Parametric evaluation and biomechanical assessment of a curved biodegradable ZK60 locking plate for femoral shaft fractures using finite element analysis

This study evaluates the biomechanical performance of a novel curved biodegradable ZK60 magnesium alloy locking plate for plate osteosynthesis in midshaft femoral fractures classified as AO/ASIF 32-A3 (Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation). Current metallic implants are associated with complications such as stress shielding, the need for secondary surgery, and limited support for biological healing. Biodegradable options offer promising solutions but remain insufficiently studied, especially regarding curved plate designs. This work addresses that gap by systematically assessing how plate thickness and curvature influence fracture stability. Finite element analysis (FEA) was performed under physiological loading of 700 N simulating a single-leg stance. Ten configurations were modeled, combining two thicknesses (4 and 6 mm) with five bending angles (0, 5, 10, 15, and 20°). A 5 mm fracture gap was simulated, and all constructs were fixed with bicortical locking screws. Axial stiffness and total deformation were calculated and compared with those of an intact femur. Results indicated that both increased plate thickness and curvature enhanced construct performance. The 6 mm plate bent at 20° showed the highest stiffness (2328.9 N/mm) and lowest deformation (0.3007 mm), representing a 6.6% increase in stiffness and 5.8% reduction in deformation compared with the flat counterpart. Similar trends were observed for the 4 mm plate. The evaluated designs achieved 23.8–25.4% of intact femur stiffness, aligning with the biomechanical window that promotes callus formation through controlled micromotion. Curved configurations also improved load transfer and screw alignment. Among the tested designs, the 6 mm plate bent at 15°–20° demonstrates the most favorable biomechanical characteristics for potential clinical translation.