Biomechanical analysis of an osteocyte model by considering bone matrix’s piezoelectricity

Osteocytes,the primary cells in bone,play a crucial role in sensing external load environments and regulating other bone cells.Due to the piezoelectric effect of the mineralized matrix and collagen that make up bone,the mechanical stimulus received is converted into an electrical stimulus to affect the reconstruction of bone.Despite the importance of osteocyte,many studies have focused on the mechanical loading and fluid flow of it,there is still a gap in the study of the piezoelectric effects of various mechanosensors on the microscale.In this paper,we developed a finite element model of osteocytes that incorporates the piezoelectric bone matrix.This model is comprehensive,comprising the osteocyte cell body enclosed by lacuna,osteocyte processes enclosed by canaliculi,and the interposed charged ionic fluid.Additionally,it features mechanosensors such as collagen hillocks and primary cilia.In our study,we subjected the piezoelectric bone matrix model to triaxial displacement,subsequently assessing the electrical signal variations across different mechanosensors within the osteocyte.The observed disparities in mechanical perception by various mechanosensors were primarily attributable to greater liquid velocity changes in the polarization direction as opposed to other directions.Collagen hillocks showed insensitivity to piezoelectric signals,serving predominantly to mechanically transmit signals through solid-to-solid contact.In contrast,processes and primary cilia were highly responsive to piezoelectric signals.Interestingly,the processes oriented in the direction of the electric field demonstrated a differential piezoelectric signal perception compared to those in other directions.Primary cilia were especially sensitive to fluid flow pressure changes,which were influenced both by loading rates and external piezoelectric effects.Overall,our findings illuminate the complexity of mechanical perception within osteocytes in a piezoelectric environment.This adds a new dimension to our understanding and suggests avenues for future research in bone reconstruction and cellular mechanical behavioral transmission.

一种新型设计的个性化椎间融合器及其生物力学分析

椎间融合器在临床上经常用于脊柱感染性和退行性疾病的治疗,然而,进一步的临床应用通常受到一些缺陷的困扰,如应力遮挡和融合器沉降.本研究旨在提出一种新的脊柱融合器个性化设计理念:从微观到宏观的多尺度联合设计方法,创建与腰椎骨终板弹性模量和手术形式皆匹配的脊柱融合器.具体而言,引入三周期极小曲面来模拟聚醚醚酮(PEEK)融合器的多孔结构,通过调整孔隙参数以实现定制的宏观力学性能和孔隙结构的渗透性能。接着,针对经皮内镜下腰椎后路椎间融合术(PE-PLIF)进行多目标(屈伸、弯曲和扭转)拓扑优化,得到二次设计的新型多孔拓扑融合器。最后,将临床常用的钛融合器、PEEK融合器和本文设计的新型融合器进行基于有限元方法的生物力学对比分析。结果表明,与其他两种融合器相比,新型多孔拓扑融合器有着较低的骨-融合器界面应力和较高的内部移植骨应力和应变能密度,证明其有着较低的融合器沉降率和应力屏蔽的风险.总之,新型多孔拓扑融合器由于其良好的生物力学性能成为椎间融合术的理想选择.本文所提出的融合器设计思路和理念也可用于指导其他不同椎间融合术.

四棱锥型钉头内固定系统用于治疗Pauwels Ⅲ型股骨颈骨折

目前治疗股骨颈骨折的临床选择包括传统的空心螺钉内固定、动力髋螺钉内固定、髋关节置换和最新的股骨颈系统(FNS).股骨颈系统因表现出优良的机械性能而受到关注和欢迎.在本研究中,采用三维有限元法对股骨颈系统进行了分析,并根据分析结果对四种不同螺钉头的新型内固定进行了优化设计.在对FNS的分析结果中,植入股骨头内的螺钉部分受力较小,移位较大,由于这里使用了两个螺钉,材料消耗增加.钢板和锁定螺钉的结构使内固定物和股骨上的内应力更加均匀.在四种类型的螺钉头内固定中,四棱锥型螺钉头内固定的机械性能更为均衡.在四棱锥型螺钉头内固定与股骨颈系统的比较中,四棱锥型螺钉头内固定的应力和位移数据都显示出其优越性.股骨颈系统的单一尺寸设计对股骨尺寸偏离平均值较大的人群没有起到最佳的治疗效果,可调节长度和角度的新型内固定可以得到更广泛的应用.

猪关节软骨三层力-电特性的实验研究

力-电特性是关节软骨中众所周知的特性之一.然而目前还不清楚软骨组织不同区域的力-电特性.因此,本文的目的是研究关节软骨各区域的力-电特性及其相关影响因素.施加载荷后,力-电特性产生的电压信号沿软骨厚度方向由浅表层向深层逐渐增加,并且这种机制只有在应力产生明显相对变化时才能表现出来.此外,关节软骨的力-电特性产生的电压信号会随着载荷峰值和加载速率的增加而明显增加.我们通过将实验结果与指数函数进行拟合,得出了软骨各区的力-电特性的电压变化规律.研究结果表明,软骨组织不同区域的力-电特性差异在很大程度上取决于胶原纤维的排列分布.另外,软骨的内部结构和外部加载条件对关节软骨的力-电特性也有重要影响.这可为组织工程学中人工植入压电材料治疗骨关节炎提供重要参考.