Reinforced Prosthetic Implant With Flexible Shell

Abstract

A fluid-filled soft prosthetic implant having a shell with a reinforced shell wall. The soft prosthetic implant may be for breast reconstruction or augmentation, or to restore the normal appearance of soft tissue in the buttocks, chin, calf, etc. The implants may be reinforced using several methods: reinforcement of the shell wall, non-homogeneous gel-filling, or both. At least a portion of the perimeter region desirably has a shell wall thickness greater than the average shell wall thickness of either the anterior face or the posterior face. The added material at the perimeter region strengthens that area in which a large percentage of implant ruptures occur. The reinforced perimeter also helps prevent the implant from collapsing or folding, which can cause undesirable rippling or wrinkling visible through the patient's skin. The remainder of the shell will desirably have a nominal wall thickness to retain the overall softness and supple feel of the implant. The implant shell may be filled with gels of different gel cohesiveness to counterbalance any reinforced area or to provide added reinforcement.

1 . A shell for a fluid-filled prosthetic implant, comprising:
 a flexible implant shell having a shell wall consisting of a single homogeneous layer of a silicone elastomer having a minimum mole percent of at least about 10% of a substituted chemical group that sterically retards permeation of the silicone gel through the shell, wherein the shell has an anterior face, a posterior face, and a perimeter region therebetween, and wherein at least a portion of the perimeter region has a shell wall thickness greater than the average shell wall thickness of either the anterior face or the posterior face.   
     
     
         2 . The shell of  claim 1 , wherein the shell wall has a convex exterior that has a maximum radius about a central axis along a radius midpoint plane through the perimeter region, and wherein the shell wall has a point of maximum thickness that is offset in the anterior direction from the midpoint plane. 
     
     
         3 . A shell for a fluid-filled prosthetic implant, comprising:
 a flexible implant shell having a shell wall consisting of a single homogeneous layer of a silicone elastomer having a substituted chemical group, the layer being capable of sterically retarding permeation of the silicone gel through the shell and having a bleed rate that is less than about 40% of the bleed rate of a shell constructed of a sandwich of an inner layer of 15% mole percent diphenyl between at least two layers of 5% mole percent diphenyl silicone elastomer, wherein the shell has an anterior face, a posterior face, and a perimeter region therebetween, and wherein at least a portion of the perimeter region has a shell wall thickness greater than the average shell wall thickness of either the anterior face or the posterior face.   
     
     
         4 . The shell of  claim 3 , wherein the shell wall has a convex exterior that has a maximum radius about a central axis along a radius midpoint plane through the perimeter region, and wherein the shell wall has a point of maximum thickness that is offset in the anterior direction from the midpoint plane. 
     
     
         5 . A shell for a fluid-filled prosthetic implant, comprising:
 a flexible implant shell having a shell wall consisting of a single homogeneous layer of a gel barrier material, wherein the gel barrier material has a wet strength that is comparable to or greater than the wet strength of a sandwich of an inner layer of 15% mole percent diphenyl between at least two layers of 5% mole percent diphenyl silicone elastomer, wherein the shell has an anterior face, a posterior face, and a perimeter region therebetween, and wherein at least a portion of the perimeter region has a shell wall thickness greater than the average shell wall thickness of either the anterior face or the posterior face.   
     
     
         6 . The shell of  claim 5 , wherein the shell wall has a convex exterior that has a maximum radius about a central axis along a radius midpoint plane through the perimeter region, and wherein the shell wall has a point of maximum thickness that is offset in the anterior direction from the midpoint plane. 
     
     
         7 . A fluid-filled prosthetic implant, comprising:
 a hollow implant shell having a generally oval vertical cross-section with a first face opposed to a second face and separated by a perimeter region;   a first silicone elastomer gel distributed generally evenly to form a ring within the perimeter region of the hollow implant shell;   a second silicone elastomer gel within the hollow implant shell and within the first silicone elastomer gel ring, the second silicone elastomer gel having a different gel cohesiveness than the first silicone elastomer gel.   
     
     
         8 . The implant of  claim 7 , wherein the second silicone elastomer gel is softer than the first silicone elastomer gel. 
     
     
         9 . The implant of  claim 7 , wherein the second silicone elastomer gel is firmer than the first silicone elastomer gel. 
     
     
         10 . The implant of  claim 7 , wherein at least a portion of the perimeter region has a shell wall thickness greater than the average shell wall thickness of either the first face or the second face. 
     
     
         11 . A method of making a shell for a fluid-filled prosthetic implant, comprising:
 providing a mold having a cavity and defining a generally oval vertical cross-section with a first face opposed to a second face and separated by a perimeter region;   introducing a first quantity of silicone elastomer into the mold cavity;   causing the first quantity of silicone elastomer to distribute generally evenly around the mold cavity perimeter region;   allowing the first quantity of silicone elastomer to coalesce and form a perimeter ring within the mold cavity;   introducing a second quantity of silicone elastomer into the mold cavity;   causing the second quantity of silicone elastomer to distribute generally evenly around the entire mold cavity;   curing the silicone elastomer to form a hollow implant shell; and   removing the implant shell from the mold cavity.   
     
     
         12 . The method of  claim 11 , wherein the mold is part of a rotational casting machine, and the step of causing the silicone elastomer to distribute generally evenly around the mold cavity perimeter region comprises rotating the mold about only one axis. 
     
     
         13 . The method of  claim 12 , wherein the step of causing the second quantity of silicone elastomer to distribute generally evenly around the entire mold cavity comprises rotating the mold about two or more axes. 
     
     
         14 . The method of  claim 11 , wherein the first quantity of silicone elastomer is between about 13-23% of the second quantity of silicone elastomer. 
     
     
         15 . A method of making a gel-filled prosthetic implant, comprising:
 providing a mold having a cavity and defining a generally oval vertical cross-section with a first face opposed to a second face and separated by a perimeter region;   introducing a silicone elastomer into the mold cavity;   causing the silicone elastomer to distribute generally evenly around the entire mold cavity;   curing the silicone elastomer to form a hollow implant shell;   introducing a first silicone elastomer gel into the hollow implant shell;   causing the first silicone elastomer gel to distribute generally evenly around a perimeter region of the hollow implant shell;   allowing the first silicone elastomer gel to coalesce and form a ring within the perimeter region of the hollow implant shell; and   removing the implant shell from the mold cavity.   
     
     
         16 . The method of  claim 15 , wherein the first silicone elastomer gel has a particular gel cohesiveness, and after the step of allowing the first silicone elastomer gel to coalesce, further including:
 introducing a second silicone elastomer gel into the hollow implant shell, the second silicone elastomer gel having a lower gel cohesiveness than the first silicone elastomer gel.   
     
     
         17 . The method of  claim 15 , wherein the first silicone elastomer gel has a particular gel cohesiveness, and after the step of allowing the first silicone elastomer gel to coalesce, further including:
 introducing a second silicone elastomer gel into the hollow implant shell, the second silicone elastomer gel having a greater gel cohesiveness than the first silicone elastomer gel.   
     
     
         18 . The method of  claim 15 , wherein the mold is part of a rotational casting machine, and the step of causing the first silicone elastomer gel to distribute generally evenly around a perimeter region comprises rotating the mold about only one axis. 
     
     
         19 . A method of making a gel-filled prosthetic implant, comprising:
 forming a hollow implant shell having a generally oval vertical cross-section with a first face opposed to a second face and separated by a perimeter region;   introducing a first silicone elastomer gel into the hollow implant shell;   causing the first silicone elastomer gel to distribute generally evenly around the perimeter region of the hollow implant shell;   allowing the first silicone elastomer gel to coalesce and form a ring within the perimeter region of the hollow implant shell;   introducing a second silicone elastomer gel into the hollow implant shell, the second silicone elastomer gel having a different softness than the first silicone elastomer gel; and   removing the implant shell from the mold cavity.   
     
     
         20 . The method of  claim 19 , wherein the second silicone elastomer gel has a lesser gel cohesiveness than the first silicone elastomer gel. 
     
     
         21 . The method of  claim 19 , wherein the second silicone elastomer gel has a greater gel cohesiveness than the first silicone elastomer gel.