Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1984-03-13
1987-04-28
Cockeram, Herbert S.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521 62, 521 63, 521905, 521916, C08G 1814, C08G 1834
Patent
active
046615300
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a new biocompatible, highly antithrombogenic material, of adjustable porosity, compliance and biodegradability, based on polylactic acid and segmented polyurethanes, for reconstructive surgery, which can be built up in layers with different compositions and characteristics and can be modelled in various shapes by including reinforcement material. The versatility of the material according to the present invention gives it a unique adaptability to the biological tissue in which it is incorporated, so that the synthetic material is built up into a new functional entity in reconstructive surgery.
Most synthetic materials used for reconstruction do not have the same mechanical proporties as the specific biological tissue and so do not match its specific function. It is known that the specific function of tissue is the trigger of the constant rebuilding of tissue in the growth during life. The variability of the elastic properties of the material according to the present invention renders it possible to match the mechanical properties of most of the biological tissue that has to be replaced in the body.
As its porosity can be varied, the ingrowth and overgrowth of tissue for complete incorporation can be regulated to provide optimum conditions for a specific replacement. Its adjustable biodegradability makes it possible, if desired, to have the synthetic material completely replaced by biological tissue.
Because of the possibility to produce the material in layers of different compositions, it is also possible to have the characteristics of each layer match the function of the biological tissue needed to rebuild that layer.
Because the material can be modelled by the shapes of mandrels by a dipping technique, every form can be produced to match the shape of an organ to be replaced, such as a tubular neo-artery for example. But also a more complex organ such as a trachea can be produced from this synthetic material, including a reinforcement material in the layers to maintain its shape during the alternating positive and negative pressures occurring in the trachea and to prevent collapsing. The constructive reinforcement material can be made of a different material, for example porous hydroxy apatite, which could induce bone formation.
Due to the biodegradability and high flexibility of the polylactide-polyurethane porous membranes, these materials can also be used to cover satisfactorily large experimental full-thickness skin wounds. Such membranes can effectively protect these wounds from infection and fluid loss for a long time.
Thus these combinations give a wide range of new possibilities in reconstructive surgery, all based on the same principle that perfect matching of the mechanical properties of biological tissue and synthetic materials creates one functional unity between biological tissue and the synthetic material which allows complete incorporation and rebuilding to a new organ. This new composition has been tested in animal experiments, primarily with rabbits, as vascular and tracheal prostheses and artificial skin. In these experiments true biocompatibility and a high degree of antithrombogenicity of the material was demonstrated. The experiments with the trachel prosthesis revealed that quick tissue ingrowth from the peritracheal tissue is induced if relatively large pores (100.mu.) were used on the outside. However, overgrowth of tissue on the luminal side needed only a thin connective tissue layer to which epithelium became firmly attached and differentiated. This was achieved with relatively small pores on the inside (10-20.mu.). Between the layers of various pore sizes a reinforcement of a spiral bead may be embedded.
This possibility of variation by means of different layers can also be used for the composition of an artificial skin where such functions as controlled evaporation, ingrowth of tissue, seeding of epithelial cells and resistance to outside micro-organism require layers with different characteristics.
More specifically the invention relates to the provisio
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Gogolewski Sylwester
Pennings Albert J.
Cockeram Herbert S.
Medtronic Inc.
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