A modified hip screw incorporating injected cement for the fixation of osteoporotic trochanteric fractures

Objective: To evaluate a modified sliding, hip screw for the fixation of trochanteric fractures that provides increased fixation strength in osteoporotic bones and allows for the safe intraoperative application of bone cement. Design: Biomechanical cadaver study. Materials: Unstable trochanteric fractures were simulated by osteotomy in nine pairs of cadaveric femurs and stabilized by a standard sliding hip screw randomly assigned to the left or right femur. The contralateral femur was stabilized with a newly designed hip screw, which was augmented with low-viscosity bone cement. Main Outcome Measurements: Femoral bone mineral density was measured by dual x-ray absorptiometry and quantitative computed tomography. Fixation stability of the hip was assessed after dynamic loading by displacement measurement of the femoral head in a simulated one-leg stance configuration. Results: Modification of the hip screw together with cement augmentation significantly (p < 0.05) increased the initial stability of the fracture fixation technique. The total displacement of the femoral head was reduced by 39 percent on average using cement augmentation in the modified screw compared with the standard sliding hip screw. The largest improvement in initial fixation stability was found for the most osteoporotic bones. Conclusions: This modified hip screw augmented with bone cement can significantly enhance the initial fixation stability of trochanteric fractures in osteoporotic femurs.