Avoiding Pitfalls: Testing Considerations
How Do I Test It? Which tests? Which specifications? What size? 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, Cervical System 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 Body Replacement Device/System (VBR) MQP 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. 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 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
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