Backgrounds Finite element analysis (FEA) is an important tool during the spinal biomechanical study. Irregular surfaces in FEA models directly reconstructed based on imaging data may increase the computational burden and decrease the computational credibility. Definitions of the relative nucleus position and its cross-sectional area ratio do not conform to a uniform standard in FEA. Methods To increase the accuracy and efficiency of FEA, nucleus position and cross-sectional area ratio were measured from imaging data. A FEA model with smoothened surfaces was constructed using measured values. Nucleus position was calibrated by estimating the differences in the range of motion (RoM) between the FEA model and that of an in-vitro study. Then, the differences were re-estimated by comparing the RoM, the intradiscal pressure, the facet contact force, and the disc compression to validate the measured and calibrated indicators. The computational time in different models was also recorded to evaluate the efficiency. Results Computational results indicated that 99% of accuracy was attained when measured and calibrated indicators were set in the FEA model, with a model validation of greater than 90% attained under almost all of the loading conditions. Computational time decreased by around 70% in the fitted model with smoothened surfaces compared with that of the reconstructed model. Conclusions The computational accuracy and efficiency of in-silico study can be improved in the lumbar FEA model constructed using smoothened surfaces with measured and calibrated relative nucleus position and its cross-sectional area ratio.

Background: Adjacent vertebral fracture (AVF) is a frequently observed complication after percutaneous vertebroplasty (PVP) in patients with osteoporotic vertebral compressive fracture. Biomechanical deterioration initially induces a higher risk of AVF. Studies demonstrated that the aggravation of regional differences in the elastic modulus of different components might deteriorate the local biomechanical environment and increase the risk of structural failure. Considering the existence of intravertebral regional differences in bone mineral density (BMD) (i.e. elastic modulus), it was hypothesized in the present study that higher intravertebral BMD differences may induce a higher risk of AVF biomechanically. Materials and Methods: The radiographic and demographic data of osteoporotic vertebral compressive fracture patients treated using PVP were reviewed in the present study. The patients were divided into two groups: those with AVF and those without AVF. The Hounsfield unit (HU) values of transverse planes from the superior to the inferior bony endplate were measured, and the differences between the highest and lowest HU values of these planes were considered the regional differences of the HU value. The data from patients with and without AVF were compared, and the independent risk factors were identified through regression analysis. PVP with different grades of regional differences in the elastic modulus of the adjacent vertebral body was simulated using a previously constructed and validated lumbar finite element model, and the biomechanical indicators related to AVF were computed and recorded in surgical models. Results: Clinical data on 103 patients were collected in this study (with an average follow-up period of 24.1 months). The radiographic review revealed that AVF patients present a significantly higher regional difference in the HU value and that the increase in the regional difference of the HU value was an independent risk factor for AVF. In addition, numerical mechanical simulations recorded a stress concentration tendency (the higher maximum equivalent stress value) in the adjacent vertebral cancellous bone, with a stepwise aggravation of the adjacent cancellous bony regional stiffness differences. Conclusions: The aggravation of regional BMD differences induces a higher risk of AVF after PVP surgery through a deterioration of the local biomechanical environment. The maximum differences in the HU value of the adjacent cancellous bone should, therefore, be measured routinely to better predict the risk of AVF. Patients with noticeable regional BMD differences should be considered at high risk for AVF, and greater attention must be paid to these patients to reduce the risk of AVF. Evidence grade: Level III b.

BackgroundType 2 diabetes mellitus (T2DM) is a metabolic disorder associated with an increased incidence of cognitive and emotional disorders. Previous studies have indicated that the frontostriatal circuits play a significant role in brain disorders. However, few studies have investigated functional connectivity (FC) abnormalities in the frontostriatal circuits in T2DM.ObjectiveWe aimed to investigate the abnormal functional connectivity (FC) of the frontostriatal circuits in patients with T2DM and to explore the relationship between abnormal FC and diabetes-related variables.MethodsTwenty-seven patients with T2DM were selected as the patient group, and 27 healthy peoples were selected as the healthy controls (HCs). The two groups were matched for age and sex. In addition, all subjects underwent resting-state functional magnetic resonance imaging (rs-fMRI) and neuropsychological evaluation. Seed-based FC analyses were performed by placing six bilateral pairs of seeds within a priori defined subdivisions of the striatum. The functional connection strength of subdivisions of the striatum was compared between the two groups and correlated with each clinical variable.ResultsPatients with T2DM showed abnormalities in the FC of the frontostriatal circuits. Our findings show significantly reduced FC between the right caudate nucleus and left precentral gyrus (LPCG) in the patients with T2DM compared to the HCs. The FC between the prefrontal cortex (left inferior frontal gyrus, left frontal pole, right frontal pole, and right middle frontal gyrus) and the right caudate nucleus has a significant positive correlation with fasting blood glucose (FBG).ConclusionThe results showed abnormal FC of the frontostriatal circuits in T2DM patients, which might provide a new direction to investigate the neuropathological mechanisms of T2DM.

Polylactic acid glycolic acid (PLGA), a polymer material, is used as a shell and perfluorooctane (PFOB) as the core. Fe3O4@SiO2 nanoparticles are distributed in the shell to prepare a magnetic phase change multifunctional nano emulsion contrast agent (Fe3O4@SiO2/PLGA/PFOB). The ultrasound, magnetic resonance imaging and CT imaging effects of the contrast agent on normal rat liver parenchyma are investigated. Methods: Single emulsification method is used to prepare Fe3O4@SiO2-loaded polymer Fe3O4@SiO2/PLGA/PFOB nanoparticles encapsulated with PLGA. In addition, polymer Fe3O4@SiO2/PLGA nanoparticles loaded with Fe3O4@SiO2 nanoparticles, PLGA@PFOB nanoparticles coated with PLGA and blank PLGA nanoparticles are prepared as experimental control group. Its surface morphology, internal structure, particle size, potential and other general characteristics are tested. RAW264.7 mouse mononuclear macrophages are cultured in vitro. Prussian blue staining is used to observe macrophage phagocytosis after Fe3O4@SiO2/PLGA/PFOB contrast agent is added to incubate for 3 hours. MTT method is used to detect the effect of contrast agent on cell activity. The macrophage suspension engulfed with Fe3O4-PFOB is examined by ultrasound, magnetic resonance and CT. The results showed that Fe3O4@SiO2/PLGA/PFOB is brown emulsion after being dissolved in double distilled water. Under the light microscope and scanning electron microscope, Fe3O4@SiO2/PLGA/PFOB is spherical, with regular shape, uniform size, good dispersity and smooth surface. Macrophages are dependent on the phagocytosis of the contrast medium without affecting the activity of macrophages. Moreover, in vitro imaging experiments, compared with the control group, macrophages phagocytized by Fe3O4@SiO2/PLGA/PFOB have obvious enhancement effects in ultrasound, magnetic resonance and CT imaging. In conclusion, Fe3O4@SiO2/PLGA/PFOB has good stability in vivo, can be engulfed by liver macrophages, and can enhance ultrasound, magnetic resonance and CT imaging of liver parenchyma. It is a safe and effective multifunctional ultrasound contrast agent.