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Biomechanical Aspects of Spinal Cord Injury

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Title: Biomechanical Aspects of Spinal Cord Injury


1
Biomechanical Aspects of Spinal Cord Injury
  • Thomas R. Oxland PhD PEng
  • Professor Director
  • Division of Orthopaedic Engineering Research
  • Departments of Orthopaedics Mechanical
    Engineering
  • The University of British Columbia
  • Vancouver Coastal Health Research Institute

2
UBC The University of British Columbia
  • 40,000 students
  • 4,000 faculty

3
UBC Department of Orthopaedics
  • 65 faculty members
  • 5 teaching hospitals
  • basic clinical research
  • seven Divisions
  • Athletic Injuries
  • Lower Limb Reconstruction
  • Upper Limb Reconstruction
  • Pediatrics
  • Spine
  • Trauma
  • Orthopaedic Engineering Research

4
Orthopaedic Engineering Research (DOER)
  • the application of engineering principles to
    clinically relevant problems in the field of
    Orthopaedics

5
DOER at UBC
  • Clive Duncan
  • Bassam Masri
  • Don Garbuz
  • Marcel Dvorak
  • Brian Kwon
  • Charles Fisher
  • Pierre Guy
  • Peter OBrien
  • Robert McCormack
  • Bill Regan
  • Thomas Oxland
  • David Wilson
  • Heather McKay
  • Karim Khan
  • Peter Cripton
  • Steve Robinovitch
  • Rizhi Wang
  • Goran Fernlund
  • Gail Thornton

6
Research Themes
  • Mechanisms of Spine and Spinal Cord Injury
    Oxland, Cripton, Kwon, Dvorak,Tetzlaff
  • Etiology of Osteoarthritis Wilson, MacKay,
    Cibere
  • Hip Fracture Prevention McKay, Khan,
    Robinovitch, Guy
  • Surgical Solutions in presence of Bone Loss
  • osteoporotic spine Oxland, Cripton, Dvorak,
    Fisher
  • revision hip Oxland, Duncan, Masri, Fernlund

7
SCI Epidemiology
  • 11,000 new injuries/year in North America
    (40/million)
  • 200,000 chronic injuries
  • Average age 32
  • 9.73 billion/year
  • hospitalization, rehabilitation, medication,
    equipment, loss productivity

-Spinal Cord Injury Information Network -
www.spinalcord.uab.edu
8
ICORD new home for Spinal Research Centre in
Vancouver
  • Vancouver General Hospital
  • 51 principal investigators
  • 120,000 square feet
  • Spinal clinics
  • Rehabilitation research
  • Molecular Biology
  • Bioengineering
  • Neuropysiology

February 2008
October 2008
9
Theme 3- Develop novel animal models of SCI
where damage can be induced within an enclosed
vertebral column, thereby more accurately
mimicking human SCI. Can only be achieved
through the combined efforts of spine surgeons,
biomechanical engineers and neuroscientists
working side-by-side.
10
Theme 3 - Overview
Spinal cord injury represents a mechanical insult
that triggers a biological response which results
in a wide range of clinical sequelae.
11
(No Transcript)
12
Type of Vertebral Injury
40 Fracture Dislocation
Burst Fracture 30
SCIWORET 10
5 Dislocation
SCIWORA 5
10 Minor Fracture
Sekhon Fehlings Spine 2001
13
Spinal Injury
BURST FRACTURE
14
Clinical Observation
  • the mechanism of column damage correlates with
    the neurological deficit
  • Marar 1974, Tator 1983

. but current treatments do not incorporate
injury mechanism!
15
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16
Methods Cord/Column
  • Surrogate Cord
  • Silicone gel
  • In vivo-like in tension
  • Barium Sulfate added
  • Oval shaped

Saari MASc 2006
17
Methods Specimen Preparation
  • Human cervical spines occiput to T2 (n 6)
  • Surrogate head attached to occiput

Saari MASc 2006
18
Methods Imaging
  • High Speed X-ray
  • Industrial X-ray source
  • 75kV, 5mA
  • 9 image intensifier
  • Internal high speed camera
  • 1000 frames per second
  • 256 x 240 pixels

Image Intensifier
X-ray Source
Saari MASc 2006
19
Saari MASc 2006
20
Effect of Constraint
Flexion-compression injury model
Zhu 2008
21
Compression to the Specimen
Zhu 2008
22
Flexion-Compression (constrained)
23
Flexion-Compression (unconstrained)
Zhu 2008
24
Spinal Canal Occlusion
T1
T2
T3
T4
25
Canal Occlusion
Zhu 2008
26
Column-Canal Relationships
constrained
unconstrained
Zhu 2008
27
Dynamic Spinal Canal Occlusion
  • Transient occlusion gtgt Post-impact
  • Effect of Constraint i.e. Boundary Conditions

28
Methods - Injury Simulation
  • Axial head-to-ground impact
  • Drop Tower
  • Drop height 0.6m
  • Speed at impact 3m/s
  • Carriage mass 15kg

29
Pro-Neck-TorTM
Standard Helmet
Dr. Peter Cripton
http//injury.mech.ubc.ca http//www.proneckto
r.com
30
Proof of Concept Study Results
  • Axial Force Escape-Angle Interaction

56 reduction
15º, Med Stiffness, Extension Escape, Vimpact
3.2 m/s
31
C4
C5
C6
Greaves 2008
32
Von Mises StrainCompression
dorsal
ventral
dorsal
ventral
Greaves 2008
33
Von Mises StrainDistraction
dorsal
ventral
dorsal
ventral
Greaves 2008
34
Von Mises StrainDislocation
dorsal
ventral
ventral
dorsal
Greaves 2008
35
Different Cord Strain Patterns
Greaves Annals BME 2008
36
Contusion
37
Dislocation
38
Dislocation FEM of rat c-spine
39
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40
Spinal Canal Occlusion Transducer
Segmental Voltage segmental resistance
constant current (resistance ? area)
Raynak 1998
41
Theme 3 - Overview
Spinal cord injury represents a mechanical insult
that triggers a biological response which results
in a wide range of clinical sequelae.
42
Spinal Injury
BURST FRACTURE
Do these well-known spinal column injury patterns
create different spinal cord injuries?
43
Injury Models
1970
1990
1980
1911
2004
44
Contusion Paradigm
central cavitation with peripheral rim of spare
white matter
Figure from McDonald Belegu. J Neurotrauma 2006
45
Type of Vertebral Injury
40 Fracture Dislocation
Burst Fracture 30
SCIWORET 10
5 Dislocation
SCIWORA 5
10 Minor Fracture
Sekhon Fehlings Spine 2001
46
Experimental Animal Model
Distraction
Compression/Contusion
Shear/Dislocation
Choo PhD 2006
47
UBC SCI Test System
Actuator 12mm
LVDT (0.001mm)
accelerometer (50 500G)
Load Cell (22 225N)
Choo PhD 2006
48
Contusion
force (N)
velocity (m/s)
displacement (mm)
Cord surface
Choo PhD 2006
49
Dislocation
velocity (m/s)
force (N)
displacement (mm)
Choo PhD 2006
50
Distraction
40
30
20
force (N)
velocity (m/s)
displacement (mm)
10
0
Choo PhD 2006
51
Hemorrhage
Choo PhD 2006
52
Anatomy
53
Study 1 Primary Injury
54
Membrane Integrity
55
Membrane Integrity
56
Membrane Damage
Neuronal Cell Bodies
Axons
57
Primary Injury
  • 275-325g Sprague-Dawley rats
  • Infused 0.375mg 10kD fluorescein dextran into
    cisterna magna
  • Incubated for 1 hour 30 min surgery
  • Injury 100cm/s _at_ C4/5
  • 5 min sacrifice primary damage

Mechanism N Severity
Contusion 9 1.1mm
Dislocation 9 2.5mm
Distraction 9 4.1mm
Shams 8 -
58
Estimating Severity
2.5mm
4.1mm
59
Membrane DamageNeuronal Cell Bodies
Lesion
Rostral
Injury
Choo J. Neurosurg. 2007
60
Membrane DamageAxons
Lesion
Rostral
Injury
Choo J. Neurosurg. 2007
61
Rostro-Caudal Distribution
62
Study 2 Early Secondary Injury
63
Early Secondary Injury
  • 275-325g Sprague-Dawley rats
  • Infused 0.375mg 10kD fluorescein dextran into
    cisterna magna
  • Incubated for 1 hour 30 min surgery
  • Injury _at_ 100cm/s
  • 0.75mg 10kD cascade-blue dextran _at_ 2hrs
  • detect persistent membrane permeability
  • 3hrs sacrifice early secondary

Mechanism N Severity
Contusion 10 1.1mm
Dislocation 10 2.5mm
Distraction 10 4.1mm
Shams 7 -
Dextran Controls 3 -
64
Membrane Integrity at 3hrs
Pre-injury Dextran
Post-injury Dextran
Merged Image
Choo Exp. Neurol. 2008
65
Secondary Axonal Injury
(ßAPP)
66
Secondary Axonal Injury
67
Secondary Axonal Injury
68
Microglial Activation
69
Microglial Activation
Choo Exp. Neurol. 2008
70
(No Transcript)
71
Neurofilament
Choo Exp. Neurol. 2008
72
Overall Patterns of Tissue Damage
73
Tissue Damage Mechanics?
74
Limitations
  • Early time-points for analysis
  • Comparable severities?
  • Behaviorial differences?
  • No therapies tested

75
Injury Velocity
1 Wilcox, Boerger et al, J Biomech 2002 35(3)
381-384 2 Elert, The Physics Fact Book 2003
76
Engineering Perspective
Bilston LE, Thibault, LE Ann Biomed Eng 1996
24(1) 67-74
77
Results Hemorrhage
Control
Slow
Fast
Sparrey MASc 2004
78
Results - Hemorrhage
Sparrey Spine in press
79
Residual Compression
  • Maintained compression following initial
    contusion injury
  • Alleviate with decompression
  • Burst fractures (30)
  • Fracture dislocations (40)
  • Residual cord compression
  • lt Transient contusion

Compression
Decompressed
(Sekhon Fehlins 2001 Basso et al. 1996)
80
Methodology Experimental
  • Stabilize in test frame
  • Lower actuator LD probe
  • Inject CSF
  • Activate heating coils
  • LD baseline measurement
  • Spinal cord injury
  • Contusion
  • Contusion 90 compression
  • Contusion 40 compression

81
Results Contusion Injury Parameters
  • Contusion
  • 40 RC
  • 90 RC

Group Peak Displacement (mm) Peak Force (N) Peak Velocity (mm/s)
Contusion -1.01 (0.004) -1.59 (0.26) -708.3 (6.3)
40 Residual -1.01 (0.005) -1.60 (0.22) -708.3 (7.7)
90 Residual -1.03 (0.002) -1.41 (0.19) -711.9 (8.13)
82
Results Load Relaxation Time
  • Median time - 75, 50, 40, 30, 20, 10 and 5
    of peak force
  • 90 RC slower than 40 RC or contusion
  • lt 5 of peak contusion force within 11.8 sec

Sjovold MASc 2006
83
Results Laser Doppler
  • Analyzed 2, 30, 58, 62 and 90 minutes

Sjovold MASc 2006
84
Results Gray Matter
Sjovold MASc 2006
85
Summary
  • SCI is a high-speed event that we are
    characterizing from a biomechanical perspective
  • Cadaver models
  • Mathematical models
  • Small animal models
  • Ultimate goal is a clinically relevant
    sub-classification of SCI

86
Next Steps..
  • Further characterize primary injury secondary
    changes
  • Assess behavioural differences between
    mechanisms
  • Determine the effectiveness of imaging (MRI) in
    differentiating between injury mechanisms
  • Evaluate the efficacy of novel therapeutic
    strategies for spinal cord injury (e.g.
    neuroprotective, remyelination)

87
Collaborators
  • Anthony Choo
  • Carolyn Sparrey
  • Carolyn Greaves
  • Simon Sjovold
  • Liz Clarke (AUS)
  • Amy Saari (PC)
  • Shannon Reed (PC)
  • Tim Bhatnagar
  • Colin Russell
  • Wolfram Tetzlaff
  • Peter Cripton
  • Marcel Dvorak
  • Brian Kwon
  • Charles Fisher
  • Mohamed Gadala
  • Piotr Kozlowski
  • Lynne Bilston (AUS)
  • Qingan Zhu
  • Jie Liu
  • Clarrie Lam
  • Chad Larson
  • Darrell Goertzen
  • Andrew Yung

88
ICORD new home for Spinal Research Centre in
Vancouver
  • Vancouver General Hospital
  • 51 principal investigators
  • 120,000 square feet
  • Spinal clinics
  • Rehabilitation research
  • Molecular Biology
  • Bioengineering
  • Neuropysiology

February 2008
October 2008
89
Acknowledgements
Canadian Institutes of Health Research
  • Canada Research Chairs Program

Rick Hansen Man in Motion Fund
  • George W. Bagby Research Fund
  • BC Leading Edge Endowment Fund

90
Professor Manohar Panjabi
  • Yale University
  • 1970-2006

91
Professor Clive Duncan
  • Chairman of Orthopaedics at UBC from 1996-2006

92
Thank you!
93
THANK YOU!!
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