JPH0698161B2 - Artificial hip joint - Google Patents

Description

TECHNICAL FIELD The present invention relates to an artificial hip joint that replaces and repairs a human joint.

[Conventional technology and its problems]

Conventionally used artificial hip joints are made of metal such as stainless steel or 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 with 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 similarly fixed to the pelvis using cement. In particular, on the femur side, the stem part is long inserted into the long bone, but due to the difference in Young's modulus between bone and metal, the amount of deformation when loaded is significantly different. Loosening easily occurs between the metal stems, resulting in the joint function being lost due to the artificial hip joint being detached from the living body or the backlash occurring between the members. Many attempts have been made in recent years to eliminate the occurrence of loosening between the cement and the bone or between the cement metal material. Regarding the material of the stem, pure titanium and titanium alloys have been used in place of conventional cobalt chrome alloys and stainless steel, and attempts have been made to follow the flexure of bone by using a material with Young's modulus closer to that of bone. However, it has not completely solved the problem.

A design attempt to fit the prosthesis to a bone with a complicated shape as much as possible, to minimize the gap between the bone and the prosthesis, and to fix the stem without using cement has also been made as one method. .

However, it is extremely difficult to make the entire outer peripheral surface correspond to the shape of bone without using cement, because there are individual differences in living bodies.

On the other hand, it is also done to process the bone into the shape of a prosthesis and push it in, but at the time of processing many healthy bones are scraped,
As a result, the strength of the whole bone is deteriorated, which also has many problems. Further, when inserting and fixing the stem into the medullary cavity of the bone, the cement itself is directly injected into the medullary cavity, so that blood is mixed into the cement and the strength of the cement itself deteriorates. It was

[Specific means for solving problems]

In order to solve the above-mentioned problems, a thin metallic sheath 4 capable of following the shape of the bone marrow cavity is used to follow the shape of the bone for fixation. At this time, it is preferable that the surface of the sheath 4 has many grooves or irregularities so as to firmly fix it to the bone, and it is more effective if the surface is coated with a ceramic or an osteogenic factor. Is.

In addition, cement is used in the sheath that is firmly fixed to the bone, and the stem is fixed using a biocompatible and elastic adhesive to obtain long-term stability.

[Action]

 The operation of this system is as follows.

1. The shape and dimensional difference due to individual difference of the bone can be followed (corresponding) by the deformation of the sheath, and the surface area in contact with the bone can be maximized to disperse the stress.

2. The shape of the stem may be simple because the sheath is deformable, which is very easy to manufacture.

3. Since the bone and cement as an adhesive do not come into direct contact with each other, the adverse effect of heat of polymerization of cement on living cells is reduced.

4. Can easily follow bone deformation.

〔Example〕

 Embodiments of the present invention will be specifically described with reference to the drawings.

In FIG. 1, reference numeral 1 is a head ball made of alumina or zirconia. This head ball 1 is taper-fitted to a stem 2 made of titanium alloy, and is inserted into a sheath 4 by using a cement 3. It is fixed. This sheath 4
The external shape shown in FIG. 2 is a perspective view.
It is made of titanium alloy, and its surface is coated with apatite, which makes it a good fit with bones.
In addition, the thickness of this sheath 4 should be plastically deformable with a thickness of about 1 μm to 2 mm, and as many types (shapes and dimensions) as possible should be prepared so that it can match the size of the medullary cavity of the bone as much as possible. You should keep it. When actually used, the operator selects and inserts the most suitable one according to the size of the bone marrow cavity, and further transforms it from the inside so as to match the shape of the bone marrow cavity as much as possible. After this work, an adhesive 3 such as biocompatible cement, ultra high molecular weight polyethylene, or silicone rubber is injected inside, and the stem 2 is inserted and fixed. The material forming the sheath 4 may be a metal such as titanium, a titanium alloy, or aluminum, as well as an alloy resin such as polyethylene.

〔The invention's effect〕

Place the metal sheath between the stem and the inner wall surface of the femur as described above, match the sheath to the shape of the medullary cavity, and fill the sheath with an adhesive to fix the stem. Therefore, the surface area in contact with the bone and the sheath can be increased regardless of the shape and size of the bone due to individual differences, and the stress can be dispersed. As a result of being able to maintain the state,
It will not come off or come loose for many years. In addition, since the sheath is deformable, the stem may have a simple shape,
Very easy to manufacture. Furthermore, since the bone and the adhesive such as cement do not come into direct contact with each other, it is possible to reduce the adverse effects on the living cells due to the heat of polymerization at the time of fixation and the elution component. Moreover, since blood does not mix into the adhesive during surgery, the adhesive strength is not reduced, and the hip joint can be restored, that is, the walking ability can be restored and long-term stability can be ensured. can do.

[Brief description of drawings]

FIG. 1 is a sectional view showing a state in which a stem of an artificial hip joint according to the present invention is attached to a femur, and FIG. 2 is a perspective view of only the sheath 4 shown in FIG. 1 ... Bony head ball, 2 ... Stem 3 ... Adhesive, 4 ... Saya 5 ... Femur, 6 ... Spinal cavity

Claims (1)

[Claims] 1. A femoral prosthesis having a stem to be inserted into a femoral bone marrow cavity and an artificial hip joint integrally formed at a free end of the stem or fitted with a conical taper. And a sheath having a thickness of 1 μm to 2 mm capable of plastic deformation between the sheath and the stem,
An artificial hip joint characterized by being filled with a biocompatible adhesive.