The lateral femoral wall thickness on the risk of post-operative lateral wall fracture in intertrochanteric fracture after DHS fixation: A finite element analysis.

BACKGROUND

Patients with a lateral femoral wall (LFW) fracture were reported to have high rates of re-operation and complication. Although the LFW thickness was a reliable predictor of post-operative or intra-operative LFW fracture, there was a paucity of literature evaluating the critical stress distributions on the femur and screws of intertrochanteric fractures treated with dynamic hip screw (DHS). This study aimed to investigate the biomechanical performance of intertrochanteric fractures with different LFW thickness treated with DHS device.

METHODS

A three-dimensional model of the proximal femur was established by computed tomography images. The intertrochanteric fracture model with three different LFW thickness (10 mm, 20.5 mm and 30 mm, respectively) was created, which was fixed by DHS. The von Mises stress on the proximal femur, lateral femoral wall, DHS and the total displacement of the device components were evaluated and compared for three different LFW thickness model.

RESULTS

The maximum von Mises stress in the proximal fragment of the 10 and 20.5 mm model increased by 80.56% and 57.97% when compared with the 30 mm model. The peek von Mises stress around the blade entry point of the 10 mm and 20.5 mm model increased by 89.26% and 66.39% when compared with the 30 mm model. The peek von Mises in the DHS located near the junction of the barrel and side plate of each model and the 30 mm model had the smallest von Mises stress compared with the other two models. Furthermore, the maximum displacement in the 30 mm model was much smaller than that in the10mm model and 20 mm model.

CONCLUSIONS

The intertrochanteric fracture with a thinner LFW tended to have a higher risk of LFW fracture stabilized by a DHS device. Thus, the intertrochanteric fractures with a thinner LFW should not be treated by DHS alone and the intramedullary nail or an addition of trochanteric stabilization plate(TSP) was recommended.