The effects of different cortical impingement scenarios on the biomechanical features of retrograde femoral nails in the management of distal femoral fractures: A finite element analysis

Abstract

Objective: This study aimed to assess the effects of different cortical impingement scenarios on the biomechanical features of retrograde femoral nails in managing distal femoral fractures. Methods: A mesh femur model was constructed using computed tomography (CT) images. Five different cortical impingement (CI) scenarios were designed: central model (CM), lateral CI (LCI), medial CI (MCI), anterior CI (ACI), and posterior CI (PCI). The fixation stability was evaluated by femoral head movement, stress, and elastic strain at the fracture site. The maximum stress on the femoral cortex and the implants were also measured. Results: The maximal femoral head movements were 3.11 mm in ACI and 2.91 mm in MCI. Among all CI models, the highest stress value at the fracture site was recorded in ACI (18.9 MPa), and the maximum stress on the femoral cortex was determined in ACI (114.3 MPa). The highest microstrain value at the fracture site was measured in MCI (599.1 μstrain). In all scenarios, maximum stress was located around the proximal hole of the nail. Conclusion: This study revealed that cortical impingement results in excessive loading on the retrograde femoral nail in managing distal femur fractures. MCI and ACI mainly cause this pathological loading. Problems related to supraphysiological loadings, such as implant failure and periprosthetic fracture, can be reduced by applying the nail in the central position.