Biomechanical evaluation of internal fixation for the treatment of comminuted subtrochanteric femur fractures.

Background: Several biomechanical studies on subtrochanteric femur fractures have reported that use of an intramedullary nail is superior to extramedullary implant. However, the optimal choice of intramedullary nail for the treatment of comminuted subtrochanteric femur fracture remains unclear. Here, we evaluated the biomechanical properties of comminuted subtrochanteric femur fracture treated with four different internal fixations.

Methods: A comminuted subtrochanteric femur fracture model was created with a 2-cm gap below the lessor trochanter in 20 synthetic femurs. The fractures were fixed with one of four implants - Antegrade Femoral Nail (AFN), Trochanteric Fixation Nail Advanced with a femoral neck blade (TFNA blade), TFNA with a femoral neck screw (TFNA screw), and the reversed distal femoral locking compression plate (DF-LCP) - all manufactured by DePuy Synthes. Axial compression tests and torsion tests were performed and the stiffness of each implant was compared.

Results: For compression, the TFNA blade, TFNA screw, and AFN provided significantly higher stiffness than DF-LCP (p < 0.001, p < 0.001, p = 0.001, respectively), and the TFNA blade provided significantly higher stiffness than AFN (p = 0.049). For torsion, there were no significant differences among the groups in internal rotation, while the TFNA screw had significantly lower torsional stiffness than the AFN, TFNA blade and DF-LCP in external rotation (p = 0.036, p = 0.034, p = 0.037, respectively).

Conclusions: These findings could help to provide biomechanical evidence regarding choice of implant for the treatment of comminuted subtrochanteric femur fracture. The TFNA blade may be more suitable for the treatment of comminuted subtrochanteric femur fracture.