Studies of bone blood flow disturbances after fracture of the adult tibial diaphysis.

Union of fractures of the adult tibial shaft is often delayed after high energy accidents, and this may result from greater devascularisation of the bone in these injuries. The aim of this study was to develop a radioactive microsphere technique for the measurement of bone blood flow in the adult rabbit in order to investigate quantitatively the routes of bone blood supply after fracture and the effects of fracturing force on blood flow after blunt trauma. After demonstrating that two isotope labels could be reliably separated in the tissue samples, the optimum size of microsphere and the number of microspheres allowing two measurements of flow in each animal were tested. This technique was employed to show that unilateral immobilisation of the hindlimb in a cast did not result in any differences between the limbs in tibial flow after one or two weeks. After unilateral surgical osteotomies of the tibial diaphysis immobilised in a cast, cortical flow increased but that to the marrow did not, indicating that the flow response in the cortex is mediated by a supply parallel to that to the marrow. The cortical blood flow changes were abolished by the exclusion of the periosteum and soft tissue by a sheath, suggesting that this parallel supply is principally from these tissues. The cortical flow was not significantly reduced by one or two weeks after exclusion of the marrow circulation by an intramedullary nail. Fractures of the tibial shaft were produced by percussion. The blood flow changes after lower and higher energy injuries were not significantly different, and were similar to those found after a surgical osteotomy although at one week the marrow flow was depressed. No evidence was therefore found in this study that higher energy fractures produced by blunt trauma are associated with a depressed blood flow response.