A murine model of distraction osteogenesis.

Distraction osteogenesis is both a valuable clinical technique and a useful tool for investigating the basic mechanisms involved in bone tissue regeneration. Here we describe the development of a murine model of this procedure that can be used in transgenic animals to investigate the role of specific genes in tissue regeneration. Ring fixators were applied to the lower leg of 12 normal adult male mice. An osteotomy was made in the diaphysis of the tibia, and 7 days after the operation the bone fragments were distracted by 0.25 mm twice a day for 10 days. Specimens were examined immediately at the end of distraction and after 14-70 days of consolidation. At the end of distraction, the distraction gap was filled with fibroblast-like cells arranged longitudinally. After 14 days of consolidation, there was radiographical evidence of bone formation in the distraction gap and, after 28 days of consolidation, the bone fragments were fused with regenerated bone. By 70 days of consolidation, the regenerated bone had been almost completely remodeled and the intramedullary canal reestablished. This study is the first to report consolidation of the distraction gap with regenerated bone in a murine model of distraction.