Resorption evaluation of a large bolus of calcium sulfate in a canine medullary defect.

New bone formation and resorption of a calcium sulfate bone graft substitute implanted in five canines were evaluated in this study. Healing was assessed radiographically at 2, 6, and 13 weeks. At 13 weeks, the dogs were sacrificed, and the humeri were retrieved. High-resolution contact radiographs of the isolated humeri were obtained and the bones were sectioned for histology. Radiographically, the calcium sulfate appeared to be completely resorbed and replaced by bone at 13 weeks. Histological findings suggest that a residual amount of calcium sulfate remained, which may continue to act as an osteoconductive scaffolding. No adverse inflammatory response was observed.