Thickness Changes of Dorsal Muscles in Upper Cervical Spine for Patients with Chronic Neck Pain ─ An Ultrasonographic Study
Date Issued
2009
Date
2009
Author(s)
Lin, Ya-Jung
Abstract
Background: Functional role of deep muscles in cervical region has been suggested to provide spinal stabilization. Patients with chronic neck pain have been found enhanced superficial and reduced deep muscle activation of their ventral neck muscles. Similar pattern of change in muscle activation has been demonstrated in the dorsal neck muscles in lower cervical spines. Whether the adaptive change of dorsal muscles in upper cervical spines would show in patients with chronic neck pain was unknown. Using real-time ultrasonography could measure the morphological changes of the superficial, intermediate, and deep layers of dorsal neck muscles in a non-invasive way. Measuring the thickness of the lower dorsal neck muscles during contraction using ultrasonography has been demonstrated good reliability. The methodology for thickness measurements for the upper dorsal neck muscles, however, has not been established. Whether the gender, side-to-side difference, anthropometry measures, psychological scores, and forward head posture influence the thickness measurements remained unclear. Purposes: (1) To examine the intraday-intrarater reliability of measuring thickness of the upper dorsal neck muscles at static condition as well as at 50% MVC of upper cervical extension using real-time ultrasonography. (2) To compare the thickness at static condition (Tsr) and at 50% MVC (Tsm). (3) To determine the relationship among the thickness measurements, gender, side-to-side difference, anthropometric measures, psychological scores and forward head posture. (4) To compare the thickness measurements between patients with chronic neck pain and asymptomatic subjects. Methods: Ten subjects (aged 21-30 years) without neck pain and headache in recent 3 months were recruited in the reliability study. Twenty-nine patients with chronic neck pain aged 24.3 ± 4.2 years old and twenty-nine asymptomatic subjects aged 27.0 ± 3.9 years old were recruited in the main study. Their upper dorsal neck muscles were measured using ultrasonography (HDI 5000, ATL, USA), including the splenius capitis (SPcap), semispinalis capitis (SScap), rectus capitis posterior major (RCPM), and oblique capitis superior (OCS). The thickness measurements included static thickness in unloading (prone position, Tpr) and loading of the cervical spines (sitting position, Tsr) conditions, the thickness at 50% MVC (Tsm) of upper cervical extension as well as the change in thickness from static condition to 50% maximal voluntary contraction (MVC, Tcc) and between unloading and loading conditions (Tcp). Intraclass correlation of coefficient (ICC), standard error of measurement (SEM), and within-subject coefficient of variation (CVw) were used to examine the reliability. Pearson correlation coefficient was used to examine the relationship among the thickness measurements of the upper dorsal neck muscles, age, anthropometric measures, psychological scores, and forward head posture. Stepwise regression model was used to find out the most influential factor for each thickness measurement. The differences of the thickness measurements between genders and between sides were examined by independent t-test and paired t-test, respectively. Analysis of covariance (ANCOVA) was used to compare the difference on thickness measurements between groups and muscles with controlling the confounders. Results: The ICC3,1 values were ranged from 0.77 to 0.99 for Tsr, and from 0.82 to 0.97 for Tsm of the upper dorsal neck muscles. The SEMs for Tsr and Tsm were 0.16 mm-0.61 mm and 0.32 mm-0.70 mm, respectively, while the CVws were 3.5%-6.1% and 3.7%-6.4%, respectively. The thicknesses of the upper dorsal neck muscles at 50% MVC (Tsm) were all significantly higher than the corresponding ones at static condition (Tsr, p<0.005-.029). Tpr (p<0.0005-0.004) and Tsr (p<0.0005-0.011) of the upper dorsal neck muscles were significantly different between genders, but not when normalized for body weight. The side-to-side differences of the thickness measurements were not significant or small. The correlation of body weight (Tpr: r=0.37~0.61, p<0.0005~0.004, Tsr: r=0.46~0.65, p<0.0005) and body height (Tp: r=0.37~0.59, p<0.0005~0.001, Tr: r=0.36~0.53, p<0.0005~0.006) with Tpr and Tsr were significant, whereas the correlation with Tcc and Tcp were small or not significant. The correlation of BMI with thickness measurements seemed weaker than body weight and height. Among the psychological scores, only score of the Beck Anxiety Inventory was correlated with the static thickness for SPcap. Body weight was the most influential factor for Tpr, Tsr, and Tsm, whereas neck pain was the most influential factor for Tcc and Tcp. The between-group comparison on the thickness measurements was therefore normalized with weight (for Tpr, Tsr, and Tsm) and controlled with the effect of anxiety (for all thickness measurements). After controlling the effect of anxiety, no significant difference of the normalized static thickness either in unloading (Tpr/w) or loading (Tsr/w) condition between groups. Patients with chronic neck pain had larger (p=0.007) Tcc for the superficial dorsal neck muscle (SPcap, 0.06 ± 0.04cm and 0.03 ± 0.02cm for symptomatic and asymptomatic subjects, respectively), and smaller Tcc (p<0.0005-0.010) for the intermediate (SScap, 0.13 ± 0.06cm and 0.20 ± 0.07cm for symptomatic and asymptomatic subjects, respectively), and the deep ones (RCPM, 0.20 ± 0.08cm and 0.31 ± 0.12cm for symptomatic and asymptomatic subjects, respectively; OCS, 0.11 ± 0.10cm and 0.22 ± 0.12cm for symptomatic and asymptomatic subjects, respectively) than asymptomatic subjects. Tcp was significantly smaller (p=0.048) in patients with chronic neck pain than asymptomatic subjects. Conclusion: Measuring the thicknesses of the upper dorsal neck muscles using ultrasonography was reliable both at static condition and during contraction. Significant influence of body weight and gender on the static thicknesses was demonstrated both in unloading and loading conditions, but not for the change in thickness from static condition to 50% MVC. Anxiety was correlated to the static thickness of the superficial dorsal neck muscle, the SPcap. After controlling the effect of anxiety, the changes in thickness during upper cervical extension in patients with chronic neck pain were increased for the superficial muscles (SPcap) and were decreased for the deeper ones (SScap, RCPM and OCS). This altered relationship of change in thickness between superficial, intermediate and deep muscles in upper dorsal neck muscles may provide an evidence of the muscle dysfunction in patients with chronic neck pain. Future studies may develop a treatment program for the muscle dysfunction in patients with chronic neck pain.
Subjects
Muscle thickness
Neck muscles
Suboccipital muscle
Ultrasonography
Gender
Weight
Neck Pain
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