Abstract
Background: Sensorimotor mechanisms that control activation of neck and trunk muscles are important in preventing injury to spinal tissues. People with back pain often show delayed reflex activation of trunk muscles, and such impairment increases the risk of future back pain. The aim of this study was to investigate whether sensorimotor impairment is evident in patients with neck pain.
Methods: Measures of sensorimotor function were assessed in fourteen patients with chronic, non-traumatic neck pain and forty healthy controls. Position sense was evaluated using the Fastrak electromagnetic tracking device to assess angular errors during head repositioning tasks. Movement sense was assessed using a KinCom dynamometer to determine the time taken to detect head motion at 1°s-1 and 10°s-1. Reflex responses were assessed using surface electromyography to determine the onset of muscle activation (reflex latency) in trapezius and sternocleidomastoid muscles, following perturbations of the head.
Results: Neck pain patients showed increased angular errors in reproducing upright postures, compared to controls (2.24±1.21° vs 1.85±1.06° respectively; p=0.01), and faster movement detection times (385±98ms vs 540±182ms respectively; p=0.0052). Reflex activation of trapezius was delayed in patients, indicated by a 20ms increase in reflex latency (89±19ms vs 69±21ms in controls; p=0.0039).
Conclusions: Sensorimotor function is altered in patients with neck pain. Enhanced movement detection suggests some afferents become hypersensitive in response to pain. However, impaired position sense and reflex activation suggest that some proprioceptors, including muscle spindles, develop a reduced sensitivity to mechanical stimuli. These changes may impair reflexive muscle protection and expose the cervical spine to repetitive minor injuries.
Conflicts of Interest: None
Source of Funding: BBSRC (Biotechnology and Biological Sciences Research Council, U.K.)
Correspondence should be addressed to: SBPR at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE, England.
