Cephalomedullary nails: factors associated with impingement of the anterior cortex of the femur in a Hispanic population.

Introduction: Impingement and penetration of the anterior cortex of the femur have been reported as complications after cephalomedullary nailing. The purpose of this study was to determine factors related to nail impingement in our population of Hispanic patients.

Materials And Methods: A non-matched case-control study was carried out and 156 patients who underwent cephalomedullary nailing from 2010 and 2013 were included; 78 cases with anterior cortical impingement and 78 control cases without impingement were documented. Demographic variables and specifications of the nails such as manufacture and radius of curvature were recorded. The presence of impingement, angle of incidence on radiographs--indirect measurement of the femoral bow on the sagittal plane--and nail entry site were determined. Bivariate and multivariate logistic regression analyses were performed to identify the factors associated with cortical impingement.

Results: The distribution by sex corresponded to 87 females (56%) and 69 males (44%) with a mean age of 75 years [SD 18.2]. Cortical impingement was presented in 78 cases (50%) and 6 (3.8%) patients evidenced penetration of the anterior cortex of the femur. On the bivariate analysis the posterior nail start site is highlighted, which showed a positive association with impingement (OR 4.3; 95% CI 1.1-36 and p = 0.04). After the multivariate analysis, the factors associated with anterior cortical impingement included female gender (OR 2.2; 95 % CI 1.1-4.6 and p ≤ 0.038), straight nails-short nails-(OR 4.9; 95% CI 2.2-10 and p ≤ 0.001) and angle of incidence ≥7° (OR 4.9; 95% CI 2.2-10 and p ≤ 0.001), the latter showing a likelihood of 57 % for impingement, increasing to 90% with an angle of incidence of 11°.

Conclusions: Posterior entry site should be avoided and an anterior site should be used. Female gender, straight nails and greater angle of incidence of the femur were associated with cortical impingement. A specific intramedullary nail design is needed for the Hispanic population due to high impingement and anterior cortical penetration rates seen with conventional nails. Short curved nails and long nails with a lower radius of curvature are required.