Finite element analysis of fixation stability according to reduction position for internal fixation of intertrochanteric fractures

In recent years, finite element analysis (FEA) has been instrumental in comparing the biomechanical stability of various implants for femur fracture treatment and in studying the advantages and disadvantages of different surgical techniques. This analysis has proven helpful for enhancing clinical treatment outcomes. Therefore, this study aimed to numerically analyze fixed stability according to location using FEA. In this study, a virtual finite element model was created based on a clinically anatomically reduced patient. It incorporated positive and negative support derived from intramedullary and extramedullary reduction from the anteroposterior (AP) view and neutral support from the lateral view. The generated model was analyzed to understand the biomechanical behavior occurring in each region under applied physiological loads. The simulation results of this study showed that the average von Mises stress (AVMS) of the nail when performing intramedullary reduction for femoral fixation was 187% of the anatomical reduction and 171% of the extramedullary reduction, and individually up to 2.5 times higher. In other words, intramedullary reduction had a very high possibility of fixation failure compared to other reduction methods. This risk is amplified significantly, especially in situations where bone strength is compromised due to factors such as old age or osteoporosis, which substantially affects the stability of fixation. Extramedullary reduction, when appropriately positioned, demonstrates greater stability than anatomical reduction. It exhibits stable fixation even in scenarios with diminished bone strength. In instances in which the bone density was low in the support position, as observed in the lateral view, the AVMS on the nail appeared to be relatively low, particularly in cases of positive support. Additionally, the femur experienced lower equivalent stress only in the extramedullary reduction-negative position. Moreover, by comparing different reduction methods and bone stiffness values using the same femoral shape, this study offers insights into the selection of appropriate reduction methods. These insights could significantly inform decision making regarding surgical strategies for intertrochanteric fractures.