Osteonecrosis of the Femoral Head in Adults

Hospital Physician February 2008 13 O steonecrosis of the femoral head (ONFH) is a potentially debilitating condition of unclear etiology that affects up to 20,000 persons in the United States each year.1 ONFH in adults can be devastating as it typically occurs in a relatively young population (age, 35–40 yr). The disease is usually progressive,2 and without treatment, ONFH frequently results in loss of the joint space, secondary osteoarthritis, and destruction of the hip joint. ONFH accounts for approximately 10% of the primary total hip arthroplasties performed in the United States.3,4 The pathogenesis of ONFH remains unclear, but this disorder is considered a final common pathway for many diseases that lead to altered blood supply to the femoral head and cell death within the femoral head. Histologically, ONFH is characterized by dead osteocytes, necrotic marrow elements, and lack of vasculature in a defined region in the femoral head; in most cases, these changes lead to subsequent collapse of the subchondral bone. ONFH commonly occurs after direct trauma, such as hip dislocation or femoral neck fracture. The etiology of atraumatic ONFH is not well understood, and often one or more risk factors are involved, such as corticosteroid use and alcoholism. Multiple therapeutic options are available for ONFH. Although surgical and nonsurgical interventions have been advocated, a universal algorithm has yet to be adopted in ONFH treatment.5 Both the appropriate course of treatment and its degree of success are thought to be dictated by the etiology and severity of the disease. Most experts believe that early diagnosis is vital if the patient is to benefit from conservative treatment.6–8 Given the importance of early diagnosis and prompt management, clinicians should know the causes, risk factors, clinical presentation, and diagnostic work-up of ONFH in adults and be familiar with currently accepted treatment.