[Osteonecrosis: natural course and conservative therapy].

The natural course of Osteonecrosis (ON) of the femoral head has yet not been evaluated sufficiently. Especially in the early forms of the disease (ARCO 0 to II) without collapse of the femoral head, useful information on the natural course could only be collected since the routine use of MR-imaging. The unspecific findings in ARCO stage I with negative radiographs are potential reversible. The "point of no return" already lies in the irreversible ARCO stage II in almost all cases. Prognosis for further progression for both early stages depends primarily on the extension and location of the lesion. Only the rare, small to medium sized lesions in the medial or central location may have a good prognostic course over a period of more than five years. The much more common large sized and lateral located lesions will have a probability of about 80% to progress to femoral head collapse within two years. Conservative therapy with single protected weight bearing has shown bad results not significantly different from the natural course of the disease. Pulsed electromagnetic fields are still discussed controversially. Until now there is no MRI controlled study available in early ON, showing superior results compared to the easy and cost-effective core decompression therapy. The extra corporal shock wave therapy has shown spontaneous pain relief in early ON. Midterm results of this new therapeutical concept are not available yet. Hyperbaric oxygen therapy has shown to stimulate the repair process in an animal experiment. The preliminary clinical results of this time and cost consuming therapy are not convincing. Vasoactive drugs in combination with limited weight bearing may play a role in the conservative management of early ON (ARCO I and part of ARCO II) in the future. For the conservative therapy in ON several other substance are currently in clinical testing. The benefit of conservative therapeutical concepts in ON in the future can only be evaluated with prospective MRI controlled clinical studies. The use of cytokines in combination with surgical debridement and bone grafting of the necrotic area may be a possible therapeutical concept for the future.