In vitro study design derived from an in vivo lifting task

Abstract

Biomechanical properties of the spinal tissue constituents, especially in the intervertebral disc (IVD), contribute to disability and high costs. The IVD is considered to be one of the main etiologies of chronic low back pain. Changes in the biomechanical properties of the spine, especially in the IVD, are related to multiple factors such as type and duration of loading, recovery periods, osmosis, relaxation, and diffusion processes. To quantify spinal burden in vivo, various dose models have been developed in the context of ergonomics research. In our work both in vivo and in vitro studies were conducted to investigate the effects of loading and rest periods alteration on mechanical properties of the spine. A multibody simulation (MBS) was used to translate the collected motion data from the in vivo study into forces and moments as boundary conditions for the in vitro study. An in vitro spine test rig is used to apply axial compression forces and pure moment loading in flexion/extension direction to spinal segments according to the conditions that have been determined in the MBS. In this article, an approach is presented to coordinate the boundary conditions in vivo and in vitro in order to carry out a holistic investigation. In addition, it is shown why cyclic preconditioning seems to be a more suitable preparation of the samples compared to a constant one in this experimental context.