Pulsed Electromagnetic Field (PEMF) in the Early Stage of Osteonecrosis of the Femoral Head (ONFH)
MC Yoo, YJ Cho, KI Kim, YS Chun, CJ Chung
Department of Orthopaedic Surgery, School of Medicine, Kyung Hee University, Seoul, Korea

Purpose: To report the result of prospective study conducted to evaluate the therapeutic value of PEMF in the treatment of the ONFH.

Materials and Methods: One hundred-eight consecutive hips (80 patients) treated with PEMF diagnosed as ONFH between June 1990 to June 1998 were analyzed. The average age was 36.8 years. The average follow-up period was 6.9 years. According to the ARCO stage, 3 hips were stage I, 85 hips stage II, 20 hips stage III. Hips were evaluated clinically with modified Harris hip scoring system and degree of hip pain relief, and radiographic progression was defined as either an advance in ARCO stage or progressive collapse more than 2 mm.

Results: Clinical improvement achieved 81 hips (75%). Especially, including these 81hips and even some progressed hips, hip pain was decreased or relieved after PEMF therapy. Hip pain has been relieved or decreased within average six months since PEMF has been started. Radiographic progression was seen in 35 hips (32.4%). THA had been performed in 20 hips (18.5%). Kaplan-Meier survivorship analysis demonstrated that the probability of conversion to THA within 5 years after PEMF was 16% in overall. Conversion to THA was significantly higher in patients who had the necrotic lesion laterally, in the subgroup C(more than 30% involvement of necrosis), and in patients older than mean age.

Conclusions: This results demonstrated that PEMF can modifiy the natural course of ONFH. PEMF is recommended in patients who are less than forty years old and early stage with small necrotic involvement. Refinement of PEMF could make it a more efficacious non-invasive method of treatment.