Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis
Reexamination Certificate
1999-05-05
2003-02-04
Prebilic, Paul B. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
C623S006640, C623S023590, C623S023750
Reexamination Certificate
active
06514286
ABSTRACT:
FIELD OF THE INVENTION
This invention is in the field of biodegradable, biocompatible polymeric materials, suitable for implantation into a patient's body.
BACKGROUND OF THE INVENTION
Many substances used for implants, such as osteochondral implants and orbital implants, e.g., made of hydroxylapatite, are rough and can cause injury to surrounding tissue or interfere with articulation. Smooth implants, however, do not allow for tissue ingrowth and muscle attachment as well as would be desired.
Polymeric films have been used in several types of medical applications in connection with implants. Colomb, G. and Wagner, D. (1991), “Development of a new in vitro model for studying implantable polyurethane calcification,” Biomaterials 12:397-405, discloses the use of non-biodegradable polyurethane films 0.2 to 0.7 mm thick to study implant calcification. Bawa, R. and Nandu, M. (1990), “Physico-chemical considerations in the development of an ocular polymeric drug delivery system,” Biomaterials 11:724-728, discloses the use of non-biodegradable silicone-based prepolymer films impregnated with gentamicin sulfate for the fabrication of ocular devices. Marchant, R. E. et al. (1990), “A hydrophilic plasma polymerized film composite with potential application as an interface for biomaterials,” J. Biomed. Materials Res. 24:1521-1537, discloses plasma deposition of a first layer polymerized from n-hexane and a second layer polymerized from N-vinyl-2-pyrrolidone to form a 420 nm thick composite film on a non-organic substrate providing a non-cytotoxic covering. Johnson, S. D. et al. (1992), “Biocompatibility studies in plasma polymerized interface materials encompassing both hydrophobic and hydrophilic surfaces,” J. Biomed. Materials Res. 26:915-935, discloses that thin plasma-deposited films (about 1 micrometer thick) made from N-vinyl-2-pyrrolidone, &ggr;-butyrolactone, hexamethyldisilazane and n-hexane on biomaterials provide good compatibility (reduced toxicity). Plastic and Reconstructive Surgery, December, 1987, 769-774, discloses the use of bioabsorbable Polyglactin 910 (Vicryl®) film implants for treatment of orbital wall wounds. The film was completely degraded within four months. The films were not seen to affect bone regrowth when compared to controls without the films, but were used to prevent herniation of orbital contents. The film was not used as a covering for another implant material to promote bone or muscle ingrowth. The film did not cause a long-standing inflammatory reaction as did a Dacron-reinforced silicone film to which it was compared. The Polyglactin 910 film used was 0.125 mm (125 micrometers) in thickness. Polyglactin 910 is a 10:90 PLA:PGA polymer film.
Use of a biodegradable polylactic acid (PLA) film 150 micrometers thick was reported in Levy, F. E., et al., “Effect of a Bioresorbable Film on Regeneration of Cranial Bone,” Plastic and Reconstructive Surgery, February, 1994, 307-311. After 24 weeks cranial defects covered with the film showed improved healing compared with untreated controls.
Gangadharam, P. R. J. et al. (1994), “Experimental chemotherapy of tuberculosis using single dose treatment with isoniazid in biodegradable polymers,” J. Antimicrobial Chemotherapy 33:265-271 discloses the use of a PLA:PGA film containing isoniazid to provide sustained release of the drug for up to four weeks. Details of the preparation of the polymeric film are provided in Gangadharam, P. R. J., et al. (1991), “Sustained release of isoniazid in vivo from a single implant of a biodegradable polymer,” Tubercle 72:115-122. The film was a 90% lactic/10% glycolic acid polymer having an average polymer molecular weight of 35,000 Daltons. Films containing the drug were prepared by dissolving the polymer in methyl chloride and passing the solution through an 0.8 mm Millipore filter. The drug was added to the solution and the solution was cast onto a clean glass surface as a thin film 0.6 mm in thickness, then air dried, followed by vacuum drying at 45° C.
Melalin, R. J. et al. (1990), “A Biomechanical Study of Tendon Adhesion Reduction Using a Biodegradable Barrier in a Rabbit Model,” J. Appl. Biomat. 1:13-39, disclosed the use of a knitted cellulose material to reduce adhesion formation.
Monsour, M. J. et al. (1987), “An Assessment of a Collagen/Vicryl Composite Membrane to Repair Defects of the Urinary Bladder in Rabbits,” Urological Res. 15:235-238, and Mohammed, R. et al. (1987), “The Use of a Biodegradable Collagen/Vicryl Composite Membrane to Repair Partial Nephrectomy in Rabbits”, Urological Res. 15:239-242, discloses a collagen-coated vicryl mesh to facilitate surgical healing. Andriano, K. P. et al. (1995), “Preliminary Effects of In vitro Lipid Exposure on Absorbable Poly(ortho ester) Films,” J. Appl. Biomat. 6:129-135, discloses poly(ortho ester) film degradation in vitro in cholesterol emulsions. Hanson, S. J. et al. (1988), “Mechanical Evaluation of Resorbable Copolymers for End Use as Vascular Grafts,” Trans. Am. Soc. Artif. Intern. Organs 34:789-793, discloses the use of PLA/&egr;-caprolactone materials as vascular graft materials.
None of the foregoing references disclose such films molded or shaped to surround implants made of other materials to improve the biocompatibility of such implants.
Schliephake, H. et al. (1994), “Enhancement of Bone Ingrowth into a Porous Hydroxylapatite-Matrix Using a Resorbable Polylactic Membrane,” J. Oral and Maxillofacial Surg. 52:57-63, discloses the use of a polylactic membrane (L/DL-Lactic Acid 70/30) to cover hydroxylapatite blocks placed in mandible and ilium defects. The membrane was nearly completely degraded after five months and the blocks covered with membrane showed more bony penetration of the HA matrix compared to blocks not covered by the membrane. The membrane had been replaced by a thin, fibrous scar. The degradation time was reported as being slow enough to prevent connective tissue cells from penetrating into the block pores so as to allow ingrowth of bone tissue from underlying host bone. The membrane was adapted to the block by a prefabricated, heated metal template which, the reference teaches, may be impossible in a situation where an individual contour is needed due to the rigidity of the polylactic material.
U.S. Pat. No. 5,584,880, issued Dec. 17, 1996 to Martinez for “Orbital Implant” discloses an orbital implant comprising hydroxylapatite granules which may be covered by a layer of synthetic material which is preferably a synthetic fabric made of a polymeric material.
None of the foregoing references disclose biodegradable films designed to fit individual contours of implants and to degrade within a short enough period, e.g., less than about four months, to promote rapid muscle and connective tissue attachment to the implant material.
It is therefore an object of this invention to provide biodegradable films which can be used to coat contoured implants, such as rounded hydroxylapatite implants used for orbital reconstruction, or to coat polymeric or other implants to provide improved, smooth articulating surfaces, to improve biocompatibility of the implants and to promote muscle and connective tissue attachment. It is also an object of this invention to provide biodegradable polymeric films designed to have different degradation rates at different locations in the film.
SUMMARY OF THE INVENTION
This invention provides a biodegradable, biocompatible polymeric film having a uniform selected thickness between about 60 micrometers and about 5 mm. Films of between about 600 micrometers and 1 mm and between about 1 mm and about 5 mm thick, as well as films between about 60 micrometers and about 1000 micrometers; and between about 60 and about 300 micrometers are useful in the manufacture of therapeutic implants for insertion into a patient's body. Films between about 60 and about 120 micrometers and between about 75 and about 125 micrometers are also useful in this invention.
The term “biodegradable” means capable of breaking down over time inside a patient's body. A number of suitable biodegradab
Kieswetter Kristine
Leatherbury Neil C.
Niederauer Gabriele
Slivka Michael A.
Greenlee Winner and Sullivan P.C.
Osteobiologics, Inc.
Prebilic Paul B.
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