title: Relationships between tissue composition and viscoelastic properties in human trabecular bone.
abstract: Trabecular bone is a metabolically active tissue with a high surface to volume ratio. It exhibits viscoelastic properties that may change during aging. Changes in bone properties due to altered metabolism are sensitively revealed in trabecular bone. However, the relationships between material composition and viscoelastic properties of bone, and their changes during aging have not yet been elucidated. In this study, trabecular bone samples from the femoral neck of male cadavers (n=21) aged 17-82 years were collected and the tissue level composition and its associations with the tissue viscoelastic properties were evaluated by using Raman microspectroscopy and nanoindentation, respectively. For composition, collagen content, mineralization, carbonate substitution and mineral crystallinity were evaluated. The calculated mechanical properties included reduced modulus (Er), hardness (H) and the creep parameters (E1, E2, η1and η2), as obtained by fitting the experimental data to the Burgers model. The results indicated that the creep parameters, E1, E2, η1and η2, were linearly correlated with mineral crystallinity (r=0.769-0.924, p<0.001). Creep time constant (η2/E2) tended to increase with crystallinity (r=0.422, p=0.057). With age, the mineralization decreased (r=-0.587, p=0.005) while the carbonate substitution increased (r=0.728, p<0.001). Age showed no significant associations with nanoindentation parameters. The present findings suggest that, at the tissue-level, the viscoelastic properties of trabecular bone are related to the changes in characteristics of bone mineral. This association may be independent of human age.
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland. Electronic address: xiaowei.ojanen@uef.fi.
authors.forename: X
authors.initials: X
authors.lastname: Ojanen
authors.affiliation: Department of Biomedical Engineering and Department of Orthopedics, Lund University, Lund, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Isaksson
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Töyräs
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
authors.forename: M J
authors.initials: MJ
authors.lastname: Turunen
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
authors.forename: M K H
authors.initials: MK
authors.lastname: Malo
authors.affiliation: School of Engineering and Technology, Savonia University of Applied Sciences, Kuopio, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Halvari
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
authors.forename: J S
authors.initials: JS
authors.lastname: Jurvelin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism / Q000502:physiology; D001696:Biomechanical Phenomena; D015519:Bone Density; D003094:Collagen / Q000378:metabolism; D004548:Elasticity; D005272:Femur Neck / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D006244:Hardness; D006801:Humans; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D014783:Viscosity; D016474:Weight-Bearing; D055815:Young Adult
chemical_list: D003094:Collagen
keywords: Aging; Bone matrix; Femoral neck; Nanoindentation; Raman microspectroscopy