ABSTRACT
BACKGROUND:Dynamic hip screws have been considered as a classic method for intertrochanteric fracture. However, migration of the hip screw resulting in cut-out of the femoral head remains the most common mechanical failure, which requires secondary surgery. OBJECTIVE:On the basis of the traditional dynamic hip screw, we modified the lag screw, designed new internal fixation system as cemented dynamic hip screws to explore the feasibility and the biomechanical properties for the treatment of osteoporotic intertrochanteric fracture. METHODS:A total of 24 hip samples were harvested from fresh cadavers with osteoporosis. Bone density was measured. According to the standards, the specimens were made into intertrochanteric fracture models of AO31-A1 type. Of each specimen, one side implanted with cemented dynamic hip screws served as experimental group, and another side implanted with traditional dynamic hip screw served as control group. Axial compression, twisting and fatigue load biomechanics were tested. Their biomechanical functions were compared. RESULTS AND CONCLUSION:Stress intensity, axial stiffness and horizontal shear stiffness were higher in the experimental group than in the control group (P<0.05). At torsion angle of 3°, torsional moment was higher in the experimental group than in the control group (P<0.05). Fatigue load was higher in the experimental group than in the control group (P<0.05). Results suggested that cemented dynamic hip screw internal fixation system in the treatment of senile osteoporotic intertrochanteric fracture can effectively enhance the hip screw holding force and prevent femoral cutting. Biomechanical property, stiffness, endurance resistance and stability of cemented dynamic hip screw are better than traditional dynamic hip screw.