Mechanical properties of the trapezius during scapular elevation in people with chronic whiplash associated disorders – A case-control ultrasound speckle tracking analysis

Abstract

BackgroundApproximately 50% of people with Whiplash Associated Disorders (WAD) report longstanding symptoms. The upper trapezius is commonly painful yet its mechanical properties are not fully understood. ObjectivesThis study examined the deformation of different depths of the upper trapezius muscle during a scapular elevation task (shoulder shrugging) before and following loaded arm abduction. Design and MethodsA cross-sectional case-control study of 36 people (26 female and 10 male, mean age 38 (SD 11)) with chronic WAD and 36 controls, matched for age and gender. Real-time ultrasound recordings of upper trapezius were taken during both scapular elevation tasks. Post-process speckle tracking analysis was undertaken of three different sections of the upper trapezius muscle (superficial, middle, deep). ResultsThe WAD group had lower deformation of the superficial section of the upper trapezius compared to the control group in both concentric and eccentric phases of scapular elevation (p < 0.05) especially before the loaded arm abduction. After arm abduction, the deformation of the trapezius was reduced in both groups but only significantly in the WAD-group (p = 0.03). Within-group analysis revealed that the control group least engaged the deep section of upper trapezius during the task (p < 0.01). ConclusionThis study, measuring mechanical deformation of the upper trapezius during a scapular elevation task indicates that persons with WAD may display different patterns in engagement of the muscle sections than those in the control group. Further research is needed to replicate and understand the reasons for and implications of this possible change in motor strategy within upper trapezius.Clinical Trials.gov, Number: NCT01547624.