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Application of a Calibration Method Provides More Realistic Results for a Finite Element Model of a Lumbar Spinal Segment
Hendrik SchmidtFrank Heuer Lutz ClaesHans-Joachim Wilke
Institute of Orthopaedic Research and Biomechanics,Center of Musculos-Skeletal Research (zmfu),University of Ulm
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Aim: Validation of a finite element model of a single spinal motion segment
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CT 3D
Philips MX 8000IPT® amira® 3.0
Determination of the geometry of bony structures
Determination of the geometry of soft tissue
macroscopical frozen cutsMRI-Slices
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L4
L5
8 Fiber Layers
Nucleus Pulposus
Cartilaginous Endplate
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Car
tilag
e
Annulus
Nucleus
Spo
ngio
sa
Cor
tex
Fibe
rs
100 Pa 1 kPa 10 kPa 100 kPa 1 MPa 10 MPa 100 MPa 1 GPa 10 GPa 100 GPa
Elasticity
Material properties of different biological structures
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moment
angl
e
Validation parameter
Range of Motion
RoM
RoM
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Material modification
ROM
Often performed validation procedures
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Angle in °
Intact
Bilateral Hemifacetectomy
Nucleotomy
w/o SSL & ISL
1086420
In-vitro Data FEMMin / Max Values
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Marco Viceconti, Clinical Biomech, 2005
“I have a question and I am sure you don‘ t like it:
How did you validate your finite element model?”M. Viceconti, S. Olsen, L. Nolte, K. Burton
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In-vitro Studies
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Intact
w/o SSLw/o ISLw/o FLw/o FC
w/o VA
w/o PLLw/o ALL
w/o Nucl
Load application
Flexion
Extension
Lateral bending
Axial rotation
Load magnitudes
1, 2.5, 5, 7.5, 10 Nm
∑= 180
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Calibrationof the
Finite Element Model
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Nucleus
FL
SSLISL
L4
L5
ALLPLL
FC
VA
Nucleus
FL
SSLISL
L4
L5
ALLPLL
FC
VA
Annulus
with ALL with PLL
with VA
with FCwith FLwith ISL
Intact
Load application
Flexion
Extension
Lateral bending
Axial rotation
Load magnitudes
1, 2.5, 5, 7.5, 10 Nm
∑= 180
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0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0
10.0 Nm 7.5 Nm 5.0 Nm 2.5 Nm
Ground substance Fibers
Annulus fibrosus
Flexion10.0 Nm 7.5 Nm 5.0 Nm 2.5 Nm
Stiffness coefficient k
You
ng’s
mod
ulus
of
grou
nd-s
ubst
ance
in M
Pa
0.6
1.0
1.4
1.8
2.0
0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0
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Annulus with NUC with ALLwith PLL with VA with FLwith ISL with SSL (INTACT)
Ran
ge o
f Mot
ion
in °
0
5
10
15
20
Applied Moment in Nm2.5 5.0 7.5 10.0
Range of Motion in Flexion
FEM Min/Max in-vitro data
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Accuracy of the calibrated FE-model
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Angle in °
Intact
Bilateral Hemifacetectomy
Nucleotomy
w/o SSL & ISL
1086420
In-vitro Data FEMMin / Max Values
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Conclusion
•Only the calibrated FE-model showed a good agreement to all defect situations
but
•The current model is only suitable for quasi-static load application
Validation is “a never ending” process!!!
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Thank you for your Attention!Thank you for your Attention!
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