Comparison of Alternate and Simultaneous Tensioning of Wires in a Single-Ring Fixator Construct

Authors: 
STEWART RYAN, BVSc, MS, Diplomate ACVS 1 , NICOLE EHRHART, VMD, MS, Diplomate ACVS 1 , KELLY ZUEHLSDORFF, MS 1 , and SUSAN JAMES, PhD 1
Volume: 
38
Number: 
1
Pages: 
96-103
Journal: 
Vet Surg
Date: 
2009

ABSTRACT Objective—To measure and compare the strain of wires tensioned with alternate (ALT) and simultaneous (SIM) tensioning in a single-ring fixator construct and compare the stiffness of these constructs under axial loading. Study Design—Experimental mechanical study. Sample Population—Twenty-four, 84 mm diameter, single-ring constructs. Methods—Twenty-four, 84 mm diameter, single-ring constructs were assembled using 2 1.6 mm wires placed at a 60° angle tensioned with either ALT or SIM technique to 90 kg tension. Voltage data from a strain gauge were recorded during the wire-tensioning process, cyclic axial loading, and load-to-failure testing. Wire strains were calculated for each wire and compared within constructs and between ALT and SIM groups. Construct stiffness was compared between groups. Results—There was no difference between the tensioning methods in final wire strains after initial tensioning for both the wire below the ring (W1; P=.698) and the wire above the ring (W2; P=.233). There was also no difference in final wire strains within each tensioning method group (ALT, P=.289; SIM, P=.583). Loss of wire strain (3.5–5%) occurred after cyclic loading for both wires in both groups. There was no difference in construct stiffness between the ALT and SIM groups (P=.126). Mode of failure was by wire breakage in all constructs and occurred most frequently in W1. Conclusion—ALT tensioning of wires produced similar wire strains within a single-ring construct after initial tensioning to SIM tensioned wires. There was no difference in construct stiffness under axial loading between AIM and SIM tensioned constructs. Clinical Relevance—ALT tensioning of wires in a single-ring fixator construct can be used as an alternative to SIM tensioning, as similar initial wire tensions are achieved.