Optimizing the Entry Point for Medullary Hip Screws

Abstract

Introduction: Medullary hip screws (MHSs) are the most common treatment of intertrochanteric hip fractures because they can be used for varied fracture patterns and resist shortening. Identifying the appropriate MHS entry point can be intellectually and technically challenging. We aimed to quantify the variability in the ideal entry point (IEP) for MHSs. Methods: Standing alignment radiographs of 50 patients were evaluated using TraumaCad (Brainlab). The femoral neck shaft angle and the offset from the tip of the greater trochanter (GT) to the femur's longitudinal axis (‘greater trochanter offset’) were measured. Five MHS system templates were superimposed on the femur's longitudinal axis, and the distance from the GT tip to MHS's top center was measured. Five independent reviewers each templated 20 images such that all images were measured at least twice. A random sample of five images was selected for all five raters to measure and to calculate an intraclass coefficient Mean IEPs were compared with an independent sample Student t-test. Results: The mean GT offset was 13.5 ± 5.6 mm (range 12.9 to 26.7 mm). The mean neck shaft angle was 129.5 ± 4.0 (range 120 to 139). The mean IEP for nail systems ranged from 5.7 to 7.1 mm medial to the GT tip; there was no notable difference in pairwise comparison of nail systems or in aggregate. Intraclass coefficient for all ratings, measurements, and nail types ranged from moderate to good. Both intra-rater and inter-rater reliability were excellent. Discussion and Conclusion: In a sample with broad variation in femoral anatomy, there is a specific, roughly 1.5 mm wide interval that is 6.4 mm medial to the GT tip that serves as the IEP for the most common MHS systems. No notable difference seems to exist in the IEP among these MHS systems.