Catalog of Regulatory Science Tools to Help Assess New Medical Devices
This regulatory science tool presents a lab method for executing in vitro human cadaver fatigue loading and multidirectional flexibility assessment of lumbar integrated fixation device constructs. Please see appendix.
Technical Description
This tool provides recommended best practices for performing in vitro human cadaver based biomechanical evaluation of lumbar integrated fixation devices (IFDs) under fatigue loading. This tool also describes recommendations for performing multidirectional flexibility assessment of IFD constructs in the intact state, before and after the fatigue loading, to quantify the effect of the IFD on segmental range of motion (ROM). The tool Appendix describes recommendations for:
- Specimen preparation
- Study design
- Biomechanical testing
- Data analysis
Intended Purpose
This tool may be helpful and applicable for medical device manufacturers in evaluating the long-term biomechanical stability of IFDs and evaluating the following post-operative risks:
- Fracture of the IFD or fixation anchors/screws, or both
- Migration of the IFD or fixation anchors/screws, or both
- Damage to the vertebral body
- Insufficient segmental stabilization
Testing
Use of this tool has been demonstrated in the following peer-reviewed publication for comparing long term biomechanical stability of a generic IFD (investigational implant) with a generic anterior plate and cage device (control implant):
- Palepu V, Peck JH, Simon DD, Helgeson MD, Nagaraja S. Biomechanical evaluation of an integrated fixation cage during fatigue loading: a human cadaver study. Journal of Neurosurgery: Spine. 2017 Apr 1;26(4):524-31.
Limitations
This tool provides best practices for the biomechanical evaluation of IFDs under fatigue loading along with multidirectional flexibility assessment of IFD constructs before and after fatigue loading. Extrapolation of this tool to other medical device types may not be appropriate. This tool may not replace the need for clinical data, animal testing, or other methods, as appropriate, and described in documents such as:
- Intervertebral Body Fusion Device - Class II Special Controls Guidance for Industry and FDA Staff
- Standard Test Methods for Intervertebral Body Fusion Devices -ASTM F2077
- Standard Test Method for Measuring Load-Induced Subsidence of Intervertebral Body Fusion Device Under Static Axial Compression - ASTM F2267
Supporting Documentation
This paper describes the recommended loading methods, specimen conditions, and analysis parameters for in vitro human cadaver biomechanical stability testing of spinal implants
- Wilke HJ, Wenger K, Claes L. Testing criteria for spinal implants: recommendations for the standardization of in vitro stability testing of spinal implants. European spine journal. 1998 May;7(2):148-54.
The multidirectional flexbility loading protocol used for our validation study was based on the following papers:
- Cardoso MJ, Dmitriev AE, Helgeson M, Lehman RA, Kuklo TR, Rosner MK. Does superior-segment facet violation or laminectomy destabilize the adjacent level in lumbar transpedicular fixation?: an in vitro human cadaveric assessment. Spine. 2008 Dec 15;33(26):2868-73.
- Agarwal A, Palepu V, Agarwal AK, Goel VK, Yildirim ED. Biomechanical evaluation of an endplate-conformed polycaprolactone-hydroxyapatite intervertebral fusion graft and its comparison with a typical nonconformed cortical graft. Journal of Biomechanical Engineering. 2013 Jun 1;135(6):061005.
- Kornblum MB, Turner AW, Cornwall GB, Zatushevsky MA, Phillips FM. Biomechanical evaluation of stand-alone lumbar polyether-ether-ketone interbody cage with integrated screws. The Spine Journal. 2013 Jan 1;13(1):77-84.
Contact
Tool Reference
- In addition to citing relevant publications please reference the use of this tool using RST24OP05.01