Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Having bio-absorbable component
Reexamination Certificate
2000-12-05
2001-10-30
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Having bio-absorbable component
C623S023580, C428S036400, C428S296400, C602S046000, C525S413000
Reexamination Certificate
active
06309423
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to continuous filament non-woven structures fabricated from semi-crystalline polymeric materials. More particularly the invention relates to said structures that are self-cohering webs fabricated from bioresorbable polymeric materials which are found useful as surgical implants.
BACKGROUND OF THE INVENTION
This invention relates to compositions that are useful in medical applications intended to provide for integration with and subsequent attachment to the surrounding mammalian tissue. A requirement for any medical device that is to become well integrated with the surrounding host tissue is an open structure on the surface of the implant that is sufficiently large for cells to readily penetrate. If the open structure is sufficiently large to allow for the ingrowth of both collagenous and vascular tissues, a well tolerated attachment between the implant and the surrounding tissue is then possible.
Porous structures for implantable devices sufficiently large to allow ingrowth and attachment of tissue can be achieved through a variety of means. Various technologies are able to deliver tailored open-celled structures with various pore sizes to fit the particular cell ingrowth applications. Use of expanded polymeric membrane materials, such as expanded polytetrafluoroethylene (e-PTFE) is one such technique. It can be tailored to provide optimal tissue integration. It is considered chemically inert and therefore possesses enhanced biocompatibility.
The use of extruded fibers or filaments and their subsequent assembly into a variety of organized structures is common. These structures fall into the categories of traditional weaving and knitting. Such weave and knit technologies can be found in various “meshes” found under the trade names of Vicryl®, Dexon®, and Proline® meshes. The resulting structural integrity is primarily due to the alignment of the component fibers into bundles, which are then weaved or knitted into the particular desired construction. Besides the high cost and complexity of the knitting and weaving equipment, a particular additional drawback of such construction is an increased potential for colonization and wicking of bacteria within the interstices of the aligned fiber bundles if the implant becomes contaminated.
Another method of assembling fibers is as a non-woven fibrous construction. This construction involves a random arrangement of fibers or filaments rather than the organized fibrous construction which typifies weaves and knits. The random nature of the non-wovens structure makes manufacturing of the fabric easier than weaves and knits. However, few fibrous implants utilize non-woven constructions since the mechanical interlocking between fibers in such webs are generally weak. Consequently only limited applications such as felts and pledgets exist for the non-woven implantables that are dependent on fiber entanglement for their mechanical integrity; these possess relatively poor cohesive or tensile strength. Non-woven strength can be added by the addition of a subsequent binding process which produces an attachment of the randomly deposited fibers at their points of contact. One of the few non-woven implantables on the market is Resolut® Regenerative Material which is disclosed in PCT #WO92/10218 and is composed of staple fibers and an adhesive binder to produce its bioresorbable non-woven structure.
Bioresorbable materials are particularly desirable for use in many medical applications, especially in implant applications, controlled release, and cell growth tissue engineering applications. Most implantable bioresorbable materials are used either in the form of sutures or in the controlled delivery of drugs or other bioactive agents. In the case of sutures or other structures which bear mechanical loads during at least part of their implantation, semi-crystalline polymer systems are utilized. Conversely, controlled release applications where no mechanical loading is required typically utilize amorphous polymer systems for their consistent diffusion properties.
A useful implant application for a non-woven construction is as a barrier material in mammalian tissue regeneration, also known as guided tissue regeneration (GTR). In one such GTR application, either a non-resorbable or bioresorbable membrane can be employed to separate an area where bone growth is desirable from adjacent areas where competing faster growing gingival tissue may be present. The implanted GTR membrane is used as a protective cover and acts as a barrier to entry by the other tissues into the space where bone growth is desired. Simultaneously the barrier must also resist collapsing into the defect under the pressure of the overlying tissues. The advantage of a bioresorbable material is that once its primary purpose is achieved it will be absorbed, thus eliminating any surgical need to remove it.
The preservation of space between the surface of the defect and the desired contours of the subsequently regenerated surface is necessary in order to allow for the regeneration of tissues into that space. Periodontal structures which may be regenerated in this fashion are the periodontal ligament, bone and cementum. The barrier material allows propagation of bone and periodontal ligament cells by precluding entry of epithelial cells and gingival connective tissue cells into the provided space.
One commercially available material that provides a cell-barrier for periodontal guided tissue regeneration is GORE-TEX® Periodontal Material. This is an expanded polytetrafluoroethylene (e-PTFE) material that serves as a cell-barrier between the gingiva and a periodontal defect and is intended to preserve the necessary space between the surface of the defect and the desired contours of the subsequently regenerated surface. This material is made of porous expanded PTFE having a microstructure of nodes interconnected by fine fibrils. One portion of the total surface area of the GORE-TEX Periodontal Material has a porous structural surface that becomes infiltrated with blood clot and ingrown with fibrous connective tissue, thereby inhibiting epithelial migration. The remaining portion of the surface area has a cell-barrier structure of low porosity for isolating the overlying gingival connective tissue from the underlying defect. It is not bioresorbable, however, and must be removed in a subsequent surgical procedure.
Another commercially available cell barrier sheet material intended for guided tissue regeneration is the previously mentioned Resolut® Regenerative Material, also from W. L. Gore & Associates, Inc. PCT application #WO09/10218 describes this material as a bioabsorbable material made of a non-woven fibrous matrix of polyglycolic acid fibers laminarly affixed to a cell-barrier sheet material that is a copolymer of polylactic acid and polyglycolic acid. The overall material is intended to provide sufficient rigidity in vivo to maintain space over the defect as it regenerates.
There have been other attempts to produce suitable surgical barriers from bioresorbable materials. A 70 micron thick solvent-cast bioresorbable polylactic acid membrane having no inherent porosity or tissue cell permeability was tested in periodontal applications as a cell-barrier material for exclusion of epithelium and gingival connective tissue during healing (I. Magnusson, et al., “New Attachment Formations Following Controlled Tissue Regeneration Using Biodegradable Membranes”, J. Periodontal, January 1988, pp. 1-6). Tests showed some new formation of cementum and bone. Reproductions of this material demonstrated poor surgical handling characteristics due to its thin friable construction and also proved to be difficult to suture because of its brittleness. This material makes no provision for tissue ingrowth on either of its surfaces.
Another commercially available material for use in guided or controlled tissue regeneration is Vicryl® Periodontal Mesh available from Johnson & Johnson. The Vicryl Periodontal Mesh is comprised of woven fibers made from a bioresorba
Gore Enterprise Holdings Inc.
House Wayne
Koh Choon P.
McDermott Corrine
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