Influence of greater trochanteric starting point on distal anterior cortical perforation during antegrade femoral nailing

Background: Distal anterior cortical perforation is 1 complication of antegrade femoral nailing. The effect of greater trochanteric (GT) starting points on cortical perforation risk has not been described in human femoral models. This study assessed the influence of sagittal plane starting point on rate of anterior cortical perforation using 3D CT-reconstructions of human femora. Secondarily, patient age and nail radius of curvature (ROC) were assessed as risk factors. Methods: CT scans of 53 patients (18 non-geriatric (<65 yr), 35 geriatric (>65 yr)) with non-fractured femora were converted into dynamic 3D-reconstructed renderings. Medullary nails from two manufacturers that differed in ROC were digitally templated in each femur from an anterior, central, and posterior ⅓ GT starting point. The rate of anterior cortical perforation and distance from the inner anterior cortex to the nail tip were recorded. Results: Perforation rate increased significantly as starting point moved from anterior (6%), to central (43%), to posterior (79%) regardless of patient age or implant manufacturer (P<0.001). On average, an anterior starting point positioned the nail tip furthest from the inner anterior cortex (5. mm), safely within the canal (P<0.001). Perforation rate was significantly increased in the geriatric versus non-geriatric population (47% vs. 34%) (P=0.028), and when using the nail with the larger versus smaller ROC (50% vs. 36%) (P=0.03). Conclusion: Distal nail sagittal alignment is sensitive to both patient and treatment factors. A posterior starting point, increased age (>65 yr), and increased implant ROC significantly increase risk for anterior cortical perforation of the distal femur. Level of Evidence: III