The effects of cervical spine posture on susceptibility to walking balance perturbations.

Abstract

Degenerative cervical myelopathy (DCM) is the most common cervical spine disorder encountered in the aging population that commonly presents with increased cervical kyphosis and impaired gait. Thus, the compounding effects of exaggerated head tilt, as a result of cervical deformity, may increase the risk of falling in individuals with DCM. What are the effects of cervical bracing and posture (i.e., kyphosis and lordosis) on outcomes relevant to the control of walking balance? This was an experimental study conducted in 15 healthy young adults. We used two discrete mechanical balance challenges designed to elicit walking-related instability. Specifically, participants walked with a series of cervical spine braces while responding to: (i) treadmill-induced slip perturbations to induce rapid reactive responses to unanticipated perturbations and (ii) a reactive lateral stepping as a goal-directed balance challenge. We used two-way repeated measures ANOVAs to determine the effect of bracing condition and balance challenges on (i) anterior-posterior and mediolateral margins of stability (MoSAP and MoSML) and (ii) reaction time and foot placement error. Our experimental manipulations successfully emulated cervical spine postures common to patient populations. Compared to unperturbed walking, treadmill belt decelerations elicited significantly smaller MoSAP and larger MoSML for all conditions, but elicited negative MoSAP indicative of instability only for braced conditions. Bracing did not increase foot placement errors during lateral reactive stepping compared to unbraced walking. However, only for kyphotic bracing did performance decrease with target distance. Individuals prescribed cervical immobilization or presenting with cervical deformities may be less capable of responding to balance challenges that could precipitate a fall in the community. We conclude that treating cervical spine deformities with cervical immobilization may benefit from educational materials and monitoring techniques to mitigate falls risks.