Comparison of bone healing by demineralized bone matrix and autogenous cancellous bone in horses

Objective-The purpose of this study was to compare bone healing induced by equine demineralized bone matrix (DBM) to autogenous cancellous bone graft (ACB) or no graft (control) in a rib-defect model in horses. Study Design-The osteogenic properties of ACB and DBM were evaluated in bil ateral 19-mm circular defects created in the outer cortex of the 6(th) and 8(th) ribs of each horse. Animals or Sample Population-Eight mature horses. Methods-Three rib defects in each horst were randomly treated with each of the 3 treatment groups, and the fourth rib defect received a random treatme nt. Rib sections, including the defects, were harvested 56 days after impla ntation and examined for bone mineral density, percent ash and calcium and graded for signs of radiographic and histological healing. Results-All ribs were fractured at the defect site and were classified as n onunion fractures 56 days after implantation. There were no significant dif ferences among groups in bone mineral density and signs of radiographic or histological healing. There was an increased volume of bone in control and ACE-treated sites compared with DBM-treated sites. Rib defects treated with ACB were significantly higher in percent ash and calcium than those treate d with DBM. DBM elicited no inflammatory reaction, and remodeling occurred around the periphery and within vascular channels of the decalcified partic les. Conclusion-DBM particles remodel from the periphery, which may explain the significantly lower percent ash, calcium, and bone when compared with ACB, because 2- to 4-mu L pieces of DBM may act as space-occupying masses until completely mineralized. There was no evidence of enhanced healing associate d with the use of DBM in this model. Clinical Relevance-Particles of 2 to 4 mm DBM should not be used as an aid to fracture repair because particles of this size interfere with normal min eralization. However, our model of nonunion fracture healing may be useful in future studies. (C) Copyright 2000 by The American College of Veterinary Surgeons.