Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Having means to promote cellular attachment
Reexamination Certificate
2001-02-20
2004-08-31
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Having means to promote cellular attachment
C623S001520, C623S023740, C606S151000
Reexamination Certificate
active
06783554
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an implantable prosthesis material suitable for repairing muscle or tissue wall defects. It can be used for supporting, reinforcing, anchoring, and stabilizing tissue due to trauma, naturally occurring defects, herniation, cancer and/or surgical intervention.
BACKGROUND OF THE INVENTION
A multitude of surgical procedures today utilize prior art flat synthetic implant fabric materials to help support, anchor, and stabilize soft tissue. A soft tissue patch is an example of a flat fabric synthetic implant commonly used for such purposes. A variety of raw materials and polymers including bovine sourced collagen, polypropylene, nylon, polyester, and expanded polytetrafluoroethylene (PTFE) are used to form flat synthetic fabrics. Various manufacturing processes take these raw materials and form them into different fabric or laminate structures. The most popular synthetic soft tissue implant is constructed of a smooth open mesh fabric structure. Since the mid 1950's, polypropylene mesh fabrics have been used for soft tissue repair because the uniform open-pore structure encourages rapid cell penetration during healing. This in-growth through a porous mesh fabric adds to the strength of the surgical repair while the mesh provides a trellis for tissue anchoring and mechanical reinforcement to the healed repair following surgery.
Surgeons utilize synthetic meshes to repair, for example, hernias. A hernia is an abnormal protrusion of an organ, tissue, or any other anatomical structure, through a weakened area or opening in a surrounding or adjacent tissue wall. Hernias most often occur in the inguinal region near the bottom of the abdominal cavity. The abdominal muscle and connective tissue wall in the inguinal region on both right and left sides of individuals can often be weaker than surrounding muscle wall, hence, the high incidence of herniation in this area of the body. A portion of intestine or other abdominal cavity tissue extrudes through the weak spot in the surrounding tissue. Under physical pressure from daily activities, for example, a section of the intestine can push the thin peritoneum membrane, which is a protective membrane that lines the abdominal cavity. The tissue typically does not tear the peritoneum, thus when the tissue protrudes, the peritoneum covers the tissue. The term “hernial sac” describes the peritoneal covering surrounding the piece of protruding tissue.
One known surgical technique to treat the hernia and eliminate the protrusion, is to make an incision in the skin, followed by dissection through the subcutaneous fat and external oblique muscle to reach the forced opening in the abdominal wall. The surgeon usually dissects free and pushes that portion of the peritoneum covered organ extending through the rupture back through the defect to the proper side of the abdominal cavity. The repair can continue by pulling the edges of the rupture together and suturing or stapling them closed. This procedure is often limited to smaller type hernias and requires careful operative care to prevent tension on the fragile tissues. Tension on such tissues can result in substantial patient discomfort, and can result in recurrence or re-herniation of the same tissue. This type of repair relies solely on the structural integrity of the connective tissue to contain and prevent the hole from reforming.
Another known surgical technique for repairing a hernia defect utilizes a biocompatible prosthetic constructed from, for example, a flat polypropylene mesh fabric. After pushing the protruding organ back through the defect, the surgeon places a piece of flat mesh or PTFE fabric on one side of the muscle wall, bridging the opening or rupture without pulling the tissues back together. This is referred to as a tension free hernia repair. Hence, use of a prosthetic mesh or PTFE fabric helps stabilize the open defect by providing a trellis for tissue to grow into, and through, without tension on the surrounding natural tissue. This repair is known to produce a lower incidence of reoccurrence of the hernia with the use of prosthetic mesh fabric implants.
Still another known prosthetic hernia technique is the use of a folded or pre-shaped flat mesh fabric placed as a plug, rather than a flat patch. If the tissue opening or rupture is relatively small, the surgeon can alternatively roll up, fold, or form the flat mesh fabric into a plug like tampon and insert it lengthwise into the defect, plugging the rupture. Cell tissue, over time, grows through and into the dense folded and formed plug to help hold and stabilize the plug in place. This particular plug technique can sometimes stabilize a defect mechanically with the addition of bulk material placed into the plane of weakened or ruptured tissue, which can aid in a more rapid patient convalescence and return to daily activity. However, since many hernia and tissue defects are non-symmetrical, not all flat mesh fabric plug shapes or preformed shapes uniformly fit the defect hole. Most preformed plugs constructed from flat mesh fabric must be appropriately sized to fit the size of the defect.
Whether a flat mesh fabric or a mesh fabric folded or formed into a 3-dimensional plug shape or structure, such prosthetic materials aid the surgeon in completion of a tension-free repair by eliminating the need to pull tissue structures together. Flat mesh fabric implants are frequently sutured over the hernia defect, thus preventing re-herniation by placing a barrier over the defect. A flat sheet or preformed flat piece of mesh fabric, in certain circumstances, does not sufficiently anchor, stabilize, or fill the hernia defect.
SUMMARY OF THE INVENTION
There exists in the art a need for a biocompatible surgical implantable prosthesis suitable for repairing, stabilizing, anchoring more completely, and filling of both naturally occlusive tissue defects, or open holes from trauma or cancer, while effectively promoting rapid tissue in-growth with less structural or material density. A more dense or less porous fabric results in a more pronounced foreign body reaction to the implant. The implant construction of the present invention provides more structural contact filling of a tissue hole or defect, with a more open and resilient 3-dimensional structure that enables quick healing, with a lower density and resultant tissue encapsulation.
A biocompatible soft tissue implant provided in accordance with one example embodiment of the present invention is a pile mesh prosthesis constructed of a plurality of strips of knitted pile mesh, interconnected by one or more monofilament connecting bridges. At least one row has a plurality of filament extensions projecting outwardly therefrom. The filament extensions, in accordance with one aspect of the present invention, are in the form of a plurality of filament loops that provide radial contact with tissue to stabilize the implant and provide resistance to compression or crushing forces applied to the prosthesis following implantation. Structurally, the rows of knitted pile mesh provide mechanical strength, compliance, and flexibility. The protruding loops, which extend radially from the rows, provide a structural tissue contact means minimizing direct contact of the knitted rows of mesh, thereby reducing the density of material to be healed after implant. The rows can be of a different foundational structure for supporting the filament extensions.
The pile mesh construction can fit into an irregularly shaped tissue hole or defect and completely fill the area as a material plug, with significantly less material mass than a traditional flat mesh fabric or patch. Such an open pile mesh prosthesis provides a relatively lighter, less dense, structural hole filler facilitating more rapid healing. Biomaterial evidence indicates that less plastic results in less inflammation, and less mass requires less cell remodeling to achieve full tissue stabilization and prevent encapsulation. The pile mesh prosthesis of the present invention, due to its 3-dimensional filament
Amara Ryan A.
Gingras Peter H.
Herweck Steve A.
Karwoski Theodore
Atrium Medical Corporation
Blanco Javier G.
Lahive & Cockfield LLP
McDermott Corrine
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