Testing Requirements for Metallic Plasma Sprayed Coatings on Orthopedic Implants
This guidance outlines testing requirements and data submission format for manufacturers of metallic plasma sprayed coatings on orthopedic implants who wish to request reconsideration of postmarket surveillance requirements. It specifically focuses on demonstrating that thermal spray coatings have mechanical properties equal to or better than sintered or diffusion bonded porous coatings.
What You Need to Know? 👇
What are the key mechanical property requirements for plasma sprayed coatings on orthopedic implants?
The coating must exceed 20 MPa in shear strength and 22 MPa in tensile strength. Shear fatigue testing should extend to 10^7 cycles, and abrasion resistance testing should show less than 65 mg total mass loss after 100 cycles using specific ASTM protocols.
How does FDA determine substantial equivalence for thermal spray coated hip prostheses?
FDA evaluates whether thermal spray coatings have mechanical properties equal to or better than sintered or diffusion bonded porous coatings. Manufacturers must provide comprehensive testing data including metallurgical analysis, microstructure characterization, and mechanical property testing per specified ASTM standards.
What documentation is required for postmarket surveillance reconsideration requests?
Manufacturers must submit metallurgical analysis, microstructure data, mechanical properties testing, manufacturing process descriptions, and detailed test reports. All information should be organized using the Modified Surface Data Forms format specified in the guidance document.
Which ASTM standards are referenced for testing plasma sprayed orthopedic coatings?
Key standards include ASTM F1854 for stereological evaluation, F1160 for shear fatigue testing, F1044 for static shear strength, F1147 for tensile strength, and F1978-99 for abrasion resistance testing using the Taber Abraser method.
What microstructural parameters must be characterized for plasma sprayed coatings?
Required parameters include coating thickness, particle shape and size, weld diameter between particles, void size at surface, minimum void intercept length, mean volume percent of voids, and photomicrographs showing all geometrical characteristics of the microstructure.
How many test samples are typically required for mechanical property testing?
Generally, five plasma sprayed coating samples are needed for each test unless statistical justification demonstrates that fewer samples provide adequate test power and acceptable Type I and Type II error rates for the specific testing protocol.
What You Need to Do 👇
Recommended Actions
- Prepare comprehensive test data package including metallurgical analysis, microstructure characterization, and mechanical testing results
- Ensure all testing meets minimum performance criteria specified in guidance
- Document manufacturing process and any differences between test samples and marketed device
- Prepare detailed test reports with all required elements (test facility, methods, results, etc.)
- Submit data using the Modified Surface Data Forms format provided
- Address any corrosion concerns if using novel material combinations
- Include statistical justification if using fewer than 5 samples for testing
- Submit reconsideration request to FDA’s Postmarket Surveillance Document Mail Center
Key Considerations
Non-clinical testing
- Metallurgical analysis including composition, trace elements, material microstructure
- Microstructure analysis of modified surface layers (thickness, particle size, void characteristics)
- Mechanical testing:
- Shear fatigue strength (10^7 cycles)
- Static shear strength (>20 MPa)
- Static tensile strength (>22 MPa)
- Abrasion resistance (<65 mg loss after 100 cycles)
Biocompatibility
- Corrosion assessment if using new material combinations
- Ion release measurements may be needed
Safety
- Interface examination between coatings and substrate for signs of corrosion
- Post-test failure analysis of specimens
Other considerations
- Manufacturing process description
- Detailed test reports including methods, materials, results
- Statistical adequacy (generally 5 samples unless justified otherwise)
Relevant Guidances 🔗
- Testing Requirements for Orthopedic Implants with Modified Metallic Bone-Interface Surfaces
- Orthopedic Device Metallic and Calcium Phosphate Coatings: Testing and Characterization Requirements (Draft)
Related references and norms 📂
- ASTM F1854: Test Method for Stereological Evaluation of Porous Coatings on Medical Implants
- ASTM F1160: Shear and Bending Fatigue Testing of Calcium Phosphate and Porous Metal Coated Medical Coatings
- ASTM F1044: Shear Testing of Porous Metal Coatings
- ASTM F1147: Test Method for Tension Testing of Calcium Phospate and Metallic Coatings
- ASTM F1978-99: Standard Test Method for Measuring Abrasion Resistance of Metallic Thermal Spray Coatings By Using the Taber Abraser
- ASTM C633: Adhesion or Cohesive Strength of Flame-Sprayed Coatings