Differential Activation of the Dorsal Neck Muscles During a Light Arm-Elevation Task in Patients With Chronic Nonspecific Neck Pain and Asymptomatic Controls: An Ultrasonographic Study

Background: Disturbance in neck muscle function is a well-known complication of chronic nonspecific neck pain (CNNP). It is, however, unclear which muscles are more susceptible to functional impairment in patients with CNNP during upper limb tasks. Objectives: To compare ultrasonographic changes in dorsal neck muscles thickness in patients with CNNP and asymptomatic controls while they performed a light load upper-limb movement. Design: Case control. Setting: University research laboratory. Participants: Twenty individuals with CNNP with a mean age of 23.35 2.94 and 20 asymptomatic controls with a mean age of 22.30 +/- 2.86, without any history of cervical diskopathy, fracture, trauma, inflammation, and spinal deformity were recruited for this study. Methods: Ultrasonographic measurement of dorsal neck muscles thickness was performed during a light load 3-second arm elevation task (shoulder scaption to 120 degrees) in the 2 groups. Associations between pain intensity and patients' perceived disability and between pain intensity and muscle thickness also were evaluated at the state of rest. Main Outcome Measurements: The thickness changes of the dorsal neck muscles throughout the arm elevation were calculated. The pain intensity and the patient's perceived disability also were measured. Results: A significant main effect of muscle activity status was revealed for the multifidus and semispinalis cervicis and the splenius capitis, indicating an increase in their thickness throughout the arm elevation (P < .001). The only muscle that showed a difference between groups was the multifidus (P = .007). Direct associations between pain and disability (r = .48, P = .03) and between pain and multifidus thickness (r = -.49, P = .03) also were observed. Conclusion: The deteriorating effect of CNNP on the neck muscles targets the deep layer of the dorsal neck muscles (ie, the multifidus) more than the superficial muscles during light upper-limb tasks.