Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Breast prosthesis – Implantable
Patent
1994-02-02
1996-03-05
Prebilic, Paul B.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Breast prosthesis
Implantable
623 11, 128839, 606191, A61F 212
Patent
active
054963680
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a self-inflating tissue expander to create cavities for the insertion of implants or to provide tissue for a self transplantation, where the tissue expander itself is implanted in the tissue and where it absorbs body fluid, especially water from the surrounding tissue due to an osmotic driving force. In order to create cavities for the insertion of implants, but also to provide healthy tissue for a self transplantation, the method of controlled tissue expansion is applied. The tissue is continually stretched under a moderate application of pressure until the desired cavity or the desired amount of additional tissue is obtained.
BACKGROUND OF THE INVENTION
From the dissertation "Controlled Tissue-Expansion in Reconstructive Surgery" (Julian H. A. van Rappard, Thesis Groningen, The Netherlands, 1988) a tissue expander is known that is expanded by the gradual filling with a liquid. The tissue expander has an impermeable, stretch-resistant skin and a self-sealing valve for the filling with liquid using a hollow needle and a syringe. The tissue expander is implanted under the tissue to be expanded, with the valve arranged so that it is accessible by the needle from the outside. For the actual expansion of the tissue, the tissue expander is gradually filled with liquid. The needle is inserted into the valve through the tissue and the liquid is injected into the tissue expander with the syringe. When fully filled with liquid, the tissue expander obtains a shape determined by the form of its skin. The forming of the skin is adaptable to various applications in this way. It is an advantageous feature of the known tissue expander that a precisely controlled expansion of the tissue is possible. A major disadvantage, though, is the occurrence of high peak pressures after each filling of liquid into the tissue expander. This concerns especially the regions of tissue to be expanded located directly next to the tissue expander. These regions are compressed so much that damage of the tissue occurrs. When reducing the amount of liquid that is injected into the tissue expander in each step, problems result from the frequent piercing of the tissue in the region of the valve. Furthermore, the valve may develop a leak, which renders the tissue expander useless. There is no danger for the tissue surrounding the tissue expander as a result of a leaky valve, as long as a physiologically safe, sterile liquid for the filling of the tissue expander.
A self-inflating tissue expander of the type described above is known from the article "A Self-Inflating Tissue Expander" (E. D. Austad et al., Plastic and Reconstructive Surgery, Vol. 70 No. 5, pages 588 ff). This tissue expander consists of a silicone membrane filled with a sodium chloride solution. The molarity of the sodium chloride solution is greater than the physiological molarity of approximately 0.3. The osmotic driving force, which drives body liquid from the tissue surrounding the tissue expander through the semipermeable silicone membrane into the tissue expander, is based on this. The inflation of the tissue expander, and therefore also of the tissue surrounding the tissue expander, occurrs without the need of any manipulations from the outside. Furthermore, the tissue surrounding the tissue expander has an exceptional, undamaged quality after the expansion. The reason for this is that the self-inflating tissue expander does not create pressure peaks on the one hand, and that the intake of body fluid into the expander stimulates the metabolism of the surrounding tissue on the other hand. A disadvantage is the small amount of volume expansion of the tissue expander, at least as long as the molarity of the sodium chloride solution initially does not exceed a physiologically acceptable value by far. Another disadvantage is that the properties of the silicone membrane change with the expansion. Especially the pore size of the silicone membrane steadily increases. In this way an increasing amount of sodium chloride ions can pass
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A Self-Inflating Tissue Expander, by Eric D. Austad, M.D., and Gregory L. Rose, Plastic And Reconstructive Surgery, vol. 70, 1982, pp. 588-594.
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