The stabilising effect by a novel cable cerclage configuration in long cephalomedullary nailing of subtrochanteric fractures with a posteromedial wedge

Background Clinical studies suggest that an adjunctive cerclage in intramedullary nailing of subtrochanteric fractures improves the outcome. Despite this, to what extent various cerclage configurations influences the fixation strength, remains undocumented. We tested the hypothesis that the stability of subtrochanteric fractures with a posteromedial wedge treated with long cephalomedullary nail varies with cerclage configuration. Methods 40 composite femurs with a subtrochanteric osteotomy including a posteromedial-wedge were locked by cephalomedullary nailing (T2 recon, Stryker) and divided into 4 groups. In Group-A no cerclage was applied. The Group-B received a lateral tension-band (cerclage cable with crimp, Depuy-Synthes). Without any fixation, the wedge-component was removed in these groups. The Group-C was fixed with a cerclage encircling the wedge-component, while in the Group-D a novel figure-of-8 cerclage stabilised the wedge-component. Each femur was tested quasi-static in a material-testing-machine for stiffness calculation, first horizontally to simulate seated-position and then vertically to simulate standing-position. Finally, cyclic testing was performed in the upright-posture to measure deformation over time. Findings In Group-D the mean stiffness in the sitting-position was 6.4, 5.8 and 3.1 times higher than the Groups-A, B and C, respectively, and correspondingly 2.0, 2.1 and 1.7 times higher in the standing-position (p