Biomechanical study on femoral neck fracture fixation in relation to bone mineral density

Twenty pairs of fresh-frozen cadaveric femurs were used in the study. The left femurs were used as control for the mechanical testings and bone mineral content scans, the right femurs were divided into two experimental groups, i.e. ‘fractured’ group and ‘healed’ group. In the ‘fractured’ group, twelve right femurs were osteotomized at the plane perpendicular to the femoral neck shaft axis, through the mid-cervical area of the femoral neck. The artificially created fractures were fixed with the AO dynamic hip screw system using a 4-hole plate and a compression screw. In the ‘healed’ group, the dynamic hip screws were applied to eight intact right femurs to simulate healed fractures. Bone mineral density scans and mechanical testings were performed on all the femurs. Good correlation was observed between bone mineral density and femoral neck strength in the control group. There was a decrease of 43.5% in strength in the ‘fractured’ group when compared to the control group. However, in the ‘healed’ group the failure load was found to be 15.2% lower than the control group. The femoral fixation strength in the ‘fractured’ and ‘healed’ groups had good correlation with the bone mineral density.