Hip and Femur Injuries

The major cause of hip dislocations is motor vehicle collisions. A great deal of force is required to dislocate a hip, and thus associated injuries are common. Up to 88% of hip dislocations will be accompanied by an associated fracture. Patients with hip dislocations have about a 25% risk for osteoarthritis and a 20% risk for avascular necrosis. In addition, sciatic nerve injuries occur in approximately 10% to 14% of patients with posterior hip dislocations. These risks may be decreased by prompt diagnosis and treatment in the emergency department (ED). Osteonecrosis (also known as aseptic necrosis, ischemic necrosis, or avascular necrosis) may be caused by acute disruption of the blood supply to the femoral head as a result of a hip fracture or dislocation. Fractures of the femoral neck can also disrupt the blood supply and result in osteonecrosis. Other causes are sickle cell disease, barotrauma, radiation therapy, chemotherapy, atherosclerosis, and Gaucher disease. Associated conditions include steroid use, excessive alcohol consumption, smoking, connective tissue diseases, pancreatitis, and chronic liver and renal diseases. The incidence of osteonecrosis after hip dislocation depends on the degree of trauma involved and the duration of the dislocation. Some data suggest that reduction of the hip within 6 hours after dislocation decreases the incidence of osteonecrosis. Therefore, every effort must be made to relocate dislocated hips as soon as possible. Femoral neck fractures are also associated with a high incidence of osteonecrosis. It is thought that the synovial fluid around the fracture site interferes with normal bone healing. Intertrochanteric fractures and other more distal fractures of the femur are rarely complicated by osteonecrosis.