Tears in the annulus fibrosus (AF) of the intervertebral disk can result in disk herniation and progressive degeneration. Understanding AF failure mechanics is important as research moves toward developing biological repair strategies for herniated disks. Unfortunately, failure mechanics of fiber-reinforced tissues, particularly tissues with fibers oriented off-axis from the applied load, is not well understood, partly due to the high variability in reported mechanical properties and a lack of standard techniques ensuring repeatable failure behavior. Therefore, the objective of this study was to investigate the effectiveness of midlength (ML) notch geometries in producing repeatable and consistent tissue failure within the gauge region of AF mechanical test specimens. Finite element models (FEMs) representing several notch geometries were created to predict the location of bulk tissue failure using a local strain-based criterion. FEM results were validated by experimentally testing a subset of the modeled specimen geometries. Mechanical testing data agreed with model predictions (∼90% agreement), validating the model's predictive power. Two of the modified dog-bone geometries (“half” and “quarter”) effectively ensured tissue failure at the ML for specimens oriented along the circumferential-radial and circumferential-axial directions. The variance of measured mechanical properties was significantly lower for notched samples that failed at the ML, suggesting that ML notch geometries result in more consistent and reliable data. In addition, the approach developed in this study provides a framework for evaluating failure properties of other fiber-reinforced tissues, such as tendons and meniscus.

References

References
1.
Iatridis
,
J.
,
MacLean
,
J.
, and
Ryan
,
D.
,
2005
, “
Mechanical Damage to the Intervertebral Disc Annulus Fibrosus Subjected to Tensile Loading
,”
J. Biomech.
,
38
(
3
), pp.
557
565
.
2.
Mengoni
,
M.
,
Jones
,
A.
, and
Wilcox
,
R.
,
2016
, “
Modelling the Failure Precursor Mechanism of Lamellar Fibrous Tissues, Example of the Annulus Fibrosus
,”
J. Mech. Behav. Biomed. Mater.
,
63
, pp.
265
272
.
3.
CDC
,
2005
, “
Prevalence and Most Common Causes of Disability Among Adults—United States
,”
Morbidity Mortal. Wkly. Rep.
,
58
(16), pp. 421–426.
4.
Adams
,
M.
, and
Roughley
,
P.
,
2006
, “
What is Intervertebral Disc Degeneration, and What Causes It?
,”
Spine
,
31
(
18
), pp.
2151
2161
.
5.
Vernon-Roberts
,
B.
,
Moore
,
R.
, and
Fraser
,
R.
,
2007
, “
The Natural History of Age-Related Disc Degeneration
,”
Spine
,
32
(
25
), pp.
2797
2804
.
6.
Weigel
,
M.
,
Armijos
,
R.
, and
Beltran
,
O.
,
2014
, “
Musculoskeletal Injury, Functional Disability, and Health-Related Quality of Life in Aging Mexican Immigrant Farmworkers
,”
J. Immigrant Minority Health
,
16
(
5
), pp.
904
13
.
7.
O'Connell
,
G.
,
Leach
,
K.
, and
Klineberg
,
E.
,
2015
, “
Tissue Engineering a Biological Repair Strategy for Lumbar Disc Herniation
,”
Biores. Open Access
,
4
(
1
), pp.
431
435
.
8.
Long
,
R.
,
Torre
,
O.
,
Hom
,
W.
,
Assael
,
D.
, and
Iatridis
,
J.
,
2016
, “
Design Requirements for Annulus Fibrosus Repair: Review of Forces, Displacements, and Material Properties of the Intervertebral Disk and a Summary of Candidate Hydrogels for Repair
,”
ASME J. Biomech. Eng.
,
138
(
2
), p. 021007.
9.
Acaroglu
,
E.
,
Iatridis
,
J.
,
Setton
,
L.
,
Foster
,
R.
,
Mow
,
V.
, and
Weidenbaum
,
M.
,
1995
, “
Degeneration and Aging Affect the Tensile Behavior of Human Lumbar Anulus Fibrosus
,”
Spine
,
20
(
24
), pp.
2690
2701
.
10.
Green
,
T.
,
Adams
,
M.
, and
Dolan
,
P.
,
1993
, “
Tensile Properties of the Annulus Fibrosus
,”
Eur. Spine J.
,
2
(
4
), pp.
209
214
.
11.
Ebara
,
S.
,
Iatridis
,
J.
,
Setton
,
L.
,
Foster
,
R.
,
Mow
,
V.
, and
Weidenbaum
,
M.
,
1996
, “
Tensile Properties of Nondegenerate Human Lumbar Anulus Fibrosus
,”
Spine
,
21
(
4
), pp.
452
461
.
12.
Skaggs
,
D.
,
Weidenbaum
,
M.
,
Ratcliffe
,
A.
, and
Mow
,
V.
,
1994
, “
Regional Variation in Tensile Properties and Biochemical Composition of the Human Lumbar Annulus Fibrosus
,”
Spine
,
19
(
12
), pp.
1310
1319
.
13.
O'Connell
,
G.
,
Vresilovic
,
E.
, and
Elliott
,
D.
,
2007
, “
Comparison of Animals Used in Disc Research to Human Lumbar Disc Geometry
,”
Spine
,
32
(
3
), pp.
328
33
.
14.
Holzapfel
,
G.
,
Schulze-Bauer
,
C.
,
Feigl
,
G.
, and
Regitnig
,
P.
,
2005
, “
Single Lamellar Mechanics of the Human Lumbar Anulus Fibrosus
,”
Biomech. Model Mechanobiol.
,
3
(
3
), pp.
125
140
.
15.
Jacobs
,
N.
,
Cortes
,
D.
,
Vresilovic
,
E.
, and
Elliot
,
D.
,
2013
, “
Biaxial Tension of Fibrous Tissue: Using Finite Element Methods to Address Experimental Challenges Arising From Boundary Conditions and Anisotropy
,”
ASME J. Biomech. Eng.
,
135
(
2
), p.
021004
.
16.
Peloquin
,
J.
,
Santare
,
M.
, and
Elliott
,
D.
,
2016
, “
Advances in Quantification of Meniscus Tensile Mechanics Including Nonlinearity, Yield, and Failure
,”
ASME J. Biomech. Eng.
,
138
(
2
), p.
021002
.
17.
Lechner
,
K.
,
Hull
,
M.
, and
Howell
,
S.
,
2000
, “
Is the Circumferential Tensile Modulus Within a Human Medial Meniscus Affected by the Test Sample Location and Cross-Sectional Area?
,”
J. Orthop. Res.
,
18
(
6
), pp.
945
951
.
18.
ASTM
,
2004
, “
Standard Test Methods for Tension Testing of Metallic Materials
,” ASTM, West Conshohocken, PA, Standard No.
ASTM E8/E8M-13
.
19.
ASTM
,
2003
, “
Standard Test Method for Tensile Properties of Plastics
,” ASTM International, West Conshohocken, PA, Standard No.
ASTM D638-14
.
20.
Kolz
,
C.
,
Suter
,
T.
, and
Henninger
,
H.
,
2015
, “
Regional Mechanical Properties of the Long Head of the Biceps Tendon
,”
Clin. Biomech.
,
30
(
9
), pp.
940
5
.
21.
Morales-Orcajo
,
E.
,
De Bengoa Vallejo
,
R.
,
Iglesias
,
M.
, and
Bayod
,
J.
,
2016
, “
Structural and Material Properties of Human Foot Tendons
,”
Clin. Biomech.
,
37
, pp.
1
6
.
22.
Yamamoto
,
N.
, and
Hayashi
,
K.
,
1998
, “
Mechanical Properties of Rabbit Patellar Tendon at High Strain Rate
,”
Biomed. Mater. Eng.
,
8
(
2
), pp.
83
90
.
23.
Cassidy
,
J.
,
Hiltner
,
A.
, and
Baer
,
E.
,
1989
, “
Hierarchical Structure of the Intervertebral Disc
,”
Connect. Tissue Res.
,
23
(
1
), pp.
75
88
.
24.
Schmidt
,
H.
,
Bashkuev
,
M.
,
Dreischarf
,
M.
,
Rohlmann
,
A.
,
Duda
,
G.
,
Wilke
,
H.
, and
Shirazi-Adl
,
A.
,
2013
, “
Computational Biomechanics of a Lumbar Motion Segment in Pure and Combined Shear Loads
,”
J. Biomech.
,
46
(
14
), pp.
2513
2521
.
25.
Sun
,
W.
,
Sacks
,
M.
, and
Scott
,
M.
,
2005
, “
Effects of Boundary Conditions on the Estimation of the Planar Biaxial Mechanical Properties of Soft Tissues
,”
ASME J. Biomech. Eng.
,
127
(
4
), pp.
709
715
.
26.
Waldman
,
S. D.
, and
Lee
,
J. M.
,
2005
, “
Effect of Sample Geometry on the Apparent Biaxial Mechanical Behavior of Planar Connective Tissues
,”
Biomater.
,
26
(35), pp.
7504
7513
.
27.
Bass
,
E.
,
Ashford
,
F.
,
Segal
,
M.
, and
Lotz
,
J.
,
2004
, “
Biaxial Testing of Human Annulus Fibrosus and Its Implications for a Constitutive Formulation
,”
Ann. Biomed. Eng.
,
32
(
9
), pp.
1231
1242
.
28.
O'Connell
,
G.
,
Sen
,
S.
, and
Elliott
,
D.
,
2011
, “
Human Annulus Fibrosus Material Properties From Biaxial Testing and Constitutive Modeling are Altered With Degeneration
,”
Biomech. Model. Mechanobiol.
,
11
(
3–4
), pp.
493
503
.
29.
O'Connell
,
G.
,
Guerin
,
H.
, and
Elliott
,
D.
,
2009
, “
Theoretical and Uniaxial Experimental Evaluation of Human Annulus Fibrosus Degeneration
,”
ASME J. Biomech. Eng.
,
131
(
11
), p.
111007
.
30.
Nagel
,
T.
,
Hadi
,
M.
,
Claeson
,
A.
,
Nuckley
,
D.
, and
Barocas
,
V.
,
2014
, “
Combining Displacement Field and Grip Force Information to Determine Mechanical Properties of Planar Tissue With Complicated Geometry
,”
ASME J. Biomech. Eng.
,
136
(
11
), p.
114501
.
31.
Guerin
,
H.
, and
Elliott
,
D.
,
2006
, “
Degeneration Affects the Fiber Reorientation of Human Annulus Fibrosus Under Tensile Load
,”
J. Biomech.
,
39
(
8
), pp.
1410
1418
.
32.
Wagner
,
D.
,
Reiser
,
K.
, and
Lotz
,
J.
,
2006
, “
Glycation Increases Human Annulus Fibrosus Stiffness in Both Experimental Measurements and Theoretical Predictions
,”
J. Biomech.
,
39
(
6
), pp.
1021
1029
.
33.
Marchand
,
F.
, and
Ahmed
,
A. M.
,
1990
, “
Investigation of the Laminate Structure of Lumbar Disc Annulus Fibrosus
,”
Spine
,
15
(
5
), pp.
402
410
.
34.
Maas
,
S.
,
Rawlins
,
D.
,
Weiss
,
J.
, and
Ateshian
,
G.
,
2011
, “
Febio Theory Manual
,” Musculoskeletal Research Laboratories, University of Utah, Salt Lake City, UT.
35.
Bezci
,
S.
,
Nandy
,
A.
, and
O'Connell
,
G.
,
2015
, “
Effect of Hydration on Healthy Intervertebral Disk Mechanical Stiffness
,”
ASME J. Biomech. Eng.
,
137
(
10
), p.
101007
.
36.
Adams
,
M.
, and
Green
,
T.
,
1993
, “
Tensile Properties of the Annulus Fibrosus
,”
Eur. Spine J.
,
2
(
4
), pp.
203
208
.
37.
Elliott
,
D.
, and
Setton
,
L.
,
2001
, “
Anisotropic and Inhomogeneous Tensile Behavior of the Human Anulus Fibrosus: Experimental Measurement and Material Model Predictions
,”
ASME J. Biomech. Eng.
,
123
(
3
), pp.
256
263
.
38.
Wagner
,
D.
, and
Lotz
,
J.
,
2004
, “
Theoretical Model and Experimental Results for the Nonlinear Elastic Behavior of Human Annulus Fibrosus
,”
J. Orthop. Res.
,
22
(
4
), pp.
901
909
.
39.
Von Forell
,
G.
,
Hyoung
,
P.
, and
Bowden
,
A.
,
2014
, “
Failure Modes and Fracture Toughness in Partially Torn Ligaments and Tendons
,”
J. Mech. Behav. Biomed. Mater.
,
35
, pp.
77
84
.
40.
Taylor
,
D.
,
OMara
,
N.
,
Ryan
,
E.
,
Takaza
,
M.
, and
Simms
,
C.
,
2012
, “
The Fracture Toughness of Soft Tissues
,”
J. Mech. Behav. Biomed. Mater.
,
6
, pp.
139
147
.
41.
Galante
,
J.
,
1967
, “
Tensile Properties of the Human Lumbar Annulus Fibrosus
,”
Acta. Orthop. Scand.
,
38
(Sup.
100
), pp.
1
91
.
42.
Noyes
,
F.
,
DeLucas
,
J.
, and
Torvik
,
P.
,
1974
, “
Biomechanics of Anterior Cruciate Ligament Failure: An Analysis of Strain-Rate Sensitivity and Mechanisms of Failure in Primates
,”
J. Bone Joint Surg. Am.
,
56
(
2
), pp.
236
253
.
43.
Crowninshield
,
R.
, and
Pope
,
M.
,
1976
, “
The Strength and Failure Characteristics of Rat Medial Collateral Ligaments
,”
J. Trauma Acute Care Surg.
,
16
(
2
), pp.
99
105
.
44.
Woo
,
S.
,
Peterson
,
R.
,
Ohland
,
K.
,
Sites
,
T.
, and
Danto
,
M.
,
1990
, “
The Effects of Strain Rate on the Properties of the Medial Collateral Ligament in Skeletally Immature and Mature Rabbits: A Biomechanical and Histological Study
,”
J. Orthop. Res.
,
8
(
5
), pp.
712
721
.
45.
Ateshian
,
G.
,
Chahine
,
N.
,
Basalo
,
I.
, and
Hung
,
C.
,
2004
, “
The Correspondence Between Equilibrium Biphasic and Triphasic Material Properties in Mixture Models of Articular Cartilage
,”
J. Biomech.
,
37
(
3
), pp.
391
400
.
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