Femoral Shaft Fragility Fractures: Peri-Implant Fracture Risk Mitigated by Femoral Neck Protection

Despite their association with high morbidity and mortality rates, limited data is available regarding subsequent fracture after femoral shaft fragility fractures. Specifically, two clinically important questions remain unanswered: (1) What is the cumulative incidence of proximal peri-implant femur fractures following femoral shaft fragility fractures? (2) Is fixation protecting the proximal femur associated with a lower cumulative incidence of proximal peri-implant femur fracture compared to when the proximal femur is not protected?

A multi-center retrospective cohort study was conducted at four level 1 trauma centers. Patients aged 50 years or older treated with reduction and fixation of a low energy femoral shaft fracture between 2005 to 2024 were included in this review.Cases were categorized by whether fixation protected the proximal femur. Descriptive statistics were reported, and Kaplan Meier survival analyses assessed associations of patient, injury and treatment characteristics with the main outcome of cumulative incidence of proximal peri-implant fracture. Statistical significance was considered for p < 0.05.

There were 245 patients with a median age of 75 years old and interquartile range (IQR) 65 to 83, 192 (78.4%) women, and median Charlson Comorbidity Index 4 (IQR 3 to 6). Assessment via the AO/OTA classification revealed 193 32A, 34 32B, and 18 32C fractures. The overall rate of subsequent proximal femur fracture was less with fixation that protected the proximal femur (0/119, 0%) than without (6/126, 4.8%), p = 0.030. Without fixation protecting the proximal femur, the cumulative incidence of proximal femur fracture climbed to 6.9% within 10 months of femoral shaft fracture and was significantly greater than a sustained 0% incidence when fixation protected the proximal femur, log-rank p = 0.015. Proximal femur fracture was not associated with age, sex, comorbidity burden or AO/OTA classification (p > 0.05 for all).

Without fixation protecting the proximal femur, approximately 1 in 15 patients treated for a femoral shaft fracture sustained a proximal femur fracture within 10 months of fixation of their shaft fracture. Protecting the proximal femur reduces the cumulative incidence of proximal peri-implant femur fracture and should be considered when possible.

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