Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Tissue
Reexamination Certificate
2001-03-08
2002-10-22
Wilson, John J. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Tissue
C623S014120
Reexamination Certificate
active
06468314
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a bio-absorbable cartilage repair system for regenerating articular cartilage and, more particularly, a system which allows for vascular invasion and cellular migration between the system and the adjacent healthy area of articular cartilage and cancellous bone, thereby resulting in regeneration of the damaged articular cartilage.
Articular cartilage on the surface of bones in joints, most particularly the knee, ankle and hip joints, is susceptible to deterioration caused by injury or disease. This deterioration of cartilage leads to pain and eventually loss of joint movement and more severe pain. As a result, various methods have been developed to treat and repair damaged or destroyed articular cartilage.
Prosthetic devices are often used to replace damaged or destroyed articular cartilage. For example, U.S. Pat. No. 4,627,853 discloses prosthesis which are used for articular cartilage replacement. The prosthesis are prepared by demineralization of a bone segment, the demineralized bone segment serving as a replacement for articular cartilage.
U.S. Pat. No. 5,176,710 discloses a prosthesis for replacing bone material on the articulating surface of a joint. The prosthesis has a specific modulus of elasticity so as to confer stiffness to the prosthesis, and contains concave shapes which are suitable for biologic ingrowth.
U.S. Pat. No. 3,745,590 discloses a prosthesis for the repair or replacement of joints, which prosthesis comprises a body portion, including a stem and ligamentous elements, and allows for tissue ingrowth.
U.S. Pat. No. 5,123,927 discloses a knee prosthesis comprising bone cement containing an antibiotic.
U.S. Pat. No. 4,904,259 discloses a resorbable gel, including ex vivo chondrocyte cells, press fit into a cartilage defect.
U.S. Pat. No. 5,270,300 discloses a scaffold into which cells grow, but without any blood supply from the subchondral bone.
U.S. Pat. No. 5,306,311 discloses a resorbable prosthesis suitable for biologic ingrowth.
PCT Publication No. PCT/WO95/30383 discloses ex vivo proliferated, denuded chondrogenic cells for synthetic cartilage use in surgically repairing cartilage defects.
Although there are several prosthetic devices which can be used in the replacement of damaged or destroyed articular cartilage, prosthetic devices have several disadvantages. For example, cements which are used to attach prosthetic devices to bones may loosen and eventually fail. In addition, fragmented cement can move into the joints and associated lymph tissue and cause inflammation and further damage. Further, cements result in the formation of fibrous tissue between the bone and the prosthesis. Another major disadvantage associated with the use of prosthesis is that the prosthetic device may be larger than the damaged cartilage that needs to be replaced, thereby requiring removal of portions of healthy bone and/or cartilage in order to accommodate the prosthetic device. Hence, the need remains for a system for repairing and regenerating articular cartilage which avoids the problems associated with prosthetic devices.
Another means used to treat damaged articular cartilage is the placement of repair pieces onto the bone, which repair pieces substitute for cut-out pieces of cartilage. For example, U.S. Pat. No. 5,067,964 discloses an articular cartilage repair piece which comprises a layer of non-woven, felted fibrous material which is limp and readily conformable to flat and curved surfaces. The articular cartilage repair piece is attached to the bone, for example, by bio-absorbable screws or pins or like temporary fixation techniques. Fibrous tissue ingrowth eventually surrounds the repair piece thereby causing the repair piece to be permanently attached to the bone. Although U.S. Pat. No. 5,067,964 discloses an alternative method for repairing damaged articular cartilage, it does not disclose any means or method of regenerating damaged or destroyed articular cartilage. Hence, the need remains for a system for regenerating damaged or destroyed articular cartilage, wherein the regenerated articular cartilage is functionally similar to non-damaged articular cartilage.
Commonly owned U.S. Pat. Nos. U.S. Patent No. 5,632,745; U.S. Pat. No. 5,749,874; and U.S. Pat. No. 5,769,899 disclose such a regenerating system and are incorporated herein by reference. However, the regenerating systems disclosed therein have not proved to be entirely satisfactory from the points of view of both the manufacturer and the surgeon installing the same in a patient.
Accordingly, an object of this invention is to provide a system for regenerating articular cartilage.
Another object is to provide a system for regenerating articular cartilage wherein the regenerated articular cartilage is functionally superior to fibrous or fibrocartilagenous repairs and is functionally similar to non-damaged articular cartilage.
A further object is to provide a cartilage repair system for use in regenerating damaged or destroyed articular cartilage.
It is another object of the present invention to provide an embodiment of the cartilage repair system which does not employ cement or non-bio-absorbable prosthetic devices.
It is a further object to provide an embodiment of the cartilage repair system for repairing bone as well where there are injuries to both cartilage and bone.
SUMMARY OF THE INVENTION
It has now been found that the above and related objects of the present invention are obtained by a bio-absorbable cartilage repair system for regenerating damaged or destroyed articular cartilage on the joint surface of a bone, which system establishes a chondrogenic growth-supporting matrix between an area of damaged or destroyed articular cartilage that has been removed and an adjacent healthy area of articular cartilage and cancellous or trabecular bone. The system comprises an assembly of a bio-absorbable delivery unit and a porous bio-absorbable insert. The delivery unit is formed of bio-absorbable material and configured and dimensioned to be mounted in both an area of damaged or destroyed articular cartilage that has been removed and an adjacent healthy area of articular cartilage and cancellous bone. The delivery unit has a central body and a plurality of radially extending, flexible support arms projecting outwardly from the central body and configured and dimensioned to support the insert at least partially thereover. The insert is supported by the delivery unit, formed of bio-absorbable material, and establishes communication between the removed area and the adjacent healthy area for a chondrogenic growth-supporting matrix.
In a preferred embodiment, the insert is disposed on the upper, lower, and outer surfaces of the support arms, and the support arms have free ends circumferentially spaced from one another to define areas for receipt of a chondrogenic growth-supporting matrix. The support arms preferably have circumferentially spaced free ends adapted to engage and at least partially spatially stabilize the insert. The support arm free ends may be horizontally or vertically barbed. The central body adjacent a bottom end thereof defines a plurality of outwardly extending flanges.
In a preferred embodiment, the insert has a top, a bottom and a sidewall connecting the top and bottom. The bottom allows vascular invasion therethrough, and the top and sidewall allow cellular migration therethrough by an adjacent healthy area of articular cartilage and subchondral cancellous bone. The insert may include cells to facilitate establishing such communication. The sidewall is preferably polygonal in plan. Each of the delivery unit and the insert preferably essentially consists of completely bio-absorbable material which is ceramic-free and dimensionally stable in synovial joint fluid against expansion due to the absorption thereof.
The system may additionally include retainer means for securing the insert to the delivery unit. The retainer means is secured to a portion of the central body below the insert and bears upwardly against the insert. The retain
Grande Daniel A.
Schwartz Robert E.
Barnes & Thornburg
DePuy Orthopaedics, Inc.
Priddy Michael B.
Wilson John J.
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