Abstract

Background: Intertrochanteric fractures with a posteromedial intermediate fragment are unstable because of the loss of medial support. Additional fixation with a cerclage is used in subtrochanteric fractures, but not in intertrochanteric fractures. The aim of this biomechanical study is to evaluate whether cerclage fixation improves stability of intertrochanteric fractures. Hypothesis: Our hypothesis is that the cerclage fixation of the intermediate fragment increases fixation stability of intertrochanteric fractures.Materials and methods: Synthetic femora with intertrochanteric fractures (AO 31.A1.3) with a posteromedial fragment were fixed with a long gamma nail. The intermediate fragment was fixed with a cerclage cable. Four groups were compared: 1: no cable fixation; 2: anatomic reduction and cable fixation; 3:anatomic reduction and fixation of a fragment where its proximal part was removed simulating comminution; 4: non-anatomic reduction and cable fixation. The specimens were loaded axially in a testing machine. The preload was 100 N, followed by ten conditioning cycles from 100 N to 500 N. The test phase consisted of the cyclic loading between 100 N and the maximum force that increased at a rate of 50 N at each cycle until failure. The stiffness was calculated from the load/displacement curve of the last three conditioning cycles.Results: There were no statistically significant differences between force to failure (group 1: 681 N; group2: 846 N; group 3: 699 N; group 4: 806 N; ANOVA p = 0.23) and stiffness (group 1: 769 N/mm; group2: 819 N/mm; group 3: 815 N/mm; group 4: 810 N/mm; ANOVA p = 0.84) between groups. There were significant differences in the widening of the lag screw canal (group 1: 2.16 mm; group 2: 4.5 mm; group3: 3 mm; group 4: 2.5 mm; ANOVA p = 0.017). In individual comparison, the differences were significant only between the anatomical reduction group and the non-anatomical reduction (p = 0.04) and the no cable group (p = 0.02).Discussion: There is a controversy in clinical literature whether cable fixation improves treatment outcome of proximal femoral fractures. This study suggests that medial wall reconstruction with a cerclage cable does not improve axial stability of the fixation. Level of evidence: Not applicable; a biomechanical study.

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