Neck muscle stiffness during craniocervical flexion under functional upper extremity conditions in patients with chronic non-specific neck pain: A shear-wave elastography study

Objective

The primary objective of the present study was to examine the differences and patterns of change in the neck extensor (NE) muscle stiffness during the Cranio-cervical flexion (CCF) task under different functional conditions of the upper extremity between CNSNP participants and asymptomatic controls.

Methods

In the current case-control study, 25 participants with CNSNP and 25 asymptomatic controls were recruited. The stiffness of the superficial (i.e., upper trapezius, splenius capitis, and semispinalis capitis) and deep (i.e., semispinalis cervicis and multifidus) NE muscles was measured at prone resting, sitting resting, and during the CCF task in different functional conditions of upper extremity using shear wave elastography.

Results

The findings showed that there was a significant main effect of condition in all NE muscles (P < 0.05), as well as a significant main effect of the group on the stiffness of superficial neck muscles (P < 0.05), indicating higher muscle stiffness in participants with CNSNP compared to the control group. There was no significant group-by-condition interaction effect on the stiffness of NE muscles (P > 0.05), except for the upper trapezius muscle (P = 0.00), indicating a different pattern of stiffness changes compared to the other muscles.

Conclusions

Individuals with CNSNP exhibited significantly greater stiffness in the superficial neck extensor muscles compared to healthy controls. Furthermore, the CCF task performed under functional upper extremity conditions, which includes bilateral shoulder scaption and shoulder abduction-external rotation while seated, resulted in increased stiffness of the NE muscles. Additionally, participants with CNSNP exhibited a higher magnitude of stiffness changes in the upper trapezius muscle across different conditions.