Abstract
OBJECTIVE: Several novel design concepts have emerged that incorporate additional augmentation screws with proximal femoral nails and lag screws to manage unstable proximal femoral fractures. However, the biomechanical performance of these additional screws across different fracture types remains unclear. This study aimed to compare the biomechanical effects of different additional augmentation screw placements combined with proximal femoral nails in the fixation of proximal femoral fractures using finite element (FE) analysis. METHODS: An FE model was developed to simulate three types of proximal femoral fractures: femoral neck, intertrochanteric, and reverse intertrochanteric fractures. Three configurations of additional augmentation screw placement were analyzed: (1) through the greater trochanter (bionic nail, BN), (2) through the subtrochanteric region (modified proximal femoral nail, PFN-M), and (3) parallel and adjacent to the lag screw (proximal femoral InterTAN nail, ITAN). For comparison, traditional proximal femoral nail (PFN) and dynamic hip screw (DHS) constructs were also included. A joint reaction force of 2800 N and a hip abductor force of 1500 N, simulating walking conditions, were applied to assess the stability of the fractured femur with each implant. RESULTS: In terms of fracture gap stabilization, the ITAN provided the greatest stability for femoral neck fractures, while the PFN-M was most effective for reverse intertrochanteric fractures. Specifically, the medial and lateral fracture gap distances for femoral neck fractures treated with ITAN were 1.64 mm and 2.08 mm, respectively. For reverse intertrochanteric fractures treated with PFN-M, the medial and lateral gap distances were 1.43 mm and 2.32 mm, respectively. No notable differences in gap deformation were observed among the PFN, PFN-M, BN, and ITAN constructs. CONCLUSIONS: The addition of augmentation screws to proximal femoral nails enhances the biomechanical stability of proximal femoral fracture fixation. Optimal screw placement should be tailored to the specific fracture pattern to achieve the best biomechanical outcomes.