JPH0136383B2 - - 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 restoring its function and form. Joint function is impaired due to trauma such as a traffic accident or joint lesions due to bone deformation such as rheumatism.
When there is little hope for healing or recovery, replacement surgery is performed to remove the joint and replace it with an artificial joint. 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 the surrounding tissue. (2) No alteration or degeneration in vivo, and no change in mechanical strength or other properties. (3) Sliding parts have excellent wear resistance,
and can perform basic joint functions. (4) It is non-toxic to the human body. The mechanical strength of the part where the bone is inserted is particularly important.
A force that is several times the weight of the living body acts on some parts, which requires great mechanical strength. For this reason, in conventional artificial joints, as shown in Fig. 1, a femoral head ball 3 made of alumina porcelain is joined with a nickel-chromium alloy stainless steel, a cobalt-chromium-molybdenum alloy stainless steel, etc. as a stem 4 to be inserted into the bone B1. A socket 1 made of high-density polyethylene that slidably rotates on a ball 3 was fixed to the iliac bone B2 with bone cement 2. However, because the alumina porcelain femoral ball and the high-density polyethylene socket were sliding, the inner surface of the high-density polyethylene socket wore out about 0.2 mm per year, causing a problem that required replacement every three years. Furthermore, metal stem 4 is attached to bone B1
The bone cement 5 is used to avoid direct contact with the metal stem 4, but if it is implanted in the bone for a long period of time, it will chemically change with the metal stem 4 and become harmful to living organisms. Later, a method of bonding via calcium phosphate instead of bone cement was considered, but this has not been put to practical use because the adhesive strength between calcium phosphate and metal is insufficient. The present invention was made in order to improve the compatibility with living organisms without impairing the advantages of the above-mentioned conventional invention, and as shown in FIG. 2, the socket 11 is made of a corrosion-resistant metal and has a spherical inner surface. The base includes a rotatably sliding femoral ball 12 and a stem 13 connected to the femoral ball, and the spherical inner surface of the socket and the femoral ball have inner layers 14, 15 of titanium nitride and outer layers 16, 17 of silicon nitride, The outer surface of the socket except for the spherical inner surface and the stem are coated with first coating layers 18 and 19 made of alumina and an alkaline earth metal oxide.
Phosphoric acid frit or alkaline earth metal oxide
The second coating layer 20, 2 is made of a frit made of phosphoric anhydride and one or more metal oxides selected from Zn, Al, Si, B, Ti, Fe, and alkali metals.
1 and a third coating layer 22 made of calcium phosphate salt,
The present invention provides an artificial joint characterized by having 23. In the present invention, a corrosion-resistant metal was selected for the socket, femoral ball, and stem because it has high mechanical strength, and if the surface is covered with a ceramic material, it has corrosion resistance to the extent that it is not harmful to living organisms, is not very expensive, and is easy to process. This is also because it is easy. Also, the reason why the outer layer of silicon nitride is provided on the spherical inner surface of the socket and the femoral ball is to increase wear resistance and corrosion resistance, and to prevent harmful wear particles and heavy metal ions from being emitted even after many years of sliding. The purpose of providing this is to improve the adhesive strength between the base and the outer layer. The inner layer of titanium nitride can be applied by chemical vapor deposition and the outer layer of silicon nitride can be applied by plasma spraying in vacuum. Next, a first coating layer made of alumina, an alkaline earth metal oxide-phosphoric acid frit, or an alkaline earth metal oxide layer is applied to the outer surface of the socket excluding the spherical inner surface and the stem.
A second coating layer made of a frit made of phosphoric anhydride and one or more metal oxides selected from Zn, Al, Si, B, Ti, Fe, and alkali metals.A third coating layer made of a calcium phosphate salt. The reason for using this is that the corrosion-resistant metal has a low affinity with living organisms, prevents it from corroding in the living body and releases harmful ions, and provides a calcium phosphate salt, which has the best affinity with living organisms, on the surface. The first coating layer made of alumina is chemically extremely stable and can be formed by chemical vapor deposition or thermal spraying, but if an intermediate layer of titanium carbide, titanium nitride, etc. is provided between the base and the corrosion-resistant metal substrate, Adhesive strength can be further improved. The frit forming the second coating layer is then useful as a bonding layer with the calcium phosphate salt forming the third coating layer. The frit forming the second coating layer is composed of an alkaline earth metal oxide and phosphoric anhydride as essential components, and one or more metal oxides selected from Zn, Al, Si, B, Ti, Fe, and alkali metals. The optimum frit composition is Frit A (hereinafter abbreviated as A) disclosed by the applicant in JP-A-55-140756 "High Strength Calcium Phosphate Sintered Body".
The composition is shown in Table 1 along with its properties.

[Table] Regarding the calcium phosphate salt forming the third coating layer, it is desirable to use a salt B (hereinafter abbreviated as B) with a Ca/P atomic ratio in the range of 1.4 to 1.75, and more preferably tricalcium phosphate Ca ₃ (PO _{4 )} . ) ₂ and hydroxyapatite
_Ca10 ( _PO4 ) ₆ (OH) ₂ is preferred. As another component of the third coating layer, a suitable frit may be added to the above B to enhance sinterability and mechanical strength. Examples of calcium phosphate salts containing frits include C (hereinafter abbreviated as C), which contains 0.5 to 15% by weight of A to 85 to 99.5% by weight of B;
There are products that contain 3-23% by weight of Y ₂ O ₃ with respect to C77-97% by weight, and these not only have high mechanical strength but also have been described in JP-A No. 55-140756 "High-strength calcium phosphate sintered body". and JP-A No. 55-80771 "High-strength calcium phosphate sintered body", both have thermal expansion coefficients of 90 to 160×.
Since the temperature is within the range of 10 ^-7 /°C, the adhesiveness with the first coating layer is good. The baking temperature is preferably 800 to 1200°C. An example of the artificial joint of the present invention and its manufacturing method will be specifically explained below using the drawings. A cylinder with a diameter of 30.0 mm and a length of 25 mm was manufactured from titanium and cobalt-chromium-molybdenum alloy stainless steel.
A hemispherical recess with a diameter of 22.4 mm is drilled in the center of the bottom.
I made socket 11. Furthermore, the second one is made of the same material.
A femoral head and a stem connected to it as shown in FIGS. 12 and 13 were created. Next, 10 μm of titanium nitride was applied to the spherical inner surface of the socket and the surface of the femoral head using a well-known chemical vapor deposition method.
It was coated to a thickness of . Next, silicon nitride was coated to a thickness of 10 μm by plasma spraying in a vacuum. The outer surface of the socket, excluding the spherical inner surface, and the outer surface of the stem were then coated to a thickness of 8 .mu.m by chemical vapor deposition. Next, commercially available H ₃ PO ₄ , BaCO ₃ , MgCO ₃ , Na ₂ CO ₃ and SiO ₂
Frit 5 whose composition after firing is shown in Table 1 using
Weigh and mix the mixture so that it has a composition of
Frit 5 was obtained by firing at 1300° C. and holding time for 2 hours to obtain a molten state, and then rapidly cooling the molten material with water. This is crushed with a trommel until particles of 5 μm or less reach 40%, and a part of the powder is
Add 1% to 100% methyl cellulose to an aqueous solution and stir to obtain a slurry, which is spread 0.5 mm onto the alumina layer of the socket 11 and stem 13.
The second coating layers 20 and 21 were provided by applying the coating to a thickness of 100.degree. C., drying, and then baking at a temperature of 700.degree.
Next, the remaining powder 5 obtained by crushing the frit 5
% and commercially available hydroxyapatite 95% with an average particle size of 0.1 μm
Wet-mix in alcohol to form a slurry, apply this onto the second coating layer and dry it at an atmospheric temperature of 900°C.
The third coating layers 22 and 23 were formed by firing under the conditions of 40 minutes at a temperature of 40 minutes. In the above example, the surfaces of the first and second covering layers are both smooth, but in order to increase the adhesive force between the artificial bone and the living bone B ₁ or B ₂ , each surface is threaded, vertically grooved, and horizontally grooved. It is desirable to provide irregularities such as corrugations. In addition, the third coating layer, which is mainly composed of calcium phosphate salt, is essentially a biological bone.
It has a good affinity with B ₁ and B ₂ , but if you mix 20 to 500 μm carbon powder or powder that can be burned off, such as organic matter, into the slurry before applying it, the 20 to 20
Pores of 500 μm are formed, further improving the affinity.
Furthermore, the method for providing the covering layer is to select the compositions of the first covering layer and the second covering layer so that the sintering temperature of the second covering layer is equal to that of the third covering layer. The coating layer may be baked simultaneously at a temperature in the range of 700 to 1200°C, or other well-known methods such as chemical vapor deposition or physical vapor deposition may be used. As described above, the artificial joint according to the present invention has high mechanical strength, is not harmful to living organisms, and has good affinity and adhesiveness with living organisms, so it brings great news to injured people.

[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. 1, 11... socket, 3, 15... femoral ball,
4, 13... Stem, 18, 19... First coating layer, 20, 21... Second coating layer, 22, 23...
Third coating layer, 14, 15... Inner layer, 15, 17...
...outer layer.

Claims (1)

[Scope of Claims] 1. A socket made of a corrosion-resistant metal and having a spherical inner surface, a femoral head ball that rotatably slides on the spherical inner surface, and a stem connected to the femoral ball; has an inner layer of titanium nitride and an outer layer of silicon nitride, and the outer surface of the socket except for the spherical inner surface and the stem have a first coating layer made of alumina, a second coating layer made of alkaline earth oxide-phosphoric acid frit, and a phosphoric acid frit. An artificial joint characterized by having a third coating layer made of a calcium salt. 2. The artificial joint according to claim 1, wherein the third coating layer has an uneven surface. 3. The artificial joint according to claim 1, wherein the third coating layer has pores of 20 to 500 μm. 4 Ca/P atomic ratio in calcium phosphate salt is 1.4~
1.75, the artificial joint according to claim 1. 5. The artificial joint according to claim 1, wherein the alkaline earth metal oxide-phosphoric acid frit is a calcium phosphate frit. 6. The artificial joint according to claim 5, wherein the calcium phosphate frit has a Ca/P atomic ratio of 0.2 to 0.75. 7. The base is made of a corrosion-resistant metal and has a spherical inner surface, a femoral ball that rotatably slides on the spherical inner surface, and a stem connected to the femoral ball, and the spherical inner surface of the socket and the femoral ball are made of an inner layer of titanium nitride. The socket has an outer layer of silicon nitride, and the outer surface of the socket except for the spherical inner surface and the stem are covered with a first coating layer of alumina, an alkaline earth oxide, Zn, Al, Si, B, Ti,
An artificial joint characterized by having a second coating layer made of a frit made of phosphoric anhydride and one or more metal oxides selected from Fe and alkali metals, and a third coating layer made of a calcium phosphate salt. 8. The artificial joint according to claim 7, wherein the third coating layer has an uneven surface. 9. The artificial joint according to claim 7, wherein the third coating layer has pores of 20 to 500 μm. 10 Ca/P atomic ratio in calcium phosphate salt is 1.4
8. The artificial joint according to claim 7, wherein the joint is 1.75 to 1.75.