Numerical comparison of the intramedullary nail for the fixation of different proximal femoral fractures.

Abstract

This study aimed to compare the mechanical responses, including the stability and implant stress, of different proximal femoral fractures stabilized with an intramedullary system by finite element simulation. Furthermore, the effect of number of the lag screws, including one and two screws, was also investigated. A numerical hip model was created first, and then four different types of proximal femoral fractures-namely femoral neck, intertrochanteric, reverse intertrochanteric, and subtrochanteric fractures-were employed in this study. An intramedullary nail system was used to fix the four fracture types. Furthermore, two different number of lag screws, either one bigger or two smaller, was also compared. The peak loading of the femur in level walking was used for comparison. The results showed that both the peak displacement and the gap opening distance in the reversed intertrochanteric fracture were obviously higher than in the other fractures. Additionally, the peak equivalent stress of the intramedullary nail in the reversed intertrochanteric fracture was the highest among all the fractures. The stress on the nail in cases of reversed intertrochanteric fracture was 4.6 times (ranging from 132.9 to 616.8 MPa) and 4.4 times (ranging from 126 to 556 MPa) higher than in intertrochanteric fractures with one and two lag screws, respectively. The intramedullary nail is a mechanically effective device for the fixation of proximal femoral fractures. However, to avoid the nail breakage the postoperative rehabilitation process for reversed intertrochanteric fracture should be slower compared to the neck, intertrochanteric and subtrochanteric fractures.