The influence of proximal femur CT value on stress distribution and stability in intertrochanteric fracture after PFNA fixation: a finite element analysis.

PURPOSE: This study was conducted to develop a finite element analysis (FEA) model for proximal femoral nail antirotation (PFNA) fixation for intertrochanteric femoral fractures, aiming to analyze the effects of varying proximal femur trabecular bone CT values on stress distribution and device stability, as well as to determine their relationships.

METHODS

We established a three-dimensional model for PFNA fixation of intertrochanteric femoral fractures based on computed tomography images. Different elastic moduli were assigned to the trabecular bone according to varying proximal femur CT values, enabling an analysis of the differences in stress distribution and maximum displacement of the model under the same loading conditions.

RESULTS

Under the same stress loading conditions, as the CT values of the proximal femoral trabecular bone decreased from 160 to 120, 80, 40, and 0 HU, the von Mises stress values around the trabecular bone decreased. Moreover, the stress values near the cortical bone, intramedullary nail, screw tip, and junction between the screws and the main nail increased. Additionally, the maximum displacement of the entire model also increased. This finding indicates that as the proximal femur CT values decreased, the load on the cortical bone and internal fixation increased, leading to greater instability of the model and a higher risk of internal fixation failure.

CONCLUSION

As the CT value of the proximal femoral trabecular bone decreases, the stability of the PFNA fixation device diminishes, leading to increased stress on both the cortical bone and the intramedullary nail, thereby increasing the risk of PFNA fixation failure.