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°) 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. Level of Evidence III