A BIOMECHANICAL VALIDATION OF A NEW FEMORAL NECK FIXATION DYNAMIC HIP SCREW FOR PROXIMAL FEMORAL FRACTURE

High failure rates are expected in the treatment of osteoporotic proximal femoral fractures. A newly designed femoral neck locking dynamic hip screw has been developed to increase the fixation strength; a biomechanical examination was performed to prove its efficacy. Femoral surrogate specimens were used for the test. Unstable intertrochanteric fractures were created on specimens. Then these specimens were divided into two groups to test two different methods of fixation: (1) the conventional dynamic hip screw and (2) the new designed femoral neck fixation dynamic hip screw. For each specimen, the peak cyclic loading was 800 N, and a total of 20,000 cycles were applied. The vertical displacement, rotation around the long axis of lag screw, and the varus rotation around the center of femoral head between the two groups were compared at specific intervals. All the conventional dynamic hip screw constructs failed within 1000 cycles, while no gross mechanical failure was recorded for the femoral neck fixation dynamic hip construct even after 20,000 loading cycles. The mechanical test comparing the two constructs at the end of each 1000 loading cycles demonstrated that the femoral neck fixation dynamic hip screw construct is stronger than that of the conventional dynamic hip screw. For the fixation of proximal femoral fractures, the femoral neck fixation dynamic hip screw can provide a stronger support than what a conventional dynamic hip screw can do. At the same time, femoral neck can be a suitable site for the application of proximal locking screws.