[Treatment of idiopathic femur head necrosis with an appropriate cup with cylindrical support].

The objective of treatment of necrosis of the femoral head by means of an appropriate cup is to protect the sequestrum and to avoid secondary arthrosis. Hemispherical cups have a tendency to be easily deformed; cups with cylindrical support should be used in preference as they are mechanically stable and make it possible to cover the femoral head in cases of relatively extensive necrosis. Good results are obtained quickly and are often spectacular : in 90 percent of the cases operated on, pain disappeared or was reduced and normal socio-professional activity was again possible. A clinical and radiological study of 30 hips treated at least 2 years previously, established that the result was stable in the majority of cases : there was one real clinical and radiological deterioration, two cases of pinching of the interspace. This operation is thus worth while in all cases of necrosis, at the stage when the sequestrum is clearly delimited and when there is clear deformation of the contour of the femoral head. It also seems to be worth while at the "eggshell" stage, when the lesions detected at the time of an operation are aften considerable and appear non-reversible : the quality of the results obtained mean that the criteria of tolerance should be much more severe.