2-Year Radiostereometric Analysis Evaluation of a Short, Proximally Coated, Triple-Taper Blade Femoral Stem Versus a Quadrangular-Taper Stem With Reinforced Proximal Body: A Randomized Controlled Trial.

BACKGROUND:Cementless stem designs with proximal metaphyseal fixation aim to achieve better load distribution, reduce stress shielding, and improve primary stability. The purpose of this prospective, randomized controlled trial was to evaluate the 2-year migration and clinical outcomes of two cementless femoral stems. METHODS:A total of 60 participants undergoing primary total hip arthroplasty for any cause were randomly allocated to receiving either a proximally coated, short blade stem or a quadrangular-taper stem with a reinforced proximal body. Radiostereometric analysis radiographs were performed postoperatively and at 6 weeks, 6 months, 1 year and 2 years. The Harris Hip Score, Oxford Hip Score and the EuroQol five-dimension were also collected. RESULTS:At two years, the median subsidence of the short-blade stem was 0.097 millimeters (mm) [Interquartile range (IQR) -0.67 to 0.08)] versus 0.086 mm(IQR, -0.29 to 0.005, P = .683); medial translation 0.023 mm (IQR 0.08 to 0.12) versus 0.029 mm(IQR -0.07 to 0.10, P = .907); anterior translation 0.035 mm (IQR -0.23 to 0.33) versus 0.07 mm (IQR -0.13 to 0.08, P = .268). At 24 months postoperatively, there were no stem revisions and Patient-Reported Outcome Measures (PROMs) were comparable between groups. CONCLUSION:Both cementless stems exhibited a predictable migration pattern and achieved initial stability. There was no difference in migration across the three Cartesian axes at any time point. Clinical outcomes and PROMs were also comparable. Biological fixation of both implants evidenced by the radiostereometric analysis and excellent PROMs are likely to translate to longer-term stability, which would need to be corroborated by longer-term outcome studies.