ABSTRACT
OBJECTIVE@#To evaluate the biomechanical stability of elastic intramedullary nail in the treatment of pubic ramus fractures by finite element analysis, and to compare the stability of elastic intramedullary nail with cannulated screw intramedullary fixation.@*METHODS@#The CT data of the pelvis of a volunteer were selected, and the three-dimensional model of the pelvis was reconstructed by reverse engineering software and the fracture of the pubic ramus fractures was simulated by osteotomy. The hollow nail model, single elastic nail model and double elastic nailmodel were assembled with different implants respectively. The mesh division, material assignment loading and other steps were carried out in the ANSYS software, and then the calculation was submitted.@*RESULTS@#The overall displacement of the pelvis of the elastic nail model was smaller than that of the cannulated screw model, in which the double elastic nail model had the smallest overall displacement, but the cannulated screw model had the smallest plant displacement and the single elastic nail model had the largest plant displacement. Although the stress of cannulated screw was small, there was obvious stress concentration, the stress of elastic nail was large, but there was no obvious stress concentration, especially the stress distribution of double elastic nail was more uniform and the overall stress of pelvis was the smallest.@*CONCLUSION@#All the three fixation methods can effectively improve the stability of the anterior ring of the pelvis. Among them, there is no significant difference in the overall biomechanical propertiesof hollow nail fixation and double elastic nail fixation, which is better than that of single elastic nail fixation. Elastic nail fixation has the advantages of minimally invasive surgery and good biomechanical stability, so it can be used as a better surgical method for the treatment of pubic ramus fractures.
Subject(s)
Humans , Biomechanical Phenomena , Bone Screws , Finite Element Analysis , Fracture Fixation, Internal , Fracture Fixation, Intramedullary , Fractures, Bone/surgery , Spinal FracturesABSTRACT
Objective There are few reports on the establishment of the finite element model of the rat femur in China, and even none on the finite element analysis of rat hip fracture. This study aimed to build a finite element model of osteoporotic rat proximal femoral fracture base on fracture mechanics. Methods We collected the CT imaging data on the femur of a healthy adult SD rat and established a preliminary three-dimensional finite element model of the rat femur. We also constructed a finite element model of femoral neck fracture in an osteoporotic rat by mesh generation, defining the material properties, setting interfacial properties and failure parameters, and loading. Then we measured the crack moment, von Mises, shear stress, stress, strains, displacement, and the starting point of fracture. Results The von Mises of stress showed that the crack moment was 0.109980s and the maximum stress and shear stress were mainly distributed on the medial inferior and lateral superior of the femoral neck when damage started, with the maximum stress of 367.9 Mpa and the maximum shear stress of 200.4 Mpa. The maximum strains was 1.2%, which was consistent with the routes of crack extension and extended from the medial inferior to the superior. The maximum displacement was 1.6 mm, mainly distributed on the proximal femoral, concentrated at the femoral head, and a displaced femoral neck model was simulated finally. Conclusion The finite element simulation model of femoral neck fracture in osteoporotic rats was successfully established, which can provide a new method for biomechanical studies in animal experiments.
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.