Does the type and length of nail affect the stability of fixation of subtrochanteric fractures under low displacement forces?

The treatment of subtrochanteric fractures is a highly contentious area, given the complex biomechanical properties and displacing muscle forces involved. Indeed, the debates cover almost all aspects of the treatment. Objective. To evaluate the biomechanical properties of three distinct intramedullary nails in order to identify the most reliable fixation method for subtrochanteric reverse oblique femur fractures. Methods. An osteotomy was performed in accordance with the 31A3 (intertrochanteric reverse oblique) fracture model on 24 synthetic femur bone models. Following the achievement of anatomical reduction, each group was fixed with a distinct implant system: An A-PFN (220 mm in length), an A-PFN (280 mm in length), and a cephalomedullary nail (360 mm in length). The evaluation of all models was conducted under both single and cyclic loading conditions, and an assessment of the fracture lines and total femur displacements was performed. Results. No significant correlation was observed between the groups with regard to fracture line displacement (p > 0.05). However, a notable distinction was evident in total femur displacement between the groups under both single and cyclic loading conditions (p < 0.001 and p = 0.004, respectively). Post-hoc analyses demonstrated that the discrepancies between the group comparisons were between the A-PFN (220 mm in length) and the other two fixation methods. Conclusions. Both short and long nails provide adequate and similar stability in an anatomically reduced reverse-oblique subtrochanteric fracture model. This suggests that anatomical reduction is more crucial than implant selection in subtrochanteric single-line fractures. While longer implants do not affect the displacement of the fracture line, they do affect the total displacement of the femur, creating a more rigid femur.