Title: Biomechanical Aspects of Spinal Cord Injury
1Biomechanical 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
2UBC The University of British Columbia
- 40,000 students
- 4,000 faculty
3UBC 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
4Orthopaedic Engineering Research (DOER)
- the application of engineering principles to
clinically relevant problems in the field of
Orthopaedics
5DOER 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
6Research 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
7SCI 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
8ICORD 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
9Theme 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.
10Theme 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)
12Type of Vertebral Injury
40 Fracture Dislocation
Burst Fracture 30
SCIWORET 10
5 Dislocation
SCIWORA 5
10 Minor Fracture
Sekhon Fehlings Spine 2001
13Spinal Injury
BURST FRACTURE
14Clinical Observation
- the mechanism of column damage correlates with
the neurological deficit - Marar 1974, Tator 1983
. but current treatments do not incorporate
injury mechanism!
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16Methods Cord/Column
- Surrogate Cord
- Silicone gel
- In vivo-like in tension
- Barium Sulfate added
- Oval shaped
Saari MASc 2006
17Methods Specimen Preparation
- Human cervical spines occiput to T2 (n 6)
- Surrogate head attached to occiput
Saari MASc 2006
18Methods 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
19Saari MASc 2006
20Effect of Constraint
Flexion-compression injury model
Zhu 2008
21Compression to the Specimen
Zhu 2008
22Flexion-Compression (constrained)
23Flexion-Compression (unconstrained)
Zhu 2008
24Spinal Canal Occlusion
T1
T2
T3
T4
25Canal Occlusion
Zhu 2008
26Column-Canal Relationships
constrained
unconstrained
Zhu 2008
27Dynamic Spinal Canal Occlusion
- Transient occlusion gtgt Post-impact
- Effect of Constraint i.e. Boundary Conditions
28Methods - Injury Simulation
- Axial head-to-ground impact
- Drop Tower
- Drop height 0.6m
- Speed at impact 3m/s
- Carriage mass 15kg
29Pro-Neck-TorTM
Standard Helmet
Dr. Peter Cripton
http//injury.mech.ubc.ca http//www.proneckto
r.com
30Proof of Concept Study Results
- Axial Force Escape-Angle Interaction
56 reduction
15º, Med Stiffness, Extension Escape, Vimpact
3.2 m/s
31C4
C5
C6
Greaves 2008
32Von Mises StrainCompression
dorsal
ventral
dorsal
ventral
Greaves 2008
33Von Mises StrainDistraction
dorsal
ventral
dorsal
ventral
Greaves 2008
34Von Mises StrainDislocation
dorsal
ventral
ventral
dorsal
Greaves 2008
35Different Cord Strain Patterns
Greaves Annals BME 2008
36Contusion
37Dislocation
38Dislocation FEM of rat c-spine
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40Spinal Canal Occlusion Transducer
Segmental Voltage segmental resistance
constant current (resistance ? area)
Raynak 1998
41Theme 3 - Overview
Spinal cord injury represents a mechanical insult
that triggers a biological response which results
in a wide range of clinical sequelae.
42Spinal Injury
BURST FRACTURE
Do these well-known spinal column injury patterns
create different spinal cord injuries?
43Injury Models
1970
1990
1980
1911
2004
44Contusion Paradigm
central cavitation with peripheral rim of spare
white matter
Figure from McDonald Belegu. J Neurotrauma 2006
45Type of Vertebral Injury
40 Fracture Dislocation
Burst Fracture 30
SCIWORET 10
5 Dislocation
SCIWORA 5
10 Minor Fracture
Sekhon Fehlings Spine 2001
46Experimental Animal Model
Distraction
Compression/Contusion
Shear/Dislocation
Choo PhD 2006
47UBC SCI Test System
Actuator 12mm
LVDT (0.001mm)
accelerometer (50 500G)
Load Cell (22 225N)
Choo PhD 2006
48Contusion
force (N)
velocity (m/s)
displacement (mm)
Cord surface
Choo PhD 2006
49Dislocation
velocity (m/s)
force (N)
displacement (mm)
Choo PhD 2006
50Distraction
40
30
20
force (N)
velocity (m/s)
displacement (mm)
10
0
Choo PhD 2006
51Hemorrhage
Choo PhD 2006
52Anatomy
53Study 1 Primary Injury
54Membrane Integrity
55Membrane Integrity
56Membrane Damage
Neuronal Cell Bodies
Axons
57Primary 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 -
58Estimating Severity
2.5mm
4.1mm
59Membrane DamageNeuronal Cell Bodies
Lesion
Rostral
Injury
Choo J. Neurosurg. 2007
60Membrane DamageAxons
Lesion
Rostral
Injury
Choo J. Neurosurg. 2007
61Rostro-Caudal Distribution
62Study 2 Early Secondary Injury
63Early 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 -
64Membrane Integrity at 3hrs
Pre-injury Dextran
Post-injury Dextran
Merged Image
Choo Exp. Neurol. 2008
65Secondary Axonal Injury
(ßAPP)
66Secondary Axonal Injury
67Secondary Axonal Injury
68Microglial Activation
69Microglial Activation
Choo Exp. Neurol. 2008
70(No Transcript)
71Neurofilament
Choo Exp. Neurol. 2008
72Overall Patterns of Tissue Damage
73Tissue Damage Mechanics?
74Limitations
- Early time-points for analysis
- Comparable severities?
- Behaviorial differences?
- No therapies tested
75Injury Velocity
1 Wilcox, Boerger et al, J Biomech 2002 35(3)
381-384 2 Elert, The Physics Fact Book 2003
76Engineering Perspective
Bilston LE, Thibault, LE Ann Biomed Eng 1996
24(1) 67-74
77Results Hemorrhage
Control
Slow
Fast
Sparrey MASc 2004
78Results - Hemorrhage
Sparrey Spine in press
79Residual 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)
80Methodology 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
81Results Contusion Injury Parameters
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)
82Results 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
83Results Laser Doppler
- Analyzed 2, 30, 58, 62 and 90 minutes
Sjovold MASc 2006
84Results Gray Matter
Sjovold MASc 2006
85Summary
- 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
86Next 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)
87Collaborators
- 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
88ICORD 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
89Acknowledgements
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
90Professor Manohar Panjabi
- Yale University
- 1970-2006
91Professor Clive Duncan
- Chairman of Orthopaedics at UBC from 1996-2006
92Thank you!
93THANK YOU!!