Comparison of alternate and simultaneous tensioning of wires in a single-ring fixator construct.

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 degrees 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.