Bone regeneration in long-bone defects: tissue compartmentalisation? In vivo study on bone defects in sheep

Regeneration of living tissue varies with species, age and type of tissue, and undoubtedly with the biological and mechanical environment of the precise tissue. Autologous cancellous bone grafting is a well-known technique that provides bony regeneration. We investigated the efficiency of autologous bone grafting in a well-vascularised muscle environment, and additionally when isolated from the muscle and connected only to the bony environment. We designed a reproducible animal model producing a stable 3 cm middiaphyseal bone and periosteal defect on sheep femurs and created a foreign-body membrane with a temporary poly-methylmethacrylate spacer. The foreign-body membrane had the outer dimension of the removed bone segment. We then ascertained the bony regeneration potential within the bone defect using autologous cancellous bone graft. Regeneration of bone is enhanced considerably by an autologous foreign-body membrane that separates the interfragmentary space from the muscular environment. This effect is independent of the autologous bone graft. The results suggest that bone behaves like a compartment that protects its specific humoral or its cellular environment, or both. Regeneration of bone can be enhanced by compartmentalisation of the bone defect.