JPH0444757A - Bone head ball for artificial hip joint - Google Patents

Abstract

PURPOSE:To situate all the contact state positions between the inserting hole of a bone head ball and a stem neck part in a position from an entrance to the spherical center of the bone head ball, and obtain a sufficient contact length without neck collar by closely adhering a tapered hole to the stem neck part from the entrance to the position of the spherical center of the bone head ball as much as possible. CONSTITUTION:A tapered inserting hole 8d to which the top of a stem neck part 3 is bored with changing the diameter according to the protruding length of the stem neck part 3 into the inserting hole 8d, so that the space between a stem 2 and an outer cup 6 can be changed by changing only a bone head ball 8 without pulling the once inserted stem 2. When the superposed length between the bone head ball 8 and the stem neck part 3 is different as t1, t2, t3, the diameter of the tapered inserting hole 8d is set so that the inserting hole 8d is closely fitted to the stem neck part 300 only in the length t4 from the entrance part of the inserting hole 8d to the spherical center O of the bone head ball 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to the shape of an insertion hole of a femoral head ball into which a stem neck at the tip of a stem is inserted in a joint prosthesis used as an artificial hip joint.

(b) Prior Art Techniques regarding the shape of the stem neck protruding from the stem of an artificial hip joint and the insertion hole of the femoral head ball have been known.

For example, there is a technique described in Japanese Unexamined Patent Publication No. 161959/1983.

Furthermore, in the conventional femoral head ball 18, especially when the center distance between the stem 2 and the femoral head ball 18 is long, as shown in FIGS.
A neck collar 18b protrudes below the neck collar 18b, and an insertion hole 18a is opened in a tapered shape.

When the neck collar 18b protrudes below the femoral head ball 8 in this way, the femoral head ball can be fixed in both the outer fixed type outer cup 6 shown in FIG. 13 and the self-aligning type outer cup 6 shown in FIG. Since there are 18 neck collars 18b, there is a problem in that the rotation angle of the stem neck portion 3 and the portion of the stem 2 that is continuous thereto in the front, rear, left, and right directions is limited.

The fact that the rotation angle of the stem 2 and the stem neck 3 is limited means that when the patient performs movements such as excessive flexion, extension, internal/external rotation, and internal/external rotation of the leg, the neck collar 18b portion If it touches the door, it will crash.

For this reason, the outer fixed type requires 1. This causes problems such as the cup becoming loose and easily coming off the bearing.

Furthermore, in the self-aligning type, the outer cup operates more frequently, resulting in the problem that injury to the hip bone E is more likely to occur.

Generally, in order to increase the rotation angle, the outer diameter of the neck collar 18b is made as small as possible, so that the femoral head ball 8 tends to lack strength at the A section.

The present invention is configured so that the neck collar 18b does not protrude from the femoral head ball 8 even when the length of L is increased.

(c) Problems to be Solved by the Invention In Japanese Patent Application Laid-Open No. 63-161959, which is a conventional technique, as shown in FIGS. 11 and 12, the insertion hole 38a of the femoral head ball 38 is The tip of the stem neck is formed into a bar-shaped hole, and the stem neck is also configured in a tapered shape. It was constructed so that it would come into contact with the rest of the world.

Therefore, if we assume that the patient's bone shape is compatible with the NJ law (4). Select the size of the artificial hip joint (), then we will need one with a different center distance, I7, as shown in Figure 3. With this dimension, to change the L dimension: 1) Make the stem neck length larger, medium, or smaller. 2. Make the fitting position of the ball and stem smaller. (Stem 2 is a type of However, in the case of ■, the revision surgery for the artificial hip joint often involves only parts other than stem 2, and when ■- wants to change the J method, it is necessary to remove stem 2 as well.

In addition, the problem (■) is that the length of the tapered fitting portion between the stem 2 and the ball and the ratio of the length to the ball diameter become small, resulting in incomplete fixation. For this reason, if the length of the fitting part is increased without changing the ball diameter, the difference in elongation dimensions between large, medium and small becomes smaller, resulting in a problem of poor compatibility with the human body.

In the present invention, the position of the femoral head ball can be adjusted by replacing the type of femoral head ball without replacing the stem, and the insertion hole 8d of the femoral head ball 8
By changing the diameter of the stem neck 3, there were cases in which it engaged with the tip of the stem neck 3, cases in which it engaged in the middle part, and cases in which it engaged with the base part.

But 2. Although the diameters of the tapered insertion holes are different, in all cases, the tapered holes are configured so as to be in close contact with the stem neck 3 from the entrance to the spherical center 0 position of the femoral head ball as much as possible. The stem neck, which protrudes into the inside of the femoral ball from the position of the ball core O, is provided with different taped parts 8a, 8b, and 8C in the insertion hole 8d, so that the insertion hole and the distal end of the stem 2 are connected to each other. It is the one that has been eliminated.

As a result, the entire contact position between the insertion hole of the femoral head ball and the stem neck is from the entrance to the ball center position of the femoral head ball, and even without a neck collar, a sufficient length of contact can be obtained, so that the stem neck The transmission of supporting force to the femoral head ball can now be reliably fixed even if the types of femoral balls are different.

(d) Means for solving the problems The problems to be solved by the present invention are as follows.The means for solving the problems will now be explained.

The stem neck at the tip of the stem to be implanted in the medullary hole of the femur A is fitted internally, and the femoral head ball Q is fitted externally into the inner diameter of the hair ring inside the femur. The insertion hole into which the neck is inserted is configured to be a tapered hole, and the insertion part of the stem neck 3 is also configured to be tapered, so that the two are closely fitted, and the femoral head ball is inserted through the tapered hole from the insertion L. The stem neck, which extends to the ball center position and projects into the interior of the femoral ball beyond the ball center position, has no retaining portion with the insertion hole.

(e) Embodiment The problems to be solved by the present invention and the means for solving them are as described above. Next, the structure of an embodiment shown in the attached drawings will be explained.

Figure 1 is a side view of a self-aligning type artificial hip joint, Figure 2 is a front view, Figure 3 is a front sectional view, Figure 4 is a side sectional view, and Figure 5 is an outer fixed type artificial hip joint. , FIG. 6 is a front sectional view, FIGS. 7, 8, and 9 are sectional views showing how the femoral head ball 8 and stem neck 3 of the present invention are fitted, and FIGS. 11 and 12 are sectional views of a conventional femoral head ball, and FIGS. 13 and 14 are sectional views of a conventional femoral head ball with a neck collar.

There are two main types of artificial hip joints. They are self-aligning type and outer fixed type.

The self-aligning type allows the outer cuff pro to slide and rotate at that part without being fixed to the acetabulum B, and also has a synthetic resin bearing 7 and a femoral head ball 8 fixed inside the outer cuff pro. By supporting the outer cup 6 in a slidable and rotatable manner and eccentrically centering the ball center of the outer cup 6 and the ball center of the femoral head ball 8, the outer cup 6 constantly maintains the supporting force from the femur A to the acetabulum B. It is configured so that it can be automatically aligned so that it can be received on the entire surface.

In addition, in the outer fixed type, the remaining condition of the acetabulum B is poor,
In cases where it is not possible to insert a self-aligning type, the outer cup 6 is directly fixed to the acetabulum B with bolts, and the sliding rotation is performed only between the bearing 7 inside the outer cup 6 and the femoral head ball 8. It is used when performing movements.

1 to 4 illustrate self-aligning artificial hip joints.

The stem 2 is inserted into the medullary hole of the femur A by drilling an insertion hole with a metal file.

A femoral head ball 8 is fitted into a stem neck 3 at the tip of the stem 2. The ball center of the femoral head ball 8 and the ball center of the outer cup 6 are eccentric, but since the outer cup 6 also slides and rotates inside the acetabulum B, even if the outer campro rotates, To prevent the femoral head from coming off the ball 8,
A locking portion bearing 1 is engaged and fixed in a groove inside the outer campro. Reference numeral 9 denotes a biasing spring configured to prevent the locking portion bearing 1 from falling out from inside the outer cup 6.

The locking part hair ring l is configured in a "c" shape when removed, and when fitted into the engagement groove inside the outer cup 6, it becomes circular, and if the femoral head ball 8 is forcibly inserted, it will not come out. It is configured to be

In the self-aligning type, the femoral head ball 8 and the bearing 7
Sliding and rotation is also possible between the acetabulum B and the outer camphor. Therefore, although the artificial hip joint has a large degree of bending, it cannot be used unless there is a sufficient remaining portion of the acetabulum B.

If the remaining portion of the acetabulum B is insufficient, an outer fixation type in which the outer cuff pro is directly bolted to the acetabulum B is used. 4 and 5 are part of the shoulder of the stem 2.

Further, the surface of the stem 2 is formed with a hemispherical uneven surface a that promotes adhesion with the bone marrow of the living body.

An outer fixed type artificial hip joint will be explained with reference to FIGS. 5 and 6.

In the case of the outer fixed type, the outer cup 6 is fixed to the acetabulum B of the pelvis with bolts.

The outer cup 6 is also provided with a fixed flange 6a, and a bolt is also screwed into the fixed flange 6a. Further, several bolt holes are opened on the outer periphery of the outer cup 6, and the acetabulum B is screwed onto the acetabulum B by bolts protruding from the bolt holes.

Reference numeral 13 denotes a fixing protrusion between the hair ring 7 and the outer cup 6, which is fitted into the center insertion hole 28 of the outer cup 6. G is the supporting force from the stem 2 to the outer force/7p6.

In the case of the outer fixed type, the ball center of the outer cup 6 and the ball center of the femoral head ball 8 match, and since the outer cup 6 is fixed to the acetabulum B of the pelvis, it cannot come off. Therefore, there is no engaging portion between the femoral head ball 8 and the bearing 7. 14 is also a rotation preventing portion between the bearing 7 and the outer cup 6.

The area around the outer cuff pro is fixed to the acetabulum B of the pelvis, so it promotes adhesion to the acetabulum B of the pelvis, which is the living body.
A hemispherical uneven surface a is provided.

In the present invention, the fitting portion between the femoral head ball 8 and the stem neck 3 of the above-mentioned outer fixed type and self-aligning type artificial hip joint is constructed as shown in FIGS. 7, 8, and 9. It is something.

The tip of the stem neck 3 is fitted so that the distance between the stem 2 and the outer cup 6 can be changed by replacing only the femoral head ball 8 without removing the stem 2 once inserted. A tapered insertion hole 8d is formed with a diameter changed according to the length of insertion of the stem neck 3 into the insertion hole 8d.

Even when the overlapping length of the femoral head ball 8 and the stem neck 3 is the shortest, the length from the insertion hole 8d's entry L'' to the position of the ball center 0 of the femoral head ball 8 is inserted into the stem neck 3. hole 8d
It is constructed so that it is tightly fitted.

Even in this state, the tip of the stem neck 3 should not come into contact with the ceiling of the insertion hole 8d, and the contact length of the taper should not become unnecessarily long, making it difficult to process the taper accurately. 1. In addition, to prevent ball fixation from becoming unstable due to lack of precision or crevice corrosion on the contact surface related to lack of precision. As shown in FIG. 7, a cut portion 8C is provided.

As shown in FIG. 8, when the overlapping part between the femoral head ball 8 and the stem neck part 3 is made slightly larger, the stolen part 8a is made even larger,
The insertion hole 8d is a tapered hole with a diameter such that it comes into close contact with the midway portion of the stem neck 3.

Further, as shown in FIG. 9, when increasing the overlapping length of the femoral head ball 8 and the stem neck 3, the insertion hole 8d of the femoral head ball 8 is
is a tapered hole having a diameter that fits into the base of the stem neck 3. In this case, the hidden portion 8b is made even thicker.

Furthermore, the tapped portion 8b can also be applied to 8C and 8a in FIGS. 7 and 8, and the tapped portion shape 8'' can be made the same shape to facilitate manufacturing.

As described above, even when the overlapping lengths of the femoral head ball 8 and the stem neck 3 are different from tl, t2, and t3, the insertion hole 8d
Length t4 from the entry [ ] part to the ball center 0 of the femoral head ball 8
Only, in order for the insertion hole 8d and the stem neck portion 3 to fit tightly,
The diameter of the tapered insertion hole 8d is set.

Therefore, for all bows/L in figures 7, 8, and 9,
The tapered fitting section has a dimension that is almost the same as the ball radius,
Similarly, the diameter of the shaft 3 can be made approximately the radius of the ball, and the ball can be securely fixed.

(-.) Effects of the Invention Since the present invention is constructed as described above, it has the following effects.

First, while the same stent 2 is inserted into the femur A, femoral head balls 8 of different diameters in the tapered insertion hole 8d are fitted into the stem neck 3. Since the overlapping length of the stem neck 3 and the femoral head ball 8 can be changed, the distance between the stem 2 and the outer cup 6 can be changed without replacing the stem 2.

In particular, the surgical time for revision hip joint replacement can be shortened.
The burden on the patient can be reduced.

Second, 1. Even if the insertion hole 8d has a different diameter of the femoral head ball 8 inserted into the stem neck 3, the length of the stem neck 3 and the insertion hole 8d for a close fit is always the same as the insertion hole 8d. In the hole 8d, a length t4 from the large L1 portion to a position close to the ball core 0 is obtained. Therefore, the fixation between the stem neck 3 and the femoral head ball 8 is ensured, and the femoral head ball 8 has a sufficient area for close fitting with the stem neck 3, and the supporting force G from the stem 2 is dispersed, thereby increasing the strength of the stem. This makes it possible to achieve excellent durability even during hypersensitive exercise by the patient.

Regardless of whether the femoral head ball 8 is replaced, the patient does not feel any discomfort.

Thirdly, the length of the tightly fitted part between the stem neck 3 and the insertion hole 8d is the same even when the overlapping length of the femoral head ball 8 and the stem neck 3 is short, and Since the length t4 to 0 is ensured, there is no need to provide the neck collar 18b as shown in Figs. Furthermore, it becomes possible to rotate the stem 2 largely relative to the outer cup 6, and there is no fear that the femoral head ball 8 will come off the bearing door, and excellent mobility can be expected.

Fourth, with the outer fixed type, it is possible to eliminate the problems that the cup tends to loosen or easily come off from the bearing.

Furthermore, in the self-aligning type, the outer cup operates more frequently, which eliminates the problem of easy injury to the acetabulum.

Generally, in order to increase the rotation angle, the outer diameter of the neck collar 8b is made as small as possible, so that the femoral head ball 8 tends to lack strength at the A section.

According to the present invention, the neck collar 18b can be configured so as not to protrude from the femoral head ball 8 even when the length of L is increased.

[Brief explanation of drawings]

Figure 1 is a side view of a self-aligning artificial hip joint, Figure 2 is a front view, Figure 3 is a front sectional view, Figure 4 is a side sectional view, and Figure 5 is an outer fixed type artificial hip joint. A front view of the hip joint, FIG. 6 is a front sectional view, FIGS. 7, 8, and 9 are sectional views showing how the femoral head ball 8 and stem neck 3 of the present invention are fitted, and FIGS. FIGS. 11 and 12 are sectional views of a conventional femoral head ball, and FIGS. 13 and 14 are sectional views of a conventional femoral head ball with a neck collar. Stem stem neck outer cup bearing femoral head ball/insertion hole/close fit between stem neck and insertion hole long ball core Applicant Yanmar Diesel Co., Ltd. agent Patent attorney Hisashi Yano

Claims (1)

[Claims] The stem neck at the tip of the stem to be implanted in the medullary hole of femur A is fitted internally, and the stem neck of the femoral head ball is inserted into the femoral head ball which is externally fitted into the inner diameter of the bearing inside the outer cup. The insertion hole is formed into a tapered hole, and the insertion part of the stem neck is also formed into a tapered form, so that the two are tightly fitted, and the tapered hole is extended from the entrance to the spherical center position of the femoral head ball as much as possible. A femoral head ball for an artificial hip joint, characterized in that a stem neck protruding into the interior of the femoral head ball beyond the spherical center position has no engagement portion with an insertion hole.