• Mathew Rawlings, David Knox, Minoo Patel, and David Ackland.
• Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria 3010, Australia.
• Injury. 2016 Apr 1; 47 (4): 893-8.

BackgroundThe purpose of this study was to demonstrate the strength characteristics of a hybrid uni-cortical construct for clavicle fixation. The technique reported aims to combine benefits of uni-cortical fixation with stability comparable to traditional bi-cortical fixation. The approach utilises long, oblique uni-cortical screws at the distal ends of the plate acting as surrogate bi-cortical screws. Locked uni-cortical screws positioned centrally provide bending and torsion strength to the construct. This alternative hybrid uni-cortical technique does not require far cortex screw or drill penetration required in bi-cortical fixation techniques, thus avoiding potentially catastrophic vascular and or neurologic injury. The purpose of this study was to compare the mechanical behaviour of the hybrid uni-cortical construct to standard bi-cortical fixations under both torsion and bending loads.MethodThirty osteotomized human cadaveric clavicles were randomly allocated to three surgical fixation techniques: bi-cortical locked screw fixation, bi-cortical non-locked screw fixation and hybrid uni-cortical screw fixation. Each clavicle construct was tested non-destructively under torsional loading, and then under cantilever bending to failure. Construct bending and torsional stiffness, as well as ultimate failure strength, were measured.ResultsThere were no significant differences between uni-cortical or bi-cortical fixation constructs in either bending stiffness or ultimate bending moment (p>0.05); however, there was a trend towards greater bending stiffness in the hybrid construct. The uni-cortical hybrid fixation technique displayed a significantly lower mean torsional stiffness value when compared with the bi-cortical locked screw fixation (mean difference: 134.4 Nmm/degrees, 95% confidence interval [32.3, 236.4], p=0.007).ConclusionA hybrid uni-cortical approach to clavicle plate fixation that may improve screw purchase and reduce risk of intra-operative vascular damage demonstrates comparable bending strength to current bi-cortical approaches.Copyright © 2016 Elsevier Ltd. All rights reserved.

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