Heterogeneity of yield strain in low-density versus high-density human trabecular bone.
Understanding the off-axis behavior of trabecular yield strains may lend unique insight into the etiology of fractures since yield strains provide measures of failure independent of elastic behavior. We sought to address anisotropy of trabecular yield strains while accounting for variations in both density and anatomic site and to determine the mechanisms governing this behavior. Cylindrical specimens were cored from vertebral bodies (n=22, BV/TV=0.11+/-0.02) and femoral necks (n=28, BV/TV=0.22+/-0.06) with the principal trabecular orientation either aligned along the cylinder axis (on-axis, n=22) or at an oblique angle of 15 degrees or 45 degrees (off-axis, n=28). Each specimen was scanned with micro-CT, mechanically compressed to failure, and analysed with nonlinear micro-CT-based finite element analysis. Yield strains depended on anatomic site (p=0.03, ANOVA), and the effect of off-axis loading was different for the two sites (p=0.04)-yield strains increased for off-axis loading of the vertebral bone (p=0.04), but were isotropic for the femoral bone (p=0.66). With sites pooled together, yield strains were positively correlated with BV/TV for on-axis loading (R(2)=58%, p<0.0001), but no such correlation existed for off-axis loading (p=0.79). Analysis of the modulus-BV/TV and strength-BV/TV relationships indicated that, for the femoral bone, the reduction in strength associated with off-axis loading was greater than that for modulus, while the opposite trend occurred for the vertebral bone. The micro-FE analyses indicated that these trends were due to different failure mechanisms for the two types of bone and the different loading modes. Taken together, these results provide unique insight into the failure behavior of human trabecular bone and highlight the need for a multiaxial failure criterion that accounts for anatomic site and bone volume fraction.
Bevill
Grant
G
Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, CA 94720-1740, USA.
Farhamand
Farhad
F
Keaveny
Tony M
TM
D000368:Aged; D000369:Aged, 80 and over; D016880:Anisotropy; D015519:Bone Density / Q000502:physiology*; D019245:Compressive Strength / Q000502:physiology; D003198:Computer Simulation; D055119:Elastic Modulus / Q000502:physiology; D005260:Female; D005272:Femur Neck / Q000502:physiology*; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D013131:Spine / Q000502:physiology*; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology*
J Orthop Res. 1999 Jul;17(4):582-5
10459766
Acta Orthop Scand. 1980 Jun;51(3):429-37
7446022
J Biomech. 2001 May;34(5):569-77
11311697
J Biomech Eng. 2004 Dec;126(6):677-84
15796326
J Orthop Res. 1985;3(4):424-34
4067701
J Biomech. 1996 Oct;29(10):1309-17
8884476
J Biomech. 1998 Jul;31(7):601-8
9796682
Bone. 1987;8(2):79-85
3593611
J Biomech. 1987;20(11-12):1121-34
3429458
J Biomech Eng. 1986 Feb;108(1):83-8
3959556
J Biomech. 2007;40(8):1670-5
17368466
J Biomech. 2004 Nov;37(11):1671-8
15388309
J Biomech. 2004 Jan;37(1):55-65
14672568
J Biomech. 1987;20(1):29-33
3558426
J Biomech. 1985;18(5):317-28
4008502
J Biomech Eng. 1999 Dec;121(6):629-35
10633264
Bone. 2006 Dec;39(6):1218-25
16904959
J Orthop Res. 1997 Jan;15(1):101-10
9066533
Bone. 1994 Jan-Feb;15(1):105-9
8024844
J Biomech Eng. 1991 Nov;113(4):353-60
1762430
J Biomech. 1982;15(3):155-64
7096368
J Biomech Eng. 1999 Aug;121(4):414-22
10464696
J Biomech. 2005 Jan;38(1):141-4
15519349
J Biomech Eng. 1989 Aug;111(3):256-60
2779192