From: Pol Merkur Lekarski. 2008 Jun;24(144):549-51 Article in Polish

In 2004 cervicogenic headache (neck related headache) was introduced into ICD-10 classification.The reasons of cervicogenic headache are changes within bones, soft tissue and nervous structures of cervical spine section. The pain may spread to the neck, occipital area of skull, area of jaw and eyeballs, and arms. There are many theories trying to explain spreading of the pain outside the area innervated by C1, C2 and C3 cervical roots. Their common denominator is communication between fibres running in those roots and neurons of trigeminal nerve. Many authors describe a possibility of such connection through the jelly-like nucleus of the trigeminal nerve located in the back funiculi of spinal cord. In this mechanism, the pain conducted via occipital nerves may affect activity of neurons of the trigeminal nerve and influence areas innervated by the trigeminal nerve. In general case history and physical examination are sufficient to make a diagnosis. Additional radiological and imaging examinations support this diagnosis. According to some authors, the necessary condition to make a diagnosis of cervicogenic headache is finding the changes of spondylosis nature of the cervical spine section (neck arthritis or degenerative disc disease) in additional examinations. In doubtful cases, diagnostic blockade of greater occipital nerve, resulting in headache relief, supports finally a diagnosis. Any treatment includes pharmacotherapy, rehabilitation, psychotherapy and surgical methods. The purpose of the study is to view literature on cervicogenic headache which causes many diagnostic problems and hence makes it difficult to choose effective treatment.

From: Spine. 2008 Jul 1;33(15):1643-9

Injury to the cervical facet capsular ligaments is a potential mechanism for chronic neck pain after acute whiplash injury. Distending the facet capsule by injecting contrast media has produced whiplash like pain patterns in normal individuals, and anesthetic blocks have isolated the cervical facet joints as the source of pain in about half of a chronic whiplash population. More recently, in vivo animal models of facet capsule loading have shown that group III and IV afferents (thought to mediate pain) from the facet capsule have a graded electrical response to mechanical loading of the facet joint in the goat and have suggested that a capsular ligament strain threshold exists above which allodynia pain in response to a normally nonnoxious stimulus is produced. These data support a facet capsule based mechanism for whiplash injury, but do not establish whether human capsular ligaments are injured in the low speed rear end collisions to which many whiplash injuries are attributed.

Whiplash patients who had their head turned at impact have more severe and persistent symptoms than patients who were facing forward. These findings have prompted biomechanical studies using human cadaveric necks to investigate why a head turned posture increases injury potential. Dynamic rear impact tests of prerotated ligamentous spines (occiput-T1) produce increased neck flexibility (interpreted as injury) in extension, lateral bending and axial rotation. Though concentrated in the lower cervical spine, these injuries were not isolated to particular spinal ligaments. Detailed measurements of the strain field in the facet capsule have also shown that a head-turned posture generates higher capsular strains than a neutral head posture, but the quasi static loads applied during those tests were limited to pure neck flexion/extension moments and did not include the axial compression or posterior shear present during whiplash loading. Thus the question of how a head turned posture combined with multiaxial whiplash loads affects facet capsular ligament strain has yet to be answered.

The goals were to use human cadaveric motion segments to: (1) quantify the intervertebral kinematics and facet capsule strains under whiplash like loads in the presence of an initial axial rotation, and (2) compare the capsule strains generated by these combined loads to the previously published strains needed to injure these ligaments in isolated shear failure. The overall hypothesis was that capsular strains during this simulated whiplash exposure are similar to those needed to injure the capsular ligament.

Axial pretorque and the resulting axial rotation of the intervertebral joint have a large effect on the maximum principal strain in the cervical facet joint capsule when combined with compression, shear, and extension loads simulating a low speed rear end automobile impact. Peak strains in the capsule with an ipsilateral pretorque were double the previously reported peak strains without a pretorque but similar to the previously reported strains to cause partial failures in these specimens. These findings potentially explain the increased severity and persistence of whiplash neck symptoms in patients who had their head turned at impact.

Previous findings suggest that the facet capsules located on the side of the neck towards which a vehicle occupant’s head is turned are most likely to be injured in a rear end crash, although they could find no clinical or epidemiological data to support or refute this proposition.

The quasi static loading rates used in the current flexibility tests and previously published failure tests were similar, but nonetheless lower than those present during actual whiplash exposures. Quasi static loading rates have been shown to affect the magnitude of the load at failure, but maximum principal capsular strain and displacement to failure are not significantly affected by loading rate. Thus aside from the unwinding effect, the capsular strains reported here are expected to be similar to those present during dynamic whiplash events.

During the multiaxial tests, 2 of 13 specimens exceeded the strain needed to cause partial failure of the capsule. Although they could not discount the possibility that other specimens experienced a partial failure during the whiplash like exposures, the potential for 15% of specimens to exceed a threshold for partial failure is consistent with earlier quasi static work and more recent dynamic work. Similar levels of capsule strains have produced behavioral and electrophysiological evidence of short and long term pain in animals, although both animal experiments strained the dorsal aspect of the capsule rather than the lateral aspect studied here. This 15% risk of partial failure in the capsule is similar to the 12% risk of whiplash exposed individuals suffering chronic symptoms ( over 6 months), though considerable work remains to determine whether these similar risk values are related or coincidental.

Two other specimens exceeded the strain needed to cause gross failure of the capsule. There was no evidence of gross failure during their tests and thus this finding likely highlights limitations in their technique. They previously assumed that failures occurred in the element with the highest maximum principal strain, yet in this study they compare whiplash and failure strains quadrant-by-quadrant rather than element-by-element. Regional differences in the ligament could also result in different mechanical tolerances at different locations within a quadrant or element. Moreover, the failure tests were conducted along the anteroposterior axis of the facet joint, whereas the whiplash tests exposed the joint to compound three-dimensional displacements. This means that different ligament fibers may have borne the loads during the whiplash and failure tests. Thus even though their technique provides more detailed strain field information than other recently published techniques, even finer techniques perhaps looking at region specific or fiber specific strains are needed to capture regional differences and properly characterize the capsular ligament’s full three dimensional behavior during whiplash.

The high strain caused by pretorque alone raises the question of why facet capsular ligaments in these joints are not injured when rotating one’s head maximally to the side. Aside from the large rotations taken up at the atlantoaxial joint, one reason may lie in the regional differences described above. The facet capsule likely develops the necessary shape, slack, and tolerance to accommodate voluntary head rotations. The superposition of vertebral retraction during whiplash loading may then shift peak strain to fibers in the capsule that are normally not highly strained during voluntary rotation or combined loading scenarios. Alternatively, the small increase in strain produced by the whiplash loads may be sufficient to injure ligament fibers that are near their limit as a result of a prerotation. Further exploration of this phenomenon will require a more detailed characterization of the dynamic, full field strains in the facet capsule, and definition of the overall and regional tolerances of the facet capsular ligament and its microstructural components.

In summary, they examined the intervertebral kinematics and facet capsule strains under whiplash like loads in the presence of an initial axial rotation. We found that an axial rotation doubles the maximum principal strain in the capsular ligament compared to the neutral posture. We also found that capsular strains during the simulated whiplash exposure with the head turned were not significantly different from maximum principal strain associated with partial failure of the capsule. Thus these findings support the overall hypothesis that excessive capsular strains experienced by some individuals during some whiplash conditions may be responsible for painful capsular whiplash neck injury.

From: Spine. 2003 Jun 1;28(11):1113-21

Low back pain is acute or chronic pain involving the lumbosacral, buttock, and/or thigh. Discogenic low back pain is aggravated by the sitting position, which is necessary in many occupations and daily activities. About 100 million workdays are lost annually in the United States due to low back pain. Despite improved knowledge and health care resources for spinal pathology, chronic disability resulting from nonspecific low back pain is rising exponentially. Although the causes of discogenic low back pain are multifactorial and complex, sitting postures could increase stresses within the disc and contribute to disc degeneration and pain. Two major occupational risk factors are static muscle load and flexed curvature of the lumbar spine; both are involved in seated work tasks.

During sitting, the head, arm and trunk weight is carried mainly by the ischial tuberosities and surrounding tissues. High pressure at the tuberosities is closely associated with high load to the spine. A significant mechanical spine loading is associated with low back pain resulting from trunk muscle coactivation. Ischial and lower back interface pressure vary with different sitting postures and body positioning. Repositioning of the lumbar support to redistribute the interface pressure and load is essential in preventing low back pain associated with inappropriate sitting in a working environment. Therefore, a device that decreases the sitting pressure and load carried by the ischial tuberosity may decrease forces within the disc and associated degeneration and pain.

Physiologic lumbar lordosis in the standing position ranges from 40° to 60°, with the lordosis occurring mainly at S1-L5 and L4-L5, and with the sacral inclination ranging from 30° to 40°. Compared to standing or lying supine, sitting could cause the pelvis to rotate posteriorly, resulting in decreased sacral inclination and lumbar lordosis and increased forces at the discs. A number of investigators have reported interaction between low back pain and biomechanical changes such as decreased lumbar lordosis, malalignment of lumbar curvature, and narrowing of disc spaces. Williams et al reported that use of a lumbar roll that increased lumbar lordosis reduced low back pain, and the chair backrest also helps increase the lumbar lordosis and decrease intradiscal pressure.

Numerous chairs or cushions have been developed to reduce or redistribute the sitting pressure on the ischial tuberosities using custom-fit seat pans. Others chairs are designed to maintain lumbar lordosis by adjusting back support or using a forward tilted seat. However, few chairs use adjustable mechanisms for both ischial release and lumbar support.

The purpose of this study was to investigate the biomechanical effects of tilting down the back part of seat and adjusting the backrest. The hypotheses were the following: 1) when the back part of seat is tilted down, load on the ischial tubercles will be reduced and shifted to the thighs, and low back muscle activity will be reduced; and 2) an increase in lumbar lordosis, forward rotation of the sacrum, and larger disc height will be observed when the back part of seat is tilted downward in combination with a properly adjusted back support.

This study investigated quantitatively the biomechanical effects induced by adjusting ischial and back supports, including the contact pressure distributions, reactive forces between the buttock-thighs and seat and between the back and backrest, muscular activity in back muscles, sacral inclination, lumbar lordosis, and intervertebral space of the lumbar spine. It was found that sitting with this lowered back part of seat and adjusted backrest distributed contact pressure more evenly, significantly reduced peak pressure under ischia, reduced muscular activity, rotated the sacrum forward, increased total and segmental lumbar lordosis, and increased lumbar intervertebral disc height.

When the back part of seat was tilted downward by θ = 18° and the backrest was utilized, Ftot exerted on the backrest was significantly increased. The peak contact pressure on the backrest was significantly increased, and it was significantly decreased on the seat; the largest change was found for the upright with backrest condition. The center of pressure and center of force were significantly shifted anteriorly to the thighs for all sitting conditions. All of these measurements for load and pressure redistribution on the seat and backrest indicated that load on the ischial tubercles was significantly decreased and shifted to the thighs, while load on the back support was increased, mainly with the load component in the posteroanterior direction to maintain lumbar lordosis. Using this new sitting concept made the thighs take up more load over a larger surface area, with less load on the ischial tubercles.

Measurement of load and contact pressure redistribution are important in assessing tissue viability, as prolonged sitting can lead to pressure sore development, increased disc degeneration, and low back pain. Repositioning of the lumbar support to redistribute the interface pressure and load is essential to prevent low back pain. Furthermore, for patients who have limited mobility, body repositioning remains the only way to change their pressure distribution at the body-seat interface.

Muscle activity was decreased in most of the sitting conditions when the back part of seat was tilted down, especially in the lumbar region. Relieving the ischial support may have made the pelvis rotate forward and relaxed muscles in the lumbar region more than in the thoracic regions. Another reason may be different amounts of pressure on the lumbar and thoracic regions during EMG recording for sitting conditions using backrest, especially for the relaxed condition. Under the relaxed sitting condition, the body did not show any significant change in muscle activity at the thoracic regions.

The upright with backrest sitting condition was found to be more efficient to change the pelvis and lumbar structures when the back part of seat was tilted down. The results from load and contact pressure redistribution on the seat and backrest indicated that this sitting condition gave the best results to reduce load on the ischial tubercles and lower spine. Thus, this sitting condition upright with backrest was used to evaluate changes in the lumbar spine and pelvis structures with the backrest fitted partially or fully to the lower spine using radiographs.

Tilting down the back part of seat maintained sacral inclination approaching that of the standing posture. The total and segmental lumbar lordosis were also increased and resulted in an appearance in which the abdomen was particularly prominent and resembled closely that of the standing position. The sacral inclination and lumbar lordosis results from other studies for sitting and standing are given. A comparison between these results and the results from the present study confirmed the similarity.

The benefit of lumbar lordosis was suggested in a postmortem study with an association between decreased lumbar lordosis and increased disc degeneration at L5-S1, suggesting a protective effect for increased lumbar lordosis on the lumbosacral junction. Andersson et al found lordosis to be inversely proportional to intradiscal pressure. Lumbar curvature affects disc pressure by changing the distribution of load between disc and apophyseal joints and also by changing tension in the intervertebral ligaments. The increased intradiscal pressure may also be the underlying factor for the association of decreased lordosis and low back pain. In a study of osteoporotic patients by Itoi, decreased lordosis was associated with increased low back pain. Keegan, in a study of the relation between lordosis and sitting, found the most important factor in low back pain with prolonged sitting to be a decreased trunk-thigh angle with consequent flattening of the lumbar curve. Using a lumbar roll that increases lordosis has been found to decrease low back pain. With decreased lordosis, sitting pressure increases over the ischium and coccyx with resultant pain. Others have also found distinct differences in lumbar lordosis when comparing low back pain patients with healthy patients.

All disc heights were significantly increased by lowering the back part of seat. Extensive and consequent segmental lordosis may decrease intradiscal pressure. The effect of disc height on mechanical properties caused by compressive forces was investigated and found that biomechanical axial stress for the intervertebral disc increased most at L4-L5 due to the decreased disc height in upright posture. The highest incidence of lumbar disc diseases was generally found at L4-L5. 52 The reason for the relatively high frequency of lumbar disc disease was connected to a relatively wide range of motion and high loads at L4-L5 and L5-S1 with lumbar flexion and extension.

It has been reported that a backrest with a protruded part to support the lumbar spine would result in an increase of the lumbar lordosis and the load on the back. The present study supports such an observation. Furthermore, a much greater load reduction was observed in this study for proper lumbar support combined with the ischial tubercles load relief. However, the benefits of unloading the ischia were investigated during a short sitting time. The outcome needs to be evaluated for longer period of sitting with unsupported ischia with the concern that load shifted to the thighs may cause hip pain. Tilting the back part of seat down and up alternately is needed during prolonged sitting. Future study is needed to find the optimal tilting angle of the back part of seat and optimal period for tilting the back part of seat down and up during long periods of sitting.

From: J Epidemiol Community Health. 2005 Sep;59(9):721-8

Work related musculoskeletal disorders and complaints constitute an important health problem in many industrialised countries, as they account for a large number of working days lost and considerable workers compensation and disability payments. For a long time, low back pain has been the dominant problem. However, pain from the shoulder and neck region now seems to occur more frequently. The prevalence of shoulder and neck symptoms is highest in the 45–65 year age bracket, as well as among women, manual workers, and certain ethnic groups.

However, its aetiology is still incompletely understood. Mechanical exposure at work and psychosocial conditions within and without the workplace, in addition to lifestyle and individual variables (age, previous symptoms, etc) are frequently discussed as causal factors in the literature.

Shoulder and neck symptoms have been linked to jobs with highly repetitive work, static work, and work above shoulder level. However, mechanical exposure explains only part of these complaints. The role of psychosocial factors in the workplace has therefore received increasing attention. On the job pressure, monotonous work, and a high perceived workload have also been associated with musculoskeletal symptoms just as much as working situations characterised by high psychological demands, low decision latitude, and low social support.

Hence, an aetiological model explaining shoulder and neck symptoms could be based on the assumption of an interaction between mechanical and psychosocial factors at work. There is, however, a need to clarify the interplay between these risk factors.

A number of shortcomings in previous research into the causes of back and neck pain have been recognised. Firstly, few studies have separated low back and neck pain, which would seem to be an important distinction because of potentially different epidemiological patterns and assumedly different risk factors. Secondly, studies regarding the role of psychosocial risk factors in these outcomes seldom have adequately controlled their risk estimates with respect to potential confounding from mechanical exposure.

Moreover, few studies have been performed on populations having a sufficient variety of both mechanical and psychosocial exposures. The presumed high correlation between the two risk factors cited can only be weighed adequately in a large study sample in which diverse job tasks are represented.

Finally, few attempts have been made to quantify the multidimensionality of mechanical exposure. Nor have such measures been used in relation to psychosocial ones—particularly not in a prospective study design.

This study has attempted to address all the mentioned issues. Based on a large general population cohort, its intentions are to analyse the importance of both mechanical and psychosocial exposures in the workplace on the incidence of shoulder and neck complaints, and evaluate the possible effect modification between these two exposures.

We found that mechanical exposure (for men) and job strain (for women)—in other words, the combination of high job demands and low job decision latitude—were the factors most strongly associated with a higher risk for developing shoulder and neck pain during the one year follow up period.

We also found evidence for a synergistic effect of these two factors in heightening the risk of developing shoulder and neck pain among women, but not among men.

Our results may have been biased by selection, misclassification, and confounding. It is probable that the most vulnerable people had left their jobs and thus were excluded from the cohort in this study—either because they were no longer pursuing a physically demanding vocation, or because they were already ill at the time of the baseline assessment. This would bias the risk estimates towards the null.

Furthermore, it is known that people who are ill have less of a tendency to participate in studies. A higher non-participation rate among people complaining of shoulder and neck pain during the follow up study could also lead to an underestimation of the true association between mechanical and psychosocial exposures and the incidence of shoulder and neck pain. In actuality, the high participation rate in our follow up study (86.6%) would render this possibility a negligible consideration.

Bias attributable to dependent misclassification should not influence the results of this prospective study, as the exposures were determined at baseline, and case status at follow up. However, another possibility of misclassification could be present, namely, between mechanical and psychosocial exposures. It is possible that exposure to one of these factors might affect the person’s assessment of the other. However, the correlation coefficient between these two exposures were rather moderate, which ought to exclude the possibility that the results were very much influenced by this type of bias.

Another bias of importance could be confounding. One potential confounder could be age, but adjustment for this factor in the multivariate analysis only resulted in a very marginal change in the ORs.

The most important confounder to account for was job strain regarding the estimated impact of mechanical exposure, and mechanical exposure regarding the impact of job strain. However, including these variables in the model only decreased the age adjusted ORs slightly, without changing their statistical significance. It can, thus, be concluded that the impact of mechanical exposure and job strain on shoulder and neck pain exhibits little or no confounding by each others’ effect.

Further potential confounding factors were marital status and country of origin. Once again, inclusion of these variables in the multivariate models hardly changed the ORs. Occupational status was not included in the multivariate analysis because of its close association with both mechanical and the psychosocial exposures. For this reason, the inclusion of occupational status in the multivariate model would most probably result in an over-adjusted model, or problems of multicolinearity. Educational level was therefore chosen as the variable denoting socioeconomic status in the confounding analysis. But even when this variable was added to the multivariate model, its effect on the risk estimate was moderate.

A number of previously published studies concerning shoulder and neck pain have included both mechanical and psychosocial exposures. Most of these have been performed within occupationally homogenous groups, such as newspaper workers, transit operators, forestry workers, carpenters, car workers, homecare workers, aluminium smelters, students, medical secretaries, and female nursing staff. However, there are a few studies that have used groups drawn from the general population.

Most of the aforementioned studies were cross sectional, and one was a case-referent study. In these investigations, the effect of mechanical exposure was controlled for psychosocial exposure, and vice versa. However, only two studies assessed possible effect modification between the two types of exposure. Both of these were cross sectional, and were based on occupationally homogenous samples (newspaper workers and female homecare workers).

Most of the studies mentioned used a kind of demand/control instrument to assess work related psychosocial exposure, while a great variety of measures were used for assessing mechanical workload. These ranged from time spent in a certain occupation to observational assessments of workload and postures. A wide array of instruments was also used in these studies to determine shoulder and neck pain. In some instances, a version of the standardised Nordic questionnaire was used.

In conclusion, there seems to be a lack of previous prospective studies that have been undertaken on large, general, population based samples (or at least samples representing a wide variety of occupations/work tasks), and that use well recognised instruments for assessing mechanical and psychosocial exposure. Such standards are required to optimally address the question of whether one or both of these exposures can be convincingly linked to shoulder and neck pain. The preceding caveat may especially hold true if the objective is a valid analysis of effect modification.

In a recently published review article concerning neck pain, in which 22 cross sectional, two prospective, and one case-referent study were evaluated, the authors concluded that awkward work postures could be linked to neck disorders with a reasonable degree of certainty. This coincides with our findings that mechanical exposure (as assessed by an index primarily based on awkward work postures) is associated with an increased risk of developing shoulder and neck pain during the follow up period, independent of psychosocial exposure.

In the case of women, we also found a statistically significant association between work related psychosocial factors such as job strain and the heightened risk of developing shoulder and neck pain during the follow up period, independent of mechanical exposure. Similarly, in some cross sectional studies, high psychosocial job demands were found to be associated with shoulder and neck pain, once again, independent of mechanical exposure. Several studies found low decision latitude associated with this outcome again, independent of mechanical exposure. Other studies, however, failed to find such an association. One prospective study, however, did find high decision latitude associated with an increased risk of shoulder and neck pain.

The most important finding in this study was that mechanical exposure has an impact on shoulder and neck pain in men and women, and so have work related psychosocial factors in women even when taking into account confounding for each others’ effect. Furthermore, evidence for the existence of a synergistic relation between these two types of exposures among women in a vocationally active, urban, middle aged, general population.

From: Ergonomics. 2008 May;51(5):637-48

The objective of this prospective cohort study was to evaluate if peak or cumulative musculoskeletal discomfort may predict future low back, neck or shoulder pain among symptom free workers. At baseline, discomfort per body region was rated on a 10 point scale six times during a working day. Questionnaires on pain were sent out three times during follow-up. Peak discomfort was defined as a discomfort level of 2 at least once during a day; cumulative discomfort was defined as the sum of discomfort during the day. Reference workers reported a rating of zero at each measurement.

Peak discomfort was a predictor of low back pain (relative risk (RR) 1.79), neck pain (RR 2.56), right or left shoulder pain (RR 1.91 and 1.90). Cumulative discomfort predicted neck pain (RR 2.35), right or left shoulder pain (RR 2.45 and 1.64). These results suggest that both peak and cumulative discomfort could predict future musculoskeletal pain.

From: Spine J. 2008 August ;33(18)630-635

Whiplash describes a process of hyperextension and hyperflexion of the cervical musculature that may result from motor vehicle collisions. The incidence of whiplash has been estimated to be of 1 case per 1000 habitants per year in Western societies, nevertheless available studies report conflicting rates. Symptoms associated with whiplash problems typically resolve in a relatively brief time (days or weeks), but chronic pain, and long-term disability may occur in 10% to 40% of the cases.

The prevention and treatment of chronic disabling pain in whiplash patients has shown to be elusive. On the one hand, predictive factors of chronic disabling problems in whiplash patients are far from being completely elucidated. Although one can hypothesize that factors from different levels (i.e., physiology, thoughts, feelings, and behavior) and units (i.e., individual, dyad, and context) of analysis play a role, very few and inconsistent findings are available. On the other hand, there is limited evidence about what is the most beneficial treatment for whom and under what circumstances. The use of many different outcome variables and assessment instruments may be responsible, in part at least, of the problems encountered in this area of research to compare results across studies and extract definitive conclusions.

One instrument that could be used as a standardized outcome in the whiplash field is the neck disability index. The neck disability index was constructed to assess disability due to neck pain, especially in whiplash injuries. It is a 10-item self-report questionnaire derived, in part, from the Oswestry low back pain index, assessing the extent to which neck pain interferes with patients’ daily functioning in ten different areas. Although other measures are available to assess disability in patients with neck pain, and recently, a specific measure for whiplash patients has been developed (the Whiplash Disability Questionnaire), the neck disability index has become one of the most used questionnaires in the neck pain field, and recommended to be used in the whiplash field because of its positive assets and strengths. Specifically, the neck disability index has adequate psychometric properties: it has shown good internal consistency, test-retest reliability, and construct validity. Another interesting and valuable characteristic of this measure is that it has been translated into several languages (i.e., Dutch, French, Korean, Brazilian-Portuguese, Swedish, and Turkish), with these new versions of the instrument showing appropriate psychometric values too. Thus facilitating transcultural studies in this field.

Although the neck disability index has shown some good psychometric properties, has been translated into different languages, and extensively used with whiplash patients, its usefulness has not been assessed in this population. Only a few studies examining the psychometric properties of the neck disability index have included small subsamples of whiplash participants, but none of them have studied the neck disability index in a sample of whiplash patients. It is also worthwhile to mention that while the neck disability index has shown acceptable psychometric properties in neck pain patients, its factorial structure has rarely been analyzed. Indeed, just 3 studies have addressed this issue, and shown inconsistent results. Hains et al found a unique factor for the original version of the neck disability index, which was later replicated with the Brazilian-Portuguese version of the neck disability index. More recently, however, Wlodyka-Demaille et al found a 2-factor structure for the French version of the neck disability index.

The main aim of our work was to study the psychometric properties of the neck disability index, including its factorial structure, in a sample of Catalan-speaking subacute whiplash patients, and its usefulness. Specifically, the study was designed to analyze the following psychometric properties of the neck disability index: (1) items properties, (2) factorial structure, (3) internal consistency, and (4) criterion-related validity.

The aim of this investigation was to study the usefulness of the neck disability index with subacute whiplash patients. Our work was designed to assess the psychometric properties of the neck disability index too, with a special emphasis in its factor structure. The results are in agreement with previous reports that showed that the neck disability index has good psychometric properties. Briefly said, the Catalan version of the neck disability index is a measure with robust psychometric properties, useful to assess disability in patients with subacute whiplash problems: (1) it is easily self-administered as it so has been supported by a very low rate of missing values, (2) individual items and total scores are normally distributed, (3) the internal consistency is good, and (4) the criterion-related validity has generously been supported too, by the correlations with the outcome variables (i.e., pain intensity, pain interference, and depression).

In relation to the factor structure of the neck disability index, our results are in agreement with Wlodyka-Demaille et al’s work, who also found a 2-factor structure. Specifically, they found that the items concerning personal care, lifting, concentration, work, driving, and recreation mainly loaded in a factor which they labeled as function and disability. The rest of the items, those referring to neck pain, reading, headache, and sleeping mainly loaded in a factor which they labeled as pain intensity. There are, however, 2 differences between the 2-factor structure reported in this study and the one found by Wlodyka-Demaille et al. First, Wlodyka-Demaille et al found that although item 6 (concentration) had loadings in both factors the highest loading was in the factor that they called function and disability. In our study, however, this item showed the highest loading on the other factor, the one which they called pain intensity. On the basis of our results, we have labeled the 2 factors in a slightly different way. Thus, the subscale originally referred to as pain intensity by Wlodyka-Demaille et al has been relabeled as pain and interference with cognitive functioning. This subscale besides the items that allude to neck pain and headache intensity, contains items that allude to the extent to which neck pain interferes with a person’s cognitive functioning (e.g., concentration and reading). The other factor that is almost equivalent to that labeled as function and disability by Wlodyka-Demaille et al, except for item 6, has been relabeled as functional disability. In this subscale, the items mainly refer to the extent to which neck pain influences on the performance of a person’s usual physical activities (e.g., work and lifting).

The second difference has to do with the correlation between the 2 factors. Wlodyka-Deamille et al used an orthogonal rotation procedure, so they did not allow the factors to correlate, whereas we have used an oblique rotation procedure and found, in fact, that the 2 factors are highly correlated.

Although our results showed that the Catalan version of the neck disability index is a useful instrument to assess disability in patients suffering from a subacute whiplash problem, further research is needed to determine the factor structure of the neck disability index. If future studies confirm this 2-factor structure, this could have clinical and research implications. That is, specialists could not only use the total neck disability index scores but also benefit from the 2 more specific scores of the subscales. The subscale scores would allow more concrete analyses, and explore specific relationships with potential relevant outcomes (e.g., pain intensity, quality of life). Similarly, additional works are warranted to analyze additional psychometric properties, that is, test-retest reliability and construct-related validity.

The neck disability index was developed to assess neck pain related disability, and several relevant components of whiplash injuries are left out of the scope and interest of this instrument (e.g., headache, shoulder pain, low back pain, dizziness). Moreover, important issues that have shown to be relevant in whiplash injuries (e.g., sleep, concentration, emotional impairments) are not targeted by the neck disability index. Thus, researchers and clinicians that would like to go beyond the boundary and scope conditions for which the neck disability index was created would have to use it within a comprehensive net of assessment instruments taping those additional levels and/or units of interest.

From: J Orthop Res. 2008 Sep;26(9):1283-8

Classic degenerative disc disease is a serious health problem worldwide, whose etiological basis mechanical stimulus, biochemical changes, or natural aging is poorly understood. Animal models are critical to the study of degenerative disc disease initiation and progression and for attempts to regulate, ameliorate, or eliminate it. The macaque represents a primate model with natural disc degeneration that might serve to advance the field; we aimed to provide radiographic (morphologic) and biomechanical evidence of natural disc degeneration in this model. A factorial study design was used to examine the relationship between the radiographic appearance of disc degeneration and its biomechanical consequences. Eighteen macaques of advanced age (22.3 +/- 0.9 years) had radiographs taken to assess the degree of thoracolumbar intervertebral disc degeneration using a standard atlas method. Each spine was harvested and dynamic biomechanical tests were performed. Advancing disc degeneration (degree of disc space narrowing and osteophytosis) was associated with increased stiffness, decreased energy absorption, and increased natural frequency of the intervertebral disc. These associations linking the dynamics of the intervertebral disc and its degree of degeneration are similar to those found in humans. Our results indicate the macaque model with morphologic and biomechanical efficacy could aid in understanding the progression of disc degeneration and in developing therapeutic strategies to prevent or inhibit its course.

From: Phys Ther. 2008 Aug 8; [Epub ahead of print]

Pain is currently evaluated with “subjective” methods (eg, patient self-report). This study aimed to test whether fatigue indexes are able to accurately discriminate between subjects with and subjects without low back pain. Sixty subjects separated into 2 groups-a group with low back pain (n=30) and a group without low back pain (n=0)-participated in this study. Electromyographic (EMG) and force data were obtained during a muscle fatigue test. The same test was repeated to monitor recovery. Linear regression analysis was used to obtain fatigue indexes. Subjects with pain produced significantly lower force values than those without pain. The use of fatigue indexes and force values permitted accurate classification in 89.5% of cases. The results confirm that subjects with pain show early myoelectrical manifestations of muscle fatigue and that EMG can be a useful tool in the evaluation of low back pain.

From: Man Ther. 2008 Aug 7; [Epub ahead of print]

Approximately 25% of all outpatient physical therapy visits consist of patients with symptoms involving the neck region. It has been found that nearly half of the individuals with neck pain will experience debilitating symptoms. Over a third of patients with neck pain will develop chronic symptoms lasting more than 6 months, and nearly a third who experience a first time onset of neck pain will continue to report continued healthcare utilization for their symptoms at a 10-year follow-up.

Physical therapists utilize a number of interventions in the management of neck pain including joint manipulation (non-thrust and thrust), exercises, massage, thermo-therapy or electrotherapy (American Physical Therapy Association, 2001). However, robust evidence to support the use of many of these therapeutic strategies for neck pain is lacking. The Philadelphia Panel Clinical Practice Guidelines concluded that many commonly used interventions for patients with neck pain lack sufficient evidence to justify their clinical use. Recently, evidence has begun to emerge for the use of manual procedures directed at the thoracic spine for patients with mechanical neck pain. Cleland et al. found that thoracic thrust manipulation results in immediate improvements in neck pain at rest as measured by the visual analogue scale, compared to patients receiving a placebo manipulation. Further, it has also been found that at short-term follow-up patients receiving thoracic manipulation exhibit superior outcomes to patients receiving non-thrust techniques.

The importance of investigating the effectiveness of thoracic spinal manipulation is necessary considering the fact that the thoracic spine is the region of the spine most often manipulated, despite the fact that more patients complain of neck pain. Further, decreased mobility in the thoracic spine has been shown to be related to the presence of neck pain symptoms, so it is possible that manipulation of the thoracic spine may alter the biomechanics of the cervical region and decrease mechanical stress. Finally, it has previously been identified that either cervical mobilization or manipulation induces an activation of descending inhibitory mechanisms; hence, thoracic spine thrust manipulations may also result in a reduction of neck symptoms.

It should be noted that the aforementioned studies solely investigated the effects of thoracic thrust manipulation (with the exception of one study which used range of motion exercise). More often physical therapists use a multi-modal treatment approach (exercise, manual therapy, electrotherapy, etc.) in the management of neck pain which may include thrust techniques directed at the thoracic spine. To date only one study has investigated the effects of thoracic spine manipulation incorporated into a physical therapy management program. Fernandez-de-las-Peñas et al. reported that patients with whiplash-associated disorders receiving thoracic thrust manipulation as a component of a physical therapy program experienced a greater reduction in symptoms than subjects whose physical therapy did not include manipulation. To date no studies have explicitly investigated the effects of thoracic manipulation when it is added to a program including electrotherapy and thermal agents in patients with mechanical neck pain.

Hence, the purpose of this study was to examine the effects of a seated thoracic distraction manipulation when added to a program including electrotherapy and thermal modalities on neck pain, disability, and cervical mobility.

Forty-five patients, 20 males and 25 females, between 23 and 44 years of age with acute mechanical neck pain referred by their primary care physician to a physical therapy clinic participated in this study. For the purpose of this study mechanical neck pain was defined as generalized neck or shoulder pain with mechanical characteristics (including symptoms provoked by neck postures, neck movement, or palpation of the cervical musculature) of less than 1month in duration. Exclusion criteria included the following: (1) contra-indication to manipulation; (2) history of whiplash or cervical surgery; (3) diagnosis of cervical radiculopathy or myelopathy; (4) diagnosis of fibromyalgia syndrome; (5) having undergone spinal manipulative therapy in the previous 2months; or (6) less than 18 or greater than 45 years of age.

Chiu et al. found that the application of transcutaneous electrical nerve stimulation with a TENS unit combined with other physical approaches was effective for improving neck muscle strength, neck pain and perceived disability. In the present study, the standardized program included the application of superficial thermal therapy and electrotherapy as follows: an infrared lamp, located 50cm distant from the patient’s neck, was applied for 15 min. After superficial thermal therapy, TENS with a frequency of 100Hz and 250ms stimulation was applied for 20 min using two 4×6cm electrodes placed bilaterally to the spinous process of C7 vertebra.

The results of our study demonstrated that patients with acute mechanical neck pain receiving an electrotherapy/thermal program plus thoracic thrust manipulation experienced a significantly greater reduction in pain and disability as well as an increase in cervical mobility compared to a group that received electrotherapy and thermal only. The effect sizes were large for all of the dependent variables assessed in favour of the thoracic spine thrust manipulation group. Additionally, it should be noted that between-group differences for pain achieved by the thoracic spine thrust manipulation group was not only statistically significant but also clinically meaningful as it exceeded the minimum clinically important difference (MCID) on the NPRS, identified as 2 points. Although the MCID for the NPQ has not been reported, within-group improvements were significantly greater for subjects in the experimental group.

The current results further substantiate the findings of previous studies, all of which demonstrated that thoracic thrust manipulation resulted in changes in pain, disability and cervical mobility in different populations of patients with neck pain. While the effect sizes in this study were large, they could have potentially been greater if the inclusion criteria had included a specific subgroup of patients who are likely to exhibit a rapid and dramatic improvement from thoracic manipulation. Cleland et al. recently developed a clinical prediction rule with 6 variables from patients with mechanical neck pain. This study identified 6 predictor variables (symptom duration less than 30 days, no symptoms distal to the shoulder, looking up does not aggravate symptoms, Fear-Avoidance Beliefs Physical Activity subscale score less than 12, decreased upper thoracic spine kyphosis (T3–T5), and cervical extension less than 30 degrees). If 3 of the 6 variables were present, the probability of experiencing a successful outcome improved from 54% to 86%. In the present study, patients with acute (less than 30 days) neck pain were included, so our patients presented with at least 1 of the predictors identified by Cleland et al.

The physiological mechanism associated with the benefits of thrust manipulation is beyond the scope of the present study and remains to be fully elucidated. Further, both biomechanical and neuro-physiological (either segmental or central) mechanisms have been suggested. For instance, the biomechanical link between the cervico-thoracic spine and neck pain described by Norlander et al. may be one reason why thoracic spine manipulation is beneficial for patients with neck pain. It is also possible that spinal manipulative therapy has inherent qualities that can alter the biomechanics of the treated region (thoracic spine), and it is likely that those segments are bio-mechanically related to the cervical region. One mechanism could be that the manipulative procedure may induce a reflex inhibition of pain or reflex muscle relaxation by modifying the discharge of proprioceptive group I and II afferents. It is also plausible that thrust manipulation decreases pain and spasm while increasing mobility through changes in muscle electrical activity; reduced muscle spasm or increased inter-segmental joint play subsequent to a spinal manipulation. Further, mechanical stimulus induced by the manipulative procedure may also alter concentrations of inflammatory mediators, or trigger segmental inhibitory mechanisms. Finally, activation of descending inhibitory pathways may explain the decreased cervical symptoms after the application of a manipulation in another region. Nevertheless, it seems that more than 1 mechanism likely explains the effects of spinal manipulative therapy, and there is insufficient evidence to claim a major role for either peripheral or central mechanisms. Future research is clearly necessary to determine if mechanisms by which manipulation exerts its effects are either mechanical or neuro-physiologic or both.

We found that the inclusion of thoracic manipulation combined with a standard electrotherapy/thermal program results in significantly greater reductions in neck pain and disability as well as increases in neck mobility in the short-term in patients with acute mechanical neck pain. Our findings suggest that when treating young adults with acute mechanical neck pain clinicians should consider the findings of this trial in their decision-making. Future studies are needed to investigate the long-term effects of thoracic spine thrust manipulation in patients with neck pain.

From: Eur J Pain. 2008 Aug 7; [Epub ahead of print]

Chronic neck pain is a common complaint in the Netherlands with a point prevalence of 14.3%. Patients with chronic neck pain are often referred to physiotherapy and, nowadays, are mostly treated with exercise therapy. It is, however, unclear which type of exercise therapy is to be preferred. Therefore, this study evaluates the effectiveness of behaviour graded activity compared with conventional neck exercises for patients with chronic neck pain. Eligible patients with non-specific chronic neck were randomly allocated to either behaviour graded activity or conventional neck exercises. Primary treatment outcome is the patient’s global perceived effect concerning recovery from complaint and daily functioning. Outcome assessment was performed at baseline, and at 4, 9, 26, and 52 weeks after randomization. Effectiveness was examined with general estimating equations analyses. Baseline demographics and patient characteristics were well balanced between the two groups. Mean age was 45.7 years and the median duration of complaints was 60 months. The mean number of treatments was 6.6 in behaviour graded activity and 11.2 in conventional neck exercises.

No significant differences between treatments were found in their effectiveness of managing patients with chronic neck pain. In both behaviour graded activity and conventional neck exercises some patients reported recovery from complaints and daily function but the proportion of recovered patients did not exceed 50% during the 12-month follow-up period. Both groups showed clinically relevant improvements in physical secondary outcomes.