Catalog of Regulatory Science Tools to Help Assess New Medical Devices
This regulatory science tool presents a laboratory method to assess the mechanical integrity of anterior vertebral body tethering (AVBT) devices.
Technical Description
This tool describes the methods to assess mechanical durability of AVBT device constructs under different loading conditions through both static and dynamic testing. This tool also provides test block and fixture drawings that can be used for mechanical testing of the AVBT systems. Furthermore, this tool describes methods for identifying failure of the AVBT device constructs based on the force-displacement data for static tests, and force/displacement-number of cycles for dynamic tests.
Intended Purpose
This tool may be used to help medical device manufacturers compare the preclinical mechanical performance of AVBT devices (product code: QHP) and assess device failure modes during device development.
Testing
Use of this tool has been demonstrated on a mock AVBT system for evaluating mechanical durability of the construct under different tensile loading conditions. Different loading conditions that may be experienced during implantation and use were simulated by varying factors such as Cobb angle-based screw angulations (0° vs 40°), tether gauge length (76 mm vs 25 mm), and setscrew reinsertion and retightening. The tool also demonstrates the methods for identifying failure of the AVBT constructs from the collected mechanical testing data. Further details on the static and dynamic testing principles can be found in the publication.
Limitations
This test method is only meant for comparisons between devices and is not expected to be a predictor of absolute values of in vivo strength. This RST has only been validated for the mock device mentioned in the Testing section and its application to other spinal devices (e.g., non-fusion devices) is unknown.
Supporting Documentation
- User Manual
- Jayaswal D, Tong J, Shetye S, Goel V, Palepu V. “An in Vitro Study to Identify Worst-Case Parameters for Assessing Mechanical Performance of Anterior Vertebral Body Tethering (AVBT) Systems.” Spine deformity 2026 (Under Review)
Contact
Tool Reference
- RST Reference Number: RST26OP08.01
- Date of Publication: 05/04/2026
- Recommended Citation: U.S. Food and Drug Administration. (2026). Method for Assessing the Mechanical Durability of Anterior Vertebral Body Tethering Devices (RST26OP08.01). https://cdrh-rst.fda.gov/method-assessing-mechanical-durability-anterior-vertebral-body-tethering-devices