Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-06-11
2001-08-21
Snow, Bruce (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S023740
Reexamination Certificate
active
06277150
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to space-filling implants useful in plastic surgery and particularly to three dimensional facial implants having a solid-core (non-hollow) construction.
BACKGROUND OF THE INVENTION
Implantable articles of various shapes have been used for some time in plastic surgery to fill space subcutaneously in order to provide a more normal or desirable profile to the exterior surface of that portion of a person's body. These implants have traditionally been made primarily of elastomeric materials, particularly silicone. These types of articles are effective for their primary purpose of filling space in order to provide the desired exterior body contours, however, they have various disadvantages including a propensity to migrate from their site of original implantation if not properly anchored or attached. The typical silicone space-filling implant intended for facial repair is a solid article made from non-porous or substantially non-porous silicone. They are most commonly used when appropriately shaped for the repair of chins, cheeks and zygomatic arches. See, for example, U.S. Pat. No. 4,344,191 to Wagner and U.S. Pat. No. 4,790,849 to Terino.
In addition to facial implants, space-filling implants of many various designs are also used in other areas of the body. In particular, implants of various designs and constructions have long been used for breast augmentation. These devices are most typically constructed from silicone envelopes containing a soft filling material such as silicone gels. Implants of this type are of hollow-core construction and are beyond the scope of the present invention.
Materials other than elastomers have also been used for facial space-filling implants, most notably porous expanded polytetrafluoroethylene (ePTFE). Materials of this type are made as taught by U.S. Pat. Nos. 3,953,566 and 4,187,390 to Gore. ePTFE is commonly used as an implantable material because it is highly inert and thus typically provokes little if any adverse reaction when implanted. It is frequently used for tubular vascular grafts, sheet materials for patching membranes and blood vessels, dental barriers and sutures. It is also sold as a facial implant available from W. L. Gore and Associates, Inc. Flagstaff Aria., as GORE SUBCUTANEOUS AUGMENTATION MATERIAL™ (S.A.M.).
U.S. Pat. No. 5,098,779 to Kranzler et al. and PCT Published Application WO 95/22359 to Sharber et al. describe ePTFE space filling implants wherein the relatively soft ePTFE is rendered carvable (for shaping by a surgeon) by either coating or impregnating the porous ePTFE with a resorbable material, or by laminating it with alternating layers of another material such as silicone or fluorinated ethylene propylene (FEP) in order to render it adequately stiff for carving.
An article entitled “The Use of Gore-Tex® E-PTFE Bonded to Silicone Rubber as an Alloplastic Implant Material” (Berman et al., LARYNGOSCOPE, Vo. 96, No. 5, May 1986) describes the evaluation of implanted composite sheets of ePTFE sheet material laminated to sheets of silicone. Another article entitled “Sheets, 3-D Strands, Trimensional (3-D) Shapes, and Sutures of Either Reinforced or Nonreinforced Expanded Polytetrafluoroethylene for Facial Soft-Tissue Suspension, Augmentation, and Reconstruction” (Lewis et al., Journal of Long-Term Effects of Medical Implants, 8(1):19-42(1998)) describes facial repair implants of ePTFE having various shapes.
Facial space-filling implants of the types described above typically have exterior surfaces which are virtually entirely non-porous (e.g., silicone implants) or alternatively are virtually entirely porous (e.g., conventional ePTFE implants). The implants with porous exterior surfaces allow tissue ingrowth into those porous surfaces if they offer adequately large void spaces, typically of about 8-10 microns or larger, preferably larger than about 20 microns and less preferably of about 50 microns or larger. Tissue ingrowth results in a stable implant which is unlikely to have any tendency to migrate from its site of original implantation. Conversely, implants having substantially non-porous surfaces, that is either completely non-porous or having pores of too small of a size to accommodate any appreciable amount of tissue ingrowth, require suturing to adjacent body tissue for the necessary anchoring. Inadequate suturing frequently allows the implant to migrate away from its intended location.
While the ingrowth of soft tissue into an implant having porous exterior surfaces is desirable for stability of location, it is possible to dissect the attached soft tissue if it should become necesssary to remove the implant for any reason. However, if hard tissue (e.g., bone) has grown into the void spaces of the porous implant, the implant can be extremely difficult to dissect free should its removal be necessary.
SUMMARY OF THE INVENTION
The present invention relates to a three dimensional facial space-filling implant adapted for filling space subcutaneously, said space being located primarily at the interface of a soft tissue surface and a bone surface. The article has a length, width and thickness wherein the thickness is oriented substantially orthogonal to first and second substantially opposing surfaces of the article. The thickness varies according to location along the length and width. The first surface is adapted to be substantially in contact with the soft tissue surface when implanted, and is substantially porous having void spaces of size adequate to allow tissue ingrowth into at least a portion of the void spaces. The second surface is adapted to be substantially in contact with the bone surface when implanted and is substantially non-porous to substantially prevent ingrowth of bony tissue into the second surface.
The different porosity characteristics of the first and second surfaces allows for the ingrowth of soft tissue into the first surface to provide stability of implant location while substantially or entirely precluding ingrowth of hard tissue into the second surface which, if it occurred to a significant degree, would render the implant difficult to remove. Thus the characteristics of the implant of the present invention allow the implant to be relatively easily removed if necessary while still allowing ingrowth of soft tissue into the first surface for implant stability.
The thickness or core of the implant is preferably a solid or non-hollow core. The core material is preferably an elastomer and most preferably a silicone (polydimethyl siloxane). Other implantable elastomers may also be used for the core including polyurethanes and fluoroelastomers.
In a preferred embodiment, the present invention comprises a three dimensional implant such as a chin, cheek or nasal implant made from silicone (polydimethyl siloxane). The silicone shape is provided with a porous covering on one surface which is adapted to face toward and contact the soft tissue following implantation. The opposing surface remains as non-porous or substantially non-porous silicone. The porous covering is preferably porous polytetrafluoroethylene and more preferably porous expanded polytetrafluoroethylene (ePTFE), made as taught by U.S. Pat. Nos. 3,953,566 and 4,187,390, incorporated by reference herein. Other porous materials may also be used. For example, a solid core implant of, for example, silicone or polyurethane may be provided with one surface of a porous material of the same type. Various methods of making elastomeric materials porous are known in the art.
Typical chin, cheek and nasal implants are suitable three dimensional shapes which usually have two opposing exterior surfaces, with one surface commonly being concave and the opposite being convex. The convex surface is adapted for facing outwardly toward the patient's skin and accordingly is intended to be primarily or entirely in contact with overlying soft tissue. Conversely, the concave surface is adapted for facing toward and substantially or entirely being in contact with the underlying bone. In a preferred emb
Crawley Jerald M.
Zukowski Stanislaw L.
Gore Enterprise Holdings Inc.
Snow Bruce
Wayne House
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