Viability of bone cement augmented compression hip screw system for the treatment of intertrochanteric fracture: a biomechanical analysis

Screw cut-out and non-union have been cited as major complications with hip screw systems for the treatment of intertrochanteric femoral fractures. Recently, cement augmentation of hip screw system has been introduced to provide better purchase of the screw. This study investigates the biomechanical efficacy of cement augmentation technique by assessing the changes in stress distributions within the femur and the surgical construct. Finite element models of the operated femur with sliding hip screw assemblies were constructed with and without bone cement augmentation. To simulate the fracture plane and other interfacial regions, 3-D contact elements were used with appropriate friction coefficients. Our results demonstrated the efficacy of the cement augmentation: 80% reduction in stresses was found in the cancellous bone due to cement augmentation, suggesting that the fractures of the cancellous bone and the cut-out of the screw are far less likely to take place. The peak von Mises stress within the cement mantle was about 1/3 of its fatigue strength. The likelihood of cement failure that might lead to osteolysis due to cement debris was not apparent. The micromotion at the hip screw interface was reduced from 0.275 mm to 0.008 mm, an indication for strong fixation after surgery.