BACKGROUND:Vertebral compression fracture is a common disease in the current orthopedic field.However,the occurrence of re-fracture in neighboring vertebrae after surgery is a problem that cannot be ignored,which has a serious impact on the normal life of patients. OBJECTIVE:The aim of this study is to establish four postoperative models with different recovery heights using computed tomography images.By using finite element analysis,we derived the stresses on the neighboring vertebrae at different recovery heights and further explored the importance of postoperative recovery of the height of the injured vertebrae. METHODS:A finite element model of the thoracolumbar spine(T11-L3)was established and validated,on the basis of which four postoperative finite element models of L1 with different recovery heights of 100%,80%,60%,and 40%were constructed,in which the cement capacity varied with the recovery height.The specific models are as follows:Model 1 was the postoperative model with normal recovery height,and the cement capacity was 8.3 mL.Model 2 was the postoperative model in which 20%of the anterior height of the L1 was removed and the posterior convexity angle became 10.41°,and the cement capacity was 6.9 mL.Model 3 was the postoperative model in which 40%of the anterior height of the L1 was removed and the posterior convexity angle became 20.17°,and the cement capacity was 4.7 mL.Model 4 was a postoperative model with 60%of the L1 anterior height removed and the posterior convexity angle changed to 28.85°,with a cement capacity of 3.6 mL.For evaluation of the postoperative model,we applied a moment of 7 Nm and an axial force of 500 N.The followings were recorded and analyzed:peak stresses in the L2 upper endplate and T12 lower endplate;peak stresses in the L2 and T12 cancellous bone. RESULTS AND CONCLUSION:(1)The highest peak stresses for each condition of the L2 upper endplate,T12 lower endplate,L2 cancellous bone,and T12 cancellous bone occurred in Model 1 and Model 4.In particular,the T12 lower endplate,except for the posterior extension condition,the anterior flexion,left and right lateral bending,and left and right rotation conditions all reached their highest peak stresses in Model 4,with stresses of 50.3,33.1,44.9,34.3,and 31.9 MPa.(2)Based on the peak stresses in the adjacent vertebral endplates and cancellous bone,after excluding Model 1 and Model 4,the minimum peak stresses for most of the conditions appeared in the Model 2,and the minimum peak stresses appeared in the Model 2 in 66.6%of the cases,especially in the upper endplates of the L2 and cancellous bone except for the posterior extension condition,the minimum peak stresses all appeared on the Model 2.(3)Therefore,controlling the recovery height at about 100%and 40%of the original height was a dangerous recovery height,which had a greater impact on the neighboring vertebrae.Controlling the recovery height at about 80%of the original height may be a more ideal choice.With a recovery height of about 80%of the original height,the adjacent vertebrae are subjected to less stress,thus reducing the risk of re-fracture of the adjacent vertebrae in the patient.

Objective:To evaluate the changes in topological properties of brain functional network after induction of general anesthesia in the patients with glioma.Methods:Twenty-two patients scheduled for elective intracranial glioma resection were selected.Resting-state functional magnetic resonance imaging was performed during wakefulness and general anesthesia with endotracheal intubation in patients with glioma. Large-scale functional brain networks of each patient were constructed based on 123 regions of interest in non-surgical hemisphere. Global properties (local efficiency, clustering parameter, shortest path length, global efficiency, small world) and nodal properties (nodal degree, nodal efficiency, and between centrality) in brain functional networks were then compared between wakefulness and general anesthesia.Results:Eighteen patients were finally enrolled. Compared with the status during wakefulness, the local efficiency and clustering parameter on non-surgical side significantly decreased ( P<0.05), no significant change was found in the shortest path length and global efficiency ( P>0.05), and small world was greater than 1 throughout the entire density range; the nodal degree, nodal efficiency and between centrality of nodes located in the medial/mesal regions, such as the medial prefrontal cortex, posterior cingulate gyrus/precuneus, medial temporal lobe, anterior cingulate gyrus, thalamus, amygdala, were significantly reduced ( P<0.05); however, these node parameters increased significantly in the lateral brain regions ( P<0.05) except for the primary auditory and somatosensory cortex, which also decreased significantly after induction of general anesthesia( P<0.05). Conclusions:The functional segregation of brain functional network is widely inhibited after induction of general anesthesia, but the functional integration is still retained. The lateral brain regions show no anticorrelation with the medial brain region during general anesthesia.

BACKGROUND:The elastic modulus of traditional bone implants is large and does not match the elastic modulus of human bone,which will cause a stress shielding effect and lead to bone resorption.The trabecular scaffold of the triply periodic minimal surface with radial gradient has elastic modulus matching with human cancellous bone,and its yield strength is greater than that of human cortical bone,which provides a new choice for the design of bone scaffold. OBJECTIVE:Triply periodic minimal surface structure with radial gradient was constructed by the implicit surface method.The sample was manufactured by laser selective melting technology,and the quasi-static compression test was carried out to obtain trabecular scaffolds with mechanical properties matching human bones. METHODS:Four types of the trabecular scaffolds of the triply periodic minimal surface with a radial gradient of G,I,P and D were established by the implicit surface method.Samples were manufactured by laser selective melting technology.We observed the surface morphology of the molded sample,evaluated the molding quality,conducted a quasi-static compression test,and evaluated the mechanical properties of the samples. RESULTS AND CONCLUSION:The quasi-static compression test results showed that compared with the four triply periodic minimal surface scaffolds,the platform stress of the G scaffold had less fluctuation and no failure or fracture,indicating that the G scaffold had the best plasticity.The mechanical properties of the G scaffolds with 45%,55%and 65%porosities were analyzed.It was found that the elastic modulus of G scaffolds with 55%porosity was within the range of elastic modulus of human cancellous bone(0.022-3.7 GPa),and the yield strength was close to the maximum yield strength of human cortical bone(187.7-222.3 MPa).In conclusion,G triply periodic minimal surface scaffold with 55%porosity can reduce the stress shielding effect,bear a higher body load,improve the stability of the implant,and prolong the service life of the implant.