Influence of wire configuration on resistance to fragment distraction of tension bands placed in a greater trochanteric osteotomy model

Authors: 
Thompson E, Robe AK, Roe SC, Cole JH.
Vet Surg. 2019 Nov 12. doi: 10.1111/vsu.13350.

OBJECTIVE: To determine the influence of wiring configurations on initial tension and resistance to tensile loads in tension band constructs without the contributions of Kirschner-wire stabilization.

STUDY DESIGN: Experimental study.

SAMPLE POPULATION: A solid brass femur model manufactured on the basis of computed tomography of a normal right femur of a 30-kg dog modified by transection of the greater trochanter and placement of two pins that did not cross the simulated osteotomy.

METHODS: Four tension band configurations were applied to the metal trochanteric osteotomy model: figure-of-eight with one twist (OT), figure-of-eight with two twists (TT), dual interlocking single loop, and double loop (DL). Configurations were tested under both monotonic loading (n = 8 per configuration) and incremental cyclic loading (n = 8 per configuration). Initial tension after tying, residual tension remaining after each cycle, and failure load at 2 mm of displacement (considered equivalent to clinical failure) were compared between configurations.

RESULTS: The initial tension and the load to 2 mm of displacement were lower for OT wires compared with TT wires. The DL was the strongest and most stable configuration, generating 2.3 to 3.5 times greater initial tension, maintaining a greater percentage of residual tension under incremental cyclic loads, and resisting 2.0 to 2.4 times greater load before failure at 2 mm. Failure load was highly correlated with initial tension.

CONCLUSION: Wire configurations reaching greater initial tension, such as the DL, allowed constructs to resist higher tensile loads.

CLINICAL IMPACT: Wire configurations allowing higher initial tension may be warranted when tension bands are expected to sustain high tensile loads.

Small animal: