Osteonecrosis
Osteonecrosis (ON), also often termed avascular necrosis, is a disease that leads pathologically to dead bone. There are many direct and indirect causes of ON, which may be multifactorial and lead to joint destruction. ON of the femoral head, the most common location for this disease, is the focus of this chapter. In more than 10% of cases, symptomatic ON of the hip also involves the knee and shoulder. In approximately 3% of patients, more than three anatomic sites are involved. Between 10,000 and 20,000 patients are diagnosed with this disease each year, and approximately 10% of the hip replacements performed in the United States are related to ON. The disease usually occurs in the fourth decade of life, but the age range of patients is wide. Because of the relative youth of many patients with ON, joint replacements in many cases are unlikely to last the full life expectancy of the patient. Thus, much effort has been aimed at preserving the femoral head. © 2008 Springer-Verlag New York.
