Extracorporeal shock wave therapy in early osteonecrosis of the femoral head: prospective clinical study with long-term follow-up.

INTRODUCTION: Extracorporeal shock wave therapy (ESWT) may exert beneficial effects in avascular necrosis of femoral head (AVNFH). PATIENTS: The current study evaluated the effectiveness of ESWT in reducing pain and in slowing down the progression of bone damage in 36 patients with unilateral AVNFH of stage Association Research Circulation Osseous (ARCO) I, II and III. At the beginning of the study, 10 hips were classified as stage I, 11 as stage II and 15 as stage III. Each treatment cycle included four sessions, with 2,400 impulses each administered at 0.50 mJ/mm(2), at 48-72 h intervals. Follow-up examinations were scheduled at 3, 6, 12 and then 24 months. METHOD: Clinical assessments included assessment of pain scores, Harris Hip Scores and Roles and Maudsley score. Plain radiographs and magnetic resonances of the hip were used to evaluate the size of the lesion, the extent of collapse of subchondral bone, and degenerative changes of the hip joint. RESULTS: Patients from ARCO stage I group and stage II group achieved significantly better results than patients from ARCO stage III group at all follow-up time points (p < 0.005). During the follow-up period, 10 of the 15 stage III ARCO patients received an arthroplasty. ARCO stages I and II lesions were unchanged on radiographs and on magnetic resonance images. CONCLUSION: ESWT in ARCO stages I and II may help to prevent progression of the area of avascular necrosis and manage pain.