ABSTRACT
BACKGROUND: At present, finite element analysis can be used to judge intertrochanteric fractures, but mostly limited in the distribution of stress. Finite element model of various intertrochanteric fractures has not been reported in detail.OBJECTIVE: To build various types of intertrochanteric fracture models with Hypermesh 14.0 and LS-DYNA software to simulate the falling-induced external force on proximal femur, and to evaluate the effect of models, and to analyze the biomechanical mechanism of intertrochanteric fractures. METHODS: Normal side CT image data of one case of elderly intertrochanteric fracture were collected and imported into Mimics software to establish the proximal femur geometric models, were then analyzed and operated by LZ-DYNA solver after imported into Geomagic studio 2013 and Hypermesh 14.0 for smoothing and meshing. Before analysis, the material parameters were set, the boundary conditions were confirmed, and given the loading parameters. The operating results were checked in Hyper View. RESULTS AND CONCLUSION: (1) The distribution of stress of proximal femur exactly matched to the previous study. EvansⅠtype intertrochanteric fracture model was obtained under continuous shear stresses, and six types of fractures were obtained by adjusting the load. (2) These results manifest that based on the Hypermesh 14.0 and LS-DYNA software, the finite element can well simulate the intertrochanteric fractures, and shear stress plays an important role in intertrochanteric fractures, which can provide experimental basis for the prevention and treatment of intertrochanteric fractures.
ABSTRACT
Objective The influence of intertrochanteric cortical thickness on hip fracture can be investigated by the finite element method (FEM), but few dynamic FEMs have been established to manifest the extension of the crack. This study aimed to investigate the influence of intertrochanteric cortical thickness on the proximal femoral fracture types by FEM.Methods We recruited a healthy male volunteer from the Department of Traumatic Orthopedics, the First Affiliated Hospital of Guangzhou University of Chinese Medicine in October 2017, established a 3-dimention model, and reconstructed thick, middle and thin intertrochanteric cortex proximal femur models by meshing, defining material properties and setting boundary conditions. We measured the crack moment and von Mises stress, distribution of the fracture line, and the time-stress curves of the earliest damage element.Results Fracture occurred the earliest in the thin-cortex femur model but the latest in the thick one. The von Mises stress contour plot showed that, when damage started, the stress was concentrated on the posterior femoral neck and intertrochanteric region, extending to the posterior inferior part of the lesser trochanter in all the three models and, with the decline of the intertrochanteric cortex thickness, the concentration of the von Mises stress gradually narrowed down and shifted to the intertrochanteric region. The narrowing of the von Mises stress was the most obvious in the thin-cortex model, mainly distributed on the junction of the basal femoral neck and the intertrochanteric region. With the thinning of the cortex, the lesser trochanter became the region of stress concentration. The time-stress curves showed that fracture occurred the earliest in the thin-cortex model, with the maximum stress of 51.6 Mpa, but the latest in the thick-cortex model, with the maximum stress of 96.4 Mpa, and the maximum stress was 89.7 Mpa in the middle cortex model.Conclusion The thickness of the intertrochanteric cortex may be a determinant in the types of hip fracture.