JPH0838525A - Artificial hip joint - Google Patents

Abstract

PURPOSE:To provide an artificial hip joint characterized by that the stress applied to the slide surface of a socket is reduced, an abrasion powder is not almost generated, bone ablating quantity is reduced because the size of the socket can be made compact and the fracture of a residual bone or the migration of the socket is not generated because residual bone quantity is much. CONSTITUTION:In an artificial hip joint 1 equipped with a metal stem 2 having a condyle ball 3 composed of metal or ceramic arranged to the leading end thereof and the plastic socket 4 receiving the condyle ball and having the slide surface 5 permitting the same to slide, the thickness of the socket 4 at a part where the straight line passing through the center of the condyle ball 3 and inclined in the direction of the center axis of the human body at an angle of about 10 deg. with respect to the vertical line in the forehead surface of the human body when the hip joint is embedded in the human body passes is made larger than that of other part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial hip joint used for repairing a human hip joint.

[0002]

2. Description of the Related Art An artificial hip joint that has been conventionally used is, like the artificial hip joint described in Japanese Patent Laid-Open No. 63-105759, a socket embedded in the hip bone and a rotatably fitted into the socket. It is composed of a stem with a head of the epiphysis.

Of these, the stem to be inserted into the femoral bone marrow cavity is made of a metal such as an alloy such as stainless steel and cobalt chrome, and the tip of the stem is provided with a separate epiphyseal ball made of ceramics or ceramics. The socket that replaces the acetabular portion is mainly made of plastic such as polyethylene. Furthermore, high-precision polishing is performed to achieve good wear and friction characteristics on the surface of the epiphysis and the sliding surface of the socket. Is applied.

The plastic socket generally has a hollow, substantially hemispherical shape and a uniform thickness, and the thickness thereof varies depending on the shape of the affected part of the patient.

Further, in order to prevent the epiphyseal ball from being dislocated from the socket, the position of the sliding surface is eccentric, and when it is embedded in the human body, a position inclined outward from the vertical line of the frontal plane of the human body. There were also artificial hip joints that were designed to be thicker than other parts.

[0006]

However, the above-mentioned conventional artificial hip joint has the following problems. That is, the position of the artificial hip joint or the sliding surface with a constant socket thickness is eccentric, and when it is embedded in the human body, it passes through the center of the artificial femoral head ball and extends outward from the human body at an angle to the vertical line in the frontal plane of the human body All of the latter artificial hip joints, which are designed to have a greater thickness in the inclined position than other parts, are highly accurate in order to achieve good wear and friction characteristics on both the surface of the condyle and the sliding surface of the socket. Despite the polishing process, it was unavoidable that abrasion powder was generated.

Particularly, in an artificial hip joint having a constant socket thickness and a thickness of 10 mm or more, the size of the socket becomes too large, and the amount of bone to be removed is large and the residual bone amount is small. There was a serious problem that the bone mass became less and more due to migration.

[0008] Then, when the product actually used in the living body was taken out and observed, it was found that the wear or deformation was biased in a specific direction, and when that direction was embedded in the human body, It was found that a straight line, which was inclined toward the center axis of the human body at an angle of about 10 ° with respect to the vertical line in the frontal plane of the human body, passed through the above.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention provides a metal stem having a head of a metal or ceramic installed on the tip thereof, and a head for receiving the head of the head. In an artificial hip joint equipped with a plastic socket having a sliding surface that slides, the artificial hip joint passes through the center of the epiphyseal ball when it is embedded in the human body, and is about 10 ° from the vertical line in the frontal plane of the human body. The thickness of the socket where a straight line inclined in the direction of the central axis passes is made larger than that of other parts.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an artificial hip joint 1 of the present embodiment. In this artificial hip joint 1, a stem 2 fixed in the femoral bone marrow cavity is made of a metal material such as stainless steel or titanium alloy that is less harmful to human body, and the tip thereof is A separate epiphyseal ball 3 made of a metal material or made of ceramic such as alumina or zirconia is provided, while the socket 4 for replacing the acetabular cap is made of a plastic material such as polyethylene.

The outer shape of the socket 4 is the hemispherical shape, and the inner surface of the socket 4 is formed with a sliding surface 5 in the shape of a dome that slides on the head ball 3. The sliding surface 5 of the socket 4 is provided at a specific eccentric position. That is, when it is embedded in the human body, it passes through the center 3a of the epiphyseal ball 3 and is about 10 relative to the vertical line A on the frontal plane of the human body.
Place the sliding surface 5 at a position where the thickness of the socket 4 at the portion through which the straight line B inclined to the central axis of the human body passes at an angle of ° (hereinafter referred to as the maximum stress portion) becomes larger than the other portions. Formed.

Since the artificial hip joint 1 thus constructed is constructed such that the maximum stress portion of the socket 4 is thicker than the other portions, the stress applied to the sliding surface 5 of the socket 4 is absorbed and reduced. That is, there is a correlation between the thickness of the plastic material and the size applied to the sliding surface 5, and when the maximum stress portion is made thicker than the other portions, the stress is absorbed and reduced, so that almost no abrasion powder is generated. It was discovered that there was no such thing, and it was made such a structure. Further, according to the above configuration, since the size of the socket 4 can be made compact, the amount of bone resection is small, and the amount of residual bone is large, so that there is no problem of fracture of the residual bone or migration of the socket 4.

In the artificial hip joint 1 of this embodiment, the socket 4 has the outer shape of the hemispherical shape. However, the outer shape of the socket 4 is not limited to this, and the elliptic hemispherical shape,
Other shapes such as other shapes can be used.

By the way, by changing the thickness of the socket 4,
The artificial hip joint 1 shown in FIG. 1 was installed in a commercially available hip joint simulator, and the simulator was continuously operated to observe the wear state of the socket 4. Table 1 shows the results.

[0015]

[Table 1]

As shown in Table 1, the following has been found regarding the thickness of the socket 4. That is, the thickness of the maximum stress portion is preferably 10 to 25 mm, more preferably 13 to 20 mm, and further preferably 15 to 18 mm.
mm is preferable, and a portion where a horizontal line C orthogonal to the vertical line A on the frontal plane of the human body passes (hereinafter,
The thickness of the horizontal portion) is preferably 3 to 10 mm, more preferably 5 to 7 mm.

This is because the maximum stress portion has a thickness of 10 mm.
Below, or if the horizontal portion is 10 mm or less, the wear amount cannot be suppressed, and if the thickness of the maximum stress portion is 25 mm or more, the size of the socket 4 may be too large and the bone resection amount may be excessive. The thickness of the horizontal part is 3
This is because if the thickness is less than or equal to mm, this portion of the socket 4 may be significantly deformed.

[0018]

As described above, according to the present invention, a metal stem having a head of a metal or ceramic installed at its tip and a sliding surface for receiving and sliding on the head of the head In a hip prosthesis equipped with a plastic socket having a hole, when it is embedded in the human body, it passes through the center of the artificial femoral head ball and is about 1 with respect to the vertical line in the frontal plane of the human body.
Since the thickness of the socket where a straight line inclined to the center axis of the human body passes at an angle of 0 ° is made larger than that of the other parts, the stress applied to the sliding surface of the socket is absorbed and reduced, so that the abrasion powder Since it has almost no occurrence, and the size of the socket can be made compact, the amount of bone resection is small, and the amount of residual bone is large. Therefore, there is no problem of fracture of residual bone or migration of socket.

[Brief description of drawings]

FIG. 1 is a fragmentary plan view of an artificial hip joint according to an embodiment of the present invention.

[Explanation of symbols]

 1 Artificial hip joint 2 Stem 3 Head head 3a Center 4 Socket A Vertical line B Straight line C Horizontal line

Claims (1)

[Claims] 1. An artificial hip joint comprising a metal stem having a head of a metal or ceramic installed at a tip thereof, and a plastic socket having a sliding surface for receiving the head of the ball and sliding the ball. The socket of a portion through which a straight line that passes through the center of the artificial bone head ball when it is embedded in the human body and is inclined in the direction of the central axis of the human body at an angle of about 10 ° with respect to the vertical line in the frontal plane of the human body An artificial hip joint characterized by having a larger thickness than other parts.