基于ANSYS/LS-DYNA的神经电极植入脑组织过程数值仿真

目的建立神经电极-脑组织数值仿真模型,研究神经电极在植入过程中对脑组织产生的植入损伤。方法采用超黏弹性模型描述脑组织材料,基于单元删除法和最大主应变失效准则模拟组织破坏与分离,并通过平均等效应变量化组织植入损伤,考察神经电极楔形角、植入速度以及电极刚度对脑组织急性损伤的影响规律。结果150°楔角所产生应变值较90°增加37.1%;100μm/s慢速植入时电极植入路径上组织应变值较大(57%),500μm/s较高速植入时植入路径上组织应变明显变小(25%);而电极刚度对组织损伤影响不明显,电极刚度从165 GPa下降至5 k Pa时,组织应变仅增加1%~2%。结论数值仿真模型可为神经电极与植入参数设计提供参考,从而减少组织植入损伤,提高电极工作寿命,满足长期临床应用。     

基于ANSYS/LS-DYNA的神经电极植入脑组织过程数值仿真

目的 建立神经电极-脑组织数值仿真模型,研究神经电极在植入过程中对脑组织产生的植入损伤。方法 采用超黏弹性模型描述脑组织材料,基于单元删除法和最大主应变失效准则模拟组织破坏与分离,并通过平均等效应变量化组织植入损伤,考察神经电极楔形角、植入速度以及电极刚度对脑组织急性损伤的影响规律。结果 150°楔角所产生应变值较90°增加37.1%;100 μm/s慢速植入时电极植入路径上组织应变值较大（>57%）,500 μm/s较高速植入时植入路径上组织应变明显变小（<25%）;而电极刚度对组织损伤影响不明显,电极刚度从165 GPa下降至5 kPa时,组织应变仅增加1%~2%。结论 数值仿真模型可为神经电极与植入参数设计提供参考,从而减少组织植入损伤,提高电极工作寿命,满足长期临床应用。     

基于ANSYS/LS-DYNA的神经电极植入脑组织过程数值仿真

目的 建立神经电极-脑组织数值仿真模型,研究神经电极在植入过程中对脑组织产生的植入损伤。方法 采用超黏弹性模型描述脑组织材料,基于单元删除法和最大主应变失效准则模拟组织破坏与分离,并通过平均等效应变量化组织植入损伤,考察神经电极楔形角、植入速度以及电极刚度对脑组织急性损伤的影响规律。结果 150°楔角所产生应变值较90°增加37.1%;100 μm/s慢速植入时电极植入路径上组织应变值较大（>57%）,500 μm/s较高速植入时植入路径上组织应变明显变小（<25%）;而电极刚度对组织损伤影响不明显,电极刚度从165 GPa下降至5 kPa时,组织应变仅增加1%~2%。结论 数值仿真模型可为神经电极与植入参数设计提供参考,从而减少组织植入损伤,提高电极工作寿命,满足长期临床应用。     

涂层修饰的柔性神经电极力学综合性能评估

目的对带有涂层修饰的柔性神经电极进行力学综合性能的评估,为电极及涂层参数的优化设计提供依据。方法对接触、植入以及微动阶段建立简化力学模型,以聚酰亚胺为电极材料,PEG为涂层材料,PDMS模具注塑法为涂层涂覆方法,设置40、80、120、160、200μm涂层厚度梯度,对3个因素(临界载荷、最大形变、脑组织最大应变)进行综合对比评估。结果厚度增加会引起临界载荷增大、最大形变减小以及脑组织最大应变减小,同时也会导致脑组织应变区域增大。均衡3个因素考虑,选择200μm作为涂层最佳厚度,在该厚度下,临界载荷为17.9 m N,最大形变为10.1μm,脑组织最大应变为0.011 4。结论涂层厚度对神经电极的力学性能有较大影响,在具体情况下可通过设置多个力学性能因素的影响因子选择最优参数。涂层的最优参数选择可提高电极的性能,对神经电极的临床应用具有重要意义。     

基于硅基电极的脑组织微动损伤仿真

目的:为预测脑组织微动损伤和解决植入电极的长期寿命问题,本研究基于硅基微电极进行建模,并对神经电极-脑组织有限元模型进行数值仿真。 方法:采用超黏弹性模型描述脑组织材料,研究不同微动模式（纵向和横向）、不同物理耦合度下电极附近脑组织应变分布。 结果:纵向载荷分析显示当摩擦系数?增加时,脑组织最大von Mises应变呈降低趋势,并且电极尖端附近的组织应变最大,这表明电极与脑组织之间的物理耦合度对脑组织微动损伤有较大影响。增强电极和脑组织间的黏附程度,可以有效减小脑组织损伤。电极尖端的形状也极大地影响着组织的应变大小。横向载荷分析显示X轴方向的载荷产生的脑组织损伤区域大约为60 ?m,这表明电极之间的间距应大于60 ?m,否则不同电极产生的组织应变会发生重叠,这对于电极之间理想间距的设计和防止重叠应变形成多余的细胞鞘有着重要的意义。 结论:数值仿真模型可以为电极-脑组织界面参数和电极间距设计参数提供参考,从而减少组织损伤,提高电极工作寿命,满足临床应用。     

Cuff电极长期植入性能初步研究

目的：研究Cuff电极长期植入性能。方法：在狗面神经颧支周围植入Cuff电极，通过这个植入电极，分别在14天、6月后提取自然发生的神经电信号，比较分析其信号的差异性；通过组织形态学的方法，在Cuff电极植人后6个月观察分析周围有电极植入的神经段落的组织形态学变化，以分析植入电极对神经的影响。结果：通过植入的Cuff电极，在电极植入后14天、6月均能提取出能反映眨眼动作发生的神经信号，所提取到的自然睁眼状态下的神经信号在幅值（RMS）和频率（MPF）方面没有明显的变化。长期植入Cuff电极的神经，未发现有明显的损伤性形态改变。结论：Cuff电极适合作为长期植入体使用。可以提取到稳定的神经电信号，对于所附着神经不会产生明显的损伤，提示这种植入电极的应用具有可逆性。     

带线锚钉植入角度对最大拔出力的影响

目的基于关节镜肩袖修复(rotator cuff repair,RCR)手术中使用带线锚钉(suture anchor,SA)植入肱骨的角度问题,对带线锚钉的最终拔出强度进行生物力学评估。方法采用密度分别为0.16、0.32 g/cm~3聚氨酯材料模拟骨质疏松性和正常松质骨,厚度3 mm、密度0.64 g/cm~3聚氨酯材料模拟人体皮质骨,两种松质骨模型分别与皮质骨模型粘连在一起构造人体肱骨模型。使用钛金属带线锚钉以45°、60°、75°和90°角度植入肱骨模型,对其进行连续的拉拔实验,其中肱骨模型表面和缝线间使用45°锚钉牵引方向模拟岗上肌的生理牵引方向,每组不间断地进行8次测试,记录最终的拔出力和破坏模式。结果高密度骨质模型的拔出力明显高于低密度骨质模型(P0.001),且在同密度下,相比45°、60°和75°,90°植入角拥有更大的拔出力(P0.01)。结论在肱骨模型中带线锚钉采用90°植入显示出更优的生物力学性能,而且在肩袖修复中锚钉的垂直植入对术中打结和术后冈上肌的恢复均有益处。     

IKVAV多肽生物活性水凝胶修复大鼠脑损伤

目的探索利用组织工程技术修复中枢神经损伤的可行性。方法人工合成PHPMA水凝胶材料,在其表面接枝具有神经生长活性的IKVAV肽段,检测分析性状后植入大鼠大脑皮层,于术后不同时期取脑切片,组织化学染色观察植入部位细胞反应;GFAP免疫组化检测星形胶质细胞在材料中的分布;Glees镀银染色显示移植物中神经纤维生长情况,DAB血管染色法观察新生血管的长入。结果制备的三维活性PHPMA水凝胶植入鼠脑皮层后能与周围组织良好整合。术后6周材料周围及内部均有细胞浸润,GFAP阳性细胞在材料内分布均匀;12周后材料内部可见新生血管;18周后材料中心有神经纤维长入。结论活性PHPMA水凝胶具有良好的脑组织相容性,植入脑缺损部位有助于细胞迁移、血管发生及神经轴突生长。     

侵入式柔性神经电极的植入策略

侵入式神经电极将人类对神经科学的认识提升到微米与毫秒尺度.由于传统的刚性电极与柔软的脑组织间存在较大的机械不匹配性,柔性电极成为新一代神经电极的发展趋势.神经电极的柔性化更迭降低免疫反应的同时却失去植入刚度.分析神经电极的植入机制并总结目前研究中关于柔性电极的植入策略,旨在帮助解决柔性电极的植入能力丧失以及急性植入损伤...     

组织工程软骨植入缺损后修复区力学特性分析

目的利用组织工程技术建立体外软骨缺损实验模型,研究修复区人工软骨和宿主软骨的力学特性。方法采用一种琼脂糖凝胶作为人工软骨,制作猪软骨深层缺损,在缺损处仿临床植入人工软骨,用生物胶黏接,建立组织工程修复膝关节软骨缺损的体外模型;在压缩载荷作用下,通过数字图像相关技术研究组织工程软骨植入缺损后修复区即刻力学行为。结果压缩过程中界面处没有出现开裂现象,压缩分别为软骨层厚度的3.5%、5.6%、7.04%和9.0%时获得了修复区中间层应变分布图和应变变化曲线。压缩量从3.5%增加到9%时,在垂直软骨面方向上宿主软骨最大压应变增加75.9%,人工软骨最大拉应变增加226.99%;在平行软骨表面方向,交界面处最大拉应变增加116.9%,增加量远高于宿主软骨区和人工软骨区;对于修复区剪应变,随着压缩量增加交界处剪应变方向发生相反的改变。结论软骨组织工程修复缺损效果有很大的不确定性,这与修复区的力学环境有关。组织工程软骨植入缺损后,修复区受到复杂应变状态,随着压缩量增加,界面处、宿主软骨、人工软骨都发生较大的应变变化,界面处垂直软骨面方向的应变由压应变可转化为拉应变,平行软骨表面方向的拉应变有显著增加,交界处剪应变方向甚至发生了相反的改变,而且剪应力数值迅速增加。这种复杂应变状态造成修复区细胞力学环境的较大变化,还可能引起界面的开裂,影响缺损修复过程,这些力学环境变化应受到临床治疗的重视。     

A novel neural electrode with micro-motion-attenuation capability based on compliant mechanisms—physical design concepts and evaluations

In order to solve the problem of the short lifespan of the neural electrode caused by micro motion, this study designed a novel neural electrode based on lumped compliance compliant mechanism to control different modes of micro-motion in a more effective way. According to the mathematical modeling of the novel neural electrode, the equivalent bending stiffness and equivalent tensile (compression) stiffness were calculated. The results of the finite element analysis based on the mathematical modeling revealed that the novel neural electrode showed excellent micro-motion-attenuation capability. The static analysis results showed that the novel design dramatically reduced the maximum displacement of the brain in 51% and the maximum stress in 41% under longitudinal micro-motion environment. It also effectively reduced the 5.1% maximum stress while maintaining the maximum displacement under lateral micro-motion environment. The experimental results based on the tissue injury evaluation system also confirmed that the novel electrode is more effective in micro-motion attenuation than the reference one. In detail, the strain of the brain tissue caused by the implantation of the neural electrode was decreased by 1.26 to 27.84% at the insertion depth of 3 mm, and 0.522 to 17.24% at the insertion depth of 4.5 mm, which has convinced the effectiveness of the design.

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Graphical abstract The schematic of the novel neural electrode and evaluationsystem of tissue injury

     

弯曲参数对软组织缝合过线器弯钩力学性能的影响

目的探究弯钩偏转角和弯钩倾斜角对软组织缝合过线器弯钩力学性能的影响。方法以远离针尖端端面(端面1)为研究对象,建立以力矩大小为因变量,弯钩偏转角和倾斜角为自变量的数学模型。探究偏转角和倾斜角为0°、10°、20°和30°时的力矩,并用数学模型求解出力矩。基于有限元分析法,使用Solid Works软件建立偏转角和倾斜角为0°、10°、20°和30°的16种弯钩三维几何模型,导入ANSYS Workbench有限元分析软件进行应力分析,在相同穿刺力作用下,求解出各弯钩最大等效应力和远离针尖端端面的反作用力矩。结果理论分析与数值模拟分析结果均表明,端面1反作用力矩随着偏转角的增大而增大,随着倾斜角的增大而减小。当弯钩偏转角为0°、弯钩倾斜角为30°时,端面1的反作用力矩最小。有限元分析结果显示,当偏转角为0°时,弯钩最大等效应力最小,且不随弯钩倾斜角的变化而变化。结论所建数学模型可以准确说明弯钩端面1处力矩与弯钩偏转角和倾斜角的关系。研究结果为软组织缝合过线器弯钩几何结构的设计提供理论依据,提高了软组织缝合过线器在手术过程中的安全性。     

Comparison of the joint laxity of total knee arthroplasty evaluated by the distraction force and the varus–valgus force

BackgroundComponent gap (CG) measurement help surgeons evaluate intraoperative soft-tissue balance. One technique is measuring the CG using tensioner devices with distraction force. Another is to evaluate the laxity under a varus–valgus force using navigation or robotics. The aim was to compare the JL evaluated by CG and varus–valgus force between the different types of total knee arthroplasties.MethodsForty-three bi-cruciate stabilized (BCS) knees and 33 bi-cruciate retaining (BCR) knees were included. After bone resection and soft tissue balancing, the CG was measured and after the final implantation and capsule closure, JL under a maximum varus–valgus stress was recorded with navigation. JL evaluated by the CG (JLCG) was defined as CG minus selected thickness of the tibial component and JL under varus–valgus force (JLVV) was defined as difference between varus–valgus angles without stress and maximum varus–valgus angles under varus–valgus force. The evaluations were performed at flexions of 10°, 30°, 60° and 90°.ResultsAlthough JLCGs of lateral compartment of BCS were larger than those of BCR, no difference was found between JLVVs of BCS and BCR. Although JLCGs of lateral compartment did not change at each knee flexion angle in both BCS and BCR, JLVVs of lateral compartment increased by 3° from 10° to 90° knee flexion.ConclusionJLVVs of BCS and BCR were equivalent, whereas BCS showed larger JLCGs of lateral compartment. JLVVs of lateral compartment increased by 3° in the range from 10° to 90° knee flexion whereas JLCGs remained stable.     

动态咬合下牙周膜的生物力学分析

目的 分析动态咬合下加载时间、角度因素对牙周膜应力和位移的影响。方法 采用逆向工程技术建立牙周膜厚度为0.2 mm的下颌前牙—牙周膜—牙槽骨的三维模型,在与牙体长轴分别成0°、15°、30°、45°、60°、75°、90°,由颊侧向舌侧的动态咬合载荷作用下,分析不同周期下牙周膜的应力、位移变化状况。结果 在单周期下,由不同角度载荷引起的牙周膜最大残余应力极大值与最小值之比为5.5,最大位移极值之比为8.1;由5周期引起的最大位移极大值与极小值之比在1.02~1.35内随载荷角度增加;由不同角度载荷引起的最大残余应力极大值与极小值之比在1.86~3.00内随咬合周期数增加;不同角度下最大应力均集中在颈缘舌侧区域, 最大残余应力位置分布随时间在颈缘不同部位间变动;0°载荷下牙根的应力累积最严重。结论 下前牙固定桥基牙选择的临床应用中,应注意牙周膜应力累积情况以及最大残余应力分布的不确定性;临床治疗中,应避免对牙齿施加大角度载荷,尽量减少连续咬合较硬食物。     

Poly(vinyl alcohol)/poly(acrylic acid) hydrogel coatings for improving electrode–neural tissue interface

A major problem which hinders the applications of neural prostheses is the inconsistent performance caused by tissue responses during long-term implantation. The study investigated a new approach for improving the electrode–neural tissue interface. Hydrogel poly(vinyl alcohol)/poly(acrylic acid) interpenetrating polymer networks (PVA/PAA IPNs) were synthesized and tailored as coatings for poly(dimethylsiloxane) (PDMS) based neural electrodes with the aid of plasma pretreatment. Changes in the electrochemical impedance and maximum charge injection (Q_inj) limits of the coated iridium oxide microelectrodes were negligible. Protein adsorption on PDMS was reduced by ～85% after coating. In the presence of nerve growth factor (NGF), neurite extension of rat pheochromocytoma (PC12) cells was clearly greater on PVA/PAA IPN films than on PDMS substrates. Furthermore, the tissue responses of PDMS implants coated with PVA/PAA IPN films were studied by 6-week implantation in the cortex of rats, which found that the glial fibrillary acidic protein (GFAP) immunoreactivity in animals (n = 8) receiving coated implants was significantly lower (p < 0.05) compared to that of uncoated implants (n = 7) along the entire distance of 150 μm from the outer skirt to the implant interface. The coated film remained on the surface of the explanted implants, confirmed by scanning electron microscopy (SEM). All of these suggest the hydrogel coating is feasible and favorable to neural electrode applications.     

Polyethylene glycol-containing polyurethane hydrogel coatings for improving the biocompatibility of neural electrodes

The instability of the interface between chronically implanted neuroprosthetic devices and neural tissue is a major obstacle to the long-term use of such devices in clinical practice. In this study, we investigate the feasibility of polyethylene glycol (PEG)-containing polyurethane (PU) hydrogel as coatings for polydimethylsiloxane (PDMS)-based neural electrodes in order to achieve a stable neural interface. The influence of PU hydrogel coatings on electrode electrochemical behaviour was investigated. Importantly, the biocompatibility of PU hydrogel coatings was evaluated in vitro and in vivo. Changes in the electrochemical impedance of microelectrodes with PU coatings were negligible. The amount of protein adsorption on the PDMS substrate was reduced by 93% after coating. Rat pheochromocytoma (PC12) cells exhibited more and longer neurites on PU films than on PDMS substrates. Furthermore, PDMS implants with (n=10) and without (n=8) PU coatings were implanted into the cortex of rats and the tissue response to the implants was evaluated 6 weeks post-implantation. GFAP staining for astrocytes and NeuN staining for neurons revealed that PU coatings attenuated glial scarring and reduced the neuronal cell loss around the implants. All of these findings suggest that PU hydrogel coating is feasible and favourable for neural electrode applications.     

颈部肌肉作用下颈椎牵引的生物力学特性

目的建立C1~7全颈椎三维有限元模型,研究其在颈部肌肉作用下颈椎牵引的生物力学特性,为临床颈椎牵引的治疗提供参考。方法建立正常颈椎的三维非线性有限元模型,在此基础上结合临床颈椎牵引的方法,利用生物力学分析软件进行建模仿真,在牵引重量一定的情况下,用后伸0°、10°、20°、30°、40°进行牵引,获得关节力和肌肉力,筛选合适的关节力和肌肉力对颈椎模型进行有限元分析。结果颈椎后伸牵引过程中,在肌肉力的作用下,颈椎椎体、椎间盘、钩椎关节的平均最大等效应力分别增加4.86、1.79、0.69 MPa,颈椎椎体的平均最大相对位移在矢状轴、垂直轴方向上分别增加5.53、0.63 mm。颈椎后伸牵引的生物力学特性与文献中的有限元分析结果相近。结论颈部肌肉对颈椎各椎体、椎间盘以及钩椎关节应力及位移的增加具有较大的促进作用。临床上行颈椎后伸牵引时,应考虑到颈部肌肉的作用,牵引角度不宜过大,推荐0°~20°是颈椎牵引初期相对安全的角度范围。     

3D bioprinting of neural stem cell-laden thermoresponsive biodegradable polyurethane hydrogel and potential in central nervous system repair

The 3D bioprinting technology serves as a powerful tool for building tissue in the field of tissue engineering. Traditional 3D printing methods involve the use of heat, toxic organic solvents, or toxic photoinitiators for fabrication of synthetic scaffolds. In this study, two thermoresponsive water-based biodegradable polyurethane dispersions (PU1 and PU2) were synthesized which may form gel near 37 °C without any crosslinker. The stiffness of the hydrogel could be easily fine-tuned by the solid content of the dispersion. Neural stem cells (NSCs) were embedded into the polyurethane dispersions before gelation. The dispersions containing NSCs were subsequently printed and maintained at 37 °C. The NSCs in 25–30% PU2 hydrogels (∼680–2400 Pa) had excellent proliferation and differentiation but not in 25–30% PU1 hydrogels. Moreover, NSC-laden 25–30% PU2 hydrogels injected into the zebrafish embryo neural injury model could rescue the function of impaired nervous system. However, NSC-laden 25–30% PU1 hydrogels only showed a minor repair effect in the zebrafish model. In addition, the function of adult zebrafish with traumatic brain injury was rescued after implantation of the 3D-printed NSC-laden 25% PU2 constructs. Therefore, the newly developed 3D bioprinting technique involving NSCs embedded in the thermoresponsive biodegradable polyurethane ink offers new possibilities for future applications of 3D bioprinting in neural tissue engineering.     

座椅椅背倾角对飞行员颈部损伤的影响

目的 探究不同椅背倾角对飞行员颈部损伤的影响。方法 基于头颈部多刚体动力学模型,对两种典型飞行工况下(急转弯和稳定盘旋)椅背倾角17°和22°进行仿真计算,得到颈部肌肉力及椎间力,并采用颈部损伤的NIC准则、N_ij准则和简明损伤分类方法对颈部损伤进行评估与预测。结果 同一飞行工况下,椅背倾角17°时,颈部前屈,斜方肌和头夹肌受到拉伸。椅背倾角22°时,颈部后伸,集总舌肌受到拉伸,且椅背倾角17°时斜方肌受到的拉力最大。同一颈椎节段,椅背倾角17°时的轴向力高于椅背倾角22°时,而22°时的后伸力矩大于17°时的前屈力矩。所有飞行工况下的力和力矩均未超过颈椎节段的损伤评估值,颈部脊髓也不会发生损伤。急转弯工况下,椅背倾角为22°时C7～T1节段N_ij在所有工况中最大,达到航空领域建议的临界值,此时颈部发生中度、重度伤的概率分别为3.93%、2.63%。结论 本研究结果可为评估椅背倾角对飞行员颈部的损伤情况提供支撑。