Upper Quadrant Pain and Disability Associated With a Cross-Sectional Area of Deep and Superficial Neck Muscles: A Computed Tomography Study.

Study design An analytical cross-sectional computed tomography (CT) study. Objective To investigate the association of the cross-sectional area (CSA) and density of neck muscles (sternocleidomastoid, upper trapezius, levator scapulae, anterior scalene, longus coli, longus capitis) with upper quadrant pain and disability. Summary of background data Neck pain, a common condition, causes substantial disability to individuals. The deep cervical flexor muscles are impaired in persons with neck pain. These muscles play a greater role in maintaining stable head postures, whereas, superficial muscles are responsible for peak exertions and reinforcing spinal stability at terminal head postures. Methods Two hundred thirty consecutive individuals suffering from neck pain were referred to CT scans; 124/230 complied with the inclusion and exclusion criteria. Subjects were interviewed and the measurements of the CSA and muscle density were extracted from the scans. Results Muscles associated with quick disability of the arms, shoulders, and hand questionnaire (QDASH) were the lateral posterior group (LPG) CSA C3-C4 on the right side (beta = -0.31, P = 0.029); the sternocleidomastoid (SCM) CSA C3-C4 on the left side (beta = 0.29, P = 0.031); the LPG CSA C3-C4 on the left side (beta = -0.49, P = 0.000); the LCM CSA C5-C6 on the right side (beta = -0.19, P = 0.049); the LPG CSA C5-C6 on the right side (beta = -0.36, P = 0.012); and the LPG CSA C5-C6 on the left side (beta = -0.42, P = 0.002). Further analyses with radiculopathy acting as an augmenting/enhancing variable (moderator), showed an increase in the model strength (r2 = 0.25) with a stronger prediction of pain and disability. Muscle measurements did not predict neck disability index (NDI) scores. Conclusion By using an accurate measuring tool, we found an association of the deep and superficial neck muscles' CSA with upper extremities' pain and disability. When performing manual work, a special load is placed on the shoulders and neck muscles. Future research should focus on examining the effectiveness of exercise-type intervention programs to strengthen the deep neck and upper extremities' muscles in order to prevent muscle fatigue.Level of Evidence: 2.