Abstract
[Background]
Bipolar hemiarthroplasty (following BHA) have historically had poor results in patients with idiopathic osteonecrosis of femoral head (OFNH). However, most recent report have shown excellent results with new generation BHA designs that incorporate advances in bearing technology. These optimal outcomes with bipolar hemiarthroplasty will be more attractive procedure for young patients who need bone stock for future total arthroplasty. The purpose of the current study was to evaluate the clinical and radiographic finding of this procedure for the treatment of OFNH at our institution after 7-to 21years follow-up.
[Subjects and Methods]
We retrospectively reviewed a consecutive series of 29 patients (40 hips) who underwent primary bipolar hemiarthroplasty for ION (36 hips with stage III and 4 hips with stage IV) with a cementless femoral component between 1992 and 2006. Osteonecrosis was associated with corticosteroid use (23 patients), alcohol (16 patients), idiopathic (one patients). The mean follow-up duration was approximately 12 (range 7 to 21) years. Patients were evaluated according to the Japan Orthopaedic Association (JOA) hip score. We evaluate osteolysis and bone response of acetabulum or femur, and migration distance of outer head were calculated at the latest follow-up. Kaplan-Meier survivorship rate was investigated to examine implant failure rate.
[Results]
The average the Japan Orthopedic Association (JOA) hip score significantly improved from 53.9±16.0 points (preoperative) to 89.6±8.0 points (final follow-up). At the time of the final follow-up, one patients (one hips) had undergone revision to total hip arthroplasty because of groin pain without mechanical failure and migration. The rate of implant survival, with revision because of any reason as the end point, was 100% for femoral components and 97.5% for bipolar head components at a average 12 years (139.9±51.1 months) respectively. A complication that include dislocation and disassembly was not occurred in this study group. Radiographically, all cases is acquired bone ingrowth fixation. Stress shielding of femoral-component was observed 13 cases (32.5%). No femoral-component loosening and osteolysis of femur and acetabular was occurred at final follow-up. Bipolar head shift greater than 2mm is 3cases (7.5%) at final follow-up point, but progressive outer head migration was not occurred (0 %).
[Discussion]
Survivorship determined in our study was more favorable than that of previous studies. The our long-term postoperative clinical results of up to Stage3 without the acetabular cartilage surface damage showed more superior to those previously reported for BHA. Recently, larger oscillation angle, proximal porous coating, highly cross-linked PE liner, improved these BHA design concept. Thus, the current BHA can be one of reliable procedure. Based on our results, The BHA for stage III ION, with appropriate surgical indications, may be a good option.
