JPH0698902A - Production of bone implant - Google Patents

Abstract

PURPOSE:To provide the bone implant having high rigidity and wear resistance by applying the surface of a metallic core with resin powder, then covering the coating with a heat resistant film and heating a resin powder layer to partially dissolve the powder layer under vacuum suction from the aperture of the film, thereby bringing the film into tight contact with the core. CONSTITUTION:The core 4 of the stem part 2 of the artificial bone head 1 is formed to, for example, a prescribed shape from a proper metallic material in the case of production of the artificial bone head of the artificial thigh joint to be implanted into the marrow hole of the femur. The resin powder layer 5 of high-performance engineering plastics, etc., is then stuck and formed on the surface of the metallic core 4 and thereafter, the circumference thereof is coated with the heat resistant glass fibers 5 having air permeability and further, the circumference thereof is coated with the polyimide film 7 which is formed to a cylindrical shape sealed on one side and has excellent heat resistant. The surface of the metallic core 4 is then heated to melt the boundary part of the resin powder layer 5 and the core 4 and the pressure in the film 7 is reduced by suction from the suction port 8, by which the film 7 is brought into tight contact with the surface of the core 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bone implant to be implanted in the human body in orthopedic treatment.

[0002]

2. Description of the Related Art Artificial joints (particularly, the stem portion on the side of the artificial femur) and fractures of the diaphysis for repairing the joint function by prosthesing the joint when the human body is deformed, missing, or necrotic. Bone implants to be implanted in the human body during orthopedic treatment, such as intramedullary nails used for intramedullary nail treatment in the case of, are made of stainless steel SUS316L, Co-Cr, Co-Cr-N.
i, Ti-6% Al-4% V, etc. were mainly used, and formed by appropriate means such as casting, forging, and sintering.

[0003]

However, bone implants using metal implant materials have various problems. For example, the bending elastic modulus of human cortical bone is about 16 GP.
a, stainless steel SUS316L, Co-
The bending elastic moduli of Cr and Ti-6% Al-4% V are 200, 213 and 124 GPa, respectively, which is about 8 to 1 of bone.
Since it is three times as large, stress may be locally concentrated due to bending or twisting of the artificial joint, and the bone may be destroyed at the stress concentrated portion.

Further, in the clinical practice of a cementless artificial hip joint in which an implant and bone are directly fixed to each other without using an acrylic-based cement, a stem that is well fitted with a bone marrow cavity and is repeatedly subjected to stress due to exercise such as weight and walking. It has been reported that the bone mass is reduced in the tip part, but bone is resorbed in the part where stress is not applied and the bone is not stimulated in the part where the stress is not applied, so that the bone mass is decreased. That is, in a portion where no stress is applied, displacement or looseness is increased in fitting of the bone and the artificial joint, and there is a possibility that the artificial joint cannot be stably held.

Further, the artificial joint made of a metal implant material having a large specific gravity has a problem that the burden on the patient during insertion is large.

Further, since bone implants have been implanted for several months even in the case of intramedullary nails and for more than 10 years in artificial joints, they are corroded in the living environment, resulting in stainless steel SUS316L and Co-Cr. In some cases, toxic substances such as nickel were eluted from -Ni and vanadium from Ti-6% Al-4% V to cause inflammation. Also,
The carcinogenicity of these toxic substances has also been pointed out.

In view of these problems, a bone implant made of a synthetic resin molding has been proposed. For example, in US Pat. No. 4,902,297, polyether ether ketone (PEEK), polyether ketone (PEK), polyallyl ether ketone (PAEK), polyphenylene sulfide (PP) is used as a matrix resin.
S), polysulfone (PS) and other high-performance engineering plastics are used, and carbon fiber (C
F), glass fiber (GF), aramid fiber (ArF) and other reinforcing fiber materials are arranged in the stem length direction, and are obtained by molding by press molding or pultrusion molding The implant is shown.

However, since extremely complicated stress is applied to the bone implant from various directions, in order to form the bone implant from such a fiber-reinforced synthetic resin, more careful study in terms of strength is required. In addition, there was not enough data on the deterioration of plastic due to implantation in the human body for a long time, and there were many unsolved problems for practical use.

In view of the above-mentioned problems of the prior art, the present invention is a novel structure excellent in various characteristics such as high strength, high rigidity, wear resistance, corrosion resistance, chemical resistance, safety and body compatibility. It is an object of the present invention to provide a method for manufacturing the bone implant.

[0010]

The method for producing a bone implant according to the present invention, which was devised to achieve the above object, comprises molding a core having a desired implant shape from a metal material, and forming a resin powder on the surface of the core. And coating the resin powder coating with a heat-resistant film having an opening, heating the resin powder coating while vacuum-sucking from the opening of the heat-resistant film to dissolve the resin at least partially, After that, the resin is cured to form a resin coating layer on the surface of the core.

The resin powder coating material is preferably heated by internal heating by a high frequency heating method to dissolve only the resin at the interface with the core.

As the core metal material, stainless steel, Co--Cr alloys, Ti and Ti alloys, which are the same as those used as materials for conventional metal implants, can be used.

In order to enhance the adhesion between the metal core and the resin coating layer, the surface of the metal core is preferably a rough surface having fine irregularities. For this reason, fine irregularities are formed on the inner surface of the cavity of the mold used to mold the metal core, and the metal core surface after molding is subjected to chemical treatment such as polishing, shot blasting, pickling, and electrolytic treatment. Etc. are performed.

The resin coating layer can be formed by laminating a plurality of layers having different compositions by sequentially applying a plurality of kinds of resin multi-coated products having different compositions and then heating.
This makes it possible to form various resin coating layers that take advantage of the characteristics of each resin powder. For example, the inner layer in contact with the metal core can be formed of resin powder having excellent adhesion to the metal core, and the outer layer can be formed of resin powder having excellent biocompatibility and affinity with bone tissue. In addition, it is desirable to effectively prevent elution of harmful substances from the core, to make the outer resin coating layer function as a protective layer for the inner resin coating layer, and to adjust the elastic modulus and strength. It is possible to provide the resin coating layer with the characteristic function of.

When the resin coating layer is formed as a plurality of layers having different compositions, the types of resins themselves can be different, but it is also possible to use the same resin as the main material and change the additive compound. For example, the inner layer is formed of additive-free resin powder, and the outer layer is formed of calcium phosphate, CaO,
It can be formed of a resin powder containing a compound powder having a good affinity for bone tissue, such as P ₂ O ₅ -containing glass and hydroxyapatite.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. This example is intended to produce an artificial hip prosthesis head that is implanted within the femoral bone marrow hole.

The stem portion 2 of the artificial bone head 1 (in this embodiment, it is shown as integrally including the ball portion 3 rotatably fitted in the recess of the cup attached to the hip bone). The metal core 4 formed into a predetermined shape by a desired metal material as exemplified above is mainly used.

On the surface of the metal core 4, a powder of high-performance engineering plastic as exemplified above is uniformly sprinkled, and a resin powder layer 5 is adhered and formed. Especially PEE
Since a ketone resin such as K or PAEK or a resin such as PPS or PI is extremely excellent in body compatibility and chemical resistance, the resin powder layer 5 should be formed using these resin powders. Is preferred.

For example, as the material for the resin powder layer 5, PEE
When K is used, the metal core 4 heated to about 360 to 380 ° C., which is the melting temperature (343 ° C.) or higher, is brought into contact with the PEEK powder in the fluidized bed, or the PEEK powder is electrostatically applied. Therefore, the uniform resin powder layer 5 can be formed.

The resin powder layer 5 generally has a thickness of 0.1 to 1 m.
Although it is about m, depending on the particle size of the resin powder and the heating temperature,
The layer thickness can be adjusted. For example, 0.5 to 5 μm
In the case of PEEK powder having a particle size distribution of 0.1 to 0.1
Layer thicknesses of 0.3 mm and, in the case of PEEK powder with a particle size distribution of 5 to 50 μm, layer thicknesses of 0.3 to 0.6 mm are obtained. The layer thickness of the resin powder layer 5 is determined so as to absorb the clearance between the size of the bone marrow hole and the size of the metal core 4 by the standard size bone marrow hole forming machine.

After the resin powder layer 5 is formed by coating on the surface of the metal core 4 in this manner, the periphery thereof is a heat-resistant glass fiber (breather) 6 having a thickness of 2 to 3 mm and having air permeability.
Then, the periphery thereof is further covered with a polyimide film 7 having a heat resistance and having a cylindrical wall thickness of about 0.05 to 0.1 mm with one side (the tip side of the stem) sealed. The thing of this state is arrange | positioned at the center of the coil (not shown) of a high frequency generator, and the high frequency current is made to flow through, and the surface part of the metal core 4 is uniformly heated to 360-400 degreeC,
Only the resin powder in the interface portion with the metal core 4 in the resin powder layer 5 is dissolved.

During heating, the polyimide film 7 can be brought into close contact with the surface of the metal core 4 by sucking air through the suction port 8 to reduce the pressure inside the polyimide film 7.
Further, the adhesion of the resin powder layer 5 to the metal core 4 is also improved through the heat resistant glass fiber 6 having air permeability.

The cross section of the artificial bone head 1 thus obtained is as shown in FIG. 2, and the resin coating layer 9 is closely formed on the outer peripheral surface of the metal core 4. The interface portion 9a of the resin coating layer 9 with the metal core 4 is a dense layer made of a completely non-porous resin because the resin melted in the previous heating is cured thereafter. Has been formed. On the other hand, the outer layer portion 9b on the outer side is in the form of powder sinter made of a resin that has not been melted during the previous heating, and has a large number of pores.

This artificial head 1 was immersed in a lactated Ringer's solution at 80 ° C. for 10 days and then subjected to ICP emission spectrum analysis. No elution of the metal component of the metal core 4 was observed, and the interface in a completely non-porous state was observed. It was demonstrated that the partial resin coating layer 9a can completely shield the metal core from the living body.

As a comparative example, a conventional artificial bone head consisting of a metal stem portion not provided with a resin coating layer was tested under the same conditions. As a result, some metal components were found to be eluted, which was a problem in terms of safety to living bodies. It was something.

[0026]

The bone implant obtained by the method of the present invention has a structure in which a metal stem core is coated with a resin which is a material having a hardness smaller than that of a metal material and relatively close to the bending elastic modulus of a living bone. Since the portion directly contacting the living bone is the resin coating layer, the bone marrow defect due to the concentrated stress, which has been a concern in the conventional bone implant consisting only of the metal stem, does not occur.

Since the core of the stem portion is made of metal, it is possible to exhibit various characteristics of the metal material such as high strength, high rigidity and corrosion resistance.

Since the interface portion with the metal core of the resin coating layer is a dense layer with no pinholes in the state of no pores, the metal material of the metal core is prevented from eluting into the living body. .

Since the outer layer portion of the resin coating layer is in the form of a porous powder sinter, it has excellent body compatibility.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the method of the present invention.

FIG. 2 is a cross-sectional view showing the structure of an artificial head prepared by the method of FIG.

[Explanation of symbols]

 1 Artificial bone head 2 Stem part 3 Ball part 4 Metal core 5 Resin powder layer 6 Heat-resistant glass fiber 7 Polyimide film 8 Suction port 9 Resin coating layer 9a Inner layer part (interface part) 9b Outer layer part

Front page continuation (72) Inventor Ichiro Soga 3-1-1, Kyobashi, Chuo-ku, Tokyo Inside Jamome Sewing Industry Co., Ltd. ) Inventor Takaaki Osawa 1500 Inoguchi, Nakai-cho, Ashigarashami-gun, Kanagawa Terumo Corporation (72) Inventor Yoshihisa Ueda 1500 Inoguchi, Nakai-cho, Ashigarakami-gun, Kanagawa Terumo Corporation

Claims (4)

[Claims] 1. A core having a desired implant shape is molded from a metal material, and a resin powder is applied to the surface of the core,
This resin powder coating material is coated with a heat resistant film having an opening, and while vacuum suction is applied from the opening of the heat resistant film, the resin powder coating material is heated to at least partially dissolve the resin, and then the resin is A method for producing a bone implant, which comprises curing to form a resin coating layer on the core surface. 2. The method for producing a bone implant according to claim 1, wherein the resin powder coating material is heated by internal heating by a high frequency heating method to dissolve only the resin at the interface with the core. . 3. The core is molded so as to have a rough surface, or the core is treated so as to have a rough surface after molding the core and before applying the resin powder. The method for manufacturing a bone implant according to claim 1 or 2, characterized in that: 4. The resin coating layer is constituted by a plurality of layers having different compositions by sequentially applying a plurality of resin powder coating materials having different compositions. A method for producing a bone implant according to claim 1.