Correlations between muscle activity and in vivo loading in the spine

Abstract

Low back pain is an epidemic affecting millions of people each year. A loss of muscle function, often observed due to muscle fatigue, is predicted to cause increased spinal loading due to co-activation of antagonistic muscles. Research suggests that increased loading can cause damage to the intervertebral disc leading to low back pain. However, little in vivo data exist to validate this hypothesis. The purpose of this research was to assess the complex interplay between muscle function and interbody loading in vivo in the cervical spine. To accomplish this goal, novel tools were developed, tested, and validated, including implantable wireless force sensors and a multi-channel EMG system. A novel interbody implant was placed in the cervical spine of a goat and interbody force measurements were collected during dynamic activities. Interbody forces were collected simultaneously with dynamic muscle activation and recruitment data. Results from in vivo testing demonstrate repeatable patterns of muscle activation and interbody force that are dependent on head and neck kinematics. Preliminary results also suggest that loss of muscle function can lead to the adoption of kinematic compensation techniques. These data demonstrate for the first time correlations between muscle activation and recruitment patterns and interbody force