[Osteonecrosis of the femoral head]

Avascular necrosis (AVN) most commonly affects the femoral head, but not exclusively. Besides post-traumatic avascular necrosis of the femoral head, other sites should also be screened, especially the other hip, the shoulders and the knees. AVN of the femoral head should systematically be considered in anyone suffering from hip pain with normal X-ray. The most useful complementary examinations are standard X-ray examination, to assess the stage of disease progression, and MRI, to establish the diagnosis when X-ray shows no abnormality and assess the prognosis. The spontaneous progression mainly depends on the lesion size and the amount of affected weight-bearing surface. Differentiating AVN from algodystrophy and especially stress fracture of the femoral head may be difficult, even with MRI. An etiology may be found in approximately _ of the cases. Medical treatment still exclusively addresses symptoms. Surgical treatment essentially consists of core decompression of the femoral head, the efficiency of which is still debated, and total hip arthroplasty, but new therapeutic options are likely to be developed. Above all, indications depend on the age, the stage of disease progression (prior to or following the subchondral fracture) and prognosis (lesion size and site on the MRI).