Biomechanical Study of the Preventive Effect of Different Cephalomedullary Fixation Methods on the Occurrence of Femoral Neck Fractures in Osteoporotic Femurs

Background and Objectives: This study aimed to investigate the biomechanical properties of different cephalomedullary fixation methods for osteoporotic femurs using a synthetic bone model. Materials and Methods: Lateral impact tests and axial cyclic loading tests were performed, and each test was divided into three groups: group 1 with one reconstruction screw, group 2 with two reconstruction screws, and group 3 without cephalomedullary fixation. To simulate a healed femoral shaft fracture, no osteotomy was performed on the specimens. Results: Groups 1 and 2 had significantly higher mean stiffness, ultimate failure load, and energy to failure in the lateral impact test compared to the native synthetic femur (p < 0.001 for all), while group 3 had significantly lower values in all outcomes (p < 0.05 for all). Groups 1 and 2 showed significantly higher average number of cycles, total load to failure, and initial axial stiffness in the axial cyclic incremental loading test compared to the native synthetic femur (p < 0.001 for all), whereas group 3 showed a significantly lower mean number of cycles and total load to failure (p < 0.001 for all). Conclusions: Under the specific test conditions of this intact synthetic bone model, cephalomedullary fixation with one or two reconstruction screws demonstrated superior relative mechanical stability compared to standard interlocking nails. Using two reconstruction screws provided the greatest biomechanical resistance to failure. In cases where inserting two reconstruction screws is technically challenging or infeasible, a single reconstruction screw may offer an acceptable biomechanical alternative to help prevent peri-implant fractures in healed or prophylactic settings. Intramedullary nailing without cephalomedullary fixation exhibited the lowest mechanical performance, suggesting a potential biomechanical vulnerability to peri-implant fractures under these test conditions.