Differences Between Atypical and Typical Subtrochanteric Fractures Due to Low-Energy Trauma

Subtrochanteric femur fractures caused by low-energy trauma are increasingly prevalent in aging populations. These fractures are categorized as atypical subtrochanteric fractures (ASF), often linked to antiresorptive therapy, or typical subtrochanteric fractures (TSF). This study aimed to compare the characteristics, surgical approaches, and clinical outcomes of ASF and TSF.

We conducted a retrospective cohort study at three hospitals in Japan, including 49 adult patients treated with cephalomedullary nails for low-energy subtrochanteric femur fractures between February 2007 and April 2024. Fractures were classified as ASF or TSF based on the American Society for Bone and Mineral Research (ASBMR) criteria. Patient demographics, surgical methods, and outcomes such as bone healing time and nonunion rate were evaluated and statistically compared.

Among the 49 patients, 23 had ASF and 26 had TSF. The ASF group was significantly younger (69.0 ± 9.8 vs. 84.0 ± 7.3 years, p < 0.01) and had a higher prevalence of antiresorptive therapy (91.3% vs. 11.5%, p < 0.01). ASF patients more frequently underwent auxiliary plating (34.8% vs. 0%, p < 0.01) and received postoperative teriparatide. Despite these interventions, the ASF group exhibited significantly delayed healing (9.0 ± 1.9 vs. 5.8 ± 2.3 months, p < 0.01) and a higher nonunion rate (39.1% vs. 0%, p < 0.01).

ASF showed inferior healing outcomes compared to TSF, even with more aggressive treatments. These findings suggest that traditional TSF strategies may be inadequate for ASF, and biological augmentation, such as bone grafting, might be considered in initial management.