Effect of Curvature on Sagittal Plane Moment Arms of Human Neck Muscles

In musculoskeletal models of the cervical spine, muscles are often modeled as straight paths from origin to insertion [ e.g., 1]. However, muscle paths in the neck are constrained by bone and other soft tissues, and some studies have found that applying curvature to muscle paths improves anatomical accuracy [2; 3] and affects muscle parameters such as moment arm [3] and moment [4]. Currently, data available in the literature for neck muscle moment arms (MA) are sparse. In this study we estimated in-vivo moment arms using MRI-derived neck muscle paths modeled with curvature and those modeled as straight paths, for head and neck rotation in the sagittal plane (flexion-extension motion). We hypothesize that moment arm estimates for curved paths will be significantly different from estimates for straight paths.