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Quantitation of regional chondro-osseous circulation in canine tibia and femur.

Regional osseous blood flow (OBF) to various regions of the femur and tibia was measured using radioactively labeled 15-micrometers microspheres injected into the right atrium of neonatal, skeletally immature, and skeletally mature canines. Each bone was divided into as many as 41 anatomically distinct sections to assess developmental and regional comparisons in OBF. A quantitative decrease in OBF with increasing chondro-osseous maturity was observed for both the whole bones as well as many regions within a given bone. This was particularly significant in the tibia in which OBF to the mature tibia was much lower than in the immature tibia or even the mature femur. In the immature and neonatal bones, the epiphyseal and metaphyseal regions nearest the physes had the highest flow. The physis had a statistically significant high flow rate. Furthermore, regional differences in OBF correlated well with known regional functions in both endochondral and membranous (periosteal) bone formation. OBF tended to be greater in regions of greater metabolic activity associated with hematopoiesis and endochondral osteogenesis. OBF values correlated well with regional predilections of various diseases such as acute hematogenous osteomyelitis prior to skeletal maturity and osseous metastases, and, by extrapolation, strongly support a physiological reason for delayed healing and nonunion in tibial fractures in the skeletally mature human.