A Frontal Plane Lumbar Spine Analogue Subjected to a Follower Load by Pneumatic Muscles

INTRODUCTION The follower load represents the path of the internal force resultant passing through the centers of rotation of successive spinal segments. An ideal follower load is perpendicular to the mid-plane of the intervertebral disc and minimizes shear and bending moments at all levels. Patwardhan and colleagues showed that a follower compressive preload increases the stability and load carrying capacity of the ligamentous spine [1]. Results from their ex-vivo experiments suggest a possible muscle activation pattern by which large compressive loads are supported in-vivo. Although several mathematical models have studied the role of the trunk muscles in generating a follower load [2, 3], no experimental technique using an idealized muscle architecture has been developed yet. Thus, the goal of this study was to develop a lumbar spine analogue with an idealized representation of multi-segmental muscles capable of generating a follower load