Biomechanical analysis of the dynamic hip screw in the treatment of intertrochanteric fractures.

A prospective study was performed in 148 elderly patients (over 60 years old) whose intertrochanteric fractures were caused by moderate trauma. The patients were treated with dynamic hip screws and followed up for at least 2 years (average 34 months). The lag screw was placed as the biomechanical analysis favored. Follow-up showed that the majority achieved good union and were without mechanical failure. The authors conclude that a lag screw should ideally be placed inferiorly toward the medial margin in the frontal plane and centrally in the sagittal plane. The length of the lag screw should be such as to extend from 1.0 cm beneath the subchondral bone to the lateral femoral cortex. At least four cortical screws (piercing the cortex at eight points) should be inserted on the distal femoral fragment.