JPS6279055A - 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 the joint function is impaired due to trauma such as a traffic accident, horseshoe disease, or a tumor or other bone degeneration, the joint function is impaired and there is little hope for healing or recovery, and the joint is removed and replaced with an artificial joint. Replacement surgery is being performed.

The artificial joint used in this case is called a bipolar type. This stem consists of a stem with a bearing insert inside an outer head that slides in contact with the bone, and an inner head that rotates within the bearing insert, and between the bone and the outer head and between the bearing insert and the inner head. It slides in two places between the heads. Such bipolar artificial joints are generally used by first inserting and fixing the stem into the femur during surgery, and then attaching the outer head to the inner head at the tip of the stem, so the inner head and outer head are combined. The structure must be such that it is easy to use and does not come apart easily after being assembled.

For example, in the device disclosed 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 arranged in the groove. It is set up. This ring was spread out in the radial direction, and the inner head was inserted into the bearing insert. When it was completely inserted, the ring returned to its original position to support the inner head so that it would not come off.

[Problems with conventional technology]

However, in the case of the above-mentioned artificial joint, a ring is placed inside the bearing insert, and the ring directly supports the inner head, and both members slide in contact with each other.
The ring is subject to a load and tends to wear out, and since the groove of the bearing insert and the ring have corners, these corners are prone to wear.

Furthermore, the portion of the bearing insert that forms the groove is thin, which causes problems such as a decrease in strength.

[Means for Solving the Problems] In view of the above, the present invention enables the opening to be enlarged by forming a plurality of notches in the depth direction from the opening of the bearing insert and further making the wall near the opening thinner. This makes it easy to attach and detach the bearing insert and inner head. Next, after the inner head mW, a slip-off prevention ring is fitted into the gap between the thin wall part near the bearing insert opening and the inner wall surface of the outer head, so that the inner head cannot be separated from the bearing insert, and the bearing insert The inner head is supported only by the inner wall surface.

〔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 to be fitted into the inner wall surface 12 of the outer head 10 has a plurality of notches 21 formed in the depth direction from the opening, a thin section 22 near the opening, and a circumferential groove in the thin section. There are 23. The inner wall surface 24 of the bearing insert 20 is a smooth spherical curved surface so as to slide in contact with the inner head 31 formed on the stem 30.
is made slightly narrower than the outer periphery of the inner head 31.

The stem 30 has an inner hood 31, and the opposite end is inserted and fixed into the femur. Since the slip-off prevention ring 40 is an elastic annular body and has a notch 41, it can be expanded in the radial direction. In addition, the outer head side is tapered and has a protrusion 42 on the inner surface, and notches 43 are provided on both sides of the notch 41.
has been established.

Next, how to assemble these members will be explained. First, the bearing inserter 20 is fitted to the outer head 10, and the hood 31 is inserted into the bearing insert 20 to the inner side of the stem 3o during surgery.

The inner head 31 is slightly larger than the opening of the bearing insert 2o, but since the area 22 near the opening is thin and has a notch 21, when force is applied, the opening of the bearing insert 2o expands and the inner head 31
can be inserted. When the inner head 31 is completely inserted into the bearing insert 20, the opening vicinity 22 returns to its original position, and the inner head 31 is supported by the opening vicinity 24a on the inner wall surface. Further, the inner head 31 can also be separated from the bearing insert 20 in the same manner. Inner head 31 and bearing insert 2
0, fit the slip-out prevention ring 40 into the gap between the opening 22 of the bearing insert 20 and the inner wall surface 12 of the outer head 10 from the tapered side, and align the protrusion 42 with the groove 23. If it is fixed in this manner, the inner head 31 cannot be removed from the bearing insert 20 because the vicinity 22 of the opening cannot expand. After this, when it is desired to remove the inner head from the bearing insert again, it is sufficient to insert a tool having a tip shape that matches the shape of the notch 43 of the removal prevention ring 40 and pull out the removal prevention ring 40. When each member is assembled in this way, the inner head 31 slides in contact with only the inner wall surface 24 of the bearing insert 20, so the strength is high and there is little wear.

In addition, during actual surgery, several types of plastic outer heads are replaced and the actual one is attached after a trial to determine the appropriate size, but in the case of the artificial joint of the present invention, Even after the actual outer head is attached, if the slip-off prevention ring 40 is not fitted, it can be easily removed and replaced with an optimal outer head.

The material of each member is as follows: outer head 0 may be metal or ceramic, or metal surface coated with ceramic such as TiN; hair ring insert 2
0 and the slip-off prevention ring 40 are made of HDP (high-density polyethylene), and the stem 30 is made of metal or metal coated with ceramic, metal beads, or mesh.
The inner head 31 is generally made of a material such as metal or ceramic.

In addition, the outer head 10 and the bearing insert 20
The method of fixing the outer head 1 is as shown in Figure 2.
A protrusion 13 is provided on the inner wall surface 12 of the bearing insert 20, and a slit 25 is formed in the outer wall surface of the bearing insert 20 so that the portion that matches the protrusion 13 is recessed, and the bearing insert 20 is mechanically inserted into the outer head 1o. Fit and secure. In addition, as shown in FIG. 3(a), claws 14 are provided on the inner wall surface of the metal outer head 1o, and the bearing insert 2o is fitted so that the claws 14 bite into the hair ring inserter 1-20. How to fix it and the third method
As shown in Figure (b), a groove 15 is provided in the outer head 10 and a protrusion 26 is formed on the outer surface of the hair ring insert 20.
It is also possible to form a bearing insert by a molding method by forming irregularities on the inner wall surface of the outer head (not shown).

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〕

According to the present invention, in a bipolar artificial joint, a notch is provided in the back direction from the opening of the bearing insert, and the area near the opening is made thinner, so that the opening can be enlarged, and the inner head can be inserted. By later fitting a fall-off prevention ring between the vicinity of the bearing insert opening and the outer head, a reliable connection mechanism can be provided, and the inner head slides in contact with the smooth surface of the inner wall of the bearing insert. Therefore, there is no uneven wear, partial wear, etc., and the durability is great.

Furthermore, since the bearing insert can be easily attached and detached without the slip-out prevention ring inserted, the outer head can be immediately replaced with an outer head with optimal dimensions during surgery, providing an excellent artificial joint with many advantages. can do.

[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 cross-sectional view of the main parts of the artificial joint shown in FIG. 1, and FIG. 3 is an artificial joint according to an embodiment of the present invention. FIG. 3 is a sectional view showing another example of an outer head and a bearing insert for configuring the bearing insert. lO: Outer head 20: Bearing insert 30: Stem 31: Inner head 40: Fallout prevention ring Distributor Kyocera Corporation Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] The outer head has a smooth, almost hemispherical outer surface that slides into contact with the bone, and a plurality of notches are provided in the depth direction from the opening, and a gap is formed between the outer head and the inner wall surface of the outer head. A bearing insert with a thin wall near the opening is inserted and fixed into the outer head, and an inner head provided at the tip of the stem is inserted so as to rotate within the bearing insert, and the inner wall of the outer head and the bearing insert are inserted. An artificial joint characterized by having a slip-out prevention ring interposed therein.