JPS62254748A - Artificial joint - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an artificial joint for artificially prosthetizing a joint of a living body and restoring its function and form.

[Conventional technology]

In cases where joint function is impaired due to trauma such as a traffic accident, or lesions in the joint due to bone degeneration such as rheumatoid arthritis, osteoarthritis, or tumors, and there is little hope for healing or recovery, the joint may be excised and replaced with artificial tissue. Replacement surgery that uses joints as a prosthesis is being performed.

The artificial joints used in this case include those called bipolar type or true bearing type.

This consists of a stem with a bearing insert inside the outer head that slides in contact with the articular cartilage or bone, and an inner head that rotates within the bearing insert, and between the cartilage or bone and the outer head. and 2 between the bearing insert and the inner head.
It is designed to slide in several places. Such bipolar artificial joints allow the external dimensions of the outer head to be freely selected during surgery according to the size of the joint, and the selected outer heads can be easily combined, and once combined, To prevent dislocation, the structure must be such that it does not easily fall off after it has been dislocated.

For example, in JP-A-59-82852, a circumferential groove is provided on the inner wall surface of a bearing insert fitted into an outer head, and an elastic ring with a notch is provided in the groove. It is set up. This ring has a structure that prevents the inner head from coming off, and after the inner head is pushed in, the ring expands in the radial direction, and as soon as the inner head enters the bearing insert, the ring returns to its original shape and supports the inner head so that it does not come off. It had become.

[Problems with conventional technology]

However, in the case of the above-mentioned artificial joint, a groove is formed inside the bearing insert to accommodate the ring to prevent it from coming off, and the width of this groove is equal to the width of the ring to allow movement of the ring. It is larger than. Therefore, a space always exists between the ring and the groove, and there is a possibility that the inner head may fall off due to movement of the ring, elastic deformation of the ring, or plastic deformation of the ring. Further, since the inner head is directly supported by the ring and both members slide in contact with each other, a large load is applied to the small ring, which causes problems such as easy wear.

[Means for solving problems]

In view of the above, the present invention makes the width of the groove formed in the bearing insert the same as that of the ring, and incorporates a shape memory alloy bonded to the outer wall of the ring into the groove. The shape memory alloy bonded to the ring deforms so that the ring holds the inner head, preventing the inner head from dislocating, and allowing the inner head to detach easily by changing the temperature of the shape memory alloy. The ring expands in the radial direction, allowing the rad to be removed from the inner ring.

〔Example〕

Hereinafter, embodiments of the present invention in the hip joint will be described with reference to the drawings. As shown in FIGS. 1 and 2, an outer head 10 has a smooth outer surface 11 having a substantially hemispherical shape that slides into contact with the acetabulum. The bearing insert 20 fitted into the inner wall surface 12 of the outer head 10 includes an opening 23, a groove 22 for the slip-off prevention ring 40, and a stem 3.
It has a smooth spherical curved surface 24 that slides into contact with the inner head 31 that is formed in the shape of 0. The outer head 10 and the bearing insert 20 are firmly fixed by the protrusion 12 of the outer head and the recess 21 of the bearing insert.

The slip-off prevention ring 40 includes a ring inner wall 43 that is made of the same material as the bearing insert and slides into contact with the inner head 31;
It is composed of a ring outer wall 42 made of a shape memory alloy and joined to a ring inner wall 43.

The ring 40 has a notch 41 in a part.

Next, how to assemble these members will be explained. First, fit the bearing insert 20 into the outer rad 10,
A slip-off prevention ring 40 is fitted into the groove 22 of the bearing insert 20. Outer wall 4 of fall prevention ring 40
The shape memory alloy No. 2 is preliminarily memorized with dimensions as shown in FIG. 1 at body temperature, that is, around 36°C. Since the shape memory alloy is easily deformed by being immersed in hot water at a temperature higher than body temperature, the slip-off prevention ring 40 can be easily fitted into the groove 22 of the bearing insert 20.

If the outer head 10, bearing insert 20, and slip-off prevention ring 40 prepared in this way are inserted into the inner part of the stem 30 and implanted into the body, the shape memory alloy will return to its memorized shape due to body temperature.
As shown in FIG. 1, in order for the inner head 31 to detach from the bearing insert 20, a detachment prevention ring 40 is required.
must be forcefully expanded in the radial direction. Therefore, by increasing the thickness of the fall-off prevention ring 40 to a certain extent, the fall-off prevention ring 40 can have a holding force for the inner head 31. After this, when you want to remove the inner ring 31 from the bearing insert 20, heat is transferred to the ring outer wall (shape memory alloy) 42 through the notch 25 of the bearing insert 20 as shown in Fig. 3 to prevent the ring from coming off. All you have to do is return 40 to its initial state.

Regarding the materials of each member, the outer head IO may be made of metal, ceramic, or a metal surface coated with ceramic such as TiN, the bearing insert 20 and the ring inner wall 43 are made of ultra-high molecular weight polyethylene, and the ring outer wall 42 is made of shape memory material. Generally, the stem 30 is made of metal or a metal coated with ceramic, metal beads, or mesh, and the inner head 31 is made of metal or ceramic.

In addition, although the embodiment of an artificial hip joint has been shown above, it goes without saying that the present invention can also be applied to other shoulder joints.

〔Effect of the invention〕

As described above, according to the present invention, the inner head can be easily fitted into the bearing insert during surgery by using a slip-off prevention ring made of a shape memory alloy, and moreover, it does not come off in the body after implantation. However, if the outer head needs to be replaced, it can be easily replaced.

Moreover, since the fall-off prevention ring fits into the groove of the bearing insert without any gaps, it is stable even when receiving a large load transmitted from the inner head to the ring, and no plastic deformation occurs.

In addition, since the inner wall of the ring, which is the sliding surface with the inner head, is lined with metal, the present invention provides an excellent artificial joint that has many advantages, such as excellent friction and wear characteristics. Can be done.

[Brief explanation of drawings]

Fig. 1 is a three-dimensional exploded view showing the configuration of an artificial joint according to an embodiment of the present invention, Fig. 2 is a sectional view of the main part of the artificial joint shown in Fig. 1, and Fig. 3 is a sectional view of the main part of the artificial joint shown in Fig. 2, excluding the stem. FIG. 10... Outer head 20... Bearing insert 30... Stem 31... Inner head 40... Fallout prevention ring

Claims (1)

[Claims] An outer head having a smooth, substantially hemispherical outer surface that slides into contact with the bone, a bearing insert that is fitted and fixed to the outer head and has a groove on the inner surface, an insert that rotates within the bearing insert, and What is claimed is: 1. An artificial joint comprising a stem connected to a stem, and a slip-off prevention ring fitted into a groove of a bearing insert, the slip-off prevention ring being lined with a shape memory alloy.