Background The objective of this study was to use three-dimensional finite element （FE） models to analyze the stability and the biomechanics of two upper cervical fixation methods：the C2 intralaminar screw method a...Background The objective of this study was to use three-dimensional finite element （FE） models to analyze the stability and the biomechanics of two upper cervical fixation methods：the C2 intralaminar screw method and the C2 pedicle screw method.Methods From computed tomography images,a nonlinear three-dimensional FE model from C0 （occiput） to C3 was developed with anatomic detail.The C2 intralaminar screw and the C2 pedicle screw systems were added to the model,in parallel to establish the interlaminar model and the pedicle model.The two models were operated with all possible states of motion and physiological loads to simulate normal movement.Results Both the C2 intralaminar screw method and the C2 pedicle screw method significantly reduced motion compared with the intact model.There were no statistically significant differences between the two methods.The Von Mises stresses of the internal and external laminar walls were similar between the two methods.Stability was also similar.Conclusions The C2 intralaminar screw method can complement but cannot completely replace the C2 pedicle screw method.Clinicians would need to assess and decide which approach to adopt for the best therapeutic effect.展开更多
A theoretical approach is presented for analyzing the ply crackingin general symmetric lami- nates subjected to any combination ofin-plane mechanical loading and uniform temperature changes. Theequivalent constraint m...A theoretical approach is presented for analyzing the ply crackingin general symmetric lami- nates subjected to any combination ofin-plane mechanical loading and uniform temperature changes. Theequivalent constraint model proposed by the authors in a previouswork is used to account for the cracking in- teraction betweenlaminae in the laminates. By using a superposition schemce and thestress field solutions the energy release rate for a ply cracking isexplicitly as a function of stiffness reduction parameters of thelaminates. The ratio of mode Ⅰ to mode Ⅱ is introduced formconstruction of the fracture criterion. The effects of the laminateparameters and the crack spacing on the energy release rate and themode mixity are illustrated. Finally, the model is used to predictthe thermomechanical load for the first-ply-cracking.展开更多
Polymer composites is a typical material consisting of a matrix reinforced with fiber/filler and the general nature of construction of the material itself provides innumerable sites for the initiation of a defect or f...Polymer composites is a typical material consisting of a matrix reinforced with fiber/filler and the general nature of construction of the material itself provides innumerable sites for the initiation of a defect or for the growth of delamination. The life expectancy of composite structure requires a clear understanding of the material’s response to the growth of interlaminar delamination under Mode I, Mode II, Mode III and Mixed Modes. Fracture testing of fiber reinforced polymer-matrix composites is an active area of research. Even though substantial progress in the area of fracture testing has been achieved, there are still several problems awaiting solution. The new aspects in the experimental studies of interlaminar and intralaminar fracture toughness of polymer matrix composites were emphasized in this review paper. The different modes to evaluate the fracture energy were listed and their suitability was mentioned.展开更多
The treatment of pathologies in the thoracic spine is a challenge. The periodic failure of pedicle screw insertion and anatomical variations make the search for an alternative to pedicle screws in thoracic spine surge...The treatment of pathologies in the thoracic spine is a challenge. The periodic failure of pedicle screw insertion and anatomical variations make the search for an alternative to pedicle screws in thoracic spine surgery necessary. The interlaminar crossed screws is a well-known and secure method for fusion in cervical spine, and in thoracic spine there used to be insufficient clinical data to support this technique, until now. We demonstrate in an initial series of 10 cases treated with interlaminar fusion in association of other fusion techniques in the thoracic spine with good results. Objective: Intralaminar screws have been shown to be a biomechanical salvage technique in the thoracic spine, especially in long cervicothoracic, thoracic and thoracolumbar fixation. The goals of this article are to demonstrate our initial experience and the range of indications for thoracic crossed intralaminar screws. Methods: In this article we describe our initial series performed at São Teotónio Hospital in Viseu, Portugal, and our results, and also provide a comprehensive review of the recent literature in the use of intralaminar crossed fixation.展开更多
目的:观察脊髓背角P物质受体(substance P receptor,SPR)阳性神经元向臂旁核及中线/板内核群的分支投射并为其参与痒觉信息传递提供证据。方法:利用小动物脑立体定位仪向10只8周龄C57BL/6小鼠的臂旁核及丘脑中线/板内核群内分别注射四...目的:观察脊髓背角P物质受体(substance P receptor,SPR)阳性神经元向臂旁核及中线/板内核群的分支投射并为其参与痒觉信息传递提供证据。方法:利用小动物脑立体定位仪向10只8周龄C57BL/6小鼠的臂旁核及丘脑中线/板内核群内分别注射四甲基罗达明(tetramethylrhodamine-dextran,TMR)及荧光金(fluoro-gold,FG),观察小鼠脊髓背角的TMR/FG双标神经元。结合免疫荧光组织化学染色方法观察双标神经元表达SPR和在急性痒模型下表达Fos的情况。结果:脊髓背角I层、脊髓外侧核(lateral spinal nucleus,LSN)及脊髓背角IV～V层均可观察到TMR/FG双标神经元,且部分双标神经元分别表达SPR及Fos蛋白。结论:脊髓背角存在同时向臂旁核及丘脑中线/板内核群发出分支投射的神经元,部分双标神经元表达SPR并参与痒觉信息的传递。展开更多
文摘Background The objective of this study was to use three-dimensional finite element （FE） models to analyze the stability and the biomechanics of two upper cervical fixation methods：the C2 intralaminar screw method and the C2 pedicle screw method.Methods From computed tomography images,a nonlinear three-dimensional FE model from C0 （occiput） to C3 was developed with anatomic detail.The C2 intralaminar screw and the C2 pedicle screw systems were added to the model,in parallel to establish the interlaminar model and the pedicle model.The two models were operated with all possible states of motion and physiological loads to simulate normal movement.Results Both the C2 intralaminar screw method and the C2 pedicle screw method significantly reduced motion compared with the intact model.There were no statistically significant differences between the two methods.The Von Mises stresses of the internal and external laminar walls were similar between the two methods.Stability was also similar.Conclusions The C2 intralaminar screw method can complement but cannot completely replace the C2 pedicle screw method.Clinicians would need to assess and decide which approach to adopt for the best therapeutic effect.
基金the National Natural Science Foundation of China (No.19972076)the Germen Research Foundation (DFG)
文摘A theoretical approach is presented for analyzing the ply crackingin general symmetric lami- nates subjected to any combination ofin-plane mechanical loading and uniform temperature changes. Theequivalent constraint model proposed by the authors in a previouswork is used to account for the cracking in- teraction betweenlaminae in the laminates. By using a superposition schemce and thestress field solutions the energy release rate for a ply cracking isexplicitly as a function of stiffness reduction parameters of thelaminates. The ratio of mode Ⅰ to mode Ⅱ is introduced formconstruction of the fracture criterion. The effects of the laminateparameters and the crack spacing on the energy release rate and themode mixity are illustrated. Finally, the model is used to predictthe thermomechanical load for the first-ply-cracking.
文摘Polymer composites is a typical material consisting of a matrix reinforced with fiber/filler and the general nature of construction of the material itself provides innumerable sites for the initiation of a defect or for the growth of delamination. The life expectancy of composite structure requires a clear understanding of the material’s response to the growth of interlaminar delamination under Mode I, Mode II, Mode III and Mixed Modes. Fracture testing of fiber reinforced polymer-matrix composites is an active area of research. Even though substantial progress in the area of fracture testing has been achieved, there are still several problems awaiting solution. The new aspects in the experimental studies of interlaminar and intralaminar fracture toughness of polymer matrix composites were emphasized in this review paper. The different modes to evaluate the fracture energy were listed and their suitability was mentioned.
文摘The treatment of pathologies in the thoracic spine is a challenge. The periodic failure of pedicle screw insertion and anatomical variations make the search for an alternative to pedicle screws in thoracic spine surgery necessary. The interlaminar crossed screws is a well-known and secure method for fusion in cervical spine, and in thoracic spine there used to be insufficient clinical data to support this technique, until now. We demonstrate in an initial series of 10 cases treated with interlaminar fusion in association of other fusion techniques in the thoracic spine with good results. Objective: Intralaminar screws have been shown to be a biomechanical salvage technique in the thoracic spine, especially in long cervicothoracic, thoracic and thoracolumbar fixation. The goals of this article are to demonstrate our initial experience and the range of indications for thoracic crossed intralaminar screws. Methods: In this article we describe our initial series performed at São Teotónio Hospital in Viseu, Portugal, and our results, and also provide a comprehensive review of the recent literature in the use of intralaminar crossed fixation.
文摘目的:观察脊髓背角P物质受体(substance P receptor,SPR)阳性神经元向臂旁核及中线/板内核群的分支投射并为其参与痒觉信息传递提供证据。方法:利用小动物脑立体定位仪向10只8周龄C57BL/6小鼠的臂旁核及丘脑中线/板内核群内分别注射四甲基罗达明(tetramethylrhodamine-dextran,TMR)及荧光金(fluoro-gold,FG),观察小鼠脊髓背角的TMR/FG双标神经元。结合免疫荧光组织化学染色方法观察双标神经元表达SPR和在急性痒模型下表达Fos的情况。结果:脊髓背角I层、脊髓外侧核(lateral spinal nucleus,LSN)及脊髓背角IV～V层均可观察到TMR/FG双标神经元,且部分双标神经元分别表达SPR及Fos蛋白。结论:脊髓背角存在同时向臂旁核及丘脑中线/板内核群发出分支投射的神经元,部分双标神经元表达SPR并参与痒觉信息的传递。
