Morphometric Analysis of the Human Lower Lumbar Intervertebral Discs and Vertebral Endplates

389 Pages·2013·8.62 MB·English

Morphometric Analysis of the Human Lower Lumbar Intervertebral Discs and
Vertebral Endplates: Experimental Approach and Regression Models
by
Ruoliang Tang
A dissertation submitted to the Graduate Faculty of
Auburn University
in partial fulfillment of the
requirements for the Degree of
Doctor of Philosophy
Auburn, Alabama
May 5, 2013
Keywords: lower lumbar spine, intervertebral disc, vertebral endplate, morphometric
analysis, regression analysis, MRI, occupational ergonomics
Copyright 2013 by Ruoliang Tang
Approved by
Richard F. Sesek, Chair, Assistant Professor of Industrial and Systems Engineering
Gerard A. Davis, Associate Professor of Industrial and Systems Engineering
Sean Gallagher, Associate Professor of Industrial and Systems Engineering
Robert E. Thomas, Professor Emeritus of Industrial and Systems Engineering
Abstract
Low back pain (LBP) has been a major socioeconomic problem to the modern society
for decades. In industry, one of the most challenging issues in occupational ergonomics and
health practices has been the reliable and accurate estimation of risks of work-related
musculoskeletal disorders (WMSDs), particularly work-related low back pain (WRLBP)
and injuries which represent a large portion of all Workers’ Compensation (WC) cost. To
date, ergonomics evaluation measures developed to pinpoint jobs with elevated risks of
WRLBP primarily rely on biomechanical models of the musculoskeletal structures of the
human spine to estimate the internal response in terms of muscle induced compressive
forces and to characterize the risk associated with the postures and forceful motions.
However, morphometric characteristics of the human spine has not yet been thoroughly
investigated and incorporated in the development of biomechanical models. In particular,
the size of the load-bearing surface (cross-sectional area) of lumbar motion segments has
been lacking in the literature, despite the fact that there is strong correlation between the
cross-sectional area (CSA) and the ultimate compressive strength. Morphometric data
regarding the human spine have been obtained with either direct measurements on
cadaveric specimens or using medical imaging techniques, which require strict measurement
protocol and incur high cost. In industry, occupational safety and health practitioners
would prefer a more cost-effective means to obtain these morphometric data to improve the
ergonomic evaluations and risk estimation of WRLBP.
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The objective of this study was 1) to develop standardized protocol using magnetic
resonance (MR) scans to measure the cross-sectional areas (CSAs) of the lower lumbar
intervertebral discs and vertebral endplates, and 2) to develop regression models to predict
these CSAs with different hierarchy of model complexity and predictor selection criteria.
MR scans were 1) collected from a medical database and 2) performed in a research
institute (Auburn University MRI Research Center). MR scans were analyzed using
imaging processing software package with a research protocol developed in this
dissertation. The protocol standardized the definitions of each geometric dimension and
the measurement techniques and achieved excellent measurement reliability.
This dissertation provides comprehensive morphometric data regarding both the
linear and planar aspects of the lower lumbar intervertebral discs (IVDs) and vertebral
endplates (EPs), which has been lacking in the literature. Results of this dissertation also
indicate that it is feasible to perform satisfactory predictions of the CSAs of the human
lower lumbar IVDs and EPs using subject variables (characteristics and anthropometric
measures). Results of this dissertation also suggest that the discrepancy in historical
geometric data regarding the human lower lumbar may not only be attributed to gender
alone but also related to other anthropometric measures. In addition, it is also evident that
superior model performance can be achieved when certain anthropometric measures, such
as the dimensions of ankle and elbow joints, are included as predictors in the prediction
equations.
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Acknowledgments
First and foremost, I would like to express my deepest and sincere gratitude to my
adviser, Dr. Richard Sesek, for his enlightening guidance and inspiring instruction in the
development and completion of this dissertation.
My heartfelt gratitude goes to the members of my dissertation committee, Dr. Sean
Gallagher, Dr. Jerry Davis, and Dr. Robert Thomas for their profound guidance,
comments, and support throughout the completion of this dissertation.
I also acknowledge and thank Dr. Kenneth Bo Foreman for his time and thoughts,
Dr. James Carnahan, who generously gave his time and statistics expertise throughout this
dissertation process, and Dr. Thomas Denney Jr, Dr. Ronald Beyers, and Dr. Nouha
Salibi at the Auburn University MRI Research Center, for their training and assistance of
protocol development and MRI operations.
A special gratitude and love goes to my family for their unfailing support and abiding
love.
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Table of Contents
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Cost and epidemiological aspects of low back pain . . . . . . . . . . . . . . . 1
1.2 Pathological aspects of low back pain . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Internal exposure and biomechanical models for lumbar spinal loading . . . . 6
1.4 Motivation and research objectives . . . . . . . . . . . . . . . . . . . . . . . 8
1.4.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4.2 Research objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.4.3 Dissertation organization . . . . . . . . . . . . . . . . . . . . . . . . . 10
2 BIOMECHANICS OF LUMBAR INTERVERTEBRAL DISC WITH RESPECT
TO THE MORPHOMETRIC CHARACTERISTICS . . . . . . . . . . . . . . . 12
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 Epidemiology of personal risk factors . . . . . . . . . . . . . . . . . . . . . . 15
2.2.1 Gender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.2.2 Age . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.2.3 Anthropometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.3 Development of biomechanical models and ergonomic tools for lifting tasks . 24
2.3.1 Biomechanical design criterion . . . . . . . . . . . . . . . . . . . . . . 24
2.3.2 Choice of measure: compressive force or compressive stress . . . . . . 27
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2.3.3 Prediction of compressive strength . . . . . . . . . . . . . . . . . . . 35
2.3.4 Intradiscal pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.4 Internal exposure and response of lumbar intervertebral disc . . . . . . . . . 44
2.4.1 Anatomy of lumbar motion segments . . . . . . . . . . . . . . . . . . 44
2.4.2 Response of lumbar motion segments to mechanical loading . . . . . 49
2.5 Degeneration of lumbar motion segments . . . . . . . . . . . . . . . . . . . . 53
2.5.1 Epidemiology of disc degeneration . . . . . . . . . . . . . . . . . . . . 53
2.5.2 Degenerative changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
2.5.3 Influence of disc degeneration on mechanical properties . . . . . . . . 59
2.5.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
2.6 Morphometry of lumbar motion segments . . . . . . . . . . . . . . . . . . . . 61
2.6.1 Significance of lumbar spinal morphometry . . . . . . . . . . . . . . . 61
2.6.2 Geometry of the lumbar motion segment . . . . . . . . . . . . . . . . 62
2.6.3 Analytical findings in the literature . . . . . . . . . . . . . . . . . . . 76
2.7 Research Void . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
2.7.1 How to prepare specimens (cadaver vs. in vivo) . . . . . . . . . . . . 92
2.7.2 How to access the structure . . . . . . . . . . . . . . . . . . . . . . . 94
2.7.3 How to define the dimensions . . . . . . . . . . . . . . . . . . . . . . 98
2.7.4 Influence of other factors . . . . . . . . . . . . . . . . . . . . . . . . . 103
2.7.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
3 MORPHOMETRY OF LUMBAR LUMBAR INTERVERTEBRAL DISC AND
VERTEBRALENDPLATES:ANALYSESOFMRI-DERIVEDMEASUREMENTS
IN TRANSVERSE SECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
3.2 Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
3.2.1 Acquisition of MR scans . . . . . . . . . . . . . . . . . . . . . . . . . 114
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3.2.2 Measurement of intervertebral disc geometry . . . . . . . . . . . . . . 116
3.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
3.3.1 Repeatability tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
3.3.2 Descriptive statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
3.3.3 Influence of ellipsoid approximation . . . . . . . . . . . . . . . . . . . 135
3.3.4 Diameters in the transverse section . . . . . . . . . . . . . . . . . . . 136
3.3.5 Morphometric index . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
3.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
3.4.1 Essence of the morphometry of the spinal motion segments . . . . . . 148
3.4.2 Research findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
3.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
4 PREDICTION OF THE CROSS-SECTIONAL AREA OF HUMAN LOWER
LUMBAR INTERVERTEBRAL DISC AND VERTEBRAL ENDPLATE: RE-
GRESSIONMODELSOFGEOMETRICDIMENSIONSDERIVEDFROMARCHIVED
MR SCANS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
4.2 Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
4.2.1 Acquisition of MRI-derived geometric dimensions . . . . . . . . . . . 187
4.2.2 Model development . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
4.2.3 Model validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
4.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
4.3.1 Preliminary analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
4.3.2 Regression analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
4.3.3 Model validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
4.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
4.4.1 Prediction equations for the cross-sectional areas (CSAs) of the lower
lumbar motion segments . . . . . . . . . . . . . . . . . . . . . . . . . 225
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4.4.2 Model exploration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
5 PREDICTION OF THE CROSS-SECTIONAL AREA OF HUMAN LOWER
LUMBAR INTERVERTEBRAL DISC AND VERTEBRAL ENDPLATE: RE-
GRESSION MODELS OF GEOMETRIC DIMENSIONS DERIVED FROM MR
SCANS USING ASYMPTOMATIC SUBJECTS . . . . . . . . . . . . . . . . . . 236
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
5.2 Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
5.2.1 Subjects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
5.2.2 Acquisition of magnetic resonance (MR) scans . . . . . . . . . . . . . 241
5.2.3 Image analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
5.2.4 Subject characteristics and anthropometrics . . . . . . . . . . . . . . 247
5.2.5 Statistical analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
5.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
5.3.1 Descriptive statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
5.3.2 Correlation analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
5.3.3 Regression analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
5.3.4 Further analyses regarding the regression models . . . . . . . . . . . . 286
5.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
5.4.1 Regression models of the CSAs of the lower lumbar intervertebral discs
(IVDs) and vertebral endplates (EPs) . . . . . . . . . . . . . . . . . . 294
5.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
6 CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
A Approval letter from the Institutional Review Boards (IRBs) at the University of
Utah and Auburn University . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
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B Documentation of research protocol (Informed Consent and subject recruitment
flyer) as approved by the Institutional Review Board (IRB) at Auburn University 347
C Data collection form used in Study 2 . . . . . . . . . . . . . . . . . . . . . . . . 355
D Best subset regression models for the CSA of the intervertebral discs (IVDs) . . 357
E Best subset regression models for the CSA of the cranial endplates (CrEPs) . . . 361
F Best subset regression models for the CSA of the caudal endplates (CaEPs) . . . 365
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List of Figures
1.1 AverageCostperBackInjuryClaim,2000-2010(inthousandUSdollars)(CHSWC,
2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Low back pain among adults 18 years of age and over by gender: United States,
selected years 1997-2009 (NCHS, 2011, Table 52) . . . . . . . . . . . . . . . . . 17
2.2 Low back pain among adults 18 years of age and over by age: United States,
selected years 1997-2009 (NCHS, 2011, Table 52) . . . . . . . . . . . . . . . . . 20
2.3 Results of cadaver studies examining compressive forces of lumbar vertebral seg-
ments (figure from Chaffin et al. 2006, based on data presented in J¨ager and
Luttmann 1987) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.4 Summary of compressive forces reported in cadaver studies with particular refer-
ence to the intervertebral discs . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.5 Summaryofcompressivestressescomputedfromdatareportedincadaverstudies
with particular reference to the intervertebral discs . . . . . . . . . . . . . . . . 33
2.6 Profiles of vertical and horizontal compressive stress along the anteroposterior
direction. Antherior (A) on the right. Vertical dashed lines indicate the extent
of the hydrostatic nucleus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
x