Multimodal quantitative ultrasound assessment of perioperative neck muscle alterations in patients with cervical spondylosis

Background: Cervical spondylosis (CS) involves degenerative changes that increase muscle fatigue and stiffness. Postoperative cervical collars are commonly used to maintain stability. This study used multimodal ultrasound to compare neck muscle thickness and stiffness between patients with CS and healthy controls (HC), and to longitudinally evaluate muscle parameter changes associated with different postoperative cervical collar wearing durations.

Methods: This prospective study enrolled 40 patients undergoing cervical spine surgery and 40 healthy volunteers matched by age, sex, and body mass index (BMI) as HC. The thickness and stiffness of eight neck muscles in the anterior and posterior cervical regions were measured. Subsequently, 18 patients were randomly allocated to two groups for longitudinal follow-up. Group A wore a cervical collar for 1 month, whereas Group B wore one for 3 months. Longitudinal changes in neck muscle parameters were quantitatively measured, and the generalized estimating equation (GEE) model was used to evaluate changes at 3 and 6 months postoperatively.

Results: No significant baseline differences were found between the case and HC groups. Regarding posterior cervical muscles, the case group showed significantly greater trapezius thickness in the neutral position (0.18 vs. 0.15 cm, P=0.008), but reduced thickness in other posterior muscles (all P<0.001, e.g., semispinalis capitis: 0.35 vs. 0.59 cm). In a forward flexion position, the case group had lower stiffness in all five posterior muscles (e.g., multifidus: 4.79 vs. 5.57 m/s, P<0.001). For the anterior cervical muscles, the case group had reduced thickness in longus capitis and longus colli in both neutral (0.21 vs. 0.30 cm, P<0.001; 0.66 vs. 0.75 cm, P<0.001) and deflection positions (0.23 vs. 0.30 cm, P=0.006; 0.59 vs. 0.65 cm, P=0.002). In the deflection position, the case group also showed lower stiffness in sternocleidomastoid (2.74 vs. 3.47 m/s, P=0.001), longus capitis (3.13 vs. 4.05 m/s, P<0.001), and longus colli (3.63 vs. 4.52 m/s, P<0.001). Longitudinally, the GEE model revealed that collar wearing duration had no significant effect on cervical muscle thickness (group effect: Wald χ²=2.396; P=0.122), but significantly influenced muscle stiffness (group effect: Wald χ²=13.306; P<0.001). Specifically, Group B had significantly higher stiffness than Group A [β=0.122; 95% confidence interval (CI): 0.049 to 0.196; Wald χ²=10.77; P=0.001]. No significant effects were observed for muscle type, cervical position, or time (all P>0.05). Furthermore, muscle thickness showed no significant changes over time in either group. By contrast, Group B had significantly greater stiffness than Group A at 3 months (mean difference =−0.122; 95% CI: −0.221 to −0.024; adjusted P=0.006) and 6 months (mean difference =−0.160; 95% CI: −0.280 to −0.040; adjusted P=0.003), postoperatively.

Conclusions: Multimodal ultrasound effectively detects changes in cervical muscle thickness and stiffness in patients with CS. Longer cervical collar wearing duration may be associated with higher muscle stiffness; however, these findings are preliminary owing to the small sample size, and further large-scale studies are warranted.