Vascular proliferation and blood supply during distraction osteogenesis: Ascanning electron microscopic observation

This scanning electron microscopic study examined the spatial and temporal features of proliferating vessels of regenerating bone tissue and blood sup ply during distraction osteogenesis. A rat model of tibial lengthening was used with a protocol divided into a latency period of 7 days, a distraction period that lasted 14 days with a daily distraction rate of 0.5 mm in two steps, and a consolidation period of 21 days. Vascular casting was done on the hindlimbs before osteotomy and on postoperative days 7, 14, 21, 28, and 42. Scanning electron microscopic findings were correlated with radiologic al and histological observations. On days 7 and 14, the proliferation of pe riosteal vessels was pronounced and there was distinct subperiosteal bone f ormation on the osteotomized surfaces. On day 21, vascular branches from th e medullary canal of the host bone formed a vascular network, which gave ri se to multiple axial, straight vascular branches, running parallel to the d irection of distraction, toward the interzone, in accordance with the progr ess of mineralization. On day 28, the periosteum provided vascularization t o the peripheral side of the interzone whereas the center of the interzone was still relatively avascular. On day 42, the periosteal and medullary vas cular channels were completely connected at the distraction site including the interzone, which was occupied by developing and mature bone trabeculae. These results suggest that vascular proliferation occurs actively during t he latency and distraction periods and then gradually decreases over time. A close temporal and spatial relationship exists between formation of regen erated bone and vascular proliferation of the periosteum and medullary cana l.