Background: Periprosthetic femur fractures are a known complication after hip hemiarthroplasty (HA) in geriatric patients. The relationship between femoral stem design and fracture risk remains unclear. This study aimed to assess (1) the association between stem geometry and fixation on periprosthetic femur fracture risk and (2) the effect of a femoral stem collar. Methods: The American Joint Replacement Registry data were analyzed for HA cases in patients aged 70+ years from 2012 to 2021. We identified 56,828 primary HAs for the diagnosis of femoral neck fracture. Patient demographics and revision surgery for periprosthetic femur fracture in the form of open reduction with internal fixation or revision arthroplasty were documented. Stems were categorized into tapered wedge or fit and fill, and cemented stems were categorized into composite beam or taper slip. Cox models and Benjamini-Hochberg adjustments were used for statistical analysis. Results: Cemented composite beam stems accounted for 38% of implants, followed by fit-and-fill stems at 32%, tapered wedge stems at 29%, and cemented taper slip stems at 1%. A collar was present in all cemented composite beam stems, 23% of tapered wedge stems, and 20% of fit-and-fill stems. After applying inverse probability weighting adjustment, cemented composite beam stems showed a markedly lower periprosthetic femur fracture risk over other stems. Compared with cemented composite beam stems, collarless tapered wedge demonstrated a markedly higher hazard ratio (HR) (3.63; P < 0.001), as did both collarless (HR, 3.4; P < 0.001) and collared fit-and-fill stems (HR, 3.45; P < 0.001). The presence of a collar reduced periprosthetic femur fracture risk across all designs, with the most pronounced reduction seen in tapered wedge stems (0.90% versus 0.41%). Conclusion: For HA in patients aged 70 years and older, cemented composite beam stems with a collar were associated with the lowest risk of periprosthetic femur fractures in the American Joint Replacement Registry database. However, these findings reflect implant utilization patterns up to 2021 and may not fully account for the recent rise in triple taper collared stem use. Surgeons should consider these implants when selecting fixation strategies for HA. Level of Evidence: Level III
DeRogatis et al. (Wed,) studied this question.