Cervical Range of Motion Associations With Subclinical Neck Pain
From: Spine. 2004 Jan 1;29(1):33-40
The problem of neck pain is common in the general population, with 70% of individuals affected at some time in their lives, and about 5% to 10% of adults suffering a disabling neck problem. A recent random population-based study suggested that, in any group of young adults, approximately one third wake up with neck pain or stiffness once per week. Despite the high prevalence of neck problems, very few studies are available indicating any physical associations with the development of neck pain. Accordingly, there is a lack of knowledge concerning early signs of pathology for neck pain, such as which movements are affected when early neck symptoms appear.
It is well understood that cervical structures can be affected by specific causes such as degenerative disease, trauma, and/or inflammatory disorders, and that neck pain can result. Another group of neck pain cases with mainly mechanical disorders, including those thought to arise from habitual postures and degenerative involvement, have been referred as nonspecific neck pain. However, most cases of nonspecific neck pain are similar in presentation to that seen when cervical structures are injured by disease or trauma, even though systemic conditions cannot be found as the underlying cause of neck complaints.
It has been proposed that nonspecific neck pain problems result from poor posture, in terms of sustained, long-term, abnormal physiologic loads on the neck. These loads compromise pain-sensitive structures and thereby affect the function of the cervical spine, causing a musculoskeletal imbalance in the upper quarter of the body. For example, a habitual excessively forward head posture has been suggested to be pain provoking, with a consequential reduction in muscle strength.
Associations between cervicothoracic spine physical dimensions and the presence of neck pain or discomfort, however, have not been firmly established. Grimmer failed to find any association between subjects having extreme cervical resting postures and reports of neck pain. There is also a lack of association reported between cervical posture and deep cervical short flexor endurance, as noted in another random population-based study. Most postural studies have used static measurements for calculating spinal angles with radiographs and photographs. While forward head posture has been suggested to cause pain and dysfunction, few studies have investigated the association between posture and active range of motion. Hanten et al measured resting head posture and total range between full protraction and retraction in the horizontal plane, in subjects with and without neck pain, and found that the neck pain group had less range than the normal group. Another study by Haughie et al with office workers who complained of neck pain also demonstrated an association between forward head posture and reduced cervical extension range.
Currently, there are not enough studies available comparing those with nonspecific neck pain to the normal population in order to make conclusions about any specific physical dimensions related to nonspecific neck pain. In those few available, the severity of neck pain is not well defined, and the techniques used to measure physical dimensions vary between studies, making it difficult to compare results. Therefore, further study is warranted to clarify the association between cervicothoracic spine physical dimensions and the presence or absence of subclinical neck pain or discomfort.
The purpose of this study was to examine physical dimensions of morphology of the neck and head, posture, range of neck motion, and the endurance strength of neck muscles, in order to determine any association between the presence or absence of neck pain or discomfort, and physical dimensions of the cervicothoracic spine. Because none of the subjects was to be receiving any treatment, questions about neck pain were held until the end of all testing to avoid any subconscious reduction in performance due to the pain subjects conforming to perceived expectation. A second set of the range of motion tests was included to determine whether there were any sensitization or stretch effects arising from repeated end-of-range measurement.
On questioning, 35% of otherwise healthy subjects in this study reported that they experienced neck pain or discomfort on a recurrent basis, a proportion similar to that observed in a recent population-based study. The point in time at which self-classification as to having subclinical neck pain takes place (i.e., before or after physical testing) has important implications for research with this group. If, after responding to an advertisement requesting subjects without neck problems or current pain, individuals undertake physical tests and perceive themselves to have performed badly, on questioning about pain they may be prompted to recall pain events that explain their poor performance, whereas good or adequate performers do not experience such prompting. Alternatively, if individuals respond to an advertisement requesting subjects experiencing neck problems, on entering the research laboratory they may perceive a demand on them to behave in ways that they think are expected of pain subjects. Demand characteristics are experimental cues that influence subjects to respond in ways that validate the experimental hypothesis, 24 which in pain research might involve restricting range or effort. Because demand characteristics have been shown to affect responding to pain questionnaires, it was considered important to control these by not questioning subjects about any neck pain until after all physical testing. Further, the subjects in the current study were kept unaware of their results on the range of movement tests so that they were unable to evaluate themselves in relation to others. For the subclinical pain group, there was no general sensitization effect from repeated testing, with only one direction (extension) showing a group-specific sensitization effect. Here there was on average 3° (of 70°) difference between testing occasions in the subclinical group, and it is unlikely that subjects would be able to produce a difference of this magnitude over the range. On the neck muscle strength test, the endurance holding time for the subclinical group ranged from 241 to 690 seconds. If performing poorly was a prompt to identifying themselves as suffering recurrent pain, it might be expected that the holding time for all these subjects would be low. However, only 3 of 14 subjects in the subclinical group had a lower holding time than the worst performer in the no pain group, and even the worst performing subclinical pain subject achieved over 4 minutes. Accordingly, we have interpreted the range of motion and strength differences between the physically similar subjects with and without neck pain as reflecting their group status, rather than determining it.
Neck muscle endurance time was found to be significantly less with subjects in the subclinical neck pain group than with subjects in the normal group. Decreased neck muscle strength has been found when clinical neck pain groups are compared to normal groups, however, there is only limited evidence that neck muscle exercise is effective for management of neck pain, from studies with both short and/or long term follow-up periods. It is possible that neck muscle dysfunction is a long standing problem for severe neck pain patients, and that it cannot be improved by short-term treatment. Therefore, it may be that management techniques should be evaluated at the subclinical stage, to determine methods of preventing the problem from progressing to become severe neck pain.
Simple physical measures of active cervical range of motion, used in the current study, discriminated between subjects having and not having neck pain or discomfort on a recurring basis, although no general effect on range tests was observed. Two of the range of motion tests found to be significantly different in the subclinical neck pain subjects were left rotation and extension. Other available data have reported rotation as the most affected direction of movement in the cervical spine and found it to differ between the normal and neck pain subjects. Extension showed a significant interaction with a reduction in range (sensitization) for those reporting pain but an improvement (stretch) for other subjects. Various authors have reported this direction of movement for the cervical spine to be commonly reduced in neck pain patients.
Currently, few studies have investigated retraction and protraction in nonspecific neck pain or discomfort subjects. In the present study, the subclinical neck pain group showed greater range of retraction than the normal, suggesting that the former use a retraction movement for relief. Retraction is comprised of maximum flexion at the upper cervical spine, from occiput to C2, and extension at the lower cervical spine, C6-C7, whereas protraction results in maximum extension at upper cervical spine and lower cervical flexion. Thus, subjects in the subclinical group may tend to use more movement in the lower cervical spine to get retraction of their cervical spine.
Both right and left side flexion range scores were significantly reduced on retesting, for both groups in the current study. All second measurements were taken within a 10-minute period after the first. It is possible that both groups of subjects in the present study were unfamiliar with moving into the end range in lateral flexion and that these are movements that might place stress on pain sensitive structures. Decreasing range in the second measurement of this movement may protect against stress on those structures and decrease discomfort.
Because the tester combination for a given subject was determined by availability, the reliability of the measurements was determined for the range of motion measurement protocols using the ICC as the statistic appropriate for this mixed raters design. The ICC reflects the proportion of the total variance which is true score variance, and except for retraction, all directions of neck range of motion and posture using the CROM device in our study demonstrated fair to excellent reliability. Other authors have also reported difficulty in the measurement of retraction range with the CROM device and advised that the retraction range measure might have poor reliability. Although subjects within groups tended not to maintain their relative rankings on the second retraction measure, a between-groups difference was detected on the first measure. However, the amount of error in this measure may have made it less sensitive to any differences between occasions.
One side specific effect was also observed in both groups, in that left rotation showed a greater range than right rotation. Differences between sides were found when examining other studies conducted in different countries. It is possible that this asymmetry arises from directional head turning to end of range during driving. Where the driving position is on the right of the vehicle, end of range head turning to the left is needed for reversing, and vice versa. Thus, further range should be available in left cervical rotation for adult subjects in United Kingdom, Australia, and Japan, and in right cervical rotation for subjects in the United States and South Korea, which seems to be the case based on current data.
Finally, postural measures of thoracic kyphosis angle and extent of forward head posture did not differ between the subclinical pain and the normal group. A recent study showed that pain was not confined to subjects with relatively low craniovertebral values indicative of a forward head posture, and this finding is consistent with data from the present study. Therefore, it can be suggested that extreme resting postures are not necessarily an indicator of neck symptoms.
Symptoms in our subclinical neck pain group were of a benign and transient nature, so that self-management was used rather than professional consultation sought. Self-management for this subclinical neck pain group consisted of changing the postures (i.e., retracting), which they felt caused neck pain or discomfort, ignoring symptoms and keeping up usual activities despite discomfort. Data for the neck pain group showing significantly greater retraction range and a trend toward a more retracted head posture in quiet sitting are consistent with this. It is possible that this active self-management may be sufficient to prevent the development of severe neck pain. However, prospective longitudinal studies are needed to determine whether this is indeed a valid method for managing neck pain in the general population.
Although their pain was subclinical, the neck pain group in the current study showed important impairment signs, notably in neck muscle endurance, rotation, and extension, and these findings give direction to future study of the clinical neck pain population.
