Proximal femur lag screw placement based on bone mineral density determined by quantitative computed tomography

Following internal fixations for intertrochanteric fractures in elderly patients, lag screws or screw blades frequently cut the femoral head, leading to surgical failure. The bone mineral density (BMD) at various parts of the proximal femur is significantly correlated with the holding force of the lag screw, which in turn is closely associated with the stability of the fixation. However, the appropriate placement of the lag screw has been controversial. As a novel detection method for BMD, quantitative computed tomography (QCT) may provide relatively accurate measurements of three-dimensional structures and may provide an easy way to determine the appropriate lag screw placement. A total of 50 elderly patients with intertrochanteric fractures were selected for the present study. The BMD of the proximal femur on the healthy side, including the femoral intertrochanter, neck and head, was measured using QCT. For testing, the femoral head was divided into medial, central and lateral sections. The BMD of the femoral head was determined to be the highest, while the BMD of the femoral neck was the lowest. In the femoral head, the central section had the highest BMD, while the lateral section had the lowest BMD. The present study used QCT to detect differences in the BMD at various regions of the proximal femur and provided a novel theoretical reference for the placement of lag screws. To obtain maximum holding power, the lag screw must be placed in the central section of the femoral head.