Effect of screw insertion site and unused drill holes on stability and mode of failure after fixation of basicervical femoral neck fractures

To evaluate the effect of screw insertion site (along the lateral cortex) and extraneous drill holes on postoperative subtrochanteric fracture after fixation of femoral neck fractures with cannulated screws, 40 embalmed proximal cadaver femora were used to create four groups designated as I, II, III, and IV. Within each group, the matched pairs were used to investigate the effect of screw placement on failure mode and stability, the effect of extra guidepin holes, and the effect of extra drill holes. Using a servo-hydraulic testing machine, loads were applied to all specimens. Following fracture-fixation, all specimens underwent progressive compressive loading to failure. The load-deformation curve, ultimate strength, and type of failure were recorded. Failure analyses enabled to identify mechanism of failure.