Hexahedral mesh development of free-formed geometry: The human femur exemplified

The objective of the present research is to develop a standard hexahedral Finite Element (FE) model of the human femur accounting for the material characteristics of cortical bone, cancellous bone and bone marrow. The anatomical data were acquired from the Visible Human Project. A detailed outline of the steps necessary in developing hexahedral FE meshes from computed tomography (CT) data is provided, along with a section on modelling strategies providing comprehensive suggestions on how to overcome meshing difficulties due to geometrical non-linearities. The stress and deformation results are discussed.     

A Method to Improve Experimental Validation of Finite‐Element Models of Long Bones

Abstract: Finite‐element (FE) simulations are extremely sensitive to boundary conditions, including the position of applied forces. This is particularly critical for FE models of bones, where the lack of a univocal reference system makes identifying the boundary conditions difficult. The aims of this work were to design a transducer (FP‐transducer) to accurately determine the position of the resultant joint force during in vitro tests, and to assess its accuracy for future application in validating numerical models of long bones. A strain gauge‐based transducer was designed to indirectly measure the position of the force applied to the long bones during in vitro tests, by measuring the reaction moments about two perpendicular axes, generated by the force applied. Validation tests were performed to quantify the intrinsic precision of the FP‐transducer (by applying calibrated forces at known locations), and the overall accuracy when the FP‐transducer was included in a typical set‐up for long bone testing. The intrinsic accuracy of the FP‐transducer when used to calculate the position of an offset force was satisfactory (0.66 mm). The overall accuracy of the FP‐transducer in measuring the position of the applied force, when included in a typical set‐up for long bone testing was 0.85 mm. In vitro validation of FE models of long bones may, therefore, be improved, thanks to a more accurate determination of the force application point.     

股骨皮质骨生物力学特性研究

为分析计算股骨皮质骨的材料特性,探讨了皮质骨的取样位置、加工方法及皮质骨拉伸试样的固定装夹方法.采用6例正常人新鲜股骨干中段皮质骨,沿外侧纵向截取4×6个股骨环段,进一步加工制备得到40个尺寸为5 mm×5 mm×30 mm和20个尺寸为5 mm×5 mm×10 mm的测试骨试样.分组进行了轴向拉伸、压缩和三点弯曲的生物力学试验,得出了股骨干皮质骨轴向的拉伸、压缩破坏载荷、强度极限、弹性模量,弯曲破坏载荷、表面硬度、抗弯强度、弯曲弹性模量等指标,并对股骨干皮质骨的材料力学特性进行了分析讨论.     

人皮质骨径向微动损伤有限元分析与试验验证

对骨哈佛氏系统径向微动进行有限元分析,分析结果显示:哈佛氏管、环骨板处和穿过环骨板和骨间质组织等多处有应力集中现象发生,高的应力梯度可导致哈佛氏骨管处、环骨处和骨间质组织等多处裂纹的萌生;高载荷条件下,穿过骨间质,联接相邻骨单位的较大塑性区也是裂纹萌生的原因。采用球-平面接触模式,在高精度液压伺服微动实验机上,对人股骨皮质骨的轴向断面的径向微动行为进行试验研究。用位移-载荷曲线对其动力学进行分析;采用LCSM、SEM等方法对磨痕进行观测分析。结果表明:径向微动条件下,在股骨密质骨中可观察到3种典型裂纹,即放射状裂纹、环状裂纹和联接裂纹。有限元分析和试验分析结果具有很好的一致性,试验结果充分验证有限元分析。     

移植隧道对股骨力学性能的影响

该文应用Mimics 8.1软件由膝关节螺旋CT数据重构3D股骨模型。基于该模型依据单束、双束韧带重建手术的要求,建立了膝关节正常股骨、含单移植、双移植隧道股骨的三种近似三维有限元模型。根据股骨在关节屈伸中承受载荷的性质提取压缩、弯曲和扭转三种作用力,分别加载到上述三种有限元股骨模型上,进行有限元仿真。该文提出截面应力比较法,从股骨截面应力云图中提取最大有效应力值与最大第一主应力值为指标来评定隧道对股骨承载性能的影响,通过对比分析表明:无论采用前交叉韧带重建的哪种方法,在正常压缩、弯曲和扭转的三种负载下,隧道对ACL重建后的截面应力分布状态影响不明显,对股骨最大有效应力值的影响较弱(应力变化量≤5.06%),对股骨第一主应力值的影响也较小(变化量≤6.85%)。总之,ACL重建移植隧道对股骨承载应力的影响较小。在临床手术中医生对股骨隧道的视点只需放在起止点的准确选取上。该文提出的截面应力比较法丰富了ACL重建术后的股骨力学性能评定的技术与方法。     

不同载荷灵敏度的股骨在全髋置换后的模态变化研究

基于股骨自适应再造理论，对具有不同载荷灵敏度的股骨在全髋置换后的自适应状况进行研究，利用有限元软件ANSYS8．1对不同载荷灵敏度的股骨在全髋置换后自适应再造进行了数值仿真。仿真结果表明，不同载荷灵敏度的股骨在置换后，在相同的载荷变化下和在相同的时间内，股骨的再造程度不同。在这一条件下，自适应再造过程中股骨的刚度、质量都有变化，且变化程度不同。在自适应仿真的基础上，以各时间段的具有不同刚度、质量的仿真模型，对其进行了模态分析，分析结果表明，不同载荷灵敏度的股骨在相同时间内模态变化程度不一样，分析结果表明，在全髋置换后的不同时期内应给予不同步态、步速的运动训练，对不同的患者在手术后的相同时期内也应该给予不同的运动训练。     

中国林蛙长白山亚种与青蛙股骨光镜下的显微结构区别

研究中国林蛙长白山亚种与青蛙的股骨显微结构的区别。方法：利用光镜观察。结果表明：中国林蛙长白山亚种与青蛙的股骨在光镜下显微结构方面存在看显著的差异。这对中国林蛙长白山亚种骨骼和青蛙骨骼的真伪鉴别和中国林蛙长白山亚种骨制品市场会产生积极的影响。     

骨肉酶解工艺条件研究

为了进行猪骨肉的综合利用,本实验以猪骨为原料,研究木瓜蛋白酶、中性蛋白酶和胰蛋白酶的水解效果以及最适蛋白酶的酶解温度、pH、酶用量、料液比和酶解时间对骨肉蛋白水解度和总氮回收率的影响。结果表明：胰蛋白酶为最佳骨肉水解酶,胰蛋白酶水解猪骨的最佳工艺参数为：酶解时间为5h、酶解温度60℃、pH8、酶用量5000U／g原料、料液比为1：5。