Teruhiko Kawakami

Safe zone for the superior gluteal nerve in the transgluteal approach to the dysplastic hip: Intraoperative evaluation using a nerve stimulator

Background The superior gluteal nerve can be damaged during the transgluteal approach to the hip in total hip arthroplasty. Methods We studied 30 patients with hip dysplasia who underwent total hip arthroplasty through the transgluteal approach. The course of the inferior branch of the superior gluteal nerve was identified using a nerve stimulator. The distance between the nerve and the tip of the greater trochanter was measured. Results The mean distance was 37 (25–45) mm at the anterior third, 40 (30–50) mm at the middle third, and 44 (35–55) mm at the posterior third of the gluteus medius. The distance was influenced by the severity of hip dysplasia and decreased as the degree of hip dysplasia became more severe. Interpretation A 3-cm safe zone is appropriate in most dysplastic hips. In severely dysplastic hips, however, the superior gluteal nerve occasionally coursed within 3 cm of the tip of the greater trochanter. In such hips, a nerve stimulator can be used to identify the nerve.

Use of vascularized pedicle iliac bone graft in the treatment of avascular necrosis of the femoral head

Abstract A vascularized pedicle iliac bone graft was performed in patients with extensive necrosis in whom the necrotic area occupied more than two-thirds of the femoral head. The purpose of this procedure is to supply vascularity and mechanical strength to the avascular femoral head. Our series consisted of 18 hips. The patients’ age at surgery ranged from 21 to 55 years. Fourteen hips were identified as stage II and 4 hips as stage III. Iliac bone graft alone was performed in 4 stage II joints. Transtrochanteric anterior rotational osteotomy of the femoral head was done additionally in 10 stage II joints and 4 stage III joints. In the group who underwent iliac bone graft alone, the mean Japanese Orthopedic Association (JOA) score improved from 58.5 to 63.8 (mean follow-up 52 months). In the group who underwent combination procedure with osteotomy, the mean JOA score improved from 71.7 to 85.0 (mean follow-up 43 months). Stage progression was noted in 3 of 4 joints in the group who underwent iliac bone graft alone. In the group who underwent the combined procedure, stage progression was noted in 2 of 10 joints at more than 1 year after operation. A vascularized pedicle iliac bone graft to treat avascular necrosis of the femoral head is considered promising for joint preservation.

Chronological changes in functional cup position at 10 years after total hip arthroplasty

Purpose This study aims to clarify the chronological changes in functional cup position at a minimum follow-up of 10 years after total hip arthroplasty (THA), and to identify the risk factors influencing a significant difference in functional cup position during the postoperative follow-up period. Methods We evaluated the chronological changes in functional cup position at a minimum follow-up of 10 years after THA in 58 patients with unilateral hip osteoarthritis. Radiographic cup position was measured on anteroposterior pelvic radiographs with the patient in the supine position, whereas functional cup position was recorded in the standing position. Radiographs were obtained before, 3 weeks after, and every 1 year after surgery. Results Functional cup anteversion (F-Ant) increased over time, and was found to have significantly increased at final follow-up compared to that at 3 weeks after surgery (p<0.01). The maximum postoperative change in F-Ant was 17.0° anteriorly; 12 cases (21%) showed a postoperative change in F-Ant by >10° anteriorly. Preoperative posterior pelvic tilt in the standing position and vertebral fractures after THA were significant predictors of increasing functional cup anteversion. Conclusions Although chronological changes in functional cup position do occur after THA, their magnitude is relatively low. However, posterior impingement is likely to occur, which may cause edge loading, wear of the polyethylene liner, and anterior dislocation of the hip. We believe that, for the combined anteversion technique, the safe zone should probably be 5°-10° narrower in patients predicted to show considerable changes in functional cup position compared with standard cases.