Recombinant human bone morphogenetic protein-2 in absorbable collagen sponge enhances bone healing of tibial osteotomies in dogs

Objective -- To compare the efficacy of 2 doses of recombinant human bone morphogenetic protein-2 (rhBMP-2) on tibial osteotomy healing in dogs. Study Design - Experimental, randomized complete block (n=7). Animals - Adult female dogs (n=21). Methods - Right midshaft tibial osteotomies were created and stabilized with a 1-mm gap using type I external fixators. Seven dogs were untreated controls and 14 with osteotomies were treated with either 0.05 or 0.2 mg/mL rhBMP-2 delivered in an absorbable collagen sponge (ACS). At 8 weeks, dogs were euthanatized and bones were mechanically tested and examined by microscopy. Results - Bone healing based on radiographic scoring, was significantly improved in dogs treated with 0.2 mg/mL of rhBMP-2 compared with the other groups; these tibiae were also significantly stronger and stiffer than 0.05 mg/mL rhBMP-2 and control osteotomized tibiae. Histologic scores were significantly better for 0.2 mg/mL rhBMP-2 group than 0.05 mg/mL rhBMP-2 group, but neither was significantly different from control. Conclusions - rhBMP-2 in ACS at a concentration of 0.2 mg/mL improves healing of tibial osteotomies in dogs compared with untreated controls and 0.05 mg/mL rhBMP-2 based on force plate analysis and radiographic evaluation. This was not confirmed histologically but treated bones had improved mechanical properties at 8 weeks. Clinical Relevance - After a long bone fracture, dogs may face a long recovery period before full return of limb function. rhBMP-2, in association with good fracture fixation principles, may enhance bone healing in dogs with diaphyseal fractures. (c) Copyright 2007 by The American College of Veterinary Surgeons.