JPH0135665B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an artificial joint for artificially repairing a joint of a living body and repairing its function and form.

When the function of a joint is impaired due to trauma such as a traffic accident or a joint lesion accompanied by bone deformation such as rheumatism, and there is little hope for healing or recovery, replacement surgery is performed to remove the joint part and replace it with an artificial joint. It is being done.

Such an artificial joint is required to have the following characteristics. (1) Because it is implanted in the body for a long period of time, it has excellent compatibility with surrounding tissues. (2) No alteration or degeneration in vivo, and no change in mechanical strength or other properties. (3) Sliding parts have excellent wear resistance,
In addition, it can perform basic joint functions. The mechanical strength of the part where the bone is inserted is particularly important.The reason for this is that in addition to the weight of the living body, the muscular strength that acts on the joints can exert a force that is several times the weight of the living body depending on the part. For this reason, great mechanical strength is required.

For this reason, in conventional artificial joints, as shown in Fig. 1, nickel-chromium alloy stainless steel, cobalt-chromium-molybdenum alloy stainless steel, etc. are joined to the femoral head ball member 3 made of alumina porcelain as the stem 4 to be inserted into the bone B1. A socket 1 made of high-density polyethylene and fixed with bone cement 2 was fixed to the ilium B2 which slidably rotated on the femoral head ball member 3. However, because the alumina porcelain femoral ball member and the high-density polyethylene socket were sliding, the inner surface of the high-density polyethylene socket wore out by about 0.2 mm per year, causing a problem that required replacement every three years. Further, the metal stem 4 is bonded with bone cement 5 so as not to come into direct contact with the bone B1, but if it is embedded in the bone for a long period of time,
There was a problem in that it caused a chemical change together with the metal stem 4 and became harmful to living organisms.

By the way, alumina ceramic is not harmful to living organisms and has high mechanical strength compared to porcelain, so it can be considered to be used in place of a metal stem. There was a risk of breakage when subjected to large stress during exercise.

The present invention has been made to solve the above-mentioned drawbacks, and provides a socket whose outer surface is made of alumina porcelain with a coating layer of calcium phosphate and has an exposed spherical inner surface of the alumina porcelain, which is rotatable with respect to the spherical inner surface of the socket. To provide an artificial joint characterized by comprising a femoral head ball member made of dense silicon nitride porcelain that slides on the femoral head ball member, and a stem made of metal having a coating layer of calcium phosphate on the outer surface and connected to the femoral head ball member. It is something.

In the present invention, polycrystalline alumina porcelain was selected for the socket because it has significantly higher wear resistance than the conventionally used high-density polyethylene and alumina single crystal, and has no directionality in wear, making it compatible with living organisms. This is because the outer surfaces of the ilium B2 and the socket 11 are threaded and screwed together, so that they can be connected to the bone tissue without causing harm to the living body. The reason for coating is that calcium phosphate is a similar component to human bone and has an affinity for it, and has a much better bonding ability with bone tissue than alumina porcelain. Furthermore, since the spherical inner surface that slides on the femoral head ball member has extremely high wear resistance compared to high-density polyethylene, replacement is almost unnecessary. In addition, the reason why the femoral head ball component is made of high-density silicon nitride is that this material has an extremely fine fibrous structure, so it has extremely high mechanical strength, with a transverse rupture strength of 100 kg/mm ²
It reaches over 150Kg/mm ² and there is no fear of cracking, so the diameter of the conventional 26mm diameter can be reduced to 22mm, and the socket can also be made smaller, which not only makes production easier and cheaper, but also It has the great advantage of reducing the burden on living organisms. Furthermore, the alumina porcelain of the socket and the silicon nitride porcelain of the femoral head have extremely high wear resistance because the silicon nitride has a fibrous structure, which not only extends the replacement period but also eliminates harmful wear particles. It has a great effect on preventing the occurrence of Next, the reason why a high-strength metal, especially stainless steel, is used for the stem 14 is that this stem requires great mechanical strength, and alumina porcelain or stabilized zirconia porcelain lacks strength and is prone to breakage. The reason why the calcium coating layer 16 is provided is that calcium phosphate has an extremely high affinity with the bone B1 and has a high bonding property with the posterior bone embedded in the bone. In addition, calcium phosphate is gradually replaced by bone when it comes into contact with bone for a long time, and eventually comes into contact with high-strength metal, so the surface of high-strength metal is coated with noble metal plating or ceramic or glass material other than calcium phosphate. It is more preferable that the In addition, the outer surfaces of the socket and stem should be porous with pores of 20 to 500 microns, rather than smooth, so that they can fit better with the bone tissue and be firmly bonded.

An example of the manufacturing method will be specifically described below. Commercially available high purity Al ₂ O ₃ 98% by weight (hereinafter "weight" will be omitted)
A cylinder with a diameter of 40.8 mm and a length of 36 mm was made using a well-known method using 1% base material for both MgO and CaO, and a hemispherical recess with a diameter of 26.4 mm was bored in the center of the bottom, and a hemispherical recess with a diameter of 26.4 mm was bored in the center of the bottom. Provide a screw with a pitch of 1 mm, and
℃ and sintered until the specific gravity is 3.85.

Next, 20 kg of CaCO ₃ and 14 kg of P ₂ O ₃ were mixed and fired at 1300° C. for 2 hours to form a semi-molten state, producing a mixture of calcium phosphate glass and crystals. In this case
The Ca/P atomic ratio is approximately 1. This was pulverized using a trommel so that 40% of the particles were 5μ or less.
This was added to water in which 1% of methyl cellulose was dissolved and stirred to form a slurry of calcium phosphate.

Next, the average particle size is 3 μ or less, which contains 70% α-Si ₃ N ₄ .
A concave portion 15 as shown in FIG. 1 is made in a part of a base material made by adding 5% Y ₂ O ₃ to Si ₃ N ₄ powder using a rubber press using a ball having a diameter of 26.4 mm. This is baked at 1700°C for 30 minutes in nitrogen to produce a femoral head.

Next, nickel - chromium alloy stainless steel and cobalt -
The stem 14 is made of chromium-molybdenum alloy stainless steel, the surface is roughened by sandblasting, and the socket 1 is made of stainless steel.
The above calcium phosphate slurry was applied by brush painting to the outer surfaces of the stems 1 and 14 that were not embedded in the femoral ball, dried, and baked at 700° C. in the atmosphere to form a calcium phosphate coating layer on the surfaces.

Next, the stem was cooled to -70 DEG C., inserted into the hole 15 of the silicon nitride femoral ball, and firmly joined by a cold tight fit. The stem and the femoral ball may be joined using an adhesive such as polyethylene. Since this part does not appear on the surface of the artificial bone, there is little harm to the living body.

Yet another method is to mix 10 to 40% of calcined organic powder or carbon powder with a particle size of 20 to 500 μm into a slurry of calcium phosphate, and apply it to the outer surface of the socket and the outer surface of the stem that does not connect to the femoral ball. If the calcium phosphate coating layer is coated before or after the calcium phosphate coating layer is provided and fired in the atmosphere, the carbon and carbon powder remaining from the organic matter will be burned out as carbon oxide gas, resulting in a product having pores of 20 to 500 microns.

Still another method is to plate the surface of the nickel-chromium alloy stainless steel or cobalt-chromium-molybdenum alloy stainless steel with a noble metal such as gold plating, or
Alternatively, a coating layer of ceramic or glass other than calcium phosphate can be applied by plasma, flame spraying, chemical vapor deposition, physical vapor deposition, or the like. In this case, during extremely long-term implantation, the calcium phosphate coating layer is transformed by the bone, and even if there is a part where the bone and the base metal come into direct contact, the presence of the noble metal plating layer or the ceramic layer prevents the bone from forming. The negative effects that occur when direct contact with stainless steel can be avoided. Here, the ceramic layer is meaningless if it is made of calcium phosphate as it replaces bone, and Be,
Of course, it must not contain substances harmful to the human body, such as Ba, Pb, and As, and Al ₂ O ₃ and the like are preferable because they are not harmful to the human body.

FIG. 3 is a longitudinal sectional view of the artificial joint, and numeral 17 indicates a noble metal plating or ceramic coating layer.

As described above, the artificial joint according to the present invention has no adverse effects on the living body, has high wear resistance on the sliding parts, and brings great news to injured persons.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a conventional artificial joint, and FIG. 2 is a longitudinal sectional view of the artificial joint of the present invention. FIG. 3 is a longitudinal sectional view of an artificial joint showing another example of the present invention. 1, 11... socket, 2... bone cement, 3, 13... femoral head ball member, 4, 14... stem, 5... bone cement, 12, 16... calcium phosphate double cover layer, 17... precious metal Or ceramic coating layer.

Claims (1)

[Scope of Claims] 1. A socket whose outer surface is made of alumina porcelain with a coating layer of calcium phosphate and has an exposed spherical inner surface of the alumina porcelain, and a dense silicon nitride porcelain that rotatably slides on the spherical inner surface of the socket. 1. An artificial joint comprising: a femoral ball member; and a stem connected to the femoral ball member, which is made of a base metal having a calcium phosphate coating layer on its outer surface. 2. The artificial joint according to claim 1, wherein the femoral head ball member and the stem are joined by cold tight fit. 3. The artificial joint according to claim 1 or 2, wherein the outer surface of the socket and/or the outer surface of the stem is a porous surface having a large number of pores of 20 μ to 500 μ. 4. The artificial joint according to any one of claims 1 to 3, wherein the base metal of the stem is stainless steel. 5. The artificial joint according to claims 1 to 4, wherein the base metal of the stem is stainless steel plated with a noble metal. 6. The artificial joint according to claims 1 to 4, wherein the base metal of the stem is stainless steel coated with a ceramic coating layer excluding calcium phosphate.