Method for treating bioabsorbable implant material

#1. Field of the Invention

#The present invention concerns a porous implant material for inducing the growth of bone or other hard tissue into the pores of the implant material, and relates also to a method for producing such material.

#2. Background of the Related Art

#FIGS. 1 and 2 are diagrammatic views illustrating the spray coating method of the present invention in a non-fluidized bed and fluidized bed, respectively.

#The present invention provides for the coating of bioabsorbable (i.e. resorbable) beads or particles for use as implantable packing material to replace, repair, or reconstruct hard tissue in the body of a patient. The particles employed in the present invention are preferably substantially spherical in shape and are prepared from a bioabsorbable material such as homopolymers and copolymers of, for example, glycolide, lactide, caprolactone, trimethylene carbonate, and dioxanone. Polymers of this type are known in the art, principally as materials for the fabrication of such surgical devices as sutures, wound clips, and the like, as disclosed, e.g., in U.S. Pat. Nos. 2,668,162; 2,703,316; 2,758,987, 3,225,766; 3,297,033; 3,422,181; 3,531,561; 3,565,077; 3,565,869; 3,620,218; 3,626,948; 3,636,956; 3,736,646; 3,772,420; 3,773,919; 3,792,010; 3,797,499; 3,839,297; 3,867,190; 3,878,284; 3,982,543; 4,047,533; 4,060,089; 4,137,921; 4,157,437; 4,234,775; 4,237,920; 4,300,565; and, 4,523,591; U.K. Patent No. 779,291; D. K. Gliding et al, "Biodegradable polymers for use in surgery--polyglycolic/poly (lactic acid) homo- and co-polymers: 1", Polymer, Volume 20, pages 1459-1464 (1979) and D. F. Williams (ed.) Biocompatibility of Clinical Implant Materials, Vol. II, Ch. 9: "Biodegradable Polymers" (1981). Co-polymers of glycolide and lactide with or without additional monomers are preferred, and of these glycolide-lactide co-polymers are most preferred.

#These particles can be prepared by a rotary atomization process, a description of which may be found in U.S. Pat. No. 5,143,662 filed Feb. 12, 1991 and herein incorporated by reference in its entirety. The particles can also be prepared by the methods disclosed in U.S. Pat. No. 5,102,783 and Ser. No. 618,652 filed on Apr. 2, 1990 and Nov. 27, 1990, respectively, both of which are herein incorporated by reference.

#The particles of bioabsorbable implant material are coated with a tissue ingrowth promoter. When applied to the body as a porous mass of particles, the bioabsorbable implant material provides interstitial space for the body tissue to enter by ingrowth. Tissue ingrowth promoters render the interstitial space conducive to the ingrowth therein of body tissue by providing chemically and/or physically improved surface characteristics in the interior of the porous mass of particles. For example, a hydrophilic coating of the particles facilitates adequate penetration of the interstitial space with body fluids. A coating of calcium containing material stimulates the ingrowth of bone and/or hard tissue. Calcium hydroxide powder is preferred as a bone/hard tissue ingrowth promoter although other calcium containing compounds may be used such as hydroxyapatite.