Biomechanical Properties of Conventional Versus Angular Stabilized-Intramedullary Nail Distal Interlocking Screw Configurations in a Distal Tibia Fracture Model

Abstract

Introduction: A new intramedullary nail (IMN) (Expert Nail) has recently been introduced with a design including an angular stable locking system (ASLS), which provides a fixed-angle interlocking construct. The study objective is to provide biomechanical assessment of IMN fixation of a distal tibia fracture using conventional versus ASLS interlocking screw options, and the effects of number of screws and/or their orientation on fracture stability. Methods: A distal segmental defect in large composite tibia models was stabilized with an Expert IMN. Distal fixation consisted of five distinct single versus double distal interlocking and ASLS versus conventional screw configurations. The IMN constructs were tested using cyclic axial and torsional loading. Results: There were no significant differences between distal interlocking screw configurations for axial loading stiffness. In torsion, a single medial-to-lateral conventional interlocking screw was significantly less stiff than the other configurations. Discussion: A single ASLS screw provides biomechanically comparable fixation to two conventional screw configurations in the fixation of distal tibia fractures with IMN. The screw orientation does not appear to affect stability of the construct.