The epidemiology and outcomes of periprosthetic femur fractures: the Scottish National Audit of Periprosthetic Femur Fractures (SNAP Femur) study

Aims: Periprosthetic femur fracture (PFF) data capture in national registries is recognised to be limited. The aim of this study was to use hospital level data to establish patient characteristics, describe PFF management and mortality (including standardized mortality rate (SMR)), and compare outcomes to native hip fractures (NHF) using Scottish Hip Fracture Audit (SHFA) data.

Methods: A nationwide retrospective cohort study was conducted of all patients aged ≥ 50 years sustaining a PFF managed in 16 centres between 1 January and 31 December 2019. Data collected included patient demographic details, PFF, and management characteristics, along with outcomes including frailty and mortality. Comparison of PFF with NHF data was performed. Independent associations of PFF and mortality were evaluated with Cox regression survival analysis that were adjusted for confounders.

Results: There were 328 PFFs (mean age 79 years (SD 10), 66% female (n = 217)). Compared with NHF, PFF patients were less frail (median Clinical Frailty Scale (CFS) 4 (IQR 3 to 5) vs 5 (IQR to 7); p < 0.001) and more likely to be home-dwelling (91% vs 76%; p < 0.001). The majority of PFFs were related to arthroplasty implants (n = 307 (93.5%) to: 228 hip (70%) and 79 knee (24%)). There were 175 patients (53%) managed with fixation, 99 (30%) with revision arthroplasty, and 50 (15%) managed nonoperatively. The one-year mortality rate and SMR were 20.8% (95% CI 16.2 to 25.0) and 2.74 (95% CI 2.10 to 3.40) for PFFs compared with 29% (95%CI 28.0-30.0) and 3.66 (95% CI 3.6 to 3.8) in NHFs, respectively. Factors independently associated with increased mortality risk were interprosthetic fractures (adjusted hazard ratio (aHR) 2.65 (95% CI 1.41 to 5.00); p = 0.003), male sex (aHR 1.76 (95% CI 1.11 to 2.78); p = 0.015), older age (per year aHR 1.07 (95% CI 1.04 to 1.11); p < 0.001), and higher pre-injury frailty (CFS 5 to 9: aHR 4.16 (95% CI 1.18 to 14.7); p = 0.027). Time to theatre and management strategy were not independently associated with increased mortality.

Conclusion: PFFs are associated with an increased mortality risk, and result in functional decline. Coding limitations mean most PFFs are likely missed in arthroplasty registries, underestimating the true incidence. National registry integration and tailored multidisciplinary pathways, similar to those for NHF, are essential for improving outcomes and healthcare planning.