Claims
- 1. A method for manufacturing a bone prosthesis formed at least in part from substantially pure porous alumina and having porosity of about 30% and a pore size of about 100 to 200 microns, comprising granulating a powder of substantially pure alumina with an organic binder into grains of a size between about 0.5 and 1.5 millimeters, heating said grains in bulk to a temperature of at least 1.400.degree. C., but lower than their sintering temperature, disintegrating the bulk so heated, compressing the disintegrated alumina grains at a pressure of at least about 1 metric ton per square centimeter into a first pressed mass, and sintering said first pressed mass at a temperature of about 1.650.degree.-1.700.degree. C. to form said porous alumina.
- 2. A method according to claim 1, wherein the granulation of the powder of substantially pure alumina is carried out by roto-granulation.
- 3. A method according to claim 1, wherein said first pressed mass is sintered in an oxidizing atmosphere.
- 4. A method according to claim 3, wherein said first pressed mass is sintered at a temperature of about 1.650.degree. C. for at least about 4 hours.
- 5. A method according to claim 4, wherein the pure alumina powder is granulated into grains of a size between 0.5 and 0.8 millimeters.
- 6. A method according to claim 1, further comprising compressing fine alumina grains with an organic binder into a second pressed mass without previous firing and disintegrating, said fine ceramic grains having a grain size substantially finer than that of the alumina grains subjected to firing and disintegrating, and then sintering said first pressed mass and said second pressed mass together so as to produce a prosthesis comprising a porous alumina portion and a dense alumina portion.
- 7. A method according to claim 2, further comprising compressing fine alumina grains with an organic binder into a second pressed mass without effecting any previous firing or disintegrating thereof, said fine alumina grains having a grain size substantially finer than the alumina grains subjected to firing and disintegrating prior to the formation of the first pressed mass and then sintering said first pressed mass and said second pressed mass together so as to produce a prosthesis comprising a porous alumina portion from said first pressed mass and a dense alumina portion from said second pressed mass.
- 8. A method according to claim 1 wherein the bulk is disintegrated to provide a plurality of separate disintegrated alumina grains, the separate disintegrated alumina grains are admixed with an organic binder, then the resulting admixture is compressed within a mold to form said first pressed mass and the pressed mass is then fired to remove the organic binder prior to being sintered at about 1,650.degree.-1700.degree. C. to form the bone prosthesis made of said porous alumina.
Priority Claims (1)
| Number |
Date |
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Kind |
| 73 01668 |
Jan 1973 |
FRX |
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Parent Case Info
This application is a continuation-in-part of application Ser. No. 739,789, filed Nov. 8, 1976, now abandoned, which is a continuation of application Ser. No. 434,685, filed Jan. 18, 1974, now abandoned.
The present invention concerns a method of manufacturing a bone prosthesis comprising at least partly a porous alumina having calibrated pore dimensions greater than 30 microns. It bears more particularly on a method of manufacturing a bone prosthesis comprising a dense first part made of alumina and at least another part made of porous alumina, intended for ensuring the connection of the first part with the natural bone. It is applied more particularly to bone prostheses in joints, such as those which were the object of British Pat. No. 1,334,584 of Oct. 24, 1973, and of U.S. Pat. No. 3,871,031. It is applied also to methods of manufacturing substitutions of a part of a bone comprising or not comprising a joint.
Bone prosthesis must meet three essential requirements: be inert to any action of biological media, have a mechanical strength compatible with the efforts to be transmitted and have a structure in the parts to be connected together to the residual bone such that it promotes bone reconstitution or retention. According to the above British patent, the acetabular part of a prosthesis of the hip may have a convex outside portion made of porous alumina having pore dimensions ranging from 10 to 30 microns, assembled to a non-porous alumina inside portion. That assembling is, however, mechanically delicate to perform and the pores have dimensions which are insufficient to enable a solid connection by rapid rebuilding of the bone. French Pat. No. 2,106,242 describes a bone prosthesis made of porous alumina having pores dimensions between 75 and 150 microns.
The above U.S. Pat. No. 3,871,031 discloses a structure of the inside portion of the part intended to be fixed to the remaining part of the bone, comprising anfractuosities, for example grooves, at least two of whose dimensions are in the order of a millimeter, so as to enable a more rapid and more complete rebuilding of the bone. This requires, however, a relatively complicated machining of a part having great hardness. Moreover, if the alumina is effectively suitable for producing prosthesis elements to be subjected essentially to compression, by reason of its high mechanical resistance to that stress, it is less suitable as a material for prosthesis elements subjected more particularly to bending.
Use is therefore made of a production based on metals inert to biological media, such as titanium or metal alloys, more particularly stainless nickel-cobalt-chromium steel, cobalt-chromium alloy or, even, titanium alloys. It would be possible to provide for depositing, on the portion of the metallic part of the prosthesis which is to be connected to the bone, a layer of alumina having sufficient porosity to enable rapid rebuilding of the bone, for example by projection with a plasma torch. That depositing is difficult to effect; the solidity of its connection to the metallic portion is questionable and keeping the optimum porosity is hazardous. It is therefore still a practice, in general, to make use of organic cements, for example acrylic resins, although the tolerance of the biological medium to such cements and the resistance of such cements throughout time still give rise to certain misgivings.
An object of the invention is to obviate the above disadvantages and to manufacturing a bone prosthesis of given porosity and pore size enabling a connection with the natural part of the bone by rebuilding of the bone, that is, by the reconstitution or retention of new bone cells coming from the residual bone and invading pores formed in the newly inserted prosthesis, that connection being formed quickly and having good solidity.
The method for manufacturing a bone prosthesis according to the invention is characterized in that a powder of substantially pure alumina is granulated with an organic binder into grains of a size between about 0.5 and 1.5 millimeters, said grains are fired in bulk to a temperature of at least 1.400.degree. C. but lower than their sintering temperature, then are disintegrated, then compressed at a pressure of at least one metric ton/cm.sup.2 into a first pressed mass, and finally are sintered at a temperature of about 1.650.degree.-1.700.degree. C. to form said porous alumina.
It comprises, moreover, preferably at least one of the following characteristics:
The granulation of the powder of substantially pure alumina is carried out by roto-granulation.
The firing of the grains of alumina is effected at a temperature of about 1.400.degree. C.
The sintering is carried out in an oxidizing atmosphere.
The sintering is effected at a temperature of about 1.650.degree. C. for at least about 4 hours.
The compressing of the grains of alumina after the firing thereof is effected at a pressure of about 1 to 4 metric tons per square cm.
The dimension of the grains of alumina is comprised between 0.5 and 0.8 mm approximately.
Other grains of alumina are compressed into a pressed mass without previous firing, then are subjected to sintering with a pressed mass of previously fired grains, so as to produce a prosthesis comprising a dense alumina portion.
The compressed grains of alumina which have not previously been fired are finer than those which are compressed after having previously been fired.
The pressed mass intended for forming the porous alumina and that intended for forming the dense alumina are pressed in a same mould having a shape corresponding to that of the part to be produced, preferably after previous pressing.
The bone prosthesis obtained by the above defined method is characterized in that the dimension of the pores of the porous alumina is comprised between 100 and 200 microns approximately, and the porosity of the alumina is about 30 %. It comprises, moreover, preferably a metallic portion in which porous alumina parts are fixed either by inclusion, the said alumina then constituting a core arranged in a mould in which the metallic portion is cast, or by crimping, screwing, clamping or a like operation.
The following text describes, by way of an example and with reference to the accompanying drawing, a coxo-femoral prosthesis and a prosthesis of a phalanx of a finger manufactured according to the invention.
US Referenced Citations (4)
Foreign Referenced Citations (1)
| Number |
Date |
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| 2096985 |
Mar 1972 |
FRX |
Non-Patent Literature Citations (2)
| Entry |
| Cahoon, "Sintering and Grain Growth of Alpha Alumina", J. Am. Cir. Soc., vol. 39, #10, pp. 337-344 (1956). |
| Chatteyie et al., "Effect of Processing Variables on the Properties of High Aluminum Ceramics", Glass and Ceramic Bulletin, vol. 23, #4, 1976. |
Continuations (1)
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| Parent |
434685 |
Jan 1974 |
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Continuation in Parts (1)
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739789 |
Nov 1976 |
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Patent Grant
4179485
