The authors state that they have no conflicts of interest.
Influence of Orthogonal Overload on Human Vertebral Trabecular Bone Mechanical Properties†
Version of Record online: 9 JUL 2007
Copyright © 2007 ASBMR
Journal of Bone and Mineral Research
Volume 22, Issue 11, pages 1690–1699, November 2007
How to Cite
Badiei, A., Bottema, M. J. and Fazzalari, N. L. (2007), Influence of Orthogonal Overload on Human Vertebral Trabecular Bone Mechanical Properties. J Bone Miner Res, 22: 1690–1699. doi: 10.1359/jbmr.070706
- Issue online: 4 DEC 2009
- Version of Record online: 9 JUL 2007
- Manuscript Accepted: 5 JUL 2007
- Manuscript Revised: 20 JUN 2007
- Manuscript Received: 20 DEC 2006
- bone mechanics;
- bone quality;
- trabecular bone architecture;
- bone strength;
- vertebral bone
The aim of this study was to investigate the effects of overload in orthogonal directions on longitudinal and transverse mechanical integrity in human vertebral trabecular bone. Results suggest that the trabecular structure has properties that act to minimize the decrease of apparent toughness transverse to the primary loading direction.
Introduction: The maintenance of mechanical integrity and function of trabecular structure after overload remains largely unexplored. Whereas a number of studies have focused on addressing the question by testing the principal anatomical loading direction, the mechanical anisotropy has been overlooked. The aim of this study was to investigate the effects of overload in orthogonal directions on longitudinal and transverse mechanical integrity in human vertebral trabecular bone.
Materials and Methods: T12/L1 vertebral bodies from five cases and L4/L5 vertebral bodies from seven cases were retrieved at autopsy. A cube of trabecular bone was cut from the centrum of each vertebral body and imaged by μCT. Cubes from each T12/L1 and L4/L5 pairs were assigned to either superoinferior (SI) or anteroposterior (AP) mechanical testing groups. All samples were mechanically tested to 10% apparent strain by uniaxial compression according to their SI or AP allocation. To elucidate the extent to which overload in orthogonal directions affects the mechanical integrity of the trabecular structure, samples were retested (after initial uniaxial compression) in their orthogonal direction. After mechanical testing in each direction, apparent ultimate failure stresses (UFS), apparent elastic moduli (E), and apparent toughness moduli (u) were computed.
Results: Significant differences in mechanical properties were found between SI and AP directions in both first and second overload tests. Mechanical anisotropy far exceeded differences resulting from overloading the structure in the orthogonal direction. No significant differences were found in mean UFS and mean u for the first or second overload tests. A significant decrease of 35% was identified in mean E for cubes overloaded in the SI direction and then overloaded in the AP direction.
Conclusions: Observed differences in the mechanics of trabecular structure after overload suggests that the trabecular structure has properties that act to minimize loss of apparent toughness, perhaps through energy dissipating sacrificial structures transverse to the primary loading direction.