Cross-sectional area of cervical multifidus muscle in females with chronic bilateral neck pain compared to controls

DESIGN: Case-control study. OBJECTIVE: To analyze the differences in muscle size and shape of cervical multifidus between patients with bilateral chronic neck pain and healthy subjects. BACKGROUND: Researchers have demonstrated atrophy of lumbar multifidus in patients presenting with low back pain; however, there are only few published reports on cervical multifidus muscle size in individuals with chronic neck pain. METHODS AND MEASURES: Bilateral ultrasound images of multifidus muscle from the third to the sixth cervical vertebrae (C3 to C6) were taken in 20 women with bilateral chronic neck pain and in 20 healthy women. Cross-sectional area (CSA [CM2]) and muscle shape ratio (ratio between lateral [Lat] and anterior-posterior [AP] dimensions, [Lat/AP]) were measured without knowledge of group assignment. Two separate 3-way (4 x 2 x 2) mixed-model analyses of variance (ANOVAs), with cervical level (C3 to C6) and side (right, left) as the within-subject factors and group (patient, control) as the between-subject factor, were used to evaluate differences in CSA and muscle shape ratio between groups, sides, and cervical levels. RESULTS: The ANOVA for CSA indicated a significant effect for cervical level (F = 6.81, P <.001) and group (F = 20.27, P <.001), but not for side (F 1.26, P =.36). There were no significant interactions among the variables (P >.5). Post hoc analysis showed that the CSA of the C3 multifidus was smaller than the CSA of the C4 (P =.025), C5 (P <.001), or C6 (P <.01) multifidus. There was no significant difference between C4, C5, and C6 multifidus CSA (P <.05). The patients with neck pain had a smaller CSA of the cervical multifidus at all levels compared to controls (P < 001). The ANOVA for muscle shape ratio indicated a significant effect for level (F = 784, P <.001) and group (F = 12.501, P < 001), but not for side (F = 0.654, P =.58). There was a significant interaction between level and group (F = 3.651, P =.01). Patients had a wider ovoid shape (greater values in muscle shape ratio) of the C3 (P <.001) and C6 (P <.01) cervical multificlus compared to controls. Further, the C4 multifidus had a smaller shape ratio compared to C6 (P <.001), but was not significantly different than the shape ratio of the C3 and C5 (P >.05) multifidus. CONCLUSIONS: Females with bilateral chronic neck pain had generalized smaller CSA of the cervical multifidus muscles compared to healthy females. LEVEL EVIDENCE: Diagnosis, level 5.