Gel-filled implants

Abstract: This invention relates to a medical implant, which comprises an outer envelope and a gel filler material , wherein the gel comprises water and a cellulose gelling agent. The gel in the implant may further contain a lubricating agent. The components of the gel are a biocompatible and do not adversely affect human beings. Implants containing the lubricating agent have a decreased tendency of failure caused by internal friction on the envelope. The implants of the present invention have similar characteristics of the human breast.

Description: Technical Field of the Invention This invention relates to medical implants, especially those used for a breast or a testicular implant. Background of the Invention The reconstruction or cosmetic variation of a breast, such is often performed following mastectomy, has become an increasingly frequent surgical procedure. The development and use of silicone-gel and silicone-filled implants have contributed to the popularity of this procedure. Recent concern over the effects of the filler of these implants, e.g. silicone-gel, on the health of women has lead to a decrease in their use. Therefore, it is desirable to provide a filler material for an implant which simulates or duplicates the characteristics of a natural breast. Further, it is desirable to provide a material that does not have an adverse effect on the human body containing the implants. U.S. Patent 4,772,284 relates to a breast prosthesis with improved biocompatibility and methods of making the same. The breast prosthesis is a single lumen implantable and bicompatible breast prosthesis composed of an outer membrane of silastic, medical grade silicone, and an inner material selected from the group consisting of purified reconstructive collagen gel and a purified gel of polyalpha amino homopolymers or random copolymers having a molecular weight of from 5,000 to 400,000. U.S. Patent 4,787,905 relates to gel for breast prosthesis. The gel is a mixture of hydroxy-terminated polybutadiene resin, diundecylphthalate, polymethylenepolyphenyl isocyanate, and dibutyltin dilaurate catalyst, wherein the mixture is cured to form the gel. U.S. Patent 4,790,848 relates to a breast prosthesis with multiple lumens. The implant comprises an inner lumen of substantially spherical shape. The inner lumen is unattached, or free-floating. The lumens are filled with silicone gel or similar fluid material. WO 90/04971 relates to improved viscoelastic fluids or gels for use in surgery and other therapies. The viscoelastic fluid or gel has as its principal ingredients polyethyleneoxide in a physiological balanced salt solution. The viscoelastic fluids or gels may include a viscosity enhancer or stabilizer. The viscosity enhancers or stabilizers include hydroxypropylmethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, hydroxethylcellulose, methylcellulose or mixtures thereof, polyvinyl pyrrolidone, or polyvinyl alcohol. Polyethyleneoxide is an essential ingredient in the viscoelastic fluids or gels. There is no suggestion that useful fluids or gels may be prepared without polyethyleneoxide. Database WPI, Derwent Publications Ltd. AN 83-31383K relates to the manufacture of an artificial breast in which first a solid latex mixture blank is made and then a chamber with an aperture is formed therein. The chamber is then filled with a solution of carboxymethylcellulose whereupon its aperture is closed. The base and walls of a press mold are then covered with a foam latex mixture, and the chamber, which is formed in the solid latex mixture blank and which is filled with the carboxymethylcellulose, is then placed into the press mold. With the chamber occupying only part of the volume of the press mold, the chamber is covered with an interlining made of cotton fabric, and the remaining volume of the press mold is then filled again with foam latex mixture. Database WPI, Derwent Publications Ltd. AN 90-30521 relates to the manufacture of a breast prosthesis. A closed air-filled sac is made by applying a layer of liquid natural rubber to the interior of a mold where it is allowed to set. After removal from the mold, the thus-formed air-filled sac has to be evacuated whereupon a solution of hydroxyethylcellulose in water is injected into the sac. U.S. Patent 4,995,885 relates to a radiolucent breast implant. The radiolucent breast implant is composed of a silicone envelope filled with any biocompatible triglyceride such as peanut oil or sunflower oil or any other material having an effective atomic number of 5.9, which is the effective atomic number of fat. This breast implant is radiolucent in that it duplicates the photo-electric interference of fat which is the major effect producing subject at low radiation levels as used in mammography. Summary of the Invention This invention relates to a sealed medical implant for replacing or augmenting body tissues, comprising an outer envelope of a medical grade elastomer, and a gel filler material wherein the gel filler material is formed from water and a cellulose derivative and wherein the characteristics of the implant may be altered by altering the density of the gel, provided that the gel filler is free of polyethyleneoxide. The gel in the implant may further contain a lubricating agent. In another aspect, the invention relates to a method of preparing medical implants comprising the steps of filling an outer envelope of a medical-grade elastomer with a gel filler material, formed from water and a cellulose derivative, and sealing the envelope to form a medical implant. The components of the gel are biocompatible so as not adversely to affect human beings. Implants containing the lubricating agent have a decreased tendency of failure caused by internal friction on the envelope. The implants of the present invention have similar characteristics to the human breast. These implants may be used for breast augmentation or reconstruction. Detailed Description of the Invention As used in the specification and appended claims, the use of the term "gel" refers to gelatinous and "jelly-like" materials which provide the physical characteristics of the medical implants of the present invention. The implants of the present invention may be used as an implant anywhere in the human body, especially as replacements for breasts and testicles. These implants are also useful for augmentation of the breasts. It should be recognized that the characteristics of the implant may be altered by altering the density of the gel of the implant. In one embodiment, the density of the gel of the implant approximates that of the human breast. The gel of the implant generally has a density from about 0.8, or about 0.9, or about 0.95 up to about 1.5, or to about 1.4, or to about 1.3 to about 1.2. The implant comprises an outer envelope. The envelope is generally a medical-grade elastomeric material. An example of a particularly useful envelope is a silicone envelope. The filler material of the implants comprises a gel formed from water and a cellulose derivative. The water is generally present in a major amount, usually an amount greater than 70%, or about 75%, or about 80% by weight of the gel. In one embodiment, the water is present in an amount from about 80%, or about 85% up to about 95%, or about 93% by weight of the gel. The water is preferably purified and sterile as is known to those in the art. The cellulose derivative provides thickening of the water to form the gel of the present invention. As is known, cellulose is a polymer of glucose rings derived from plants. In one embodiment, the cellulose thickening agent is a cellulose ether. Examples of cellulose thickening agents include methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylethylcellulose, sodium carboxymethylcellulose, and sodium carboxymethylhydroxyethylcellulose. Preferably, the cellulose thickening agent is hydroxyethylcellulose, hydroxypropylcellulose or methylcellulose, more preferably methylcellulose. The cellulose thickening agent is present in an amount sufficient to gel the water. In one embodiment, the cellulose thickening agent is present in an amount to produce a density which approximates the density of the human breast. The cellulose thickening agent is generally present in an amount from about 0.5%, or about 1%, up to about 15%, or to about 10%, or to about 8% by weight of the gel. In one embodiment, the gel further comprises a lubricating agent. The lubricating agent can be any agent which reduces the internal friction in the envelope. The lubricating agent may be a polyol. Examples of useful polyols include ethyleneglycol, propyleneglycol, butanetriol, butanediol, hexanediol, hexanetriol and the like. Preferably, the lubricating agent is glycerol or propyleneglycol. In another embodiment, the lubricating agent may be any glyceride, preferably a triglyceride. Examples of glyceride lubricants include coconut triglycerides, and oleyltriglycerides. In addition to the water, cellulose thickening agents and optionally lubricating agents, the gel may additionally contain other additives which act as preservatives, antioxidants, pH controlling agents and antibacterial agents. Examples of these agents include methylparaben, propylparaben, sodium hydroxide, glucono delta lactate, chlorhexidine gluconate, propyleneoxide and the like. In one embodiment, the implants of the present invention may comprise commercially available surgical and personal lubricant gels. Examples of these gels include Surgilube® surgical lubricant available commercially from E. Fougera & Company, HR® Lubricating Jelly available commercially from Carter-Wallace, Inc. and K-Y Lubricating Jelly available commercially from Johnson & Johnson. As described above the implants of the present invention may be used as replacements for body tissues or augmentation of body tissues. In one embodiment, the implants are used for breast reconstruction and/or augmentation. The process for using the implants involves placing the implants of the present invention subcutaneously in a human being in a region where replacement and/or augmentation is desired. For instance, for breast augmentation, the implant is subcutaneously placed into the breast region. The process for placing the implant into a human is known to those skilled in the art and generally involved inserting the implant through an incision in the chest. Methods of placing implants are known to those in the art. The invention further comprises the process of preparing medical implants which involves the steps of filling an outer envelope of a medical grade elastomer with a gel as described herein. The envelope is sealed to form the medical implant. The envelopes in the sealing procedure are known to those skilled in the art. While the invention has been explained in relation to its preferred embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification.

Claims: A sealed medical implant for replacing or augmenting body tissues comprising an outer envelope of a medical-grade elastomer, and a gel filler material, wherein the gel filler material is formed from water and a cellulose derivative and wherein the characteristics of the implant may be altered by altering the density of the gel, provided that the gel filler is free of polyethyleneoxide. The implant of claim 1 wherein the cellulose gelling agent is a cellulose ether. The implant of claim 1 wherein the cellulose gelling agent is methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylethylcellulose, sodium carboxymethylcellulose, or sodium carboxymethylhydroxyethylcellulose. The implant of claim 1 wherein the cellulose gelling agent is hydroxyethylcellulose, hydroxypropylcellulose or methylcellulose. The implant of any one of claims 1-4 wherein the envelope is a medical-grade silicone. The implant of any preceding claim wherein the gel comprises a lubricating agent. The implant of claim 6 wherein the lubricating agent is a polyol lubricating agent. The implant of claim 6 wherein the lubricating agent is propyleneglycol or glycerol.

Inventors: MAXWELL G PATRICK, PERRY LARRY C, MAXWELL, G. PATRICK, PERRY, LARRY C.
Applicants: MAXWELL G PATRICK, PERRY LARRY C, MAXWELL, G. PATRICK, PERRY, LARRY C.
Application year: 1993
Main classification: A61L27
IPC codes: A61L27, A61F2