Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-09-10
2003-03-11
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
Reexamination Certificate
active
06530956
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is in the field of surgery, and more particularly, surgery to repair cartilage in joints such as knees, shoulders, or hips. It relates to the use of “scaffold” devices that can be implanted in a joint with damaged cartilage, to help support certain types of transplanted cells (such as “chondrocyte” cells) which can generate new cartilage. As used herein, the phrase “damaged cartilage” is used broadly, and includes cartilage which has been damaged by mechanical trauma or other physical or inflicted injury or abrasion, or by a disease process, such as arthritis or osteoarthritis.
Background information on knee, hip, and shoulder joints, on cartilage tissue, and on “classical” techniques and devices that have been used for many years to repair damaged cartilage in knee joints are discussed in numerous medical texts, such as
Campbell's Operative Orthopedics,
a five-volume treatise. Additional information is periodically issued by the American Academy of Orthopedic Surgeons in a series of books called “Orthopedic Knowledge Updates”; volume 6 in that series was issued in 1999.
A number of recent articles and patents describe efforts to use transplanted chondrocyte cells, and various types of “precursor” and “stem” cells, to generate new cartilage. Such articles include Brittberg et al 1994, Chen et al 1997, Minas et al 1997, and Thornhill 1997 (complete citations are provided below).
Most of the patents in this field tend to concur that the best way to promote cartilage regeneration inside a joint involves the use of a “resorbable” matrix, made of a material such as collagen, the protein that normally holds together connective tissue and provides the three-dimensional matrix that tissue cells grow in. In any type of connective tissue, the existing collagen fibers are slowly and gradually digested, mainly by an enzyme called collagenase. This process of gradual digestion of the old collagen is matched by a gradual secretion of new collagen fibers by the cells in the tissue, resulting in a process of turnover and replacement that helps keep tissue flexible, healthy, and strong. Accordingly, collagen implants (usually made from cowhide, which offers an abundant source of the fibrous protein, treated with cross-linking and other chemical agents to control the rate of enzymatic degradation) were developed for other purposes beginning in the mid-1970's (e.g., U.S. Pat. No. 4,060,081, Yannas et al 1977).
Clearly, implantation of chondrocyte or similar cartilage-secreting cells in a damaged cartilage surface in a joint is a difficult and challenging task, which requires the cells to be anchored in position and then protected and sheltered from compressive and shear forces for a period of weeks or months, to give the transplanted cells a chance to generate firm and anchored cartilage without simply being squashed out of the joint. Accordingly, researchers began to realize by about the mid-1980's that resorbable collagen matrices could be used to help position, protect, and anchor such cells in cartilage repair operations, and if properly designed, the matrix would gradually disappear once it had accomplished its task, leaving behind regenerated cartilage.
Accordingly, a large number of US patents were issued which centered around this theme, and which proposed various ways to enhance and improve the ability of the “resorbable collagen matrix” approach to repairing damaged cartilage. For example, U.S. Pat. No. 4,846,835 (Grande 1989) discloses techniques for giving chondrocyte cells (preferably taken from the same patient who has suffered the joint damage, so that no risk of rejection will be present) a headstart, by growing them outside the body in an in vitro cell culture solution, seeded and embedded into a collagen matrix. After the cells have been growing inside the collagen matrix for a suitable number of days, under lab conditions, the entire matrix (including the cells) can be surgically implanted into the damaged joint.
U.S. Pat. No. 4,880,429 (Stone 1989), U.S. Pat. No. 5,007,934 (Stone et al 1991), and U.S. Pat. No. 5,306,311 (Stone et al 1994) also relate to porous matrices made of collagen or similar compounds, which can be shaped or sculpted in various desired shapes, then implanted or “seeded”, under laboratory conditions, with cells that reproduce to form large numbers of chondrocyte cells (which generate cartilage) or meniscal fibrochondrocytes (which generate meniscal tissue);
U.S. Pat. No. 5,041,138 (Vacanti et al 1991) describes a similar type of cell growth, in a biodegradable matrix made of a synthetic polymer rather collagen.
U.S. Pat. No. 5,206,023 (Hunziker 1993) relates to a multi-step process for repairing damaged cartilage, involving (i) enzymatic treatment to remove proteoglycans from the defect area, followed by (ii) packing the cleaned area with a degradable matrix that encourages ingrowth of repair cells.
U.S. Pat. No. 5,518,680 (Cima et al 1996) discloses the use of various “solid free-form” manufacturing techniques which can be aided by “computer-assisted design” (CAD techniques, such as stereo-lithography, selective laser sintering, fusion deposition modeling, and three-dimensional printing, to rapidly manufacture colagen or other resorbable matrices in precise dimensions that are determined based on the dimensions of the defect in a particular patient. The '680 patent also discloses the incorporation of certain inorganic particles in such matrices, both to strengthen the highly porous matrices, and to provide a source of minerals for regenerating tissue.
U.S. Pat. Nos. 5,749,874 and 5,769,899 (both Schwartz et al 1998) disclose a two-component implant, where one component is a holding and anchoring device, made of a relatively hard yet biodegradable material such as polyglycolic acid, polylactic acid, or combinations therof. This anchoring device is designed to to hold a more porous and flexible matrix, made of a material such as collagen or hyaluronic acid, which will hold chondrocyte cells.
Various other patents focus on alternatives to collagen, in biodegradable matrices. Such patents include U.S. Pat. No. 5,294,446 (Schlameus et al 1994), which discloses that alginate (a naturally occurring polysaccharide) can be used to encapsulate of live cells. U.S. Pat. No. 5,041,138 (Vacanti et al 1991), U.S. Pat. No. 5,709,854 (Griffith-Cima et al, 1998) and U.S. Pat. No. 5,736,372 (Vacanti et al 1998) provide extensive information on various synthetic polymers (such as polyphosphazines, polyacrylates, polyanhydrides, and polyorthoesters, as well as “block copolymers” such as mixtures of polyethylene oxide and polypropylene glycol) which can be used to generate hydrogels which can used for cartilage replacement.
These listed patents also contain citations to numerous published articles that are directly relevant in this field. Alternately, an Internet search of the National Library of Medicine database, available for free at http://www.igm.nih.gov, combining “cartilage” as a subject or title word combined with “Langer” or “Vacanti” as an author name, will quickly provide a generous supply of information on the current state of the art in this field.
It should be noted that some of the polymers listed in the Vacanti et al patents cited above were chosen and developed to repair facial cartilage (mainly in the nose and ears) rather than for repairing load-bearing cartilage in joints. In general, cartilage in the nose and ears is softer and more flexible than “hyaline” or “articulating” cartilage which occurs in knees, hips, and other joints. Accordingly, although the '854 and '372 patents disclose and discuss a long list of potentially suitable biocompatible synthetic polymers, all of which can support chondrocyte growth for a prolonged period and then eventually disappear due to resorption, any synthetic polymer intended for use in a knee, hip, or other load-bearing joint will need to be selected accordingly, with careful attention to its load-bearing traits.
Two quantifiable traits which ar
Kelly Patrick D.
McDermott Corrine
Phan Hieu
LandOfFree
Resorbable scaffolds to promote cartilage regeneration does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Resorbable scaffolds to promote cartilage regeneration, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Resorbable scaffolds to promote cartilage regeneration will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3076805