US 3681786 A
A surgically implantable prosthesis formed from a single piece of inherently flexible elastomeric, physiologically inert material and a polyester felt pad embedded within the prosthesis and having an exposed surface to provide for ingrowth of body tissue. The one piece prosthesis is radiated to provide areas of different flexibility in accordance with the function to be performed by the prosthesis.
Description (OCR text may contain errors)
1 United States Patent [15 1 3,681,786 [45 1 Aug. 8, 1972 Lynch  SOLID HUMAN PROSTHESIS OF VARYING CONSISTENCY  Inventor: Henry W. Lynch, Racine, Wis.
 Assignee: Medical Engineering Corporation,
 Filed: July 13, 1970  Appl. No: 54,443
 U.S. Cl. ..3/1, 128/92 C, l28/DIG. 21, 264/22  Int. Cl ..A61f l/18, A6lf H22  Field of Search...3/l 6; 128/92 R, 92 C, 92 CA, 128/DIG. 21; 264/22; 204/158 R, 158 HE  References Cited UNITED STATES PATENTS 3,462,765 8/1969 Swanson ..3/1
3,257,668 6/ l 966 Braley ..3/1 3,461,869 8/1969 Hargest ..3/1 X 2,763,609 9/1956 Lewis et a]. ..204/158 HE 3,335,428 8/1967 Gajdos ..3/7 2,945,795 7/1960 Cummin ..204/158 HE Primary Examiner-Richard A. Gaudet Assistant Examiner-Ronald L. Frinks Attorney-Ronald E. Barry and James E. Nilles 5 7] ABSTRACT A surgically implantable prosthesis formed from a single piece of inherently flexible ellastomeric, physiologically inert material and a polyester felt pad embedded within the prosthesis and having an exposed surface to provide for ingrowth of body tissue. The one piece prosthesis is radiated to provide areas of different flexibility in accordance with the function to be perfonned by the prosthesis.
3 Claims, 6 Drawing Figures SOLID HUMAN PROSTHESIS OF VARYING CONSISTENCY BACKGROUND OF THE INVENTION The use of silicone rubber in a device designed for replacement of a damaged or diseased part of the body is well known. Various types of prosthetic devices have been made to replace the joints and various bone and cartilage structures in the body. A typical example of such a device is shown in the Swanson US. Pat. No. 3,462,765, entitled Surgically Implantable Prosthetic Joint which has an enlarged center portion that forms the joint and two stem portions that are inserted into the intramedullary canals of the adjacent bones. Difficulties have been encountered in using this device since it has substantially an identical degree of flexibility throughout its length and tends to bend in the smaller portions rather than in the joint. The stem portions, due to the nature of the silicone rubber, are not susceptible to tissue ingrowth and tend to become loose in the intramedullary canals of the bones.
SUMMARY OF THE INVENTION The surgically implantable prosthesis of this invention provides a one piece device having different degrees of flexibility in order to more readily duplicate the body function for which it is intended. This is accomplished by subjecting the inherently flexible member to different degrees of radiation allowing for greater flexibility at the joints and greater rigidity in the other portions of the prosthesis. Tissue ingrowth is also promoted by embedding a polyester felt pad in the device leaving exposed sections of the feltpad on the surface of the device for attachment by tissue ingrowth.
Other objects and advantages of this invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.
DRAWINGS FIG. 1 is a perspective view of an implantable prosthesis according to the invention in the form of a finger joint;
FIG. 2 is a sectional view taken on line 2--2 of FIG. 1 of the prosthesis shown in FIG. 1;
FIG. 3 is an enlarged view of one of the stems showing the felt pad in one of the stem portions;
FIG. 4 is a view partly in cross-section showing the prosthesis of FIG. 1 in position within the adjacent bones of a finger;
FIG. 5 is a view of a one piece surgically implantable cartilage for an ear;
FIG. 6 is a cross-section taken on line 5-5 of FIG. 4 showing the varying degrees of flexibility of the cartilage for the ear.
DESCRIPTION OF THE INVENTION The invention as disclosed herein is described for use as a finger joint or the cartilage for an ear. Obviously, a device can be shaped to replace any other bone or cartilage structure where different degrees of flexibility are required to more accurately duplicate the function of the part of the body which has been replaced. In FIGS. 1 through 3, a finger joint is shown having substantially the same shape as shown in the Swanson U.S.
Pat. No. 3,462,765. This joint includes a body 10 molded of inherently flexible elastomeric, physiologically inert material such as silicone rubber. The body has an enlarged center portion 12 with a pair of oppositely projecting stem portions 14 and 16. The stem portions are tapered for insertion into the intramedullary canals 18 of the adjacent bone ends 20 of the finger. The center portion 12 which is wider than it is thick is provided with a groove or slot 22 to reduce the thickness of the joint to allow the joint to flex.
In accordance with the invention, the center portion 12 is provided with a greater degree of flexibility than the stem portions 14 and 16 by subjecting the center portion 12 to a lesser amount of radiation than the stem portions. As an example, the center portion 12 is radiated for a maximum of 2 minutes, while the stem portions are radiated for at least 4 minutes. This is accomplished by masking the center portion 12 for the first 2 minutes and then removing the mask and radiating the entire device for 2 minutes more.
Tissue ingrowth is promoted by means of polyester felt pads 26 which are embedded within the stem portions 14 and 16. These pads 26 (as seen in FIG. 3) are formed from Dacron felt and are slotted (as shown in dotted line) prior to molding of the joint. The pad is laid across the mold at the parting line, and after molding, the edges are trimmed to leave an exposed edge 28 around the parting line in the stems l4 and 16.
In FIGS. Sand 6, a complete ear cartilage 40 is shown having a center portion or base 30, an outwardly projecting connecting portion 32 and an outer edge 34. The ear cartilage 40 is initially molded to the approximate shape of the ear to be replaced from a silicone rubber. The center portion 30 is made substantially harder than the connecting portion 32 and rim 34 of the ear to provide a solid base for attachment to the ear. The softness of the outer edge 34 is retained to give a natural flexibility to the whole ear.
The density of the center portion 30 is increased by selectively radiating the center portion 30 to a greater extent than the connecting portion 32. This can be done by masking the connecting portion 32 and outer edge 34. The center portion 30 is then subjected to a predetermined amount of radiation. The middle connecting portion 32 is then exposed and both the center portion 30 and the connecting portion 32 are exposed to radiation for a predetermined period of time.
The ear cartilage 40 is initially secured to the body by promoting tissue ingrowth into a Dacron felt pad 25 located on the center portion 30. The pad 25 is formed from a plurality of Dacron fibers randomly arranged into a compact permeable felt-like pad. The pad is molded into the base allowing the silicone rubber to penetrate into a small amount of the pad 25. The exposed side of the pad 25 is then free for tissue ingrowth.
After attachment, skin is progressively grafted to the surface of the cartilage until it is completely covered. The grafted skin is retained on the cartilage by means of small felt pads 42 provided in. recesses 44 on the outer edge 34 of the cartilage. These pads 42 are also formed of Dacron fiber and are secured in the recesses 44 by molding in place. The pads 42 are molded in place in the silicone rubber by allowing the silicone rubber to impregnate the portion of felt lying next to it and anchoring it thereby.
Although the prosthesis disclosed has been described only in connection with replacement as joints or as an ear, it should be understood that any other cartilage could be replaced with the prosthesis of this invention where various degrees of flexibility are required. For example, the nose can be rebuilt by a single piece having a hard center and flexible projecting portions to duplicate the function of the cartilage of the nose.
1. A surgically implantable prosthesis comprising:
a one-piece body of inherently flexible elastomeric, physiologically inert material, said body having an enlarged center portion and an outwardly projecting connecting portion, an enlarged edge around the outer periphery of said connecting portion,
said center portion and said outwardly projecting portion having a greater density than said outer edge,
and a number of polyester felt pads in said enlarged edge, each pad having an exposed section on the surface of said edge for promoting ingrowth of tissue.
. A surgically implantable joint comprising:
3. The joint according to claim 2 wherein said outwardly projecting portions have a greater rigidity than said center portion.