in a circular arc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial knee joint for replacing a surface of a knee joint which has lost normal function, and more particularly, to a posterior stability having a post protruding from a tibial member and a cam of a femoral member engaging with the post. Type artificial knee joint.

[0002]

2. Description of the Related Art A posterior stable artificial knee joint 30 has a cam 32 of a femoral member 31 and a post 34 of a tibial member 33 engaging with each other as shown in FIG. The member 31 is prevented from excessively moving forward, and stability and movability are ensured.

As such a backward-stabilized artificial knee joint 30, only metal ones have been conventionally used.

The conventional artificial knee joint 30 described above is shown in FIG.
5, ribs 35 for reinforcing the cam 32 of the femoral member 31 are provided along the post engagement groove 39 that divides the rear wall 36, the rear slant wall 37, and the bottom wall 38 into left and right. The front end of 35 was substantially aligned with the corner 41 of the inner surface 40 of the main body.

[0005]

By the way, the rib 3 is used.
At the end of 5 and the corner 41 of the inner surface 40 of the main body, stress is likely to be concentrated independently because of a large change in rigidity, but if they match, stress is more likely to be concentrated due to a synergistic effect. Therefore, if this shape is applied to a ceramic product, there is a high possibility that it will be damaged due to stress concentration. However, since the ceramic femoral member 31 has excellent sliding characteristics with the sliding portion 42 made of the polymer material in the tibial member 33, the ceramic femoral member 30 is also used in the posterior stable artificial knee joint 30. 31 is desired.

In view of the problems of the prior art as described above, the present invention makes it possible to provide an artificial knee joint that makes use of the excellent slidability of ceramics and has a sufficiently large mechanical strength.

[0007]

In order to solve the above-mentioned conventional problems, the artificial knee joint of the present invention has a front wall on which a femoral member stands in a substantially vertical direction, an anterior oblique wall connected to the rear thereof, and a rear wall thereof. A continuous bottom wall and a posterior oblique wall that is connected to the rear of the posterior wall, and a posterior wall that is connected to the posterior of the posterior wall, the posterior wall, the posterior oblique wall, and the bottom wall that are divided into left and right and extend in the front-rear direction that receives the post formed in the tibial member A post-engaging groove and a cam located at a rear end of the post-engaging groove and bridging the two rear walls, and extending in a direction substantially perpendicular to the inner surface of the femoral member following the cam. A first rib extending to the post engagement groove is formed at a ridge portion with the post engaging groove, and a second rib extending obliquely forward to the first rib is provided, and a front end of the second rib is Forward from the corner between the rear slanted wall and the bottom wall on the inner surface Wherein the away 10mm from mm.

With this structure, it is possible to effectively prevent excessive stress from concentrating on the corner between the posterior oblique wall and the bottom wall on the inner surface of the femoral member. Therefore, in the posterior stable artificial knee joint in which the cam of the femoral member and the post of the tibial member are engaged to stabilize the movement in the anterior-posterior direction, the femoral member can be made of ceramic. This makes it possible to make use of the excellent slidability of ceramics and an artificial knee joint with sufficiently large mechanical strength.

When the front end of the second rib comes closer than 3 mm from the corner between the rear slanted wall and the bottom wall of the inner surface, excessive stress is concentrated and the front end of the second rib is 10 from the corner between the rear slanted wall and the bottom wall of the inner surface
If the distance is more than mm, the amount of bone resection of the femur may be excessive because the second rib is received.

Further, the artificial knee joint according to claim 2 is characterized in that the front end of the second rib is continuous with the inner surface of the femoral member in an arc shape.

With this structure, the stress concentration at the joint between the front end of the second rib and the inner surface of the femoral member can be further alleviated.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show an artificial knee joint 1 of the present invention. This artificial knee joint 1 comprises a tibial member 2 and a femoral member 3 made of ceramic. As the ceramic to be used, a material having excellent biocompatibility and sliding characteristics such as alumina or zirconia is used, and among them, zirconia having high material strength is preferable.

The tibial member 2 is composed of a metal base 4 fixed to the tibia and a sliding portion 5 made of a polymer material that slides on the femoral member 3. As a metal to be used, one having excellent biocompatibility, for example, a cobalt chromium alloy or the like is used. In addition, polyethylene or the like, which is excellent in biocompatibility and sliding properties, is suitable as the polymer material. The base 4 has a structure in which a stem 4a protruding downward is fixed in the tibial bone marrow cavity and the sliding portion 5 is fitted and held on the opposite side of the stem 4a.

A post 6 that engages with the femoral member 3 is formed on the sliding portion 5. The post 6 engages with a cam 13 of the femoral member 3 described later to stabilize the movement in the front-rear direction. On the other hand, the left and right concave curved surfaces 5a of the post 6 are adapted to slide on the outer surface 3b of the femoral member 3.
As shown in FIG. 2, the femoral member 3 includes a front wall 7 standing in a substantially vertical direction, a front slant wall 8 connected to the rear of the front wall 7, a bottom wall 9 connected to the rear of the front wall 7, and a rear slant wall 10 connected to the rear of the front wall 7. It is composed of a rear wall 11 extending in one direction. Further, the femoral member 3 divides the posterior wall 11, the posterior oblique wall 10, and the bottom wall 9 into right and left parts, and receives a post 6 formed in the tibial member 2 and extends in a post engaging groove 12 extending in the front-rear direction. And a cam 13 located at the rear end of the post engaging groove 12 and provided so as to bridge the two rear walls 11. Further, as shown in FIG. 2, a first rib 14 extending substantially vertically to the inner surface 3a of the femoral member 3 following the cam 13 is formed at the ridge of the post engaging groove 12, and The second rib 1 extending obliquely downward and forward continuously from the first rib 14.
5 is provided. The first rib 14 and the second rib 15
Has a width t (see FIG. 1) of 3 mm to 10 mm and is provided to reinforce the cam 13. If the width t is smaller than 3 mm, the strength is insufficient, and if the width t is larger than 10 mm, the amount of resection of the femur is too large to receive the first rib 14 and the second rib 15. Bone strength may be significantly reduced.

A front end 15a of the second rib 15 is a distance w (see FIG. 1) = 3 m from the corner between the posterior oblique wall 10 and the bottom wall 9 on the inner surface 3a of the femoral member 3.
It is important that they are separated by m to 10 mm.

That is, when the front end 15a of the second rib 15 comes closer than 3 mm from the corner between the posterior oblique wall 10 and the bottom wall 9 on the inner surface 3a of the femoral member 3, excessive stress concentrates, Front end 15 of the second rib 15
When a is more than 10 mm away from the corner between the posterior oblique wall 10 and the bottom wall 9 on the inner surface 3a of the femoral member 3, the amount of osteotomy of the femur becomes too large to receive the second rib 15. Bone strength may be significantly reduced.

It is desirable that the front end 15a of the second rib 15 be continuous with the inner surface 3a of the femoral member 3 in an arc shape.

That is, by forming the arcuate connection, it is possible to further alleviate stress concentration at the joint between the front end 15a of the second rib 15 and the inner surface 3a of the femoral member 3.

Although the embodiment of the present invention has been illustrated above, it is needless to say that the present invention is not limited to this embodiment and can take any form without departing from the object of the invention.

[0021]

As described above, according to the present invention, in the posterior stable artificial knee joint in which the cam of the femoral member and the post of the tibial member are engaged to stabilize the movement in the anteroposterior direction, the femoral member is provided. Can be made of ceramic.

This makes it possible to make a posterior stable artificial knee joint that takes advantage of the excellent slidability of ceramics and has a sufficiently large mechanical strength.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an artificial knee joint according to an embodiment of the present invention.

FIG. 2 is a side view of a femoral member in the artificial knee joint of FIG.

3 is a perspective view of the femoral member of FIG.

FIG. 4 is an exploded perspective view of a conventional artificial knee joint.

5 is a perspective view of a femoral member in the artificial knee joint of FIG. 4. FIG.

[Explanation of symbols]

1 artificial knee joint 2 tibia member 3 Femoral members 3a inner surface 3b exterior 4 base 4a stem 5 Sliding part 6 posts 7 front wall 8 forward slope 9 bottom wall 10 Back slope 11 rear wall 12 Post engagement groove 13 cams 14 First rib 15 Second rib 15a front end w distance t wall

Claims (2)

[Claims] 1. An artificial knee joint comprising a tibial member and a femoral member made of ceramic, wherein the femoral member is connected to a front wall standing upright in a substantially vertical direction, an anterior oblique wall connected to the rear thereof, and a posterior oblique wall thereof. A bottom wall and a posterior oblique wall connected to the rear thereof and a posterior wall connected to the posterior of the posterior wall, the posterior wall, the posterior oblique wall, and a post that divides the posterior wall into left and right parts and extends in the anterior-posterior direction for receiving the post formed on the tibial member. An engaging groove and a cam provided at a rear end of the post engaging groove and provided so as to bridge the two rear walls, and in a direction substantially perpendicular to the inner surface of the femoral member following the cam. A first rib that extends is formed at a ridge line with the post engaging groove, and a second rib that extends obliquely forward in a continuous manner with the first rib is provided, and a front end of the second rib is the inner surface. From the corner between the rear slanted wall and the bottom wall in Artificial knee joint which is characterized in that the property is approximately 10mm from 3mm. 2. The front end of the second rib is continuous with the inner surface of the femoral member in an arc shape.
The described artificial knee joint.