JPH05344991A - Joint prosthesis device - Google Patents

Abstract

PURPOSE:To prevent the generation of fine powder from a bearing and facilitate the correct installation of the bearing. CONSTITUTION:At the opened port edge part of a cup 2 and the outer peripheral edge part of a bearing 3 which corresponds to the cup 2, a positioning engagement part 5 consisting of a recessed part 5a and a projection part 5b and a slip-off preventing engagement part 6 consisting of a recessed part 6a and a projection part 6b are formed. Accordingly, the shape of each engagement part can be made simple, and a metal acute part can be eliminated, and fixation of the bearing is secured, and the generation of fine powder from the bearing is prevented. Further, since the position in the circumferential direction of the bearing for the cup is regulated, the correct installation of the bearing having a hood is facilitated by correctly installing the cup.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved joint structure for a cup and a bearing in a joint prosthesis.

[0002]

2. Description of the Related Art FIG. 6 is a schematic view of a known prosthesis for joints used as an artificial joint, especially an artificial hip joint. The inner ball 1 and a cup-shaped cup 2 supporting the inner ball 1 and the inner ball 1 and the cup are shown. Bearing 3 provided between 2
It consists of and. The inner ball 1 is attached to the upper end of a stem 4 fixed to the femur at a predetermined angle, and the cup 2 is fixed to the pelvis 5 with a screw.

The bearing 3 is fixed to the cup 2, and various coupling structures have been put to practical use. FIG. 7 shows an example thereof, in which a notch A is formed in the opening edge of the cup 2 to form a claw B and the claw B is bent inward as shown in FIG. A groove C is formed on the outer peripheral edge of the bearing 3, and the bearing 3 is pushed into the cup 2 so that the claw B is engaged with the groove C. According to the above structure, the bearing 3 is prevented from rotating and coming off from the cup 2 at the same time,
Although there is an advantage that the fixed position in the circumferential direction of the bearing 3 can be arbitrarily set, the bearing 3 is scraped during pushing and fine particles are generated, or the fixing is apt to be incomplete, so that the bearing 3 slightly moves during use. There is a high possibility that fine powder will be generated. In addition, if the biting amount of the claw B is increased in order to secure the fixing, there is a problem that it becomes difficult to push in the bearing 3.

The shape of the bearing 3 is generally designed such that the mounting angle θ of the cup 2 shown in FIG. 6 is about 30 °, but the angle θ may be considerably larger than this due to individual differences in the pelvis shape. The larger the angle, the smaller the pressure receiving area of the bearing 3 and the more likely it is to wear, and the inner ball 1 easily comes off the bearing 3. For this reason, the hood 3a may be provided on the bearing 3 as shown by the broken line in the figure, and the hood 3a is often provided only on the upper part so as not to narrow the movable range.
In the case where the hood 3a is partially provided as described above, it is necessary to properly position the bearing 3 in the circumferential direction and to position the hood 3a above where pressure is easily applied.

However, conventionally, although the cup 2 can be mounted on the pelvis by accurately setting the position in the circumferential direction by using a surgical tool such as a cup positioner, there is no surgical tool for mounting the bearing 3. 7 does not have a positioning function, and in the structure of FIG. 7, the position of the bearing 3 with respect to the cup 2 in the circumferential direction is arbitrary, so that the hood 3a can be accurately positioned so that the hood 3a is at a desired position during actual mounting. It was surprisingly difficult to install.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of these problems, and an object thereof is to eliminate generation of fine powder from the bearing and to facilitate accurate mounting of the bearing.

[0007]

In order to achieve the above object, the joint prosthesis of the present invention is a combination of a concave portion and a convex portion at the opening edge portion of the cup and the outer peripheral edge portion of the bearing corresponding thereto. Thus, a positioning engaging portion for preventing rotation between the cup and the bearing and a retaining engagement portion for preventing the bearing from coming off from the cup are formed by the combination of the concave portion and the convex portion.

[0008]

Since the functions of positioning and retaining are shared by the two types of engaging portions formed by the combination of the concave portion and the convex portion, the shape of each engaging portion is simplified and a metal that generates fine powder is generated. Since there is no sharp portion and it is easy to securely fix the bearing to the cup, fine particles are not generated due to fine movement during use. In addition, since the circumferential position of the bearing with respect to the cup is restricted, if the cup is correctly attached using a surgical tool, the bearing attachment position will also be accurate automatically, and it is especially easy to attach the hooded bearing. Becomes

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in FIGS. 1 to 5 will be described below. 1 and 2 are an overall sectional view and an exploded perspective view, and the inner ball, the cup, the bearing, and the stem are respectively denoted by the same reference numerals 1 to 4 as in FIG.

The cup 2 has a hemispherical shell shape with a collar-shaped fixing piece 2a, and a plurality of holes 2b for fixing screws are provided.
Is selectively and appropriately used and screwed to the pelvis. The bearing 3 is a hemispherical shell having an outer surface having a shape corresponding to the inner surface of the cup 2 and an inner surface corresponding to the diameter of the inner ball 1, and a flange 3b is formed on the outer peripheral edge portion. The bearing 3 is connected to the cup 2 by an engaging portion having the structure described below, and the inner ball 1
By being inserted into the bearing 3, the is supported so that it can slide and rotate. FIG. 3 is a diagram showing the details of the cup 2, and FIG. 4 is a diagram showing the details of the bearing 3.

The cup 2 is made of, for example, titanium or a titanium alloy. The outer surface of the cup 2 is continuously provided with minute protrusions 2c as shown in FIG. Inside the hemispherical shell-shaped edge, a plurality of recesses 5 are arranged at equal intervals.
a is formed. The bearing 3 is made of, for example, ultra-high molecular weight polyethylene, and a plurality of protrusions 5b are formed in the outermost peripheral portion of the outer surface near the flange 3b so as to correspond to the respective recesses 5a of the cup 2. .. The concave portion 5a and the convex portion 5b constitute a positioning engaging portion 5 for preventing rotation of the cup 2 and the bearing 3 from each other. The shape and size of the concave portion 5a and the convex portion 5b are such that the bearing 3 is provided on the inner surface of the cup 2. It is selected so that it can be inserted into each other without play when inserted.

Further, a shallow recess 6a is formed in an annular shape along the edge of the inside of the edge of the cup 2, and the opening side thereof is a locking portion 6a '. Further, a small convex portion 6b is formed on the outermost peripheral portion of the outer surface of the bearing 3 so as to be positioned between the adjacent convex portions 5b, 5b, respectively, and the concave portion 6a and the convex portion 6b form a bearing for the cup 2. A retaining engagement portion 6 for retaining the retaining portion 3 is configured. That is, the shape and size thereof are selected so that when the bearing 3 is inserted into the inner surface of the cup 2, there is no play, and the projection 6b is engaged with the locking portion 6a 'of the recess 6a. Although the engaging portions 5 and 6 are provided at an interval of 60 ° in the drawing, this interval can be made smaller.

A plurality of notches 7 are formed on the outer periphery of the upper surface of the flange 3b so as to be positioned in the middle of the adjacent protrusions 5b and 5b. These notches 7 are used for inserting a surgical tool when the bearing 3 is removed from the cup 2. FIG. 5 exemplifies the shape of the bearing with a hood, and a part of the flange 3b of the bearing 3 is extended in the axial direction to be thicker to thereby increase the thickness of the hood 3.
a is formed.

This embodiment is constructed as described above, and when the bearing 3 is pushed into the cup 2, the positioning engaging portion 5 is inserted.
The bearing 3 is positioned in the circumferential direction with respect to the cup 2, and the retaining engagement portion 6 prevents the bearing 3 from retaining with respect to the cup 2. The position in the circumferential direction can be selected at an angle according to the formation interval of the concave portion 5a and the convex portion 5b, and in the case of the figure, a combination angle can be selected every 60 °. In this way, the functions of positioning and retaining are divided between the two types of engaging portions 5 and the engaging portions 6, and the engaging portions 5 and 6 are combined by the combination of the concave portion and the convex portion. , 6 can be easily structured to have a simple shape and can be securely fixed, and a sharp metal part is also eliminated. Therefore, when the bearing 3 is pushed into the cup 2, fine powder is not generated, and the bearing 3 is securely fixed to the cup 2, and generation of fine powder due to fine movement during use is prevented.

Further, a plurality of engaging portions 5 and 6 provided respectively are circumferentially dispersed and arranged at equal intervals, and moreover, on the flange 3b far from the position where the pressing force from the inner ball 1 is applied. Since they are provided as close to each other as possible, it is easy to prevent the deformation of the inner surface of the bearing 3 due to the shape mismatch between the outer surface of the bearing 3 and the outer surface of the cup, and the increase in the frictional force and the wear amount resulting from these. Further, the position of the bearing 3 in the circumferential direction with respect to the cup 2 is restricted by the positioning engagement portion 5, so that the cup 2 is accurately attached to the bearing 3 with the hood 3a as shown in FIG. It becomes easy to attach the to accurately. The present invention can be applied not only to the hip joint shown in FIG. 1 but also to a shoulder joint prosthesis.

[0016]

As is apparent from the above description, according to the present invention, a positioning engaging portion and a retaining member are formed at the opening edge portion of the cup and the outer peripheral edge portion of the bearing corresponding thereto by a combination of the concave portion and the convex portion. The engaging portion for use is formed. Therefore, the shape of each engaging part is simplified and there is no sharp metal part that generates fine powder, and it becomes easy to securely fix the bearing to the cup, so that fine powder generation from the bearing is prevented. Since it can be eliminated and the position of the bearing in the circumferential direction relative to the cup is restricted,
If the cup is attached correctly, the bearing can also be attached accurately, which is particularly effective in the case of a hooded bearing. In addition, due to these comprehensive effects, it is possible to reduce the occurrence and deformation of excessive surface pressure on the bearing sliding surface, reduce the amount of wear, extend the life of the joint prosthesis, and reduce the amount of wear debris on bone tissue. The pain due to adverse effects and sagging is prevented.

[Brief description of drawings]

FIG. 1 is an overall sectional view of an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the same.

FIG. 3 is a cross-sectional view, a bottom view and an enlarged cross-sectional view of a main part of the cup of the same embodiment.

FIG. 4 is a plan view of a bearing of the embodiment, a cross-sectional view taken along the line AA, an enlarged plan view of a main part, and an enlarged cross-sectional view of the main part.

5A and 5B are a sectional view and a bottom view of the hooded bearing according to the embodiment.

FIG. 6 is a cross-sectional view of a general joint prosthesis.

FIG. 7 is a cross-sectional view of a conventional cup, a bottom view of essential parts, and a side view of a bearing.

[Explanation of symbols]

 1 Inner Ball 2 Cup 3 Bearing 3a Hood 5 Positioning Engaging Part 5a Recess 5b Convex 6 Retaining Engaging Part 6a Recess 6b Convex

Claims (1)

[Claims] 1. An inner ball and a cup for supporting the inner ball,
And a joint prosthesis composed of an inner ball and a bearing provided between the cup and a cup formed by combining a concave portion and a convex portion on the opening edge portion of the cup and the outer peripheral edge portion of the bearing corresponding thereto. A joint prosthesis characterized in that a positioning engagement portion for preventing rotation between bearings and a retaining engagement portion for preventing the bearing from slipping out of the cup are formed by a combination of a concave portion and a convex portion. ..