Abstract
BACKGROUND: Proximal femur fracture fixation fundamentally alters load transfer, which can trigger adverse bone remodeling, particularly after healing in osteoporotic bone. While previous studies have focused on early fixation stability or acute fracture healing, the long-term mechanical environment after fracture consolidation remains poorly understood. This study examines implant-specific strain behavior in the post-healed state to identify patterns that may predispose to late-stage implant failure or remodeling. METHODS: Subject-specific finite-element models were created from CT scans of a healthy 22-year-old and an osteoporotic 90-year-old female. Cannulated screws (CS), a dynamic hip screw (DHS), and a femoral neck system (FNS) were virtually implanted in each model and subjected to simulated gait loading. Maximum implant stresses and regional principal strains across the proximal femur were quantified throughout the stance phase. FINDINGS: The FNS demonstrated the highest maximum von Mises stresses in both normal and osteoporotic bone, notably at the anti-rotation screw and bolt interface. In osteoporotic bone, the FNS exhibited significantly higher tensile (mean 0.36 % ± 0.22 %) and compressive strains (mean - 0.41 % ± 0.28 %) compared to CS and DHS implants, while in normal bone, FNS strains were comparable to intact femur strains. The CS model showed reduced peak strains and stresses throughout the gait cycle compared to DHS and FNS. INTERPRETATION: This study provides a comparative assessment of healed-state strain distributions across common fixation constructs. By characterizing these environments, these data establish a biomechanical framework and highlight the interplay between implant design and bone quality. Further population-based studies are required to refine implant selection.