Study design: Cross-sectional design.
Objective: The purpose of this study was to isolate the contribution of cervical spine range-of-motion (ROM) asymmetry to postural control in a group of older adults with neck pain.
Summary of background data: Previous research has suggested that the upper cervical spine plays an important role in postural stability. However, it remains unclear whether the upper cervical spine rotation ROM asymmetry is associated with postural stability.
Methods: Using the cervical range-of-motion device to assess upper cervical spine ROM via the cervical flexion-rotation test, we classified 54 older adults with neck pain (30 females; mean [standard deviation] age, 66  yr) into the (1) symmetrical group (SYM; n = 20; ≤5° side-to-side difference) or (2) asymmetrical group (ASYM; n = 34; >5° difference). Standing postural control was characterized by the center-of-pressure (CoP) movements measured using a Balance Board. Other measures included habitual, fast-paced gait speed and neck pain. Both groups were compared on the various measures using Welch t tests.
Results: Although the ASYM group had 26% greater anteroposterior postural sway than the SYM (P < 0.01), both groups did not differ on postural sway velocity, gait speed, and neck pain intensity. Analyzing the frequency content of the postural sway using wavelet analysis (a modern, nonlinear signal processing method) shed further light: the standing postural sway in the ASYM group was skewed toward lower frequency movement (ultralow [< 0.10Hz] frequency content, anteroposterior: 6.7% in ASYM, 4.7% in SYM, P = 0.01; medial-lateral: 4.2% in ASYM, 3.4% in SYM, P = 0.045).
Conclusion: The ASYM group seemed to have compensated for their altered somatosensory input to achieve similar functional levels as the SYM group. Given what is known about the association between ultralow frequency postural sway and visual input, we speculated that the postural strategy adopted by the ASYM group was adaptive and that this group may be relying on the visual system to achieve these compensations.