In the present study, a finite element model of L4-5 lumbar motion segment was established based on the CT images and a combination with image processing software, and the analysis of lumbar biomechanical characteristics was conducted on the proposed model according to different cases of flexion, extension, lateral bending and axial rotation. Firstly, the CT images of lumbar segment L4 to L5 from a healthy volunteer were selected for a three dimensional model establishment which was consisted of cortical bone, cancellous bone, posterior structure, annulus, nucleus pulposus, cartilage endplate, ligament and facet joint. The biomechanical analysis was then conducted according to different cases of flexion, extension, lateral bending and axial rotation. The results showed that the established finite element model of L4-5 lumbar segment was realistic and effective. The axial displacement of the proposed model was 0.23, 0.47, 0.76 and 1.02 mm, respectively under the pressure of 500, 1 000, 1 500 and 2 000 N, which was similar to the previous studies in vitro experiments and finite element analysis of other people under the same condition. The stress distribution of the lumbar spine and intervertebral disc accorded with the biomechanical properties of the lumbar spine under various conditions. The established finite element model has been proved to be effective in simulating the biomechanical properties of lumbar spine, and therefore laid a good foundation for the research of the implants of biomechanical properties of lumbar spine.
Biomechanical Phenomena ; Finite Element Analysis ; Humans ; Intervertebral Disc ; anatomy & histology ; Lumbar Vertebrae ; anatomy & histology ; Models, Anatomic ; Pressure ; Prostheses and Implants ; Range of Motion, Articular ; Rotation

Based on the surgical model using transforaminal lumbar interbody fusion (TLIF) to treat lumbar spondylolisthesis, this paper presents the investigations of the biomechanical characteristics of cage and pedicle screw in lumbar spinal fusion implant fixed system under different combinations with finite element method. Firstly, combining the CT images with finite element pretreatment software, we established three dimensional nonlinear finite element model of human lumbar L4-L5 segmental slight slippage and implant under different fixed combinations. We then made a comparison analysis between the biomechanical characteristics of lumbar motion range, stress distribution of cage and pedicle screw under six status of each model which were flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation. The results showed that the motion ranges of this model under different operations were reduced above 84% compared with those of the intact model, and the stability of the former was improved significantly. The stress values of cage and pedicle screw were relatively larger when they were fixed by single fusion device additional unilateral pedicle screw, but there was no statistically significant difference. The above research results would provide reference and confirmation for further biomechanics research of TLIF extracorporal specimens, and finally provide biomechanical basis for the feasibility of unilateral internal fixed diagonal intervertebral fusion TLIF surgery.
Biomechanical Phenomena ; Finite Element Analysis ; Humans ; Lumbar Vertebrae ; Models, Anatomic ; Motion ; Pedicle Screws ; Posture ; Range of Motion, Articular ; Rotation ; Spinal Fusion

significantly save the time of diagnosis and facilitate the clinical application of large samples.

Objective:To analyze the differences in neuronal activation during fear memory extinction in various sub-regions of the hippocampus in post-traumatic stress disorder(PTSD)mice.Methods:Two immediate early gene-pro-tein labeling strategies were employed to label neurons associated with fear extinction in PTSD mice.In the first group,Arc protein in hippocampal neurons was labeled and observed through immunofluorescence staining in wild-type mice.In the second group,Fos-CreERT2;Ai9 transgenic mice were injected with tamoxifen 23 hours prior to inducing fear memory extinction,and the relevant neurons were labeled with fluorescent proteins for observation.The number of labeled hippocampal neurons and the dendritic branch structure were analyzed to compare the activation levels of hipp-ocampal neurons and the plasticity of neuronal dendrites.Results:The two groups of Arc and Fos positive neurons were mainly distributed in the dorsal hippocampus,in which Arc protein chromogenic was enriched in CA3 and DG subre-gions,while CA1 and CA2 subregions were scattered,while Fos-positive neurons were enriched in the DG subregion of hippocampus and scattered in CA1,CA2 and CA3 subregions.Compared to the control group,there was no significant difference in the number of neurons expressing Arc protein in each subregion of the hippocampus in the PTSD group.The number of Fos-positive neurons in CA1,CA3 and DG subregions in the hippocampus of the PTSD group was signifi-cantly increased(P＜0.01).The dendritic branches of neurons in the hippocampal region were observed and analyzed in Fos-CreERT2;Ai9 mice from both groups,but no significant changes were found.Conclusion:Abnormal activation of neurons occurs in different subregions of the hippocampus during fear extinction in PTSD mice,although there are no significant plasticity changes in the dendritic branches of the activated neurons.

Objective:To investigate the safety and feasibility of the CHESS endoscpic ruler (CHESS ruler), and the consistency between the measured values and the interpretation values by endoscopic physician experience.Methods:From January 2021 to January 2022, a total of 105 liver cirrhosis patients with portal hypertension were prospectively enrolled from General Hospital, Xixia Branch Hospital, Ningnan Hospital of People′s Hospital of Ningxia Hui Autonomous Region (29 cases), and the First People′s Hospital of Yinchuan (25 cases), General Hospital of Ningxia Medical University (18 cases), Wuzhong People′s Hospital (10 cases), the Fifth People′s Hospital of Ningxia Hui Autonomous Region (10 cases), Shizuishan Second People′s Hospital (6 cases), Yinchuan Second People′s Hospital (5 cases), and Zhongwei People′s Hospital (2 cases) 8 hospitals. The clinical characteristics of all the patients, including gender, age, nationality, etiolog of liver cirrhosis, and Child-Pugh classification of liver function were recorded. A big gastroesophageal varices was defined as diameter of varices ≥5 mm. Endoscopist (associated chief physician) performed gastroscopy according to the routine gastroscopy procedures, and the diameter of the biggest esophageal varices was measured by experience and images were collected, and then objective measurement was with the CHESS ruler and images were collected. The diameter of esophageal varices of 10 randomly selected patients (random number table method) was determined by 6 endoscopists (attending physician or associated chief physician) with experience or measured by CHESS ruler. Kappa test was used to test the consistency in the diameter of esophageal varices between measured values by CHESS ruler and the interpretation values by endoscopic physician experience.Results:Among 105 liver cirrhosis patients with portal hypertension, male 65 cases and female 40 cases, aged (54.8±12.2) years old, Han nationality 82 cases, Hui nationality 21 cases and Mongolian nationality 2 cases. The etiology of liver cirrhosis included chronic hepatitis B (79 cases), alcoholic liver disease (7 cases), autoimmune hepatitis (7 cases), chronic hepatitis C (2 cases), and other etiology (10 cases). Liver function of 32 cases was Child-Pugh A, Child-Pugh B 57 cases, and Child-Pugh C 16 cases. All 105 liver cirrhosis patients with cirrhotic portal hypertension were successfully measured the diameter of gastroesophageal varices by CHESS ruler, and the success rate of application of CHESS ruler was 100.0% (105/105). The procedure time from the CHESS ruler into the body to the exit of the body after measurement was (3.50±2.55) min. No complications happened in all the patients during measurement. Among 105 liver cirrhosis patients with cirrhotic portal hypertension, 96 cases (91.4%) were recognized as big gastroesophageal varices by the endoscopists. Totally 93 cases (88.6%) were considered as big gastroesophageal varices by CHESS ruler. Eight cases were recognized as big gastroesophageal varices by the endoscopist, however not by the CHESS ruler; 5 cases were recognized as big gastroesophageal varices by the CHESS ruler, but not by the endoscopists; 4 cases were not recognized as big gastroesophageal varices both by the endoscopists and CHESS ruler; 88 cases were recognized as big gastroesophageal varices both by the endoscopists and CHESS ruler. The missed diagnostic rate of big gastroesophageal varices by the endoscopists experience was 5.4% (5/93), and the Kappa value of consistency coefficient between the measurement by the CHESS ruler and the interpretation by endoscopists experience was 0.31 (95% confidence interval 0.03 to 0.60). The overall Kappa value of consistency coefficient by 6 endoscopists measured by CHESS ruler in big gastroesophageal varices diagnosis was 0.77 (95% confidence interval 0.61 to 0.93).Conclusion:As an objective measurement tool, CHESS ruler can make up for the deficiency of subjective judgment by endoscopists, accurately measure the diameter of gastroesophageal varices, and is highly feasible and safe.