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.