Accuracy of the lesser trochanter for guiding lag screw insertion in hip fracture management

Abstract

The goal of this study was to evaluate the accuracy of the lesser trochanter for entry of lag screw placement in the fixation of hip fractures. Radiographs of the pelvis with both hips in 50 Chinese patients were analyzed to determine the accuracy of using the lesser trochanter as a reference landmark for inserting lag screws. The femoral neck was divided into 4 parts, and the second distal part was classified as the safe zone. Cobb angles of 125° and 130° were used as representative lag screw insertion angles, referencing the lateral cortex of the lesser trochanter for measurement, and insertion tracks were drawn on the neck of the femur. The accuracy of lag screw placement in the defined safe zone was evaluated. Accuracy of placement in the safe zone for entry points at the superior tip, apex, and inferior tip of the lesser trochanter were 78%, 39%, and 0%, respectively, for the 125° Cobb angle. Rates for the superior tip, apex, and inferior tip of the lesser trochanter were 31%, 74%, and 6%, respectively, for the 130° Cobb angle. The entry point at the level of the inferior tip of the lesser trochanter had incidence rates of 95% and 71% for cutout for 125° and 130° screws, respectively. The authors found that the superior tip of the lesser trochanter was a good reference point for 125° lag screw insertion and that the apex of the lesser trochanter was a good reference point for 130° lag screw insertion. Entry at the level of the inferior tip of the lesser trochanter has a very high rate of cutout and should be avoided.