Multilevel finite element analysis on the biological tribology damage of water on bone tissue

doi:10.3969/j.issn.2095-4344.2017.07.011

Abstract

Abstract:

BACKGROUND: Many studies reported the relationship of the mechanical properties and water content about bone tissue, which is one of organizations containing the lowest water content on human body. Researches on effect of water on biological tribology behavior of bone tissue have been rarely reported and are the experimental study generally.

OBJECTIVE: To explore the influence and the damage mechanism of water on biological tribology behavior of bone tissue, by comparing multiscale numerical model established with the experiment.

METHODS: Dehydration of the bone tissue was studied by nanoindentation test and both reciprocating sliding and impact wear tests. A multi-scale finite element model was constructed under a flat-on-ball configuration.

RESULTS AND CONCLUSION: The viscoelasticity and the tribological properties of bone tissue significantly decreased as well as the different wear mechanisms under applied loading after drying. The analytical results indicated that there were high stress condition, which incurred the micro-crack initiation and the appearance of peeling and wear, around the Haversian canal, circumferential lamellas and the interstitial tissues. Meso-scale: dehydration weakened the function of absorption and interruption of stress, which facilitated crack extension in pore. Micro-scale: the high stress gradient of structure of canaliculi and lacunae is an important cause of tissue damage.

中国组织工程研究杂志出版内容重点：人工关节；骨植入物；脊柱；骨折；内固定；数字化骨科；组织工程

Key words: Bone and Bones, Water, Finite Element Analysis, Tissue Engineering

CLC Number:

R318

He Ze-dong, Zhao Jing, Chen Liang-yu, Li Ke, Weng Jie. Multilevel finite element analysis on the biological tribology damage of water on bone tissue [J]. Chinese Journal of Tissue Engineering Research, 2017, 21(7): 1041-1045.

Figures/Tables 4

2.2 有限元结果分析不同载荷下新鲜模型的misses应力云图如图8所示，模型在Fn=20 N的低载条件下，大部分区域未达到屈服状态，只有接触中心的小范围区域有较高应力场，因哈佛系统微结构的特殊性，系统已不满足中心区域应力最高，骨板介质和中央管区域均有较明显的应力集中。随着法向载荷增大，应力集中区域逐渐扩大，应力集中处存在较高的应力梯度，应力的剧烈变化和组织反复的变形更易引发骨组织的机械式损伤，从而引起裂纹的萌生和扩展，并最终导致骨组织的剥落和磨损。物体受到拉应力时，物体有分离或拉长的趋势，反之，受到压应力时，物体会呈现出缩短和紧凑的状态。在循环的受力变形下，骨组织凹面不断受到挤压，而在凸面不断受到拉伸。图9为不同法向载荷下的主应力云图，间骨板的主应力值相对于骨单元均明显偏大。而且，高载时应力最大值较低载时增加了近1倍，在高应力状态的循环拉压作用下，必然会导致间骨板区域的组织损伤，发生疲劳破坏，萌生连接裂纹，这与实验有良好的对应性。图10为中心横截面A(图5中A-A所在位置)的应力云图，可以看出，干燥模型的应力值明显大于新鲜模型，且多数区域高于骨组织的屈服强度，表明干燥大幅加深其损伤程度；其次，新鲜模型的应力大致沿着径向递减，黏合线和骨板介质对应力的打断有利于骨组织的自我保护。相反，干燥模型因孔隙增加和组织硬化，引发多区域高于其强度极限，结构的打断作用也不明显，且浮克曼氏管管壁均处于高应力状态，表明干燥后损伤区域更易沿着孔隙向内部延伸。循环变形加载会导致内部孔隙的微裂纹破坏和组织损伤，进而导致整体的塌陷和磨损剥落。在数值模型中发现骨板介质处伴有应力集中现象，但实验中该区域并未发现明显的裂纹，有文献报道，骨板间的连接方式为粘结的胶原蛋白纤维束网[8-9，23]，水环境下柔软的骨板介质通过胶原纤维的解锁和分离，对力的传递有一定的吸收和打断作用。而胶原蛋白对水分比较敏感，因此水含量的减少将引起胶原蛋白硬化，并导致骨板之间的粘结强度降低，进而削弱应力的吸收和打断作用，最终造成骨组织的力学及摩擦学性能整体下降。"

References

[1] Bouxsein ML, Boyd SK, Christiansen BA, et al. Guidelines for assessment of bone microstructure in rodents using micro-computed tomography. J Bone Miner Res. 2010;25(7): 1468-1486.

[2] Gautieri A, Vesentini S, Redaelli A, et al. Hierarchical structure and nanomechanics of collagen microfibrils from the atomistic scale up.Nano Lett. 2011;11(2):757-766.

[3] Olszta MJ,Cheng X, Sang SJ, et al. Bone structure and formation: A new perspective. Materials Science & Engineering R Reports. 2007; 58(3-5):77-116.

[4] 王成焘.人体生物摩擦学[M].北京:科学出版社,2008.

[5] 葛世荣.人体生物摩擦学的基础科学问题[J].中国科学基金, 2005, 2: 74-79.

[6] Gebeshuber IC. Biotribology inspires new technologies. Nano Today. 2007; 2(5): 30-37.

[7] 戴振东,佟金,任露泉.仿生摩擦学研究及发展[J].科学通报, 2006, 51(20): 2353-2359.

[8] Braidotti P, Bemporad E, D'Alessio T, et al. Tensile experiments and SEM fractography on bovine subchondral bone. J Biomech. 2000;33(9):1153-1157.

[9] Nyman JS, Roy A, Shen X, et al. The influence of water removal on the strength and toughness of cortical bone. J Biomech. 2006;39(5):931-938.

[10] Cowin SC. Bone poroelasticity. J Biomech. 1999;32(3):217-238.

[11] Fornells P, García-Aznar JM, Doblaré M. A finite element dual porosity approach to model deformation-induced fluid flow in cortical bone. Ann Biomed Eng. 2007;35(10):1687-1698.

[12] Cowin SC, Cardoso L. Blood and interstitial flow in the hierarchical pore space architecture of bone tissue. J Biomech. 2015;48(5):842-854.

[13] Cowin SC, Gailani G, Benalla M. Hierarchical poroelasticity: movement of interstitial fluid between porosity levels in bones. Philos Trans A Math Phys Eng Sci. 2009;367(1902):3401-3444.

[14] Nobakhti S, Limbert G, Thurner PJ. Cement lines and interlamellar areas in compact bone as strain amplifiers - contributors to elasticity, fracture toughness and mechanotransduction. J Mech Behav Biomed Mater. 2014;29: 235-251.

[15] 蔡振兵,朱旻昊,高姗姗,等.人股骨密质骨横断面径向微动行为[J].上海交通大学学报, 2008, 42(5): 707-710.

[16] 刘冠辉.骨组织力学特性和重建的数值模拟及分析[D].南京:南京航空航天大学,2005.

[17] 刘娟,沈火明,蔡振兵,等.人皮质骨径向微动损伤有限元分析与试验验证[J].润滑与密封, 2010, 35(9): 13-17.

[18] Verbruggen SW, Vaughan TJ, McNamara LM. Strain amplification in bone mechanobiology: a computational investigation of the in vivo mechanics of osteocytes. J R Soc Interface. 2012;9(75):2735-2744.

[19] Zheng J, Weng LQ, Shi MY, et al. Effect of water content on the nanomechanical properties and microtribological behaviour of human tooth enamel. Wear.2013; 301(1-2): 316-323.

[20] Lievers WB, Poljsak AS, Waldman SD, et al. Effects of dehydration-induced structural and material changes on the apparent modulus of cancellous bone. Med Eng Phys. 2010; 32(8):921-925.

[21] Hogan HA.Micromechanics modeling of Haversian cortical bone properties.J Biomech. 1992;25(5):549-556.

[22] 罗吉.股骨多尺度有限元分析[D].重庆:重庆大学,2011.

[23] Johnson TP, Socrate S, Boyce MC. A viscoelastic, viscoplastic model of cortical bone valid at low and high strain rates. Acta Biomater. 2010;6(10):4073-4080.

[24] Reilly GC. Observations of microdamage around osteocyte lacunae in bone. J Biomech. 2000;33(9):1131-1134.