The relationship of bone blood flow, bone tracer deposition, and endosteal new bone formation.

Bilateral defects of 4.5 by 11 mm were made in the distal one-third of the tibias of eight dogs and unilaterally in four dogs. Bone blood flow was measured by I-Ap washout, tracer deposition of 85Sr was determined, and extraction of 85Sr and [14C]sucrose was measured by the indicator-dilution technique. Endosteal new bone formation was determined by a combined tetracycline-microradiography method. There was a significant correlation between blood flow determined by washout (I-Ap determined over the area of healing bone) and endosteal new bone formation, p < 0.001, expressed as relationships (percent) of the area of new endosteal bone to the total area enclosed by the defect and the medullary cavity of the tibia, p < 0.001. This percentage ranged from 12% to 62% and was directly related to bone blood flow. This suggests that the increase in blood flow in new bone may be secondary to increased metabolic demands.