Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Breast prosthesis – Implantable
Reexamination Certificate
1998-01-07
2001-02-13
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Breast prosthesis
Implantable
C516S198000, C424S070310, C623S023710
Reexamination Certificate
active
06187044
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to filler materials for implantable prostheses for use in plastic and reconstructive surgery, as might be particularly useful in breast reconstruction and augmentation.
Subcutaneous reconstructive implant procedures for augmenting or reconstructing certain soft tissues in humans, including breast and facial implants, have been in wide use since at least the early 1960s. The implants consist of hollow, physiological shells filled with a filler material. The physiological shells are typically formed from silicone rubber or other elastic biocompatible materials which have enough memory to preserve a desired shape. In order to minimize the risk of leakage, the physiological shell often consists of multiple layers.
Controversy has surrounded the materials used to fill the physiological shells. One filling material that was previously quite popular was silicone gel. However, the use of silicone gel is associated with a number of problems. For example, silicone gel is not sufficiently radiolucent and can thus obscure mammographic signs of breast cancer. In fact, some researchers have suggested that breast implants containing silicone gel fillers prevent early detection of breast cancer and hence reduce the probability of a promising prognosis once cancer is detected. Because an estimated one in nine women will develop breast cancer, and, with cancer recurring in another 1 in 3, the risk of delay of detection caused by silicone gel implants is quite significant. Another problem with silicone gel fillers is that the body is unable to metabolize or excrete the silicone gel. In the event of a leak from the shell, the silicone gel is apt to migrate or leak into surrounding tissue where an undesirable body reaction can ensue, thereby requiring surgical removal or other treatment.
In recent years, saline has supplanted silicone gels as the most prevalent implant filler material. However, saline is also ill-suited for use as an implant filler material. Significantly, saline has a relatively low viscosity and is a poor lubricant thereby resulting in an excessively soft implant that is prone to rippling, fold flaws and spontaneous deflation. Saline fillers also suffer from an unnatural “feel.” In the event of containment sac perforation, filler escape is immediate with spontaneous deflation. Further, if air enters the containment sac during filling, a postoperative audible noise may result.
Other previous approaches have involved the use of soybean oil, hyaluronic acid and polyethylene glycol. However, the long-term safety and stability of these materials has yet to be determined. For example, breakdown of the materials when implanted is unknown. Soybean oil has the added problem of being difficult to intraoperatively inject into the containment sac. In the case of hyaluronic acid, the interaction of the filler material with the containment sac is not established.
In addition, in U.S. Pat. No. 5,067,965, Ersek, et al., propose a bio-osmotic gel material comprising polyvinylpyrrolidone for use as an implant filler material. However, the materials disclosed by Ersek, et al., are quite expensive and are not capable of injection, thereby requiring filling prior to implantation. As such, the filler materials of Ersek, et al., do not permit modification of the filling procedure following implantation in situations where the initial filling operation proves to be unsatisfactory.
Despite the availability of the foregoing approaches, it will be appreciated that there still exists a need in the art for implant filler materials which are relatively inexpensive, radiolucent, physiologically absorbable, and which have a sufficient viscosity to minimize the risk of deflation. There also exists a need for implant filler materials that can be injected into the physiological shell either before, during, or after the surgical implantation procedure.
SUMMARY OF THE INVENTION
The aforesaid problems are solved, in accordance with the present invention, by methods and materials for filling subcutaneous reconstructive prostheses, for example, breast or facial implants, comprising at least one nonionic surfactant such as at least one polyoxyethylene fatty acid ester. Preferably, the nonionic surfactant comprises at least one polysorbate and, most preferably, includes polysorbate 80. Significantly, the nonionic surfactants of the present invention exhibit a moderately high viscosity ranging from approximately 250-300 centistokes to approximately 500 centistokes at a temperature of approximately 25 degrees centigrade, which is typically the temperature during manufacture.
Polysorbates are a group of fatty acid esters of sorbitol and its anhydrides copolymerized with approximately 20 moles of ethylene oxide for each mole of sorbitol and its anhydrides. Polysorbates are hydrophilic nonionic surfactants which are used as emulsifying agents for the preparation of stable oil-in-water emulsions in pharmaceutical products; they are frequently used with a sorbitan ester in varying proportions to produce products with a range of texture and consistency. They have been used in the formulation of insecticide and herbicide sprays, industrial detergents, cosmetic products, and as emulsifiers in the food industry. They are also used as solubilizing agents for a variety of substances including essential oils and oil-soluble vitamins such as vitamins A, D, and E, and as wetting agents in the formulation of oral and parenteral suspensions. An estimated acceptable daily intake of polysorbates 20, 40, 60, 65, and 80 is up to 25 mg per kilogram of body weight as total polysorbate esters.
Advantageously, the nonionic surfactant implant fillers under the present invention are safe and biodegradable in the event of leakage into surrounding tissues. If filler material escapes from the containment sac, the material is physiologically broken down by normal metabolic processes without inflammatory tissue reaction. The filler materials of the present invention are also radiolucent, thereby permitting facile detection of underlying malignancies or masses with radiologic imaging such as mammograms. Because of the moderately high viscosity of the nonionic surfactants as compared to saline, the fillers of the present invention are less apt to deflate or to develop ripples or fold flaws. The moderately high viscosity of the fillers also results in a more natural appearance and “feel” that substantially mimics the appearance and feel of normal breast tissue. In addition, the fillers of the present invention are injectable, for example, through a peripheral injection port, into one or more lumens of the prosthesis either before, during or even after surgical implantation. The filler materials of the present invention also have a documented history of clinical use in topical, oral, and parenteral forms of human administration. The fillers of the present invention are capable of being mixed with water which creates the potential for varying ratios of polysorbate-water filler materials.
The present invention will be more fully understood upon reading the following detailed description of the preferred embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The following portion of the specification sets forth the preferred embodiments of the present invention. The embodiments of the invention disclosed herein includes the best mode contemplated by the inventor for carrying out the invention in a commercial environment, although it should be understood that various modifications can be accomplished within the parameters of the present invention.
The present invention provides methods and compositions for filling physiological shells, also known as “containment sacs”, of prostheses used in subcutaneous implantation such as implants used in breast reconstruction or augmentation. The containment sacs of the prostheses are typically formed from a thin, silicone elastomer envelope. One of ordinary skill in the art will appreciate that the containment sac can include a combination of an
Advanced Research And Technology Institute, Inc.
Koh Choon P.
Leydig , Voit & Mayer, Ltd.
Willse David H.
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