Precision of nanoindentation protocols for measurement of viscoelasticity in cortical and trabecular bone

• Published in: Journal of biomechanics 2010-08, Vol.43 (12), p.2410-2417
• Main Authors: Isaksson, Hanna, Nagao, Shijo, MaŁkiewicz, Marta, Julkunen, Petro, Nowak, Roman, Jurvelin, Jukka S
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Biological variation; Biomechanical Phenomena; Biomechanics. Biorheology; Bone and Bones - physiology; Bones; Bovine; Cattle; Collagen; Creep; Dissipated energy; Elastic Modulus; Femur - physiology; Fundamental and applied biological sciences. Psychology; Hardness; In Vitro Techniques; Low density polyethylenes; Mechanical properties; Methods; Nanoindentation; Nanotechnology - methods; Nanotechnology - statistics & numerical data; Physical Medicine and Rehabilitation; Semi-dynamic; Skeleton and joints; Strain-hardening; Studies; Tibia - physiology; Tissues, organs and organisms biophysics; Vertebrates: osteoarticular system, musculoskeletal system; Viscoelastic; Viscosity
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2010.04.017

Abstract Nanoindentation has recently gained attention as a characterization technique for mechanical properties of biological tissues, such as bone, on the sub-micron level. However, optimal methods to characterize viscoelastic properties of bones are yet to be established. This study aimed to compare the time-dependent viscoelastic properties of bone tissue obtained with different nanoindentation methods. Bovine cortical and trabecular bone samples ( n =8) from the distal femur and proximal tibia were dehydrated, embedded and polished. The material properties determined using nanoindentation were hardness and reduced modulus, as well as time-dependent parameters based on creep, loading-rate, dissipated energy and semi-dynamic testing under load control. Each loading protocol was repeated 160 times and the reproducibility was assessed based on the coefficient of variation (CV). Additionally, three well-characterized polymers were tested and CV values were calculated for reference. The employed methods were able to characterize time-dependent viscoelastic properties of bone. However, their reproducibility varied highly (CV 9–40%). The creep constant increased with increasing dwell time. The reproducibility was best with a 30 s creep period (CV 18%). The dissipated energy was stable after three repeated load cycles, and the reproducibility improved with each cycle (CV 23%). The viscoelastic properties determined with semi-dynamic test increased with increase in frequency. These measurements were most reproducible at high frequencies (CV 9–10%). Our results indicate that several methods are feasible for the determination of viscoelastic properties of bone material. The high frequency semi-dynamic test showed the highest precision within the tested nanoindentation protocols.