Impact of Stem Design on Periprosthetic Femoral Fracture Risk: Findings from 182,118 Primary Total Hip Arthroplasties in the Swiss National Joint Registry.

Abstract

Periprosthetic femoral fractures (PFFs) are an increasingly common indication for revision total hip arthroplasty (THA). While patient-related risk factors are well documented, the influence of femoral stem design on PFF risk remains poorly characterized. In this study using nationwide data, we assessed the association between stem design and PFF risk. We analyzed 182,118 primary THAs (performed from 2015 to 2023) from the Swiss National Joint Registry (SIRIS). Cementless stems were categorized according to the Kheir classification, and cemented stems were categorized as double-tapered polished, triple-tapered polished, composite-beam, or custom. A multivariable Cox regression model, including variables such as age, sex, American Society of Anesthesiologists (ASA) class, body mass index (BMI), surgical indication, prior ipsilateral hip surgery, stem design, collar, dual-mobility cup, bearing, and head size, was analyzed. Hazard ratios (HRs) with 95% confidence intervals (CIs) are reported. Among 182,118 THAs (mean patient age, 68.9 ± 11.5 years; female sex in 53.1% of cases), 1,226 (0.7%) were complicated by PFF. The cumulative incidence of PFF reached 0.7% at 5 years and 1.3% at 10 years. Higher PFF risk was associated with an age of 75 to 84 years (HR = 1.68 [95% CI = 1.44 to 1.96]) and ≥85 years (HR = 1.86 [95% CI = 1.47 to 2.35]), ASA class of 3 to 5 (females, HR = 1.70; males, HR = 1.73), BMI of <18.5 kg/m2 (HR = 1.61) or ≥40 kg/m2 (HR = 1.64), prior ipsilateral hip surgery (HR = 1.32), and use of a dual-mobility cup (HR = 1.56). Elective procedures (HR = 0.36) and collared stems (HR = 0.26) were associated with a lower risk. Compared with cementless type-3 stems, cementless type-7 (anatomic) stems showed a higher risk of PFF (HR = 1.88), whereas cementless type-1B (HR = 0.62) and composite-beam cemented stems (HR = 0.45) were protective. In this large nationwide registry study, femoral stem design independently influenced PFF risk after primary THA. Cementless anatomic stems increased the risk, whereas composite-beam cemented stems and the presence of a collar conferred a protective effect. These findings support personalized implant selection, particularly for older patients or those with frailty. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.