Clinical Differences Between Periprosthetic and Native Distal Femur Fractures

Introduction Periprosthetic distal femur fractures (PDFF) are becoming more prevalent as total knee replacements become more common. This study compares the demographics, fracture characteristics, treatment, and outcomes of periprosthetic versus native distal femur fractures (NDFF). Materials and Methods This is a retrospective cohort study of patients ≥ 18 who underwent surgical fixation of NDFF or PDFF from 2012-2020 at a level-1 trauma center. Primary outcomes included demographics, AO/OTA fracture classification, fixation construct, and unexpected return to the operating room (UROR). Secondary outcomes were concomitant fractures, polytrauma rates, low bone density, and reduction quality. T-test, Fisher’s exact test, and multivariable analysis were used for statistical analysis. Results 209 patients were identified, including 70 PDFF and 139 NDFF. PDFF patients were elderly females (81%) with isolated (80%) and comminuted (85%) 33A.3 (71%) fractures. NDFF patients included 53% females, were commonly middle-aged, and displayed comminuted (92%) 33C.2 fractures. 48% of NDFF patients had concomitant fractures. Intramedullary nailing was the primary fixation for both groups, followed by nail-plate combination (37%) for PDFF and lateral locking plates (21%) for NDFF. NDFF patients experienced lengthier hospital stays and higher UROR rates (p<0.05). PDFF patients had a significantly higher prevalence of low bone density (p<0.05). Conclusion PDFF occur as isolated injuries with significant metaphyseal comminution in elderly females with low bone quality. NDFF commonly occurs in younger patients with less metaphyseal comminution and concomitant fractures. Intramedullary nailing was the most common treatment for both groups, though preference for nail-plate combination fixation is increasing. NDFF type 33C fractures are at higher risk of UROR.