Measurement of Thickness of the Lower Trapezius Muscle Using Ultrasound Imaging in Individuals with Chronic Neck Pain

Abstract

Background: Altered behavior of the lower trapezius muscle has been consistently demonstrated in patients with neck pain. However, little has investigated size of the lower trapezius muscle at rest and during contraction in patients with neck pain. Objective: To determine thickness of the lower trapezius at rest 0° and 120°, and contraction at 120° of shoulder abduction in patients with neck pain. Methods: Twenty-four participants with chronic unilateral neck pain and 24 matched controls were recruited into the study. A real-time ultrasound scanner (12-MHz linear transducer) was used to measure thickness of the lower trapezius muscle in prone at rest 0° and 120°, and contraction at 120° of shoulder abduction bilaterally. Images were taken twice at the spinous process of T8 and measured using Image J program. Results: The neck pain group had smaller thickness of the lower trapezius muscle than the control group on the right side at resting at 0° of shoulder abduction condition (p < 0.05). There was no significant difference in the lower trapezius muscle thickness during contraction between groups (p > 0.05). The neck pain group had similar thickness of the lower trapezius muscle on the right and left sides. The control group had greater thickness of the lower trapezius on the right (dominant) side than the left (non-dominant) side (p < 0.05). Conclusion: Ultrasound imaging can be used to detect impairment in size of the lower trapezius muscle at rest at 0° of shoulder abduction in patients with neck pain. However investigation of size of the lower trapezius muscle during contraction is still warranted.