Influence of the most proximal screw fixation mode on implant stress in lateral locking plate fixation for distal femoral fractures

Abstract Implant failure after lateral locking plate fixation for distal femoral fractures is a clinically important complication. Although the fixation mode of the most proximal locking screw may influence the stress distribution within the construct, its biomechanical role remains unclear. This study aimed to evaluate the effect of proximal screw fixation on stress distribution using finite element analysis. A three-dimensional finite element model of an osteoporotic femur was constructed using computed tomography data. Eight distal femoral fracture fixation models were generated with 2 fracture gaps (1 and 10 mm), 2 plate lengths (5-hole and 9-hole), and 2 fixation modes for the most proximal screw (monocortical and bicortical). A 1500-N load, simulating a single-leg stance, was applied. The maximum equivalent stresses in the proximal screws and the entire implant were evaluated. In the 10-mm gap models, the maximum equivalent stress exceeded the ultimate tensile strength of the titanium alloy in all configurations (1618–1874 MPa). In the 1-mm gap models, maximum implant equivalent stress was lower with monocortical fixation than with bicortical fixation (5-hole plate: 397 vs. 474 MPa; 9-hole plate: 413 vs. 451 MPa). In conclusion, monocortical fixation of the most proximal screw may reduce stress concentration within the implant when the medial cortical contact is preserved, thereby potentially lower the risk of implant failure.