Altered neck muscles function during cervical rotation in chronic whiplash-associated disorders improved after neck-specific exercises: a real-time ultrasound case-control study

Abstract The deep cervical muscles are very important for stability and initiation of movement of the cervical spine. A whiplash injury can alter neck muscle function, which remains years after the injury and may explain why symptoms such as persistent pain and disability occur. There is currently limited knowledge of dynamic neck muscle function in chronic whiplash-associated disorders (WAD), and to what extent altered muscle function can improve after rehabilitation. Therefore, we used ultrasound to measure deformation and deformation rate in five dorsal neck muscles in participants with chronic WAD versus matched controls in neck rotation. We accomplished real-time, non-invasive ultrasound measurements with speckle tracking, multivariate and mixed design ANOVA analyses. The results showed altered deformation in the three deepest neck muscle layers, with less deformation area in the WAD group compared to controls in rotation to the most painful side at baseline. Participants in the WAD group performed three months of neck-specific exercises, resulting in improved deformation in the deep neck muscles in WAD and to a similar deformation pattern as controls, and the significant group differences ceased. We reveal new and important insight into the capability of ultrasound to diagnose altered neck muscle function and evaluate an exercise intervention.