Characterization of nano-structural and nano-mechanical properties of osteoarthritic subchondral bone

Abstract

BackgroundAlthough articular cartilage is the primary tissues affected by osteoarthritis (OA), the underlying subchondral bone also undergoes noticeable changes. Despite the growing body of research into the biophysical and mechanical properties of OA bone there are few studies that have analysed the structure of the subchondral sclerosis at the nanoscale. In this study, the composition and nano-structural changes of human osteoarthritis (OA) subchondral bone were investigated to better understand the site-specific changes.MethodsOA bone samples were collected from patients undergoing total knee replacement surgery and graded according to disease severity (grade I: mild OA; grade IV: severe OA). Transmission electron microscopy (TEM), Electron Diffraction, and Elemental Analysis techniques were used to explore the cross-banding pattern, nature of mineral phase and orientation of the crystal lattice. Subchondral bone nano-hydroxyapatite powders were prepared and characterised using high resolution transmission electron microscopy (HR-TEM) and fourier transform infrared spectroscopy (FTIR). Subchondal bone mechanical properties were investigated using a nano-indentation method.ResultsIn grade I subchondral bone samples, a regular periodic fibril banding pattern was observed and the c-axis orientation of the apatite crystals was parallel to the long axis of the fibrils. By contrast, in grade IV OA bone samples, the bulk of fibrils formed a random and undulated arrangement accompanied by a circular oriented pattern of apatite crystals. Fibrils in grade IV bone showed non-hierarchical intra-fibrillar mineralization and higher calcium (Ca) to phosphorous (P) (Ca/P) ratios. Grade IV OA bone showed higher crystallinity of the mineral content, increased modulus and hardness compared with grade I OA bone.ConclusionsThe findings from this study suggest that OA subchondral sclerotic bone has an altered mineralization process which results in nano-structural changes of apatite crystals that is likely to account for the compromised mechanical properties of OA subchondral bones.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-016-1226-1) contains supplementary material, which is available to authorized users.

Tibial subchondral trabecular bone micromechanical and microarchitectural properties are affected by alignment and osteoarthritis stage

“…To the best of our knowledge, this study is the first to report a difference in STB elastic tissue moduli between overloaded and underloaded tibial condyles. This is consistent with a previous study showing a higher nanoindentation modulus on a sclerotic bone sample than on a relatively normal one from the same OA subject 33 . The STB elastic tissue moduli we measured are in the range of those measured by Wolfram et al on rehydrated vertebrae trabecular bone 34 , and consistent with those measured on dehydrated tibial and femoral STB by Peters et al, allowing for the ~30% lower modulus for hydrated bone tissue 34 .…”

Morphological, biochemical and mechanical properties of articular cartilage and subchondral bone in rat tibial plateau are age related

“…Increases in the indentation modulus and hardness of SP and ST bone in the first phase (1-9 months of age) were also observed in our study; these increases are associated with the changes in bone mineral content and organization (Brama et al 2002;Hamann et al 2013;Zuo et al 2016). Moreover, condensation of SP may result in nanostructural changes in the mineral grains, which probably accounts for changes in the mechanical properties of subchondral bones (Brama et al 2002).…”

“…; Zuo et al. ). Moreover, condensation of SP may result in nanostructural changes in the mineral grains, which probably accounts for changes in the mechanical properties of subchondral bones (Brama et al.…”

Osteointegration Characterization of Additive Manufactured Porous Titanium Scaffold Based on Microhardness and Ca/P Ratio

“…The calcium to phosphorus ratio in the animal bony samples had value of 1.67 and amounted to 1.70 [13]. According to Zuo Q. et all Ca/P ratio of human subchondral bone was 1.52 ± 0.04 [14].…”