Biomechanical evaluation of the risk of secondary fracture around short versus long cephalomedullary nails.

Abstract

For proximal femur fractures, long cephalomedullary nails (CMNs) are often selected to avoid a diaphyseal stress riser at the tip of a shorter nail. Secondary peri-implant fracture rates for long and short CMN have not been shown to differ clinically. This study biomechanically compares both CMN in a cadaveric model. Ten matched pairs of cadaveric femora with short or long CMN were axially loaded and internally rotated to failure. Resulting fractures involved distal interlocking screws of the short and long CMN. Energy and rotation to failure were significantly greater for short CMN. Torque at failure trended higher for short CMN but not significantly. No statistical difference was detected in stiffness of the short and long CMN. A greater risk of secondary fracture is not indicated for short versus long CMN under torsional stress. Short CMN may be suitable in the younger patient.