title: Characterization of nano-structural and nano-mechanical properties of osteoarthritic subchondral bone.
abstract: Although 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.
  
  
  
  OA 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.
  
  
  
  In 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.
  
  
  
  The 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.
authors: Ministry Education Key Laboratory for Oral Biomedical Engineering, School of Stomatology, Wuhan University, Wuhan, 430079, People's Republic of China.|Xiamen Dental Hospital, Xiamen, Fujian Province, China.|Institute of Health and Biomedical Innovation, School of Chemistry, Physics, Mechanical Engineering, Queensland University of Technology, Brisbane, Australia.
authors: Qiliang
authors: Q
authors: Zuo
authors: Institute of Health and Biomedical Innovation, School of Chemistry, Physics, Mechanical Engineering, Queensland University of Technology, Brisbane, Australia.
authors: Shifeier
authors: S
authors: Lu
authors: Institute of Health and Biomedical Innovation, School of Chemistry, Physics, Mechanical Engineering, Queensland University of Technology, Brisbane, Australia.
authors: Zhibin
authors: Z
authors: Du
authors: Institute of Health and Biomedical Innovation, School of Chemistry, Physics, Mechanical Engineering, Queensland University of Technology, Brisbane, Australia.
authors: Thor
authors: T
authors: Friis
authors: Xiamen Dental Hospital, Xiamen, Fujian Province, China.
authors: Jiangwu
authors: J
authors: Yao
authors: Institute of Health and Biomedical Innovation, School of Chemistry, Physics, Mechanical Engineering, Queensland University of Technology, Brisbane, Australia.|Orthopedic Department, Prince Charles Hospital, Brisbane, Australia.
authors: Ross
authors: R
authors: Crawford
authors: Institute of Health and Biomedical Innovation, School of Chemistry, Physics, Mechanical Engineering, Queensland University of Technology, Brisbane, Australia. i.prasadam@qut.edu.au.|Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove Campus, Brisbane, Qld, 4059, Australia. i.prasadam@qut.edu.au.
authors: Indira
authors: I
authors: Prasadam
authors: Ministry Education Key Laboratory for Oral Biomedical Engineering, School of Stomatology, Wuhan University, Wuhan, 430079, People's Republic of China. yin.xiao@qut.edu.au.|Xiamen Dental Hospital, Xiamen, Fujian Province, China. yin.xiao@qut.edu.au.|Institute of Health and Biomedical Innovation, School of Chemistry, Physics, Mechanical Engineering, Queensland University of Technology, Brisbane, Australia. yin.xiao@qut.edu.au.|Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove Campus, Brisbane, Qld, 4059, Australia. yin.xiao@qut.edu.au.
authors: Yin
authors: Y
authors: Xiao
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D015519:Bone Density; D002118:Calcium / Q000032:analysis; D002358:Cartilage, Articular / Q000473:pathology; D017886:Durapatite / Q000032:analysis; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D046529:Microscopy, Electron, Transmission; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D010026:Osteosclerosis / Q000473:pathology*; D010758:Phosphorus / Q000032:analysis; D011859:Radiography; D012720:Severity of Illness Index; D017550:Spectroscopy, Fourier Transform Infrared; D013977:Tibia / Q000737:chemistry / Q000000981:diagnostic imaging / Q000473:pathology* / Q000648:ultrastructure*
chemical_list: D010758:Phosphorus; D017886:Durapatite; D002118:Calcium
keywords: Bone hierarchical structure; Ca/P; Crystallinity; Nano-structure; Osteoarthritis; Subchondral bone