The application of physiological loading using a dynamic, multi-axis spine simulator
Medical Engineering and Physics
©2016 IPEM. Published by Elsevier Ltd. All rights reserved.
Reason for embargo
In-vitro testing protocols used for spine studies should replicate the in-vivo load environment as closely as possible. Unconstrained moments are regularly employed to test spinal specimens in-vitro, but applying such loads dynamically using an active six-axis testing system remains a challenge. The aim of this study was to assess the capability of a custom-developed spine simulator to apply dynamic unconstrained moments with an axial preload.Flexion-extension, lateral bending, and axial rotation were applied to an L5/L6 porcine specimen at 0.1 and 0.3. Hz. Non-principal moments and shear forces were minimized using load control. A 500. N axial load was applied prior to tests, and held stationary during testing to assess the effect of rotational motion on axial load.Non-principal loads were minimized to within the load cell noise-floor at 0.1. Hz, and within two-times the load-cell noise-floor in all but two cases at 0.3. Hz. The adoption of position control in axial compression-extension resulted in axial loads with qualitative similarities to in-vivo data.This study successfully applied dynamic, unconstrained moments with a physiological preload using a six-axis control system. Future studies will investigate the application of dynamic load vectors, multi-segment specimens, and assess the effect of injury and degeneration.
The authors would like to thank the Higher Education Investment Fund, The Enid Linder Foundation, and the University of Bath Alumni Fund for their support with this study.
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.
Available online 30 December 2016