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.
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.
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AIM: To evaluate the effects of 23G vs 20G pars plana vitrectomy ( PPV ) combined with internal limiting membrane peeling, phacoemulsification and intraocular lens implantation for macular epiretinal membrane with cataract. ·METHODS: Totally 45 eyes of 45 patients with macular epiretinal membrane and cataract were enrolled in this retrospective non-randomized controlled clinical study. All eyes were treated with PPV combined with internal limiting membrane peeling, phacoemulsification and intraocular lens implantation. There were 20 eyes in 23G PPV group, and 25 eyes in 20G PPV group. The best corrected visual acuity ( BCVA ) , intraocular pressure (IOP), counting of corneal endothelial cells ( CEC) and central retinal thickness ( CRT ) were examined before surgery. BCVA results were converted to the logarithm of the minimum angle of resolution ( LogMAR ) visual acuity. All operations were performed by the same doctor. Operation time for vitrectomy and membrane peeling, average ultrasound energy ( AVE) and effective phacoemulsification time ( EPT ) were recorded. BCVA and CRT were observed postoperatively at 30d and 90d, counting of CEC was observed postoperatively at 90d. IOP was observed postoperatively at 1d and 7d. ·RESULTS:The mean operation time for vitrectomy were 12. 57± 1. 35min in 23G group and 17. 30 ± 1. 19min in 20G group. The difference was statistically significant ( t =-12. 488, P<0. 01). There were no statistical significances in operation time for membrane peeling, AVE and EPT between 23G and 20G groups ( t=-0. 68,-1. 186,-0. 737, P=0. 500, 0. 242,0. 465). On 1d after surgery, IOP in 23G group was lower than that in 20G group, the difference was statistically significant (t= -2. 345, P=0. 024). The BCVA and CRT of the two groups both improved after operations. There were no statistically significant differences between two groups in terms of IOP, BCVA, and CRT ( F = 0. 465, 1. 895, 0. 689; P = 0. 499, 0. 176, 0. 411). IOP, BCVA and CRT were significant statistical different in different time-point within each group ( F=291. 245, 103. 06, 665. 402, P<0. 01 ). Different surgical methods of 23G and 20G had interactive effects on IOP with different time points ( F = 13. 245, P<0. 01 ), but different surgeries had no interactive effects on BCVA and CRT with different time points (F=1. 212, 2. 293;P=0. 283, 0. 129). The counting CEC in 23G group was more than that in 20G group postoperatively at 90d, the difference was statistically significant (t=2. 049, P=0. 048). ·CONCLUSION: The 23G PPV combined with internal limiting membrane peeling, phacoemulsification, intraocular lens implantation for macular epiretinal membrane with cataract is effective. Compared with 20G PPV, 23G PPV has advantages in operation time for vitrectomy and counting CEC. But lower IOP is likely in 23G PPV on 1d after surgery
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AIM: To explore the frequency of drug injection of alloxan diabetes on the established model of rabbit.METHODS: Thirty-six healthy rabbits, weighing 2-2.5kg, were randomly divided into one time drug injection group (group A, n=12), two times drug injection group (group B, n=12) and three times drug injection group (group C, n=12). Each rabbit was injected with a total amount of 150mg/kg of alloxan. Fasting blood glucose was measured. The success rate and death rate of each group were also calculated.RESULTS: The success rate of diabetic rabbit model in group B was higher than that in group A (P<0.01) and its death rate was lower than that of group A (P<0.01); the success rate of diabetic rabbit model in group C was highest and the death rate was the lowest in three groups(P<0.01). CONCLUSION: Multiple administration of alloxan can improve success rate in establishing diabetic rabbit model with decreased death rate and increased stability.