The effect of recombinant human bone morphogenetic protein-2 on femoral reconstruction with an intercalary allograft in a dog model

This study compared the effect of augumentation of allograft-host bone junc tions with recombinant human bone morphogenetic protein-2 (rhBMP-2) on an a bsorbable collagen sponge (ACS), autogenous cancellous bone graft (CBG), an d a collagen sponge alone in a canine intercalary femoral defect model repa ired with a frozen allograft. Outcome assessment included serial radiograph s, dual energy X-ray absorptiometry scans, and gait analyses, and mechanica l testing and histology of post-mortem specimens. The distal junction heale d more quickly and completely with rhBMP-2 than ACS alone based on qualitat ive radiography and histologic evaluations. The primary tissue in the unhea led gaps in the ACS group was fibrous connective tissue. The proximal allog raft-host bone junction had complete bone union in the three treatment grou ps. There was significantly greater neu bone callus formation at both junct ions with rhBMP-2 than with CBG or ACS alone that resulted in increased bon e density around the allograft-host bone junctions. All dogs shifted their weight from the treated leg to the contralateral pelvic limb immediately af ter surgery. Weight bearing forces were redistributed equally between the p elvic limbs at 12 weeks after surgery with rhBMP-2, at 16 weeks after surge ry with CBG, and at 24 weeks after surgery with ACS alone. Bending and comp ressive stiffnesses of the whole treated femora were equal to the contralat eral control femora in all treatment groups, whereas torsional rigidities o f the whole treated femora for the CBG and ACS groups were significantly le ss than the control. Both the proximal and distal junctions the treated wit h rhBMP-2 had torsional stiffnesses and strengths equal to intact control b ones, Ultimate failure torques of the proximal junctions of the CBG group a nd of both junctions of the ACS group were significantly less than the BMP- treated bones. Augmentation of the allograft-host bone junctions with rhBMP -2 on an ACS gave results for all parameters measured that equaled or excee ded autogenous graft in this canine intercalary femoral defect model. (C) 2 001 Orthopaedic Research Society, Published by Elsevier Science Ltd. All ri ghts reserved.