The measured mechanical properties of osteoporotic trabecular bone decline with the increment of deformation volume during micro-indentation

Jin, Yongqiang; Zhang, Teng; Lui, Yuk Fai; Sze, Kam Yim; Lu, William Weijia

Affiliations

¹Department of Orthopaedics and Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China

²Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong, China

³Qiongtai Normal University, Hainan, China

Abstract and keywords

Purpose: Osteoporosis is a critical global health issue. However, the biomechanical properties of osteoporotic trabecular bone have not been well understood due to its hierarchically complex structure mingled with accumulated microcracks. Previous studies indicated the mechanical behaviors of trabecular bone may differ with varying amounts of deformation. Therefore, this study aims to further reveal the relationship between the measured mechanical properties of osteoporotic trabecular bone and various amounts of deformation volume during micro-indentation.

Methods: Two trabecular specimens were dissected transversally and frontally from an osteoporotic lumbar vertebral (L5) cadaver and embedded into Methyl methacrylate. On each specimen, two orthogonal cuts were performed to make a right-angle, followed by five parallel slicing. On each slice, the region of interest was gridded into 16 (4 × 4) sub-regions with the size equal to the microscope field. Within each sub-region, indentations were made on a single trabecula with five different indentation depths (3, 4, 5, 6, 7 μm) to induce different deformation volume. Both the indentation hardness and modulus were computed from the indenting curve for each measurement. The results of the five slices are pooled together to represent the longitudinal and circumferential mechanical characteristics, respectively. Linear regression was performed to investigate the relationship between the measured mechanical properties and various deformation volumes.

Results: A total of 1055 indents were made. After eliminating outliers, 840 indents were left for data analysis with 490 indents from transversal slices and 350 indents from frontal slices. Both the hardness and modulus decreased with the increasement of indentation depths. The hardness decreased by slopes of −0.65 (R² = 0.72, p = 0.044) and −0.869 (R² = 0.95, p = 0.003) longitudinally and circumferentially while the modulus decreased by slopes of −0.39 (R² = 0.82, p = 0.02) and −0.348 (R² = 0.94, p = 0.004) longitudinally and circumferentially.

Conclusions: Mechanical properties of trabecular bone measured by micro-indentation can alter with the variation of deformation volume, which reflects the nonlinear behavior of vertebra from the material perspective.

Keywords: Mechanical properties; Trabecular bone; Micro-indentation; Deformation volume

Links

DOI: 10.1016/j.jmbbm.2019.103546

PubMed: 31786511

WoS: 000517856400019

History

Received: 2019-06-27

Revised: 2019-09-14

Accepted: 2019-11-18

Online: 2019-11-19

Cited Works (20)

Year	Entry
2000	Reilly GC, Currey JD. The effects of damage and microcracking on the impact strength of bone. J Biomech. March 2000;33(3):337-343.
2002	Hengsberger S, Kulik A, Zysset P. Nanoindentation discriminates the elastic properties of individual human bone lamellae under dry and physiological conditions. Bone. 2002;30(1):178-184.
1990	Evans GP, Behiri JC, Currey JD, Bonfield W. Microhardness and Young's modulus in cortical bone exhibiting a wide range of mineral volume fractions, and in a bone analogue. J Mater Sci Mater Med. June 1990;1(1):38-43.
2001	Grant JP, Oxland TR, Dvorak MF. Mapping the structural properties of the lumbosacral vertebral endplates. Spine. April 15, 2001;26(8):889-896.
2008	Zhang J, Niebur GL, Ovaert TC. Mechanical property determination of bone through nano- and micro-indentation testing and finite element simulation. J Biomech. 2008;41(2):267-275.
1992	Oliver WC, Pharr GM. An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J Mater Res. 1992;7(6):1564-1583.
1997	Guo XE, Goldstein SA. Is trabecular bone tissue different from cortical bone tissue? Forma. 1997;12(3-4):185-196.
1997	Weiner S, Arad T, Sabanay I, Traub. W. Rotated plywood structure of primary lamellar bone in the rat: orientations of the collagen fibril arrays. Bone. June 1997;20(6):509-514.
2006	Donnelly E, Baker SP, Boskey AL, van der Meulen MC. Effects of surface roughness and maximum load on the mechanical properties of cancellous bone measured by nanoindentation. J Biomed Mater Res. May 2006;A77(2):426-435.
1996	Ziv V, Wagner HD, Weiner S. Microstructure-microhardness relations in parallel-fibered and lamellar bone. Bone. May 1996;18(5):417-428.
1997	Rho J-Y, Tsui TY, Pharr GM. Elastic properties of human cortical and trabecular lamellar bone measured by nanoindentation. Biomaterials. 1997;18(20):1325-1330.
1999	Zysset PK, Guo XE, Hoffler CE, Moore KE, Goldstein SA. Elastic modulus and hardness of cortical and trabecular bone lamellae measured by nanoindentation in the human femur. J Biomech. October 1999;32(10):1005-1012.
2009	Zysset PK. Indentation of bone tissue: a short review. Osteoporos Int. June 2009;20(6):1049-1055.
1966	Weaver JK. The microscopic hardness of bone. J Bone Joint Surg. March 1966;48A(2):273-288.
2005	Hoffler CE, Guo XE, Zysset PK, Goldstein SA. An application of nanoindentation technique to measure bone tissue lamellae properties. J Biomech Eng. January 2005;127(7):1046-1053.
1989	Hodgskinson R, Currey JD, Evans GP. Hardness, an indicator of the mechanical competence of cancellous bone. J Orthop Res. September 1989;7(5):754-758.
1990	Currey JD, Brear K. Hardness, Young's modulus and yield stress in mammalian mineralized tissues. J Mater Sci Mater Med. June 1990;1(1):14-20.
1992	Blackburn J, Hodgskinson R, Currey JD, Mason JE. Mechanical properties of microcallus in human cancellous bone. J Orthop Res. March 1992;10(2):237-246.
2004	Bushby AJ, Ferguson VL, Boyde A. Nanoindentation of bone: comparison of specimens tested in liquid and embedded in polymethylmethacrylate. J Bone Miner Res. January 2004;19(1):249-259.
1998	Burr DB, Turner CH, Naick P, Forwood MR, Ambrosius W, Hasan MS, Pidaparti R. Does microdamage accumulation affect the mechanical properties of bone? J Biomech. April 1998;31(4):337-345.