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 inter- locking 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 conven- tional screw configurations in the fixation of distal tibia fractures with IMN. The screw orienta- tion does not appear to affect stability of the construct. Keywords: Distal tibia fracture; Intramedullary nailing; Distal interlocking. Biomechanical Properties of Conventional Versus Angular Stabilized-Intramedullary Nail Distal Interlocking Screw Configurations in a Distal Tibia Fracture Model Raj H. Shani, MD; Randal P. Morris, BS; Zbigniew Gugala, MD, PhD; Ronald W. Lindsey, MD Department of Orthopaedic Surgery and Rehabilitation University of Texas Medical Branch, Galveston, TX ABSTRACT Intramedullary nailing (IMN) has become a common and effective fixation option in de- finitive management of tibia fractures (1-7). Although typically indicated for tibia shaft fractures, IMN fixation of the very proximal or distal tibia fractures is challenged by the limited cortical bone contact with the nail and the risk for loss of fracture alignment, implant failure, or nonunion (8-14). In such cases, IMN frequently requires supplemen- tal fixation (eg, blocking screws), cast/brace support, and/or protective weight bearing. Recent modifications in tibia IMN designs aim to enhance the proximal and distal IMN INTRODUCTION ORIGINAL RESEARCH orthopaedic journal texas ® Corresponding Author: Zbigniew Gugala, MD, PhD Department of Orthopaedic Surgery & Rehabilitation University of Texas Medical Branch 301 University Blvd. Galveston, TX 77555-0165, USA e-mail: zgugala@utmb.edu DOI: 10.18600/toj.0101.09 TOJ 1: 69-77, 2015