Pain-side related difference in cross-sectional area of the longus colli muscle and its relationship with standing balance in persons with non-specific neck pain

Abstract

Background: Longus colli muscle has a significant role in postural control. A reduction of longus colli cross-sectional area (CSA) has been demonstrated in neck pain patients. However, pain-side related difference and its relationship with clinical features and standing balance remain unclear. Objective: To investigate side-to-side difference in the longus colli CSA and to determine the relationships of the CSA with clinical characteristics and standing balance in neck pain patients. Study design: Cross-sectional study. Materials and methods: Fifty participants with chronic non-specific neck pain (20 unilateral and 30 bilateral) were recruited. CSA of the longus colli muscle was measured using ultrasound imaging. Balance was measured using a force platform during a narrow stance with eyes open, eyes closed, and neck torsion (left and right). Balance outcomes were sway area and displacement in anterior-posterior (AP) and medial-lateral (ML) directions. Clinical characteristics were neck pain intensity, disability, and duration. Results: The longus colli CSA was reduced on the painful side in patients with unilateral neck pain (p < 0.01). There was a trend towards reduced CSA on the more painful side in those with bilateral neck pain (p = 0.08). The reduced CSA was mostly correlated with the greater AP sway displacement and sway area (r ranged from −0.27 to −0.54, p < 0.05). The longus colli CSA was not correlated with pain intensity, disability, and duration (p > 0.05). Conclusion: The longus colli CSA was reduced on the painful side of neck pain. The reduced CSA was correlated with impaired standing balance, but not with clinical characteristics of neck pain.