JPH03195550A - Thigh member for artificial knee joint - Google Patents

Abstract

PURPOSE:To increase the resistance against the bending of a thigh member and remove a bone breakage accident and the trouble on the joint movement by forming a connection section with a slowly increased longitudinal section at the portion from joint front and rear walls to reinforcing ribs. CONSTITUTION:The upper edge a5 of each reinforcing rib a4 has a shape approximate to the inner periphery shape of a thigh member A constituted of inner wall faces of a front wall al, a support wall a2, and a rear wall a3, and a connection section a6 with a slowly increased longitudinal section from the front wall a1 and the rear wall a3 to a reinforcing rib a4 is formed. When connection sections all, a31 at the front and rear ends of the rib a4 are considered as dangerous cross sections against the bending load, the dangerous cross sections are continuously distributed in the spread of the connection section a6 without being concentrated at one vertical position along the longitudinal direction, and the resistance against the bending load is sharply improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is applicable to knee joints that are highly deformed due to rheumatism and osteoarthritis, causing pain and difficulty walking,
Destruction due to trauma such as sports accidents or bone tumors (
This invention relates to improvements in artificial knee joints used in the field of orthopedics to restore normal function to damaged knee joints.

(Prior art) Although the history of the study and practice of artificial knee joints is relatively short, like artificial hip joints, the knee joint does not receive the load of bending and extending the knee due to walking or exercise by sliding on the joint surface. Since the knee joint functions as a load-bearing joint, there are many cases of joint disease and destruction due to pathological or traumatic injuries, and the number of replacement repair cases with artificial knee joints has been increasing in recent years. Figure 1 shows a typical structure of an artificial knee joint. This joint consists of a femoral component A fixed to the lower end surface (referred to as the distal surface) of the femur F, and a tibia T.
It includes a tibial member B fixed to the upper end (referred to as the proximal tibia), of which member A has a single anterior joint wall a1 that stands up on the front side, and a tibial member A that forms a generally arc shape and extends on the rear side. The concave articular surface b of the sliding member b1 of the tibial member B
A pair of joint walls sliding into 2, a2. a2, and a rear joint wall a3 that stands up in a sharp arc behind this temporary joint wall a2°a2. a3, the tibial member B includes the sliding member b1, a concave joint surface b2 formed on the surface thereof, and an implanted part b3 implanted in the medullary canal T1 at the proximal end of the tibia T, The distal lower end of the bone F is resected and the femoral bone component A is attached via bone cement; - the upper end (proximal end) of the right abdominal bone T;
The tibial component B is implanted and fixed to the joint surface b2 of the sliding member b1.
Mainly the joint U of member A (for normal knee flexion and extension)
wall a2゜a2, and when the knee is deeply bent, the rear wall a3. a3 is also slidably received on the joint surface b2 to accommodate bending and extension of the knee.

By the way, the femoral bone component A and the tibial component B are made of a combination of metal-metal materials or ceramic-ceramic materials, and they have advantages and disadvantages, but in particular, in the case of the ceramic femoral component A, the femoral bone component A is made of a ceramic material, and the femoral bone component A is a combination of metal materials or ceramic-ceramic materials. Dynamic load, i.e. articular wall a2 of femoral component A. Due to the inherent nature of the material, it is fragile against external forces that act on the inside of a2 and cause it to slide onto the joint member bl, so the upper edge is reinforced with a horizontal edge as shown in Figures 2 and 3. A pair of ribs A4 were formed in parallel. The strength of the ceramic femoral bone member A against the above external force can be approximated by a bending strength test shown in FIG. That is, the femoral bone component A, which is upside down, is fixedly placed on the abutment via the cement +-C, and a load E is gradually applied downward from above the component A to move the component A outward (front and back). The bending fracture strength is defined as the load that causes a crack to occur or break on the inner surface when a force is applied to warp and bend the material. In these tests, cracks and breaks occur especially in the reinforcing rib a4. A4 joint anterior wall a1
This indicates that bending stress is concentrated in this area near the connection part all that is coupled to the . Stress is concentrated on the connecting part a31 on the rear side of the reinforcing rib a4 when the knee is folded deeply.In this case, the joint rear wall a3 slides on the joint surface b2 and receives the above-mentioned external bending force. Become. By the way, if a rack or fracture occurs in the femoral bone component A in the artificial knee joint as described above, the joint movement becomes impossible or a fracture occurs, which is extremely dangerous.

(Problems to be Solved by the Invention) In view of the above, an object of the present invention is to improve the resistance of the femoral bone member to bending and eliminate fracture accidents and obstacles to joint movement.

The present inventor considered various measures to improve the bending brittleness of conventional reinforcing ribs. The most primitive method was to increase the thickness and height of the rib;
Since the rib receiver increases the slot size and the amount of natural bone removed, it is considered a tab from the surgeon's point of view. As a result of various other trials and errors, in the end, without increasing the thickness of the reinforcing rib A4, we decided to take into consideration the (mechanical) dangerous cross-section for the load so that the dangerous cross-section is not concentrated in one place but is gradually dispersed. In other words, by forming the reinforcing ribs a4 in the inner cavity of member A in a shape that does not cause sudden changes in the cross section that resists bending loads, we succeeded in exhibiting more than twice the bending fracture strength.

(Means for Solving the Problems) To explain the configuration of the present invention with reference to embodiment drawings, the femoral F.
In an artificial knee joint consisting of a femoral component A fixed distally and a tibial component B fixed proximally to the tibia T, there is a single anterior joint wall a1 that stands up on the front side, and a generally arc-shaped A pair of outer joint walls a2. a2, and a rear joint wall a3 that stands up in a sharp arc shape behind this wall a2゜a2. a3 and the above-mentioned IC wall a2. A pair of reinforcing ribs a4 arranged along the joint movement direction on the inner surface of a2. a4, and the upper edge a5 of this reinforcing rib a4
has a shape similar to the shape of the inner peripheral surface of the femoral bone member A in which the inner wall surfaces of the anterior joint wall a1, the outer joint wall a2, and the posterior joint wall a3 are interconnected, and This is a femoral bone member for an artificial knee joint characterized by forming a connecting portion a6 whose vertical cross section gradually increases with respect to a reinforcing rib a4.

The ceramic material of the femoral bone component A is typically alumina ceramic or zirconia ceramic, and the metal material is pure titanium, titanium alloy or G
An o-Cr alloy is a typical example.

(Function) In the embodiments shown in FIGS. 5 and 6, the upper edge a of each reinforcing rib a4
5 has a shape similar to the shape of the inner peripheral surface of the femoral bone member A in which the inner wall surfaces of the front wall a1, the inner wall a2, and the rear wall a3 are interconnected, and the reinforcing rib 5 is connected from the front wall a1 and the rear wall a3 to A connecting part a6 whose vertical cross section gradually increases with respect to a4 is formed, that is, the front and rear walls a, as in the conventional one shown in Fig. 3, are formed.
l, A3 does not have a configuration in which the vertical cross section changes abruptly with respect to the reinforcing rib a4, but the cross section increases gradually.In other words, in FIG.
1 and a31 are considered as dangerous cross sections against bending loads, in the case of the present invention, the dangerous cross sections are not concentrated at vertical points along the longitudinal direction as in the conventional case, but are continuously distributed over the expanse of the connecting portion a6. Therefore, the resistance to the above-mentioned bending load can be significantly improved. Such characteristics were confirmed by the following experiment.

(Example: Structure corresponding to Figures 5 and 6) A) Femoral bone member: Alumina ceramic mouth) Reinforcement rib width: 3 mm C) Reinforcement rib height near mm (Comparative example: 2nd and 3rd The structure corresponds to the figure, and the specifications except for the reinforcing ribs are exactly the same as in the examples.) A) Femoral bone component: Alumina ceramic opening) Width of reinforcing ribs: 3ma+ C) Height of reinforcing ribs: 10m++ (Test) A) Contents : Corresponding port in Figure 4) Result: 2,500k for comparative example
g, but in the case of this example it broke at 5.g. No cracks or cracks occurred even at OQOkg (5 tons).

(Effects of the Invention) As understood from the description, according to the present invention, by forming a connecting portion whose vertical cross section gradually increases at the transition portion from the front and rear walls of the joint to the reinforcing rib, the present invention is superior to conventional products. Since it can exhibit a bending strength that is at least twice as strong as that of other materials, it has the excellent effect of significantly reducing the risk of joint disorders and fractures.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a state in which a conventional artificial knee joint is installed;
Figure 2 is an exploded perspective view of the same joint, Figure 3 is a longitudinal cross-sectional view including reinforcing ribs, Figure 4 is an explanatory diagram showing a bending load test, and Figure 5 is an explanatory diagram showing a bending load test.
The figure shows a plan view of the femoral component of the present invention, and FIG. 6 shows a side view of the same. (Explanation of symbols) F...femur, A...femoral bone member, al...
Front wall of joint, a2... joint #wall, a3... back wall of joint, a4... reinforcing rib, a5... upper edge of reinforcing rib,
a6...Connection part, T...Tibial bone, B...Tibial bone member. -End- Figure 1

Claims (1)

[Claims] 1. In an artificial knee joint consisting of a femoral component fixed to the distal femur and a tibial component fixed to the proximal tibia, there is a single anterior wall of the joint that stands up on the front side, and a generally arc-shaped joint wall. A pair of joint walls that gently extend behind the wall, a rear joint wall that stands up in a sharp arc on the back of this wall, and a joint wall that is located on the inner surface of the joint wall and arranged along the direction of joint movement. The upper edge of the reinforcing rib has a shape that approximates the shape of the inner circumferential surface of the femoral bone component, where the inner wall surfaces of the anterior joint wall, joint wall, and posterior joint wall are interconnected. A femoral bone member for an artificial knee joint, characterized in that a connecting portion is formed from the anterior joint wall and the posterior joint wall to the reinforcing rib, the longitudinal section of which gradually increases.