Subtrochanteric fracture location effect on surgical management using intermedullary nail (IMN) versus extramedullary plate (EMP): a finite element method analysis

Background: Finite element method (FEM) analysis of the subtrochanteric fracture (STF) location effect in the subtrochanteric region (STR) fixated with the intermedullary nail (IMN) versus extramedullary plate (EMP) implant. Material and methods: A femur computed tomography (CT) scan was used to create a femur FE-model with a straight-line fracture located at the STR. During the analysis, the fracture was stepwise lowered from 0.5 to 4.5 cm below the lesser trochanter (LT) with a total of 9 steps of 0.5 cm. The IMN (using proximal femoral nail antirotation) and EMP (using dynamic hip screw) implants were modelled and implemented for fracture management. Results: EMP illustrated lower Von-Mises stress for the proximal fractures (until 3.5 cm below LT); whereas IMN showed lower stress for distal fractures (from 4 cm below LT). The mean Von-Mises stress ratio for IMN versus EMP also decreased from proximal (1.93) to distal (0.47) of STR, with an intersection cross-point at 3.8 cm below LT. Conclusions: the simulation shows that for the straight-line STF, EMP seems more favourable for proximal and IMN is more likely favourable for distal fractures. However, more FEM studies need to be conducted (e.g., with different fractures or implant types) on this topic