Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Miscellaneous
Patent
1985-09-13
1988-09-13
Apley, Richard J.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Miscellaneous
623 1, 623 12, 623 15, 427 2, 264 41, A61F 206, A61F 210
Patent
active
047706643
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the provision of a multilayered prosthesis material for use with a living body, the material produced showing mechanical compliance vis-a-vis soft body tissue and, furthermore, possessing biocompatibility. The invention also covers a method for the manufacture of such material.
In using synthetic polymers as replacement material for various types of human tissue, it is not only the biocompatibility properties of the polymer which is of critical importance to the performance of the material when used with a living body. In addition to biocompatibility, and blood compatibility the mechanical compliance and porosity features are of basic importance. The available materials are not satisfactory in this respect. In other words, due to mechanical factors the applied material does not possess a mechanical performance which is in line with that of the surrounding natural tissue.
Accordingly, it is an object of the present invention to provide a prosthesis material of a synthetic nature showing mechanical compliance vis-a-vis soft body tissue at the same time possessing biocompatibility or blood compatibility.
Another object of the invention is to provide a multilayered prosthesis material for such use, which shows desirable porosity in combination with mechanical resistance and compliance.
Yet another object of the invention is to provide a method for producing such prosthesis material, the method comprising a new feature of using a solvent of a special nature.
In connection with extensive research and experimentation it has been found that a multilayered prosthesis material can be prepared starting from a solution of a copolymer in a suitable solvent and coating a substrate with a uniform thickness of such solution. It is known from U.S. Pat. No. 4,173,689 to manufacture a replacement material by precipitating a polymer in a concentration of the polymer in solvent between 5-12% by weight. However, at this concentration the viscosity of the polymer solution is relatively high, resulting in thick layers of polymer solution when coating a substrate e.g., a mandrel by dipping. Therefore, only one or few coating-precipitating steps are needed to produce a prosthesis wall, such as a graft, of a desired thickness.
Even if the products made according to above described U.S. patent have a better compliance than, for instance, other synthetic materials used as prosthesis in tissue replacement, they have a spongy texture (column 3, line 29) which doe not give satisfactory tissue compatibility. At the high concentration of polymer used in this prior art method, many of the pores in the polymer matrix are not interconnected. Another disadvantage of this known technique when preparing a multilayered product, is the fact that delamination of the layers after implantation may occur due to the lack of interconnection between same.
According to the present invention it has been surprisingly found that by using a polymer solution containing less than 5% by weight of polymer, a polymer layer, when precipitated, will be obtained which has a fibre-like structure, the pores of which are interconnected. The precipitated fibre-like material consists of fibres of different thickness from tiny fibres to relatively thick ones. Each precipitated layer is very thin and has a thickness of for example about 0.01-0.5 mm and, therefore, usually up to about 100 and even more layers may be applied in subsequent operations to produce a multilayered prosthesis material of a required mechanical strength. Due to the fibre-like porous structure, the prosthesis wall is strong, highly compliant and mechanically compatible with the tissue to be replaced.
It is preferred to use an even more dilute polymer solution such as less than about 3% by weight, and more particularly, less than about 2% by weight of polymer. In some cases, even concentrations as low as about 1% and less may be useful.
After coating the substrate with the polymer solution the coating applied is precipitated by treatment with a precipitating solution whi
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Apley Richard J.
Cannon Alan W.
Mendinvent S.A.
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