Association of cervical sagittal alignment and mid-cervical muscle density with degeneration: a CT-based quantitative analysis of regional and sex-specific muscle patterns.

BACKGROUND

Quantitative assessment of cervical paraspinal muscle quality may provide useful information regarding degeneration, pain, and sagittal balance. However, regional and sex-specific patterns remain unclear. This study evaluated cervical extensor muscle density using computed tomography (CT) and examined factors associated with degeneration and pain.

METHODS

This retrospective cross-sectional study included 260 symptomatic patients with neck pain who underwent cervical CT. Mean Hounsfield Unit (HU) values of cervical extensor muscles were measured at C3, C5, and C7 as deep, superficial, and combined compartments. Sagittal parameters included T1 slope, C2-C7 angle, and C2-C7 sagittal vertical axis (SVA). Repeated-measures ANOVA, multivariable regression, and receiver operating characteristic (ROC) analyses were performed.

RESULTS

Muscle density differed across cervical levels, with the highest HU values at C5 in all compartments (p < 0.001). A significant cervical level × sex interaction was observed (p < 0.001). Greater C2-C7 SVA, lower C2-C7 angle, and lower C5 HU were independently associated with higher pain severity (all p < 0.05). Age, VAS, T1 slope, and C2-C7 SVA were associated with degeneration. The combined model showed good discrimination (AUC = 0.833, 95% CI 0.777-0.889).

CONCLUSIONS

Cervical muscle quality shows marked regional variation with a mid-cervical peak at C5 and significant sex-specific patterns. Sagittal malalignment, reduced lordosis, and lower mid-cervical muscle density were associated with greater pain severity. Quantitative CT-based muscle assessment may serve as a useful imaging marker in cervical degeneration.