Avoiding Pitfalls: Testing
Considerations
How Do I Test It?
– Which tests?
– Which specifications?
• ASTM, ISO, Custom Protocols
– What size?
– How many?
– What targets? Minimum Acceptance
Criteria?
– What predicate devices?
How do I test it? Guidance Documents
• FDA Guidance Documents:
– Guidance for Industry and FDA Staff: Spinal System 510(k)s
– Guidance for Industry and FDA Staff - Class II Special
Controls Guidance Document: Intervertebral Body Fusion
Device
• Information about Indications, Mechanical
Testing, Wear Testing, Animal and Clinical
studies, Sterilization, Worst Case Scenarios,
etc.
How do I test it? Guidance Documents
System Type
Anterior, Cervical
System
Product Code
KWQ
Recommended
Testing
Recommended Additional
Information
•Static and dynamic
axial compression
bending testing
•Static torsion testing
•A statement clarifying whether
the system is intended for
unilateral and/or bilateral
fixation
•A comparison of the worst
case construct’s width and
prominence to a predicate
system
How do I test it? Guidance Documents
System Type
Vertebral Body
Replacement
Device/System
(VBR)
Product Code
MQP
Recommended
Testing
Recommended Additional
Information
Static and dynamic axial
compression bending
testing
· Static and dynamic
torsion testing
· Expulsion
For the dynamic axial
compression
bending tests, we
recommend that you
meet one of the
following conditions:
Depending on the design of
the VBR system, we may
recommend additional testing
(e.g., shear loading of a
composite material, off-axis
compression loading)
· A clinical rationale for all sizes
of the proposed VBR
ASTM Specifications
• Test methods intended to provide a basis for the
mechanical comparison among past, present, and
future implant assemblies.
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Scope
Reference Documents
Terminology
Summary of Test Method
Significance and Use
Apparatus
Sampling
Procedure (Starting place for protocol development)
Report
Precision and Bias (Repeatability)
Know your target - Predicate Device &
Worst Case Evaluation
– Know what predicate values you are
targeting ahead of time
– Perform testing (feasibility if necessary)
– Identify and Evaluate Worst Case Scenario
• Finite Element Analysis (FEA) – Allows for quick
evaluation of stresses in various loading
conditions
Static Testing
• How much force will it take to break it?
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Ultimate force
Yield force
Stiffness
Failure Mode
• Differentiates between elastic and plastic
deformation regions
• Determines starting points for fatigue curve
Dynamic Testing (Fatigue)
• What is the highest load that will survive a
particular cycle count?
– Load versus cycle count endurance curve
Testing - Common Spine Specifications
• Pedicle screw, rod, and hook systems
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ASTM F1798
ASTM F1717
ASTM F2706
ASTM F2193
• Spacers and cages
– ASTM F2077
– ASTM F2267
• Screws
– ASTM F543
ASTM F1798
• Spinal Implant Connection Testing
– Flexion/Extension
– Axial Slip
– Torsional Grip
– Transverse Moment
ASTM F1717
• Spinal Implant Constructs in
Vertebrectomy Model
– Static Compression
– Dynamic Compression
– Static Tension
– Static Torsion
ASTM F1717 Failure Modes
• Common Failures
– Screws
– Rods
– Laser Markings
• Laser markings
create stress risers
• Alpha Case
ASTM F2077
• Intervertebral Body Fusion Devices
– Static & Dynamic Compression
– Static & Dynamic Compression Shear
– Static & Dynamic Torsion
– Subsidence (ASTM F2267)
– Expulsion
ASTM F2077- Failure Modes
• Static Failure Mode – Plastic Deformation
• Dynamic Failure Mode - Fatigue Cracks
Wear Testing
• Articulating Surfaces, Mixed Material Devices
• In vitro Testing – Wear
– Mass Loss Analysis
– SEM particulate evaluation
• Multi-Axis Wear Testing
– ISO 18192-1:2011
– Mass Loss Analysis
– SEM particulate evaluation
Resources Available
• Pre-510(k) meeting with the FDA
– Draft Guidance for Industry and FDA Staff Medical Devices: The PreSubmission Program and Meetings with FDA Staff
• Regulatory and Consulting Agencies
– Highly recommended if performing submissions for the first time
– Help determine worst case scenario, testing needs, and put together
510(k) submissions
• Consult your testing laboratory
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Familiar with Specifications (Participate in ASTM)
Test similar devices, see newest technologies and methods
Provide recommendations based on experience
Develop fixturing and protocols