Investigation of head repositioning accuracy as a measure of cervicocephalic kinaesthetic sensibility in patients with chronic neck pain

Abstract

The majority of people can expect to experience neck pain in their lifetime and some will go on to develop prolonged or repetitive episodes of neck pain or related symptoms. These persistent complaints have become a major cause of disability around the world. Although chronic ‘mechanical’ neck pain can be defined in clinical terms, the underlying pathology remains unclear. Research has failed to demonstrate a consistent relationship between the presence of neck pain and pathology such as degenerative changes. As such, there has been an increasing interest in altered neuro-muscular-articular function in the pathogenesis of neck pain. Over the last 17 years, the role of cervical proprioceptive (mechanoreceptive) dysfunction in the perpetuation of chronic neck pain has received increasing attention from researchers and clinicians. This is commonly referred to as cervicocephalic kinaesthetic sensibility (KS). Cervicocephalic KS has generally been studied utilising head repositioning accuracy (HRA) tasks. At the beginning of this study only seven reports had been published in the area. Following review of this literature, several focused areas of interest were apparent for further study - 1) comparison of KS in various patient subgroups (e.g., insidious onset vs ‘whiplash’); 2) development of more sophisticated methods of measuring head movement and repositioning errors; 3) establishing the characteristics of the tests such as method agreement and reliability; 4) comparison of the discriminative value of repositioning tasks to both subjective ‘straight ahead’ (SSA) and to non-neutral set points within the cervical range of motion (non-straight ahead or nSA). Investigation 1 used a laser pointer method to study head repositioning errors in patients with chronic neck pain of insidious onset. The results suggested that these patients with chronic neck pain show little evidence of impaired cervicocephalic KS, when measured as HRA-SSA. The study also served to highlight several difficulties with the laser pointer method of measurement and the relatively poor knowledge of HRA in healthy subjects. Most previous studies used the mean of 10 repetitions for the measurement but more recent studies utilised fewer repetitions. Although the laser pointer method is simple, inexpensive and easy to use, the method involves a degree of experimenter bias and inaccuracy. It also does not lend itself to concurrent evaluation of variables such as range of motion and speed of head movement. Investigations 2 & 3 focused on the development of the testing method and the introduction of the Zebris CMS 70P ultrasound system for the recording of HRA-SSA, namely; method agreement between a 5 and 10 repetition measuring protocol; method agreement between the laser pointer and Zebris system; the intra/inter-examiner reliability of measurement methods. The Zebris system results suggested that the two methods of measurement agree sufficiently well for the 5 repetition method to replace the 10 repetition method to obtain a mean HRA score and that both could be used interchangeably. Further results suggested that the Zebris and laser pointer methods do not agree sufficiently well to be used interchangeably. The test-retest reliability was comparable between both methods suggesting that from this perspective, either could be used for measuring HRA-SSA. The inter-rater test-retest reliability was comparable to the test-retest reliability suggesting that trained examiners could be interchanged when carrying out repeated measurements. Investigation 4, the final study in this thesis, investigated HRA with the Zebris system using the 5 repetition protocol in two groups of chronic neck pain patients; insidious onset and neck pain from a ‘whiplash’ injury. The results suggested that patients with chronic neck pain of both insidious onset and from a ‘whiplash’ injury show little evidence of impaired cervicocephalic KS when measured using HRASSA and nSA tests. These results conflict with previous studies Despite numerous investigations over the last 17 years, a test that can be routinely applied in the clinical setting for the purposes of diagnosis and treatment monitoring has not been established. Studies to date suggest that an active HRA test to SSA/NHP that is established by the patient may have the greatest discriminative value. Although HRA testing shows some promise in identifying deficits in ‘whiplash’ patients, it is unlikely that the KS tests identify specific subgroups of chronic neck pain patients. There have been several contradictory studies which have shown considerable overlap between patient and healthy groups. It is also unlikely that HRA tests represent a unique test of cervical proprioceptive function (peripheral or central integration) and therefore provide a test exclusive to neck disorders.

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