Assessment of complications depending on the sliding screw position - finite element method analysis

The study was aimed at the assessment of specific complications depending on the sliding hip screw position.

The finite element method in the biomechanical analysis of this implant may be used to predict the mechanical failure due to the screw position.

380 sliding screw osteosyntheses for stable pertrochanteric fractures of 365 patients were included in the study. We divided and analysed the osteosyntheses with five various screw positions and focused on the specific complications development. For the construction of the finite element model of the femur, the program ABAQUS 6.9 was used. Analyses were performed with evaluation of the bone response to the different screw locations (strain and stress) with maximum low-cycle high stress loading.

The specific complication rate was 10 %, with the re-operation rate of 4.2 %. If placing the screw in the middle third of the neck it reduced significantly strain patterns of the plate and screw. A screw position in the superior third of the neck significantly increased the strain of the plate and screw by more than 63 %.

The conformity in the clinical and biomechanical analyses was observed. The finite element model can be considered as valid in predicting sliding screw failures (Tab. 4, Fig. 8, Ref. 30).