A Long-Term Comparison of Periprosthetic Femoral Bone Mineral Density Between a Short and a Standard Stem Used in Total Hip Arthroplasty

Introduction and aim: Short femoral stems in total hip arthroplasty (THA) were developed to preserve proximal femoral bone stock by minimizing stress shielding. However, their long-term outcomes remain debated when compared to standard-length stems. We hypothesized that short stems would allow better preservation of proximal periprosthetic bone mineral density (BMD) compared to standard stems. The primary objective of this study was to evaluate long-term periprosthetic BMD in patients receiving either short or standard femoral stems, with the hypothesis that short stems would provide superior preservation of proximal bone. The secondary objective included the comparison of clinical and radiological outcomes. Methods: This single-center retrospective study included patients who underwent THA between 2010 and 2018 using either the Optimys short femoral stem (Bettlach, Switzerland: Mathys) or the standard-length twinSys stem (Bettlach, Switzerland: Mathys). Periprosthetic BMD was evaluated using dual-energy X-ray absorptiometry (DEXA) across six modified Gruen zones. Radiographs were evaluated by two reviewers and clinical outcomes were evaluated using the Harris Hip Score (HHS) and the presence or absence of thigh pain. Results: At a mean follow-up of 9.4 years, the analysis of 24 hips (10 short stems, 14 standard stems) revealed no significant differences in periprosthetic BMD. Clinical outcomes, including HHS (median {IQR}; standard: 95.8 {80.8-100.0}; short: 88.4 {80.0-93.0}) and thigh pain incidence, were comparable, and radiographic evaluation revealed no difference in stress shielding or osteolysis. Conclusions: Our findings suggest that, over the long term, both the Optimys and twinSys stems are subject to stress shielding. These results contrast with some prior studies and highlight the potential influence of stem design and follow-up duration on bone remodeling outcomes.