[MRI-controlled outcome after core decompression of the femur head in aseptic osteonecrosis and transient bone marrow edema].

PURPOSE

We evaluated the signal changes of avascular necrosis and transient bone marrow oedema before and after core decompression of the femoral head to deduce prognostic factors for this operative procedure.

METHOD

38 to 40 cases with core decompression (35 patients, medium age 44 years) were analysed with a mean follow-up time of 26 months. Preoperatively patients were staged by the ARCO classification. MR-images were judged in accordance to the criteria of Mitchell and Steinberg. The clinical outcome was analysed according to the hip index of Merle D'Aubigne.

RESULTS

All hips with transient bone marrow oedema showed normal signal patterns at an average of 3 months after core decompression. In stage I and II, all patients with a preoperative necrosis area less than 30% of the femoral head showed a reduction of the necrotic zone and good clinical results. An unchanged or progressive appearance was observed in necrotic lesions with more than 30% head involvement. Because of failure a renewed operation had to be done in all patients with stage III and IV.

CONCLUSION

In the case of transient bone marrow oedema, a restitutio ad integrum can be achieved with core decompression. In stage I and II of avascular necrosis, the successful outcome depends on the lesion size of the femoral head. Necrotic lesions less than 30% seem to have the best prognosis. In stage III and IV, core decompression cannot be recommended.