RADIOMORPHOMETRY AND BIOMECHANICAL ASSESSMENT OF RECOMBINANT HUMAN BONE MORPHOGENETIC PROTEIN-2 AND POLYMER IN RABBIT RADIUS OSTECTOMY MODEL

The study objective was to determine the mechanical integrity and radi opacity of regenerated bone within critical-sized defects (CSDs) in ra dii of rabbits using recombinant human bone morphogenetic protein 2 (r hBMP-2) with a porous, biodegradable poly(D,L-lactic acid) (PDLLA) car rier (designated PLA). Twenty millimeter, unilateral radial ostectomie s were created in 96 skeletally mature New Zealand white rabbits. The rabbits were randomly assigned to six treatment groups with two euthan asia periods. Treatment groups included unfilled defect (n = 8), segme ntal autograft (n = 8), PLA + 0 mu g rhBMP-2 (n = 8), PLA + 17 mu g rh BMP-2 (n = 8), PLA + 35 mu g rhBMP-2 (n = 8), and PLA + 70 mu g rhBMP- 2 (n = 8). The radiopacity was significantly greater for the 35- and 7 0-mu g rhBMP-2 groups at 4 weeks compared to unfilled controls, PLA on ly, and 17-mu g rhBMP-2 groups and equivalent to the autograft. At 8 w eeks all groups receiving rhBMP-2 were equivalent to the autograft and significantly greater than unfilled defects and PLA alone. Similarly, the biomechanical analysis indicated significantly greater torque at failure for the 35-mu g rhBMP-2 group compared to all other groups at 4 weeks. By 8 weeks all groups receiving rhBMP-2 and autograft had sig nificantly greater torque than unfilled controls and PLA alone. These radiomorphometric and biomechanical results indicate PLA may be a suit able carrier for rhBMP-2 used for skeletal regeneration. (C) 1998 John Wiley & Sons, Inc.