Muscle Elasticity and Thickness of the Sternocleidomastoid and Transversus Abdominis in Patients with Chronic Non-Specific Neck Pain and Cervical Hypolordosis: an Ultrasound Elastography Study

Abstract

Background: Chronic non-specific neck pain (CNP) may extends beyond the cervical region, affecting trunk stability through altered function of the transversus abdominis (TrA). Biomechanical links suggest an interaction between the TrA and sternocleidomastoid (SCM) muscles in maintaining spinal stability. This study aimed to assess SCM and TrA elasticity using shear-wave elastography in individuals with CNP due to cervical hypolordosis and examine their associations with pain, disability, and physical activity. Methods: A cross-sectional observational study was conducted to investigate the relationship between sternocleidomastoid (SCM) and transversus abdominis (TrA) muscle properties using shear-wave elastography (SWE) in individuals with chronic neck pain and asymptomatic controls. Twenty patients with cervical hypolordosis and 21 matched asymptomatic individuals were included. Demographic data, pain intensity (VAS), disability (Neck Pain and Disability Scale), and physical activity levels (IPAQ) were recorded. Muscle thickness and elasticity were measured in resting supine positions with SWE. Elastic modulus was calculated from shear wave velocity (E = 3·ρ·SWV²). Group comparisons were performed using independent t-tests or the Mann–Whitney U test, and Pearson correlation analyses explored the associations between muscle properties and clinical outcomes. Statistical significance was set at p < 0.05. Results: Groups were similar in demographic characteristics. Compared with controls, the CNP group demonstrated significantly greater TrA thickness (0.32 ± 0.03 vs. 0.28 ± 0.05 cm, p = 0.03) and higher TrA elasticity (12.99 ± 0.42 vs. 12.06 ± 1.06 kPa, p = 0.001), while SCM parameters did not differ between groups. Correlation analyses revealed that TrA thickness and elasticity were positively associated with IPAQ, whereas TrA elasticity showed a moderate negative correlation with VAS (r = − 0.50) and NPDS (r = − 0.55), and a moderate positive correlation with IPAQ (r = 0.52). No significant correlations were observed for SCM parameters. Conclusion: Individuals with chronic non-specific neck pain exhibit altered transversus abdominis thickness and elasticity, which are associated with physical activity, pain, and disability, while sternocleidomastoid characteristics remain unaffected. These findings emphasize the potential of core stabilization training in managing chronic neck pain with hypolordosis.