Bone Density and Architecture of Nonunion Fractures in Dogs Treated with Rigid Fixation, Compression Resistant Matrix, and Recombinant Human Bone Morphogenetic Protein-2. Castilla A, Filliquist B, Spriet M, Garcia-Nolen T, Arzi B, Kapatkin A. University of California, Davis, Veterinary Medical Teaching Hospital, Davis, CA.
Long-term outcomes assessing bone regeneration following use of bone morphogenetic protein (BMP) in dogs have not been evaluated. The objective was to assess bone density and architecture in defect nonunion distal appendicular long bone fractures treated with rigid fixation, compression resistant matrix (CRM), and recombinant human bone morphogenetic protein-2 (rhBMP-2). The hypothesis was that treated fractures would undergo restoration of bone architecture similar to control bone. Patients > one year posttreatment underwent examination and computed tomography of treated and contralateral limbs. Quantitative measurements from treated limbs were compared to contralateral limbs using ANOVA. Six patients met the inclusion criteria. All patients were weight bearing on the treated limb. All fractures were healed. BMP-treated bone exhibited higher density at the periphery and lower density in the center. The median cortical density was significantly lower and the median medullary density was significantly higher for BMP-treated bone compared to control bone. This study demonstrates that treatment of defect nonunion fractures using BMP can result in complete union and acceptable function. While BMP-treated bone underwent restoration of normal architecture, peripheral bone was less dense and central bone was more dense when compared to normal bone. This warrants investigation into the biomechanical properties between BMP-treated bone and normal bone. Limitations include small sample size and a heterogenous population of dogs. This study assessed bone density and architecture after use of rhBMP-2 and can serve as a basis for long-term outcome in dogs treated for defect nonunion fractures.