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 Product Code Recommended Testing

Recommended Additional Information

Anterior, CervicalSystem

KWQ •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 Product Code Recommended Testing

Recommended Additional Information

Vertebral BodyReplacementDevice/System(VBR)

MQP Static and dynamic axialcompression bending testing· Static and dynamic torsion testing· ExpulsionFor the dynamic axial compressionbending tests, we recommend that youmeet one of the following conditions:

Depending on the design ofthe VBR system, we mayrecommend additional testing(e.g., shear loading of acomposite material, off-axiscompression loading)· A clinical rationale for all sizesof the proposed VBR

ASTM Specifications

• Test methods intended to provide a basis for the mechanical comparison among past, present, and future implant assemblies.– 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?– 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– 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 Pre-

Submission 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- Familiar with Specifications (Participate in ASTM)- Test similar devices, see newest technologies and methods- Provide recommendations based on experience- Develop fixturing and protocols