[Transient osteoporosis and osteonecrosis of the femoral head. Risk factors, classification and differential diagnosis].

Osteonecrosis of the femoral head usually affects patients in their third to fifth decade of life. Common risk factors are alcohol, nicotine, corticosteroids, hyperlipidaemia and hypercoagulability. Depending on the stage of the osteonecrosis, the diagnosis is confirmed by radiographs, magnetic resonance imaging or scintigraphy. The ARCO classification (Association Research Circulation Osseous), which is based on older classifications recommended by Ficat/Arlet, Steinberg, Koo or Marcus/Enneking, is a valuable prognostic tool for finding an adequate treatment option. Transient osteoporosis of the hip is controversially discussed as a pre-stage of osteonecrosis or a self-limiting condition based on reflex dystrophy. Conservative and operative treatment options are reported in the literature. Recently published data favour core decompression as an effective procedure for early stage osteonecrosis and transient osteoporosis.