Abstract
Fracture of bone disrupts its circulation and leads to necrosis and hypoxia of adjacent bone. Under normal circumstances, fractured bone undergoes the orderly regeneration of its component tissues with complete restoration of mechanical properties. Reestablishment of the circulation is an early event in fracture healing. Several experimental models of protracted, impaired, or compromised healing have been developed to evaluate the effects of angiogenic factors in accelerating or enhancing repair.