The hardness variations and characteristics of the human thoracolumbar segments by Vickers microindentation
Li Sheng, Zhang Xiaojuan, Wu Weiwei, Liu Guobin, Wang Jianzhao, Yin Bing, Hu Zusheng, Fu Lei, Zhang Yingze
Department of Orthopaedic Surgery, the Third Hospital of Hebei Medical University, Key Laboratory of Biomechanics of Hebei Province, Shijiazhuang 050051, China
Abstract:Objective To explore the distribution characteristics and clinical application prospects of micro-hardness of the human thoracolumbar segments.Methods Three fresh adult cadaver T11-L2 vertebrae specimens were selected and the soft tissue was removed. Each vertebra was divided into a vertebral body region and an attachment region. All of the bones were prepared in to a plurality of 3 mm bone tissue slices by using a high-precision slow saw and then sanded by sandpaper.A total of 72 bone tissue sections were generated from 12 vertebral specimens. The Vickers method was used to measure the microhardness values of cortical bone and cancellous bone in different areas of bone sections. Five effective microhardness values were selected for each region, and the average value of all effective values was used as the hardness value of the region.Results A total of 660 effective indentation experiments were performed on 12 vertebrae. (1) The total hardness of the thoracolumbar segment was 11.6-48.3 HV, including the average hardness of the cortical bone was 13.8-48.3 (31.62±5.66) HV, and the average hardness of the cancellous bone was 11.6-44.9 (29.62±5.38) HV. (2) The average hardness of the cortical bone in the vertebral body region and the accessory region were (29.99±5.27)HV and (32.92±5.63) HV, respectively. The average hardness of cancellous bone were (28.44±4.79) HV and (30.81±5.71)HV, respectively. The attachment area was higher than the vertebral body area,and the difference was statistically significant(t=5.098, 2.011, all P values<0.05). (3)The hardness of the cortical bone in the vertebral body region from high to low was the lower endplate (33.94±4.31) HV, the upper endplate (29.76±4.35) HV, and the peripheral endplate (28.13 ±5.07) HV. The bone hardness of the lower endplate was higher than that of the upper endplate and the peripheral endplate.The difference was statistically significant (all P values<0.05). (4)In the cortical bone of the attachment area,the hardness from high to low was the pedicle cortex(34.78±5.30) HV, the upper articular process (33.73±5.68) HV, the vertebral plate(33.15±5.28) HV, the transverse process(31.69±5.37) HV and the inferior articular process (31.26±5.91) HV. The bone hardness of the pedicle cortex was significantly different from those of the transverse process and the inferior articular process(all P values<0.05).Conclusions This study is the first to apply the Vickers microhardness method to study the distribution of microhardness of human thoracolumbar segments. It is found that the cortical bone hardness and cancellous bone hardness of the attachment region are higher than those of the vertebral body region. There are differences in the microhardness of the T11-L2 and the thoracolumbar segments of different people, but the distribution law is relatively consistent.It is the result of the joint action of microstructure and mechanical load, which is consistent with the normal physiological and weight-bearing functions of the human body. The results of this study provide data support for the preparation of artificial vertebrae with gradient hardness in 3D printing.
李升, 张晓娟, 吴卫卫, 刘国彬, 王建朝, 殷兵, 胡祖圣, 付蕾, 张英泽. 人体脊柱胸腰段椎骨显微骨硬度分布特征研究[J]. 中华解剖与临床杂志, 2019, 24(4): 313-317.
Li Sheng, Zhang Xiaojuan, Wu Weiwei, Liu Guobin, Wang Jianzhao, Yin Bing, Hu Zusheng, Fu Lei, Zhang Yingze. The hardness variations and characteristics of the human thoracolumbar segments by Vickers microindentation. Chinese Journal of Anatomy and Clinics, 2019, 24(4): 313-317.
Eberl R, Kaminski A, Müller EJ, et al. Importance of the cross-sectional area of the spinal canal in thoracolumbar and lumbar fractures. Is there any correlation between the degree of stenosis and neurological deficit?[J]. Orthopade, 2003, 32(10): 859-864. DOI:10.1007/s00132-003-0531-1.
Öhman C, Zwierzak I, Baleani M, et al. Human bone hardness seems to depend on tissue type but not on anatomical site in the long bones of an old subject[J]. Proc Inst Mech Eng H, 2013, 227(2): 200-206. DOI:10.1177/0954411912459424.
[6]
Dall'Ara E, Schmidt R, Zysset P. Microindentation can discriminate between damaged and intact human bone tissue[J]. Bone, 2012, 50(4): 925-929. DOI:10.1016/j.bone.2012.01.002.
[7]
Allman FL Jr. Fractures and ligamentous injuries of the clavicle and its articulation[J]. J Bone Joint Surg Am, 1967, 49(4): 774-784.
[8]
Zwierzak I, Baleani M, Viceconti M. Microindentation on cortical human bone: effects of tissue condition and indentation location on hardness values[J]. Proc Inst Mech Eng H, 2009, 223(7): 913-918. DOI:10.1243/09544119JEIM634.
Dall'Ara E, Ohman C, Baleani M, et al. The effect of tissue condition and applied load on Vickers hardness of human trabecular bone[J]. J Biomech, 2007, 40(14): 3267-3270. DOI:10.1016/j.jbiomech.2007.04.007.
[11]
Ziv V, Wagner HD, Weiner S. Microstructure-microhardness relations in parallel-fibered and lamellar bone[J]. Bone, 1996, 18(5): 417-428. DOI: 10.1016/8756-3282(96)00049-X.
[12]
Evans GP, Behiri JC, Currey JD, et al. Microhardness and Young's modulus in cortical bone exhibiting a wide range of mineral volume fractions, and in a bone analogue[J]. J Mater Sci Mater Med, 1990, 1(1): 38-43. DOI:10.1007/bf00705352.
[13]
Broz JJ, Simske SJ, Greenberg AR. Material and compositional properties of selectively demineralized cortical bone[J]. J Biomech, 1995, 28(11): 1357-1368. DOI: 10.1016/0021-9290(94)00184-6.
[14]
Edwards WT, Zheng Y, Ferrara LA, et al. Structural features and thickness of the vertebral cortex in the thoracolumbar spine[J]. Spine(Phila Pa 1976), 2001, 26(2): 218-225. DOI: 10.1097/00007632-200101150-00019.
[15]
Silva MJ, Wang C, Keaveny TM, et al. Direct and computed tomography thickness measurements of the human, lumbar vertebral shell and endplate[J]. Bone, 1994, 15(4): 409-414. DOI: 10.1016/8756-3282(94)90817-6.
[16]
Weaver JK. The microscopic hardness of bone[J]. J Bone Joint Surg, 1966, 48(2): 273-288. DOI:10.2106/00004623-196648020-00006.
[17]
Fields AJ, Eswaran SK, Jekir MG, et al. Role of trabecular microarchitecture in whole-vertebral body biomechanical behavior[J]. J Bone Miner Res, 2009, 24(9): 1523-1530. DOI:10.1359/jbmr.090317.
Blackburn J, Hodgskinson R, Currey JD, et al. Mechanical properties of microcallus in human cancellous bone[J]. J Orthop Res, 1992, 10(2): 237-246. DOI:10.1002/jor.1100100211.
[21]
Johnson WM, Rapoff AJ. Microindentation in bone: hardness variation with five independent variables[J]. J Mater Sci Mater Med, 2007, 18(4): 591-597. DOI:10.1007/s10856-007-2306-4.
[22]
Huja SS, Katona TR, Moore BK, et al. Microhardness and anisotropy of the vital osseous interface and endosseous implant supporting bone[J]. J Orthop Res, 1998, 16(1): 54-60. DOI:10.1002/jor.1100160110.