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

Abstract

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.