Facet Screw Systems - Safety and Performance Based Pathway
This guidance covers facet screw systems consisting of metallic bone screws and optional washer components intended for bilateral immobilization of facet joints to stabilize the spine as an aid to fusion. The devices must be made from titanium alloy (ASTM F136) and fall within specific dimensional ranges. The guidance excludes combination products, resorbable devices, coated devices, additively manufactured devices, devices with complex geometries or unique characteristics.
What You Need to Know? 👇
What are the dimensional requirements for facet screws under the FDA’s Safety and Performance Based Pathway?
Facet screws must fall within specific dimensional ranges: screws <4.5mm diameter should have 3.5-4.3mm nominal major diameter with 6.0mm minimum total and threaded length, while screws ≥4.5mm diameter should have 4.5-6.0mm nominal major diameter with 15mm minimum total length and 12mm minimum threaded length.
Which facet screw systems are excluded from the Safety and Performance Based Pathway?
Excluded systems include combination products, resorbable devices, coated devices, additively manufactured devices, devices with complex geometries or unique technological characteristics, devices using non-standard surgical techniques, and devices sterilized using novel sterilization methods outside standard practices.
What are the static cantilever bending performance criteria for facet screws?
Static cantilever bending yield moment requirements are 2.6 Nm for screws <4.5mm diameter (cervical) and 3.7 Nm for screws ≥4.5mm diameter (lower thoracic/lumbar). Testing must follow ASTM F2193 standards with minimum five samples meeting acceptance criteria.
How is axial pullout strength evaluated for facet screw systems?
Axial pullout strength is assessed through engineering analysis using Chapman et al.’s equation with Grade 20 polyurethane foam material properties. Theoretical pullout strength must meet minimum values: 190N for <4.5mm diameter screws and 390N for ≥4.5mm diameter screws.
What biocompatibility endpoints must be evaluated for facet screw systems?
Required biocompatibility endpoints include cytotoxicity, sensitization, irritation, acute systemic toxicity, material-mediated pyrogenicity, sub-acute/sub-chronic toxicity, genotoxicity, implantation, chronic toxicity, and carcinogenicity, as these devices are categorized as permanently implanted devices with >30 days contact duration.
What sterilization validation requirements apply to facet screw systems?
Sterilization validation must demonstrate cleanliness and sterility to a sterility assurance level of 10⁻⁶ following FDA-recognized ISO standards (17665-1, 11135-1, 11137-1, 11607-1, 11607-2). Submissions require packaging descriptions and sterilization method information but typically not complete validation data.
What You Need to Do 👇
Recommended Actions
- Verify device dimensions fall within specified ranges
- Confirm material compliance with ASTM F136
- Conduct static cantilever bending testing per ASTM F2193
- Perform axial pullout strength engineering analysis
- Complete biocompatibility evaluation for all 10 required endpoints
- Validate sterilization process if device is provided sterile
- Validate reprocessing instructions if end-user sterilized
- Prepare documentation including test reports and Declarations of Conformity
- Consider Pre-Submission if additional testing beyond guidance scope is needed
- Prepare 510(k) submission following Safety and Performance Based Pathway format
Key Considerations
Non-clinical testing
- Static cantilever bending testing per ASTM F2193
- Axial pullout strength evaluation through engineering analysis
- Specific acceptance criteria based on screw diameter (<4.5mm vs ≥4.5mm)
Biocompatibility
- Testing required for 10 endpoints as permanent implant:
- Cytotoxicity
- Sensitization
- Irritation
- Acute systemic toxicity
- Material-mediated pyrogenicity
- Sub-acute/sub-chronic toxicity
- Genotoxicity
- Implantation
- Chronic toxicity
- Carcinogenicity
Safety
- Sterilization validation required for sterile devices
- Reprocessing validation required for end-user sterilized devices
- Must achieve SAL of 10-6
Other considerations
- Device dimensions must fall within specified ranges
- Material limited to ASTM F136 titanium alloy
- Washer inner diameter must be larger than screw thread diameter but smaller than screw head
Relevant Guidances 🔗
- Use of ISO 10993-1 for Biological Evaluation and Testing of Medical Devices
- Safety and Performance Based Pathway for 510k Substantial Equivalence Demonstration
- Reprocessing Instructions for Reusable Medical Devices and Non-Sterile Single-Use Devices - Development and Validation
- Submission Requirements for Terminally Sterilized Medical Devices
Related references and norms 📂
- ASTM F136: Standard Specification for Wrought Titanium-6 Aluminum-4 Vanadium ELI Alloy for Surgical Implant Applications
- ASTM F2193: Standard Specifications and Test Methods for Components Used in the Surgical Fixation of the Spinal Skeletal System
- ISO 17665-1: Sterilization of health care products – Moist heat
- ISO 11135-1: Sterilization of health care products – Ethylene oxide
- ISO 11137-1: Sterilization of health care products – Radiation
- ISO 11607-1/2: Packaging for terminally sterilized medical devices
- ISO 10993-1: Biological evaluation of medical devices