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A telematic tool for computer aided lumbar spine
surgery planning
CRAFT-1999-71634 / IST-1999-57
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Context and Introduction
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MODEL VIRTUAL ANALOGUE
PREDICT RESPONSE
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Background
ISO 17025
Numerical simulation
In vitro experiments
complementary
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Comparison of implant designs
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Lumbar Spine surgery
WHAT IS THE BEST STRATEGY FOR A GIVEN PATIENT?
Long term disc degenerescence (Guigui 98,
Schlegel 96, ...).
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Some biomechanical Finite Element Method (FEM)
models exist but
not accessible to non-FEM experts such as
surgeons, implant designers and implant
manufacturers.

Devaspim a tool accessible via internet, to
calculate the biomechanical behaviour of the
instrumented spine using the FEM and to aid for
surgery planning
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This tool will help to minimise the number of
implant failures
- Optimise design process of lumbar spine implants

• by reducing failure due to implant design and
  improving competitiveness of the manufacturers
  (implant industries) in the segment of spine
  implants.

- Minimise technical failures

• due to the selection of inappropriate
  configurations, through a better preoperative
  planning.

The application use will be a service offered to
surgeons/designers by the implant manufacturers
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DESCRIPTION
Biomechanical behaviour of instrumented spine
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Description of the full process, step by step
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STEP1 Morphology
Spine Morphology

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STEP1 Morphology
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STEP1 Morphology
3D Reconstruction
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STEP1 Morphology
Example degenerative L4/L5 Spondylolisthesis
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STEP 2 General Data

• Bone quality
• Imbalance
• Weight
• Height

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STEP 2 General Data

• Bone quality
• Imbalance
• Weight
• Height

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STEP 3 Pathology definition

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STEP 3 Pathology definition

• Pathology type
• Spondyloarthrose
• Spondylolisthesis
• Fractures
• Affected level
• Restoration estimation

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STEP 3 Pathology definition

• Pathology type
• Spondyloarthrose
• Spondylolisthesis
• Fractures
• Affected level
• Restoration estimation

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STEP 3 Pathology definition

• Pathology type
• Spondyloarthrose
• Spondylolisthesis
• Fractures
• Affected level
• Restoration estimation

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STEP 3 Pathology definition
IT IS POSSIBLE TO MODEL AUTOMATIQUELY A WIDE
RANGE OF LESIONS
Disc Disease Modification of components
Osteoporosis Modification of the bones Young
Modulus
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STEP 4 Kind of instrumentation
Choose the implant system to simulate

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STEP 4 Kind of instrumentation
Choose the implant system to simulate

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STEP 5 Implant Configuration

• Characteristics to define for the implant system
  chosen
• Material
• Symmetric or not
• Screw diameter by level
• Screw length by level
• Connectors by level
• Rod diameter

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STEP 5 Implant Configuration
Parameterization Material Connector For each
instrumented vertebra, kind of connector to model
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STEP 5 Implant Configuration
Parameterization Material Connector For each
instrumented vertebra, kind of connector to model
Screw For each instrumented vertebra, diameter,
length, angle of insertion
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STEP 5 Implant Configuration
Parameterization Material Connector For each
instrumented vertebra, kind of connector to
model Screw For each instrumented vertebra,
diameter, length, angle of insertion
Rod diameter Hooks DTT Kind, number and
localization
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STEP 6 Surgical technique (optional)
A surgical gesture is associated to the implant
chosen

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STEP 6 Surgical technique (optional)
A surgical gesture is associated to the implant
chosen

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STEP 7 Results
SPECIFIC IMPLANTS RESULTS

• Assembly stiffness
• Rods stress
• Screw stress
• Biomechanical behaviour of the assembly

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STEP 7 Results
The simulation outputs
An html report automatically generated will be
send to the user Result.html
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STEP 7 Results
Analysis of the anatomical entities

• Stress in the adjacent intervertebral disc
• Facets loads

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STEP 7 Results
Bone implants stresses
Qualitative estimation of configuration
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Calculation. Example
L4 L5 Degenerative Spondylo L4 L5 instrumenation
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Calculation. Example
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Conclusion
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Lumbar Spine surgery
PATIENT
SURGICAL ACT
Devaspim
IMPLANT
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CONCLUSION
Computer aided surgery planning innovative tool
For Surgeons
understand mechanical effects of a given strategy
minimise implant failures Better clinical outcome
For implant designers
implant design improvements implant effects in
expected indications
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CONCLUSION
DEVASPIM SPIN-OFF
- Implant manufacturers decreased design
costs - Orthopaedic surgeons better
preoperative planning - Patients
increased clinical outcome and quality of life
- Health Services cost reduction due to less
re-operations.

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