JPS6311906B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a socket for an artificial joint and a method for manufacturing the same.

Artificial joints are useful for people who do not have normal joint function due to disabilities caused by disasters or diseases.As a result of trial and error with various substitutes, at present, artificial joints are mainly made of stainless steel femoral heads and polyethylene resin. Combinations with manufactured sockets have been put into practical use. However, since the joints are subject to a load equivalent to 5 to 6 times the body weight during activity, the combination of stainless steel and polyethylene resin described above is generally recommended for people with a weight of less than 90 kg, a height of less than 180 cm, and an age of 50 years or older.
Moreover, it is said to be suitable for women who are less active if possible, and if the above conditions are not met, the polyethylene resin socket will wear out and deform, making it difficult to withstand long-term use and causing significant problems. This drawback is due to the following reasons.

(a) Conventional sockets made of polyethylene resin, for example, when manufactured by cutting from a resin material, have minute grooves created by cutting on the inner surface of the socket, and self-lubricating activity cannot be obtained.

(b) The cutting process thermally or mechanically cuts the polyethylene molecules on the surface of the polyethylene resin, reducing its strength and causing wear.

(c) Depending on the history of the material, distortion that causes deformation after processing and placement in the body is unavoidable.

As a result of research to solve the above-mentioned conventional drawbacks, the present inventors mixed a synthetic resin and a hydrogel, molded it into a predetermined shape and cured it, then heated the cured product while dipping it in a water-containing solvent to form a hydrogel. By using the elution method (described in Japanese Patent Application No. 187681/1987 by the present inventor), a porous layer formed by elution and removal of the hydrogel is provided on the inner surface of the socket.
It was discovered that wear and tear is reduced because body fluid can be retained between the femoral head and the socket of an artificial joint, and the present invention was completed based on the above findings.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a spherical socket A for an artificial joint, which is an embodiment of the present invention.
It consists of a synthetic resin layer indicated by 2 in the figure and a porous layer indicated by 1 in FIG. Various synthetic resins can be used as the synthetic resin forming the synthetic resin layer, but polyethylene resin, especially ultra-high molecular weight polyethylene resin, is called polyethylene resin, which has little reaction with living organisms when worn inside the human body. Molecular weight 2×10 ⁶ to 6.5×10 ⁶ , especially 3×
10 ⁶ to 6×10 ⁶ is particularly preferably used.
However, the present invention is not limited to the above-mentioned polyethylene resins, and may also include polypropylene, polystyrene, polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyacetal, nylon, etc., which have chemical resistance, low coefficient of friction, and wear resistance. If so, you can use it.

Next, we will talk about the porous layer formed by eluting and removing hydrogel. First, hydrogel is a type of polymer material with polar groups, and when it comes into contact with water, it interacts with the large dipoles of water and hydrogen bonds. Some hydrogels have a high water absorption capacity and can absorb several thousand times their own weight in water. for example,
Polyacrylate (Japanese Unexamined Patent Publication No. 53-46389),
Hydrolyzed salts of starch/acrylonitrile graft polymers (J.Appl, Polym, Soi 22 1343
(1978)) and vinyl alcohol/acrylate copolymer (Japanese Patent Application Laid-Open No. 53-50290).

The hydrogel used in the present invention is most preferably a vinyl alcohol/acrylate copolymer hydrogel. The reason for this is that the hydrogel is heat resistant within the molding temperature (150-210℃), and when immersed in water, it swells to 500 times its own weight, and the pressure at the time of swelling causes the thin wall of the synthetic resin to swell. This is because it destroys pinholes, enlarges pinholes, and helps create complete through holes in synthetic resins.Furthermore, it is soluble in water at around 120°C, so it can be eluted from synthetic resins.

In addition, in the present invention, in addition to the above-mentioned vinyl alcohol/acrylate copolymer, starch/
Other hydrogels such as acrylonitrile and sodium polyacrylate can also be used without any problem.

In order to form a porous layer by eluting and removing the hydrogel using the above hydrogel, for example, a mixture of 50 to 30 parts by weight of the hydrogel to 50 to 70 parts by weight of the synthetic resin described above is used. After molding and curing into a predetermined shape by a known method, the cured product is immersed in a water-containing solvent and heated to dissolve the hydrogel.

Regarding the shape of the artificial joint socket of the present invention, the thickness of the synthetic resin layer indicated by 2 in Fig. 1 is 12 mm.
mm to 3 mm, especially 8 mm to 5 mm, and the thickness of the porous layer indicated by 1 in FIG. 1 is 0.1 mm to 5.0 mm, especially 0.8 mm.
mm to 2.0 mm is preferred. Also, the diameter of a socket for an artificial joint varies depending on where it is installed in the body, but it is 10 mm.
~40 mm, especially 25 mm to 32 mm, and can be determined by considering the attachment site, bone size, and frequency of use. In addition, in order to prevent the femoral head from falling out of the socket, the center of the spherical surface of the spherical socket should be moved 0 to 5.0 mm further into the socket than the opening surface of the socket, preferably.
It is best if they are closer together by 0.2mm to 3.0mm.

In addition, in the present invention, it is necessary to provide the above-mentioned porous layer on the inner surface of the socket, but providing a porous layer on the outer surface also improves the adhesion of the socket, especially the adhesion between the bone and the socket via the bone cement. This is preferable because it improves the adhesion during the process.

An example of the use of the socket for an artificial joint of the present invention is shown in FIG. The socket 3 is attached to the bone 7 through the socket 3, and body fluid is present in the gap between the socket 3 and the skull 4 to smooth the rotation.

Next, a method for manufacturing a socket for an artificial joint according to the present invention will be explained one embodiment using an ultra-high molecular weight polyethylene resin.

First, a molded body corresponding to the synthetic resin layer shown by 2 in FIG. 1 is molded by first compression molding using ultra-high molecular weight polyethylene resin powder. A mold is used for molding, and the mold temperature is 130°C to 190°C, preferably 140°C.
Molding is performed at ~170°C to obtain a preform.

Next, as described above, a mixture of 50 to 70 parts by weight of ultra-high molecular weight polyethylene resin and 50 to 30 parts by weight of hydrogel is applied to the inner surface of the socket of the above-mentioned preform.
supplying 1.0 to 6.0 g, preferably 2.5 g to 4.5 g;
Furthermore, if the required weight of resin corresponding to the volume of the final molded object is insufficient, replenish the resin on the cavity side.
Replenish preferably by increasing 10-30% of the replenishment amount,
A second compression molding is performed. For the second compression molding, the temperature on the core side is 125℃~150℃, preferably 135℃~145℃.
℃, cavity side 170℃~210℃, preferably
Perform at 185°C to 195°C. Note that both the first and second compression molding may be performed using any type of mold, such as a flash mold, a positive mold, or a semi-positive mold. Through the above steps, a semi-finished product of a socket for an artificial joint having a hydrogel on the inner surface is formed.

Further, the semi-finished artificial joint socket having the hydrogel on the inner surface is immersed in pure water or physiological saline, and then heated while being immersed. Heating is carried out in an autoclave at 110°C to 125°C to elute the hydrogel and form a porous layer on the inner surface of the socket consisting of micropores that remain after the hydrogel has been eluted and removed. After forming the porous layer, it is thoroughly washed with pure water and physiological saline and dried to obtain the artificial joint socket of the present invention.

Furthermore, the artificial joint socket obtained above has γ
When irradiated with radiation, it is possible to crosslink the decomposition products produced by oxidative decomposition of the resin during molding, further improving wear resistance and sterilization, but the irradiation conditions are 5 to 30 Mrad, especially 10 to 20 Mrad. dose is preferred. Furthermore, γ-ray irradiation may be performed before or after heating in an autoclave. Furthermore, it is practically preferable to plasma-treat the inner surface of the socket to improve its wettability, since it is compatible with body fluids.

According to the present invention, since the inner surface of the socket for an artificial joint has a porous layer formed by eluting and removing hydrogel, when such a socket is incorporated into an artificial joint, body fluids can be absorbed between the femoral head and the socket due to the presence of the porous layer. It can be held, reduces friction and wear, and therefore has no problems or limitations in use as in the conventional products as described above, and can withstand long-term use.

The present invention will be explained in more detail below with reference to Examples.

Example 1 Using ultra-high molecular weight polyethylene resin powder with a molecular weight of 4 x 10 ⁶ (manufactured by Hoechst, Hostalen GUR412), a hemispherical socket with an inner diameter of 28φ was prepared by compression molding at a temperature of 160°C for both the core and cavity parts. Molded.

Next, the above ultra-high molecular weight polyethylene resin powder 100
A dry blend of 45 parts by weight of Sumikagel S-50 manufactured by Sumitomo Chemical Co., Ltd. as a hydrogel was supplied to the core part, only ultra-high molecular weight polyethylene resin powder was supplied to the cavity part, and the core part temperature was 140 ° C.
At a cavity temperature of 190°C, it was molded by compression molding using a mold separate from the preform, and was integrated with the preform.

The obtained molded product was first immersed in pure water at room temperature for 30 minutes to sufficiently swell the hydrogel, then immersed in hot water in an autoclave at a temperature of 120°C for 1 hour to elute the hydrogel, and washed with physiological saline. After drying, γ-rays were irradiated at 15 Mrad.

When the resulting artificial joint socket was used for hip joints and compared to a conventional product, the coefficient of friction related to rotation was reduced to 1/2, and the deformation due to repeated loads corresponding to the amount of annual walking was 20% less than the conventional product. .

Example 2 The process was carried out in the same manner as in Example 1, except that a mixture of ultra-high molecular weight polyethylene and hydrogel was supplied to the inner and outer surfaces of the preformed product, and the molding was performed in the same manner as in Example 1. A socket with excellent adhesion to bone cement was obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of the artificial joint socket of the present invention, and FIG. 2 is a schematic cross-sectional view showing an example of use of the artificial joint socket of the present invention. 1...Porous layer, 2...Synthetic resin layer, A , 3...
...Socket, 4...Female head, 5...Bone cement,
6,7...Bone.

Claims (1)

[Scope of Claims] 1. A socket for an artificial joint made of a synthetic resin, characterized in that the socket has a porous layer formed by eluting and removing hydrogel on the surface. 2 A composition made by mixing a synthetic resin of the same quality as the synthetic resin and a hydrogel is placed on the surface of a molded body made of synthetic resin, and then molded to integrate, and then heated while being immersed in a water-containing solvent. , a method for producing a socket for an artificial joint, characterized in that the hydrogel is eluted. 3. The method for producing a socket for an artificial joint according to claim 2, which comprises eluting the hydrogel and then crosslinking it by irradiating it with ionizing radiation.