Cerclage cable augmentation does not increase stability of the fixation of intertrochanteric fractures. A biomechanical study.

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 100N, followed by ten conditioning cycles from 100N to 500N. The test phase consisted of the cyclic loading between 100N and the maximum force that increased at a rate of 50N 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: 681N; group 2: 846N; group 3: 699N; group 4: 806N; ANOVA p=0.23) and stiffness (group 1: 769N/mm; group 2: 819N/mm; group 3: 815N/mm; group 4: 810N/mm; ANOVA p=0.84) between groups. There were significant differences in the widening of the lag screw canal (group 1: 2.16mm; group 2: 4.5mm; group 3: 3mm; group 4: 2.5mm; 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.