Temporal and spatial increases in blood flow during distraction osteogenesis.

Ten adult mongrel dogs underwent left tibial lengthening at the proximal metaphysis. They were divided into three groups on the basis of distraction period: 14, 28, and 56 days. Quantitative technetium scintigraphy was used to measure regional blood flow within the tibiae during distraction, and periodically during consolidation, up to 17 weeks after operation. Blood flow was measured from regions of interest during the flow phase of the scan and expressed as a ratio of lengthened side to control side. At the distraction site, the flow increased to nearly ten times control, peaked at two weeks postoperatively, then decreased to four to five times the control for the remainder of the distraction period. During the consolidation period, significantly increased flow persisted at levels of two to three times control. The distal tibiae, away from the distraction gap, showed similar amplitude and temporal patterns of increased flow. No significant differences were found between the groups tested or when compared with similar fracture models. These findings lend credence to Ilizarov's hypothesis that distraction osteogenesis may contribute to healing of chronic osteomyelitis or hypovascular nonunions at distant sites by inducing a prolonged hypervascular state. Whether distraction osteogenesis transforms the normal reparative response of bone injury to a regenerative response remains conjectural.