Biomechanical comparison of screw-based zoning of PHILOS and Fx proximal humerus plates

Abstract

Background Treatment of proximal humerus fractures with locking plates is associated with complications. We aimed to compare the biomechanical effects of removing screws and blade of a fixed angle locking plate and hybrid blade plate, on a two-part fracture model. Methods Forty-five synthetic humeri were divided into nine groups where four were implanted with a hybrid blade plate and the remaining with locking plate, to treat a two-part surgical neck fracture. Plates’ head screws and blades were divided into zones based on their distance from fracture site. Two groups acted as a control for each plate and the remaining seven had either a vacant zone or blade swapped with screws. For elastic cantilever bending, humeral head was fixed and the shaft was displaced 5 mm in extension, flexion, valgus and varus direction. Specimens were further loaded in varus direction to investigate their plastic behaviour. Results In both plates, removal of inferomedial screws or blade led to a significantly larger drop in varus construct stiffness than other zones. In blade plate, insertion of screws in place of blade significantly increased the mean extension, flexion valgus and varus bending stiffness (24.458%/16.623%/19.493%/14.137%). In locking plate, removal of screw zones proximal to the inferomedial screws reduced extension and flexion bending stiffness by 26–33%. Conclusions Although medial support improved varus stability, two inferomedial screws were more effective than blade. Proximal screws are important for extension and flexion. Mechanical consequences of screw removal should be considered when deciding the number and choice of screws and blade in clinic.

Publication DOI: https://doi.org/10.1186/s12891-018-2185-5
Divisions: College of Health & Life Sciences
College of Health & Life Sciences > School of Biosciences
Additional Information: © The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Publication ISSN: 1471-2474
Last Modified: 01 Jan 2024 08:17
Date Deposited: 07 Aug 2020 08:40
Full Text Link: http://www.scop ... tnerID=MN8TOARS
Related URLs: https://bmcmusc ... 2891-018-2185-5 (Publisher URL)
PURE Output Type: Article
Published Date: 2018-07-25
Accepted Date: 2018-07-11
Authors: Jabran, A. (ORCID Profile 0000-0002-2354-281X)
Peach, Chris
Zou, Zhenmin
Ren, Lei

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