JPH072173B2 - Artificial hip joint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a human joint, particularly an artificial hip joint.

[Conventional technology and its problems]

Conventionally used artificial hip joints are made of metal such as stainless steel and cobalt chrome alloy, and the head ball and stem are fixed integrally or by taper fitting,
The stem is inserted into the femur, and the gap between the bone and the stem is fixed with cement. On the other hand, on the acetabular side, a socket made of synthetic resin for receiving the bone head is fixed to the pelvis by using cement. Especially on the femur side, the stem is inserted into the long bone for a long time, but the difference in Young's modulus between bone and metal causes a large difference in the amount of deformation under load. It is easy to cause slack between the stems, especially the subsidence due to the slack of the stem has become a big problem, and the joint function is lost due to the artificial hip joint separating from the living body or backlash between members. Become. In recent years between this cement and bone,
Or, many attempts have been made to eliminate the slack between the cement and the metallic material. That is, regarding the material of the stem, pure titanium and titanium alloys have been used in place of conventional cobalt chromium alloys and stainless steel,
Attempts have been made to follow the bending of the bone by using a Young's modulus closer to the bone, but this alone has not completely solved the problem.

Adapting the prosthesis to bones with complex shapes as much as possible,
An attempt has been made to improve the design by minimizing the gap between the bone and the prosthesis and fixing the stem without using cement.

However, it is extremely difficult to make the entire shape resemble the shape of bone without using cement, because of the problem of individual differences. The incompatibility that occurs due to the insertion of the straight-shaped stem S with respect to the shape of the femur B which is particularly curved as shown in FIG. 2 occurs most frequently.

On the other hand, it is also done to process and insert bone into the shape of a prosthesis, but during processing, many healthy bones are scraped off, resulting in a decrease in strength of the bone as a whole. I have a problem.

[Means for solving problems]

As the most effective means for solving these problems, it is most effective to insert a curved stem into a curved bone shape, and it can be said that this is a method of improving conformity. Therefore, there is also a difference in the degree of curvature between individuals, and since it is not a constant degree of curvature, the stem has a mechanism that can be adapted and changed according to each individual degree of curvature, so that it can perfectly follow the curvature of the bone marrow cavity and It is possible to fix it firmly.

[Action]

The effects of such an artificial hip joint are as follows: 1. Bone cement does not necessarily have to be used, and when cement is not used, it is possible to eliminate the adverse effects on the living body due to the heat of polymerization of the cement.

2. Very easy and strong fixed support can be obtained operatively.

3. It is possible to follow the individual difference in the bending size of the bone marrow cavity with the bendable function of the support member and eliminate the difference in the fixing force due to the gap in the bending size of the stem and the bone marrow cavity.

〔Example〕

In the embodiment of the present invention, as shown in FIG. 1, reference numeral 1 is a ball made of alumina, zirconia, or the like, which is fitted to the tip of a metal stem body 2 made of titanium alloy or stainless steel. The stem member 3 to be inserted into the bone canal is connected to the stem body 2 with a pin 4 as a rotation axis by a bending mechanism. By fastening the pressing pin 5, the stem member 3 and the stem body 2 are separated from each other at an arbitrary angle. It is fixed in a bent state. Further, the washer 6 for preventing loosening prevents the presser pin 5 from coming out. The surfaces of the stem body 2 and the stem member 3 may be coated with apatite or a bone morphogenetic protein (BMP) to make them well compatible with bone. In actual use, several types of stem body 2 and stem member 3 are prepared so that the size of the femur B of the patient can be accommodated. After assembling, insert the pin 4 to assemble and use.

〔The invention's effect〕

As mentioned above, according to the artificial hip joint of the present invention, a strong fixed support of the stem can be obtained without using cement,
Furthermore, the age of adaptation for artificial hip joints has been traditionally said to be 60.
It is possible to greatly reduce from the restriction of being aged or older, and it is possible to exert great power for gait recovery for people who have lost walking ability, and to maintain the stability of the performance of the artificial joint for a long period of time.

[Brief description of drawings]

1 (a) and 1 (b) are a longitudinal sectional view and a lateral sectional view, respectively, showing a state in which a stem of an artificial hip joint according to an embodiment of the present invention is attached to a femur, and FIG. 2 shows a conventional artificial hip joint. It is a longitudinal cross-sectional view showing a state in which the stem is attached to the femur. 1 ... Bony head ball 2 ... Stem body 3 ... Stem member 4 ... Pin 5 ... Presser pin 6 ... Washer B ... Femur

Claims (1)

[Claims] 1. A hip prosthesis having a stem inserted into the medullary cavity of the femur and an epiphyseal ball at the tip of the stem, and a bending mechanism provided at least at one location of the stem inserted into the femoral medullary cavity. An artificial hip joint that is characterized by