NONTRAUMATIC AVASCULAR NECROSIS OF THE HI P IN THE ADULT .1. PATHOPHYSIOLOGY, CLINICAL ASPECTS AND TREATMENT OPTIONS

Intraosseous vascularization is the common pathway of the multifactori al causes of avascular necrosis of the hip (AVN). Recurring ischemic p hases could lead to bone necrosis in the initial stage of the disease, when it is still reversible. A spontaneous repair mechanism can lead to complete healing at this stage. The necrotic area demarcates the su peroranterior aspect from the residual femoral head with a reactive in terface in the irreversible early stage of the disease. In this stage damage to the femoral head can only be delayed with core decompression or femoral osteotomy, because a sufficient repair mechanism is no lon ger possible. When the articular surface collapses the early stage giv es way to the late stage. Cartilage incongruency and microfracture lea d to progressive destruction of the femoral head and to secondary oste oarthritis. In this late stage femoral osteotomy is only successful in carefully selected patients. Total hip replacement is the last resort for patients with painful destruction of the joint. As clinical sympt oms are unspecific, MRI plays an important role for early diagnosis of AVN in the initial or early stages. Conservative treatment is not suc essful in any of the three stages of the disease.