Abstract
Purpose of Study: The neck is the most mobile region of the spine, so neck muscles must provide stability, and control spinal movements. This action requires effective sensory and motor control mechanisms which, if impaired, may increase the risk of injury and pain. The aim of this study was to investigate sensorimotor function of neck muscles in healthy volunteers in order to provide normative data for comparative studies on neck pain patients.
Methods: Thirty-one healthy volunteers participated. Position sense was evaluated using an electromagnetic tracking device (3-Space FASTRAK) to assess errors in repositioning the head in upright and flexed postures. Movement sense was assessed as time to detect head motion at 1°s-1 and 10°s-1, using a KinCom dynamometer. Latency of reflex muscle activation following rapid perturbation of the head was assessed bilaterally in trapezius and sternocleidomastoid muscles using surface electromyography.
Results: Mean repositioning errors were 2.20±1.46° and 2.54±1.69° for upright and flexed postures respectively. Time to detect head motion was greater at 1°s-1 (739±349ms and 556±213ms, in extension and flexion respectively) compared to 10°s-1 (375±89ms and 377±66ms). Mean reflex latencies were shorter for trapezius (left: 77.9±43.4ms, right: 72.3±35.1ms) than for sternocledomastoid (left: 106.1±29.2ms, right: 102.7±35.9ms).
Conclusion: Position sense in the cervical spine is superior to that reported in thoracolumbar regions, especially in flexed postures. Detection of head movement is velocity-dependent suggesting input occurs from both phasic and tonic mechanoreceptors. Reflex latencies were shorter for trapezius than for sternocledomastoid suggesting that stretch reflexes in trapezius play a predominant role in preventing excessive flexion of the cervical spine.
Correspondence should be addressed to SBPR at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE, England.
