ORIGINAL ARTICLE Internal Fixation of the Distal Humerus: A Comprehensive Biomechanical Study Evaluating Current Fixation Techniques Paolo Caravaggi, PhD,* Joseph L. Laratta, MD,* Richard S. Yoon, MD,† Justin De Biasio, BS,‡ Michael Ingargiola, BS,* Matthew A. Frank, MD,* John T. Capo, MD,† and Frank A. Liporace, MD† Objectives: The purpose of this study was to evaluate current fixation techniques in the operative fixation of distal humerus fractures, both with conventional and locked plating in both parallel and orthogonal orientation. Methods: Twenty-eight upper extremities from 14 cadavers were prepared to create 4 implant testing constructs: Synthes locking plates (IMP1) (medial and posterolateral with lateral flange), Acumed parallel locking plates (IMP2), Smith & Nephew orthogonal locking plates (IMP3), and Synthes orthogonal 3.5-reconstruction plating (IMP4) (1 posterolateral and 1 medial). A 5-mm supracondylar osteotomy was made to simulate the fracture. Stiffness in axial and sagittal plane loading, fatigue properties (over 5000 cycles), and ultimate strength were determined for each construct by biomechanical testing. Results: The parallel locking plates (IMP2) exhibited the highest stiffness in axial load and the highest ultimate strength (P , 0.05). No significant differences in sagittal plane stiffness and in the fatigue properties were seen across the locking plate groups, regardless of orientation. Locked plating constructs performed significantly better in all categories when compared with conventional nonlocked plating. Plastic deformation and implant loosening were the main modes of failure after ultimate strength test. Conclusion: Parallel locking plate configuration showed signifi- cantly higher stiffness to axial load and ultimate failure strength when compared with orthogonal locked and nonlocked plating. Locked plating configurations performed significantly better than nonlocked plating configurations, regardless of orientation. Although parallel orientation seems biomechanically superior, translation to the clinical setting may prove difficult when taking surrounding soft tissue and exposure into consideration. Key Words: distal humerus, orthogonal, parallel, stiffness, fatigue (J Orthop Trauma 2014;28:222–226) INTRODUCTION Distal humerus fractures, although only accounting for 2% of all fractures, are complex injuries that are particularly challenging to treat. 1 These injuries will often require open reduction with bicolumnar internal fixation, which has been shown to provide more predictable outcomes and earlier joint mobilization. 2–6 However, even with surgical treatment, between 20%–25% of cases result in unsatisfactory outcomes. 4,7,8 Potential complications after operative fixation include stiffness, decreased range of motion, nerve dysfunction, extensor mecha- nism dysfunction, posttraumatic degenerative changes, wound and skin infections, avascular necrosis, and implant failure. 9 Implant failure, often the consequence of inadequate fixation techniques, is a major hindrance to successful fracture healing. 10–12 Overcoming and avoiding these complications, especially in the setting of poor bone quality, has led to an active search to identify the gold standard for fixation of distal humerus fractures. 2,4–6,8,13–18 Originally, Helfet and Hotchkiss 19 described the biome- chanical concepts behind several fixation methods. However, with the advent and advancement of surgical technique and technology, several fixation techniques have since been intro- duced and continue to fuel debate and controversy. 2,6,9,14 At the forefront of the fixation debate is parallel versus orthogonal plating (or 90-90 plating) with either locking or conventional plate techniques. Without a general consensus on optimal fixa- tion strategy, individual surgeon preference and design advance- ments continue to be the subject of emerging biomechanical and clinical comparative studies. 13,14,16,18 Although many head-to-head biomechanical studies have been reported, comparing both reconstruction and locking plate variants in both orthogonal and/or parallel constructs, no single study has yet to compare all of the possibilities concurrently. The purpose of this study was to compare the most current locking and conventional plating options in both orthogonal and parallel orientations in the setting of a simulated meta- physeal distal humerus fracture created in a cadaveric model. MATERIALS AND METHODS Specimen Preparation Twenty-eight upper extremities from 14 cadavers (68 6 13 years) were harvested (Musculoskeletal Transplant Founda- tion, Edison, NJ). All soft tissues were dissected from the humeri, and the bones were stored frozen until use. All specimens were Accepted for publication July 23, 2013. From the *Division of Orthopaedic Trauma, Department of Orthopaedic Surgery, Rutgers New Jersey Medical School, Newark, NJ; †Division of Orthopaedic Trauma, Department of Orthopaedic Surgery, NYU Hospital for Joint Dis- eases, New York, NY; and ‡Mount Sinai School of Medicine, New York, NY. The authors report no conflict of interest. Reprints: Frank A. Liporace, MD, Division of Orthopaedic Trauma, Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, 301 E 17th St, Suite 1402, New York, NY 10003 (e-mail: liporace33@gmail.com). Copyright © 2013 by Lippincott Williams & Wilkins 222 | www.jorthotrauma.com J Orthop Trauma  Volume 28, Number 4, April 2014