Mechanisms of initial endplate failure in the human vertebral body.
Endplate failure occurs frequently in osteoporotic vertebral fractures and may be related to the development of high tensile strain. To determine whether the highest tensile strains in the vertebra occur in the endplates, and whether such high tensile strains are associated with the material behavior of the intervertebral disc, we used micro-CT-based finite element analysis to assess tissue-level strains in 22 elderly human vertebrae (81.5 ± 9.6 years) that were compressed through simulated intervertebral discs. In each vertebra, we compared the highest tensile and compressive strains across the different compartments: endplates, cortical shell, and trabecular bone. The influence of Poisson-type expansion of the disc on the results was determined by compressing the vertebrae a second time in which we suppressed the Poisson expansion. We found that the highest tensile strains occurred within the endplates whereas the highest compressive strains occurred within the trabecular bone. The ratio of strain to assumed tissue-level yield strain was the highest for the endplates, indicating that the endplates had the greatest risk of initial failure. Suppressing the Poisson expansion of the disc decreased the amount of highly tensile-strained tissue in the endplates by 79.4 ± 11.3%. These results indicate that the endplates are at the greatest risk of initial failure due to the development of high tensile strains, and that such high tensile strains are associated with the Poisson expansion of the disc. We conclude that initial failure of the vertebra is associated with high tensile strains in the endplates, which in turn are influenced by the material behavior of the disc.
Fields
Aaron J
AJ
Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, CA, USA. afields@me.berkeley.edu
Lee
Gideon L
GL
Keaveny
Tony M
TM
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D019245:Compressive Strength; D003198:Computer Simulation; D005260:Female; D020342:Finite Element Analysis; D006132:Growth Plate / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D066298:In Vitro Techniques; D007403:Intervertebral Disc / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D000072042:Salter-Harris Fractures; D016103:Spinal Fractures / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D013131:Spine / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013718:Tensile Strength; D055114:X-Ray Microtomography
Spine (Phila Pa 1976). 1984 Mar;9(2):120-34
6233710
Eur Spine J. 2010 Mar;19 Suppl 1:S2-7
19851793
Spine (Phila Pa 1976). 2007 Dec 1;32(25):2860-8
18246009
J Bone Joint Surg Br. 1996 Nov;78(6):965-72
8951017
Bone. 2009 Apr;44(4):573-8
19110082
Spine (Phila Pa 1976). 2001 Apr 15;26(8):889-96
11317111
Spine (Phila Pa 1976). 1983 Nov-Dec;8(8):851-6
6670020
J Bone Miner Res. 2006 Feb;21(2):307-14
16418787
Bone. 2003 Oct;33(4):494-504
14555252
J Bone Miner Res. 2006 Sep;21(9):1409-16
16939399
Acta Orthop Scand Suppl. 1957;25:1-101
13443913
Spine (Phila Pa 1976). 1999 Jan 1;24(1):10-7
9921585
J Orthop Res. 2004 Jul;22(4):901-9
15183453
Spine (Phila Pa 1976). 2004 Apr 1;29(7):774-82
15087801
J Biomech. 1975;8(6):393-405
1206042
Bone. 2003 Mar;32(3):316-23
12667560
Calcif Tissue Int. 1993;53 Suppl 1:S121-5; discussion S125-6
8275365
J Biomech. 2008;41(1):78-85
17915227
Bone. 2009 Feb;44(2):372-9
19049912
J Biomech. 1999 Jul;32(7):673-80
10400354
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 Biomed Mater Res. 1999 Feb;44(2):191-7
10397920
Eur Spine J. 2000 Apr;9(2):92-6
10823423
Spine (Phila Pa 1976). 1996 May 15;21(10):1174-84
8727192
Spine (Phila Pa 1976). 2001 Oct 1;26(19):2080-9
11698883
Proc Inst Mech Eng H. 2002;216(5):299-314
12365788
Bone. 1994 Jul-Aug;15(4):409-14
7917579
J Biomech. 1995 Jan;28(1):69-81
7852443
Spine (Phila Pa 1976). 1981 Mar-Apr;6(2):147-53
7280815
J Biomech. 2000 Dec;33(12):1575-83
11006381
Spine (Phila Pa 1976). 1986 Sep;11(7):726-31
3787344
Bone. 2007 Oct;41(4):733-9
17643362
J Biomech. 1978;11(1-2):1-14
659451
Eur Spine J. 1994;3(4):184-201
7866834
J Bone Miner Res. 1997 Jan;12(1):89-95
9240730
J Clin Invest. 1996 Aug 15;98(4):996-1003
8770872
J Orthop Res. 1997 Mar;15(2):318-22
9167638
Bone. 2007 Dec;41(6):946-57
17913613
Spine (Phila Pa 1976). 2010 Feb 15;35(4):386-94
20110846
Osteoporos Int. 2005 Jul;16(7):717-28
15868071
Spine (Phila Pa 1976). 2004 Dec 1;29(23):2733-41
15564922
J Biomech. 2004 Sep;37(9):1413-20
15275849
Spine (Phila Pa 1976). 2001 Jan 15;26(2):218-25
11154545
Bone. 1991;12(3):219-24
1910963
J Biomech Eng. 1998 Apr;120(2):289-95
10412392
Bone. 1996 Mar;18(3 Suppl):179S-183S
8777085
Spine (Phila Pa 1976). 1992 Mar;17(3):286-92
1566166