Abstract
This report was based on our clinical results of treatment of 23 hips in 16 patients (9 male with 15 hips and 7 female with 8 hips) with atraumatic osteonecrosis of the femoral head (ONFH), that were treated with bipolar hemiarthroplasty from 1985 to 1998. The average age at operation was 53 years old (23-72), and the mean follow-up interval was 62.7 months (15-145). The cases included 5 idiopathic, 9 steroid-induced and 9 alcohol-induced necrosis. According to the Japanese Ministry of Health staging of ONFH, two hips were stage 2, seventeen were stage 3, and four were stage 4. The mean Japanese Orthopaedic Association (JOA) score at preoperation was 52.0 points (24-79) (pain 14.1, ROM 17.3, gait 9.1 and ADL 11.5), and at the final follow up was 91.4 points (40-100) (pain 37.0, ROM 18.2, gait 17.9 and ADL 18.3). The distance of migration of the femoral head correlated negatively with the JOA score, but the distance of sinking of the stem correlated with the JOA score (p<0.001). Stem sinking was observed in 4 hips, and the worst JOA score was associated with 8.5mm stem sinking. Careful follow-up to monitor sinking of the stem should be continued for the ONFH patients treated with bipolar hemiarthroplasty.
