Reaction of the circulatory system to injury and regeneration.

The anatomy of the bone blood supply is well known. Techniques to measure bone blood flow are available, but no accurate method is available for clinical use. Ion movement from the capillary to the matrix is by diffusion, and efflux appears to be controlled by a concentration-dependent binding mechanism in the extravascular space of bone. The resistance vessels of bone are regulated by local, neural, and humoral factors. Fractures of long bone provoke a decrease in blood flow followed by a large increase in blood flow driven by metabolic demand. Fractures heal by coordinated formation of new bone, which is a combination of interstitial and surface remodeling. Age affects bone remodeling. Fixation of an experimental fracture may modify blood flow as well as bone remodeling. Fluid fluxes in bone may produce streaming potentials that in turn stimulate the osteoblasts to form new bone.