JP2543747B2 - Artificial head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an artificial head effective for use in a patient who needs replacement of the head due to a femoral head of the human body, a fracture of the neck, or osteoarthritis.

Conventional technology: In the case of a conventional artificial head with a double head structure consisting of an inner sphere and an outer sphere, insert a resin-made sliding bearing between the inner and outer spheres and fit the inner sphere. It is known that it is assembled with a fixing ring. The material of the bone head is generally a metal such as titanium alloy, stainless steel, cobalt-chromium-molybdenum alloy for both the inner and outer spheres. Recently, a material composed of a ceramic material for the inner and outer spheres was developed, and some of them have been put to practical use, but this is also a sliding bearing system, and since the material of the inner and outer spheres is a ceramic material, the bearing Wear resistance is poor and wear is large.

Problems to be Solved by the Invention: In the conventional artificial head having a double structure, the bearing portion is a slide bearing,
The outer sphere and the inner sphere are made of metal, and high-density polyethylene is used for the material of the intermediate bearing part, but this bearing is subject to large wear, and especially when the outer surface of the metal inner sphere is deteriorated due to corrosion etc. The wear of the bearing is accelerated, and the bearing is broken and loosened, which may cause complications such as a fracture, which has been a problem.

Means for solving the problem: The inner surface of the concave portion on the human body side where the outer surface of the outer ball contacts is the same as the conventional slide bearing system, but the structure of the rolling bearing system between the inner and outer ball of the artificial bone head having the double structure is as described above. It is intended to eliminate the drawbacks of. That is, a rolling ball is installed as a bearing in the intermediate layer between the inner sphere and the inner surface of the outer sphere, or a cage with the rolling sphere is installed, and the outer sphere opening is the rotation of the inner sphere. The ring is fixed and closed to prevent the rolling ball from coming off. On the other hand, the bearing portion on the outer ball side is a sliding bearing system of the outer surface by directly inserting the outer ball in the case of a human body, for example, an acetabular lid, and the material is ceramic or metal material. The ceramic material is preferably a high strength ceramic such as alumina, zirconia, silicon nitride, sialon, or silicon carbide. The metal material is preferably stainless steel, titanium alloy, high carbon steel cemented carbide and high carbon chrome steel. High density polyethylene or polymethylmethacrylate (PMMA) may be used for the outer sphere.

Embodiment: FIG. 1 shows an embodiment of the artificial head according to the present invention.
The outer surface 2, inner surface 3 and outer surface 5 of the inner sphere 4 are mirror-finished spherical surfaces, and the rolling sphere 6 is inserted into the hole 7 of the retainer 8 and the end face 9 of the hole 7 is caulked by heat to roll the rolling sphere 6. Do not escape from the cage 8. The holder 8 is inserted into the inner surface 3 of the outer sphere 1. Next, the inner sphere 4 is fitted and the fixing ring 10 is fitted in the groove 11, so that the inner sphere 4 does not come off from the outer sphere 1. The fixing ring 10 is brought into spherical contact with the inner sphere 4 so that both can slide.
FIG. 2 is a sectional view showing a state in which the artificial head of the present invention is inserted into the acetabular cover 13 of a human body. FIG. 3 shows another embodiment, and is a sectional view showing a state in which the rolling balls 6 are not assembled with a retainer but are filled and interposed between the inner and outer balls and are closed by a ball mounting ring 14. The material of the cage is a resin such as ceramic metal or high density polyethylene, polyacetal, etc., together with the outer sphere. FIG. 4 is a cross-sectional view of an embodiment of a conventional double-structured bone head, showing a double-structured structure in which a high-density polyethylene sliding bearing 16 is interposed between the outer sphere 15 and the inner sphere 17. It is an example of a method.

In the above-described embodiment of the present invention, the material of the outer sphere 1, the inner sphere 4, and the rolling sphere 6 is ceramics such as alumina, zirconia, silicon nitride, sialon, silicon carbide, but this may be metal.
The material of the retainer 8 and the fixing ring 10 is high density polyethylene, but it may be metal. Further, the material of the rolling ball 6 is different from the outer ball 1 and the inner ball 4, for example, when the outer ball 1 and the inner ball 4 are made of ceramic and the rolling ball 6 is metal, or the outer ball 1 and the inner ball 4 are metal. It is also possible to combine the rolling balls 6 with ceramics. Further, in the embodiment, the shape of the rolling sphere is a perfect circle, but it may be a spherical roller assembled to the cage. The outer sphere 1, the inner sphere 4, and the rolling sphere 6 may be made of a metal whose main body is made of metal and whose surface is coated with ceramic. The material of the fixing ring 10 is high density polyethylene, polyacetal, and the metal is a ceramic such as zirconia, which is the same alloy as the outer sphere, including shape memory alloy.

Action and effect: In the artificial bone head of the present invention, since the inner and outer spheres of the double-structured head have a rolling bearing system, the friction coefficient is small, and there is a gap in the rolling bearing portion, so that the synovial fluid is well lubricated. , The friction coefficient of the articular cartilage of the human body becomes approximately equal, and the motion of the joint becomes smooth. Furthermore, if the material of the outer sphere, inner sphere and rolling sphere is made of ceramic, the mirror surface of the sphere can be maintained for a long period of time without corrosion, so it can be used stably without damaging the acetabular cap of the human body. . The range of movement of the hip joint of the human body is the most frequently in the range of 50 ° to 60 ° in daily life, and this range is adopted as the rolling bearing system. Since the sliding bearing system in which the inner surface of the acetabular lid and the outer surface of the outer sphere act to slide, there is almost no wear and therefore no abrasion powder is generated, so complications are reduced and the gospel sound is improved for the patient. Is. The surface contacting the rolling sphere due to point contact, that is, the outer surface of the inner sphere and the inner surface of the outer sphere do not necessarily need to be mirror-finished, and there is no problem in use if only the sphericity is good. As a result, mirror finishing is not required and the cost is reduced.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part of an artificial bone head of the present invention, FIG. 2 is a vertical sectional view of a case where the artificial bone head of the present invention is adopted for a human acetabular lid, and FIG. FIG. 4 is a vertical cross-sectional view of a state in which a rolling ball is provided without a cage therebetween, and FIG. 4 is a vertical cross-sectional view of a conventional double-structured slide bearing type artificial bone head. 1 ... Outer sphere, 2 ... Outer sphere outer surface, 3 ... Outer sphere inner surface, 4 ...
Inner sphere, 5 …… Inner sphere outer surface, 6 …… Rolling sphere, 7 …… Rolling ball insertion hole, 8 …… Cage, 9 …… Hole end face caulking part, 10 ……
Fixing ring, 11 ... Ring groove, 12 ... Stem, 13 ... Human acetabular lid, 14 ... Ball mounting ring, 15 ... Conventional metal outer ball, 17 ... Conventional metal inner ball, 16 ...... Conventional plain bearing

Claims (3)

(57) [Claims] 1. An outer sphere slidably engages an inner surface of a human body-side recess on its outer surface, and an inner surface forms a rolling ball between the inner surface and the outer surface of a hemispherical inner sphere of a metal stem head. An artificial bone head, characterized in that they are interposed to form mutually rotatable bearings and the opening of the outer sphere is closed by a fixing ring that rotatably supports the inner sphere. 2. The artificial bone head according to claim 1, wherein the rolling ball according to claim 1 is installed in a cage by being inserted therein. 3. The artificial bone head according to claim 1 or 2, wherein at least one of the outer sphere, the inner sphere, and the rolling sphere of claim 1 or 2 is made of a ceramic material.