Abstract
Aim: Nanoindentation is a technique, developed over the last 15 years which is now widely used in the materials science for probing the mechanical properties of thin films. The properties most commonly measured are Young’s modulus (E), and Hardness (H). One of the great advantages of the technique is its ability to probe a surface and map its properties on a spatially – resolved basis, often with a resolution of better than 1μm.
Materials and methods: specimens from 5 lumbar vertebrae (L-4) were obtained from fresh, unembalmed human cadavers (2 males and 3 females), aged from 16 to 90 years. After carefully removing posterior elements and soft tissues, the vertebral bodies were cut to a thickness of 5mm and embedded in epoxy resin to provide support for the porous network. Then the samples were metallograpically polished to produce smooth testing surfaces and nanoindentation tests were conducted to measure Young’s modulus and hardness of individual trabeculae. Measurements were made in both longitudinal and transverse direction in relation to the longitudinal axes of the trabeculae. The indentation load – displacement data obtained in these tests were analyzed, using the method of Oliver and Pharr.
Results: a total of 719 nanoindentations were produced in this research. A mean of 7–8 indentations were made in 103 separate trabeculae both in longitudinal and transverse direction. The mean Young’s modulus was found to be 13.7(2.5) Gpa, which is higher than the one obtained by classic micromechanical tests. There were no significant differences of elastic moduli among the longitudinal and the transverse directions of the trabeculae (13.8. Gpa and 13.5 Gpa, respectively).
Conclusion: nanoindentation is a very promising technique for evaluating intrinsic mechanical properties of bone at sub-micro level of organization. It may have many applications and may contribute to the improvement of our knowledge concerning bone biomechanics, the effects of metabolic bone diseases on bone mechanical properties and the capabilities of surgical treatment
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
