PULSED ELECTROMAGNETIC FIELDS TREATMENT FOR THE EARLY STAGES OF OSTEONECROSIS OF THE FEMORAL HEAD

Abstract

Introduction: The purpose of this prospective study was to evaluate the therapeutic value of Pulsed Electromagnetic Fields (PEMF) in the treatment of the osteonecrosis of the femoral head (ONFH).

Materials and Methods: One hundred-eight consecutive hips with ONFH (80 patients) treated with PEMF between June 1990 and June 1998 were analyzed. The average age was 37 years. The average follow-up period was 6.9 years. According to the ARCO staging system, 3 hips were stage I, 85 hips stage II, and 20 hips stage III. Hips were evaluated clinically with a modified Harris hip scoring system and degree of pain relief. Radiographic progression was defined as either an advance in ARCO stage or progressive collapse of the femoral head more than 2 mm.

Results: Clinical improvement was achieved in 81 hips (75%). Hip pain was relieved or decreased at an average of six months following initiation of PEMF therapy in the 81 hips with clinical improvement as well as some radiographically progressed hips. Radiographic progression was seen in 35 hips (32.4%). Total hip arthroplasty (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% 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 the mean age.

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