Result of Modular Necks in Primary Total Hip Arthroplasty with a Average Follow-up of Four Years

PURPOSE This study aimed to investigate the outcomes of modular neck-utilization in primary total hip arthroplasty (THA). MATERIALS AND METHODS Thirty patients (34 hips) who had modular stem THA between April 2011 and January 2013 were evaluated. There were 19 men and 11 women with a mean age of 61.2 years at the time of surgery. There were 20 cases of osteonecrosis of femoral head, 7 cases of osteoarthritis, 6 cases of femur neck fracture, and 1 case of rheumatoid arthritis. No patients presented with anatomical deformity of hip. Patients were operated on using a modified Watson-Jones anterolateral approach. All patients underwent clinical and radiological follow-up at 6 weeks, 3, 6, and 12 months, and every year postoperatively. The mean duration of follow-up was 48.2 months (range, 39 to 59 months). RESULTS The average Harris hip score improved from 63.7 to 88.1 at the final follow-up. Radiographically, mean acetabular cup inclination was 45.3°(range, 36°-61°) and anteversion was 21.7°(range, 11°-29°). All were neutral-positioned stems except 5 which were varus-positioned stems. In only 3 cases (8.8%), varus or valgus necks were required. A case of linear femoral fracture occurred intraoperatively and 1 case of dislocation occurred at postoperative 2 weeks. No complications at modular junction were occurred. CONCLUSION Our study shows that the use of modular necks had favorable clinical and radiographic results. This suggests that the use of modular neck in primary THA without anatomical deformity is safe at a follow-up of 39 months.