Excellent midterm survival and functional outcomes of a fully hydroxyapatite-coated cementless stem: first results of a prospective multicenter study

Abstract Background The Polarstem (Smith & Nephew, Baar, Switzerland) is a tapered straight stem, an implant with an excellent survival rate. Although the most recent annual report of the National Joint Registry in the United Kingdom also reports excellent survivorship for the cementless Polarstem, no prospective studies have been published focusing on both its efficacy and clinical performance. Therefore, the present study was designed to prospectively evaluate its functional and radiographic outcomes at midterm. Methods This prospective observational study conducted at 3 independent orthopaedic hospitals was designed to collect data in patients undergoing cementless primary total hip arthroplasty (THA). A total of 225 total hip arthroplasties (75 at each site) were performed. The predominant diagnosis was primary osteoarthritis. Anteroposterior and lateral radiographs were obtained at each follow-up (3 months, and 1, 3, and 5 years). Survivorship and the Harris Hip Score (HHS) and Western Ontario and McMaster Universities Index (WOMAC) were calculated. Results Subjects experienced statistically significant improvements from baseline in mean HHS (48.5 to 88.0, P Conclusions A revision rate of the femoral stem for any reason of 0.4%, as well as good clinical results based on HHS and WOMAC scores, was noted at 5-year follow-up. Therefore, safety and efficacy of the cementless Polarstem at midterm follow-up is confirmed.