title: A computational assessment of the independent contribution of changes in canine trabecular bone volume fraction and microarchitecture to increased bone strength with suppression of bone turnover.
abstract: This study addressed the effects of changes in trabecular microarchitecture induced by suppressed bone turnover-including changes to the remodeling space-on the trabecular bone strength-volume fraction characteristics independent of changes in tissue material properties. Twenty female beagle dogs, aged 1-2 years, were treated daily with either oral saline (n=10 control) or high doses of oral risedronate (0.5mg/kg/day, n=10 suppressed) for a period of 1 year, the latter designed (and confirmed) to substantially suppress bone turnover. High-resolution micro-CT-based finite element models (18-mum voxel size) of canine trabecular bone cores (n=2 per vertebral body) extracted from the T-10 vertebrae were analyzed in both compressive and torsional loading cases. The same tissue-level material properties were used in all models, thus providing measures of tissue-normalized strength due only to changes in the microarchitecture. Suppressed bone turnover resulted in more plate-like architecture with a thicker and more dense trabecular structure, but the relationship between the microarchitectural parameters and volume fraction was unaltered (p>0.05). Though the suppressed group had a greater tissue-normalized strength as compared to the control group (p<0.001) for both compressive and torsional loading, the relationship between tissue-normalized strength and volume fraction was not significantly altered for compression (p>0.13) or torsion (p>0.09). In this high-density, non-osteoporotic animal model, the increases in tissue-normalized strength seen with suppression of bone turnover were entirely commensurate with increases in bone volume fraction and thus, no evidence of microarchitecture-related or "stress-riser" effects which may disproportionately affect strength were found.
authors.affiliation: Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, CA 94720, USA. senthilk@me.berkeley.edu
authors.forename: Senthil K
authors.initials: SK
authors.lastname: Eswaran
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Allen
authors.forename: David B
authors.initials: DB
authors.lastname: Burr
authors.forename: Tony M
authors.initials: TM
authors.lastname: Keaveny
mesh_terms: D000818:Animals; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000166:cytology* / Q000378:metabolism*; D003198:Computer Simulation; D004285:Dogs; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D023421:Models, Animal; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed