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Mid-Term Outcome of a Modular, Cementless, Proximally Hydroxyapatite-Coated, Anatomic Femoral Stem

Purpose. To report the mid-term outcome of a modular, cementless, proximally hydroxyapatite-coated, anatomic femoral stem in total hip arthroplasty (THA). Methods. 160 consecutive patients aged 42 to 92 (mean, 70) years underwent 185 cementless THAs for primary osteoarthritis or femoral neck fractures. All procedures were performed by a single surgeon using the same modular, cementless, proximally hydroxyapatite-coated, anatomic femoral stem, regardless of age and bone quality. Clinical evaluation (pain, range of movement, and ability to walk) was based on the Merle d'Aubigne and Postel scores. Radiological assessment was based on criteria by Engh et al. in the 7 Gruen zones with regard to the presence of radiolucent lines, osteolysis, cancellous condensation, cortical hypertrophy or atrophy, reactive lines, and pedestal formation. Failure of the stem was defined as revision or impending revision because of aseptic loosening or pain. Results. Of the 160 patients, 21 died and none were lost to follow-up. In 3 of the 21 patients, the femoral stems were revised for periprosthetic fractures after a fall at 6 weeks, 10 months, and 3.8 years. 138 patients (162 THAs) completed a mean follow-up of 7.8 (range, 5.5–10.4) years. Their overall mean Merle d'Aubigne and Postel scores increased from 7.09 preoperatively to 16.36 postoperatively. The mean Engh score was 24.9 out of 27, with the mean score for femoral stem fixation 10 out of 10 and 14.9 out of 17 for femoral stem stability. No reactive lines at the bone-stem interfaces and no subsidence or osteolysis were evident in any of the radiographs. There were 5 periprosthetic femoral fractures, 2 deep infections, 3 dislocations, and 2 aseptic loosening (one each for the femoral stem and acetabular socket). Survivorship of the femoral stem at 10 years was 99% when revision secondary to only aseptic loosening of the stem was the endpoint. It was 96% when failures due to all causes (infection, periprosthetic fracture, and aseptic loosening) were the endpoints. Conclusion. The MBA femoral prosthesis provides a predictably stable fixation, with excellent mid-term outcome.