Biomechanical comparison of fixed-versus variable-angle locking screws for distal humerus comminuted fractures

• Type of Material: Article
• Authors: Ali Nourbakhsh, WellStar Atlanta Medical Center; Adam G. Hirschfeld, MetroHealth Medical Center; Sravan Dhulipala, Atlanta Medical Center; William Hutton, Emory University; Timothy Ganey, Atlanta Medical Center; Luis Lozada, Atlanta Medical Center; Daniel Schlatterer, Atlanta Medical Center; Gary Mark Lourie, Hand and Upper Extremity Center of Georgia
• Language: English
• Date: 2019-09-01
• Publisher: Korean Orthopaedic Association
• Publication Version: Final Published Version
• Copyright Statement: © 2019 by The Korean Orthopaedic Association.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.4055/cios.2019.11.3.302
• Title of Journal or Parent Work: Clinics in Orthopedic Surgery
• ISSN: 2005-291X
• Volume: 11
• Issue: 3
• Start Page: 302
• End Page: 308
• Grant/Funding Information: This study was funded by Depuy-Synthes in the amount of US $102,680 (grant no. 11934).
• Keywords: Stress, Mechanical; Humeral Fractures; Elbow Joint; Humans; Humerus; Biomechanical Phenomena; Cadaver; Aged; Bone Screws; Male; Bone Plates; Bone screws; Fractures, Comminuted; Fracture Fixation, Internal; Fracture fixation; Equipment Failure Analysis
• Research Categories: Health Sciences, Medicine and Surgery

Abstract

Background: To compare the stability of fixed-versus variable-angle locking constructs for the comminuted distal humerus fracture (AO/OTA 13-A3). Methods: Eight pairs of complete humeri harvested from eight fresh frozen cadavers were used for the study. We fixed the intact humeri using 2.7-mm/3.5-mm locking VA-LCP stainless steel distal humerus posterolateral (nine-hole) and medial (seven-hole) plates. An oscillating saw was used to cut a 1-cm gap above the olecranon fossa. The specimens were loaded in axial mode with the rate of 1 mm per 10 seconds to failure, and stress-strain curves were compared in each pair. The mode of failure was recorded as well as the load needed for 2-and 4-mm displacement at the lateral end of the gap. Results: The stiffness of the constructs, based on the slope of the stress-strain curve, did not show any difference between the fixed-versus variable-angle constructs. Likewise, there was no difference between the force needed for 2-or 4-mm displacement at the lateral gap between the fixed-and variable-angle constructs. The mode of failure was bending of both plates in all specimens and screw pull-out in four specimen pairs in addition to the plate bending. Conclusions: Our results did not show any difference in the biomechanical stability of the fixed-versus variable-angle constructs. There was not any screw breakage or failure of the plate-screw interface.