The pathogenesis of discogenic low back pain
From: J Bone Joint Surg Br. 2005 Jan;87(1):62-7.
Discogenic low back pain is a common cause of disability, but its pathogenesis is poorly understood. We collected 19 specimens of lumbar intervertebral discs from 17 patients with discogenic low back pain during posterior lumbar interbody fusion, 12 from physiologically ageing discs and ten from normal control discs. We investigated the histological features and assessed the immunoreactive activity of neurofilament and neuropeptides such as substance P and vasoactive-intestinal peptide in the nerve fibres. The distinct histological characteristic of the painful disc was the formation of a zone of vascularised granulation tissue from the nucleus pulposus to the outer part of the annulus fibrosus along the edges of the fissures. Substance P, neurofilament and vasoactive-intestinal peptide immunoreactive nerve fibres in the painful discs were more extensive than in the control discs. Growth of nerves deep into the annulus fibrosus and nucleus pulposus was observed mainly along the zone of granulation tissue in the painful discs. This suggests that the zone of granulation tissue with extensive innervation along the tears in the posterior part of the painful disc may be responsible for causing the pain of discography and of discogenic low back pain.
Intensive group training protocol versus guideline physiotherapy for patients with chronic low back pain: a randomised controlled trial
From: Eur Spine J. 2008 Jul 29; [Epub ahead of print]
Intensive group training using principles of graded activity has been proven to be effective in occupational care for workers with chronic low back pain. Objective of the study was to compare the effects of an intensive group training protocol aimed at returning to normal daily activities and guideline physiotherapy for primary care patients with non-specific chronic low back pain. The study was designed as pragmatic randomised controlled trial with a setup of 105 primary care physiotherapists in 49 practices and 114 patients with non-specific low back pain of more than 12 weeks duration participated in the study. In the intensive group training protocol exercise therapy, back school and operant-conditioning behavioural principles are combined. Patients were treated during 10 individual sessions along 20 group sessions. Usual care consisted of physiotherapy according to the Dutch guidelines for Low Back Pain. Main outcome measures were functional disability (Roland Morris disability questionnaire), pain intensity, perceived recovery and sick leave because of low back pain assessed at baseline and after 6, 13, 26 and 52 weeks. Both an intention-to-treat analysis and a per-protocol analysis were performed. Multilevel analysis did not show significant differences between both treatment groups on any outcome measures during the complete follow-up period, with one exception. After 26 weeks the protocol group showed more reduction in pain intensity than the guideline group, but this difference was absent after 52 weeks. We finally conclude that an intensive group training protocol was not more effective than usual physiotherapy for chronic low back pain.
Performance of the Craniocervical Flexion Test in Subjects With and Without Chronic Neck Pain
From: J Orthop Sports Phys Ther. 2007;35(9):567-571. Epub 2007 Feb 5
To compare the performance of the deep cervical flexor muscles on the craniocervical flexion test in individuals with and without neck pain. Significant weakness of the superficial neck muscles is often found in patients with neck pain. However, there is scant work on deep cervical flexors performance in subjects with chronic nonspecific neck pain. Twenty asymptomatic subjects and 20 subjects with chronic neck pain (duration, >3 months) were recruited. The craniocervical flexion test was performed with the subject supine and required performing a gentle head-nodding action of craniocervical flexion (indicating yes) for 5 incremental stages of increasing difficulty. Each stage was held for 10 seconds, as guided by the pressure biofeedback unit. The data used for analysis were the highest pressure level each subject was able to hold for 10 seconds, up to a maximum of 30 mmHg.
Reliability data obtained on 10 asymptomatic subjects indicated that the craniocervical flexion test was reliable, with a kappa coefficient equal to 0.72.
Subjects with chronic neck pain had significantly poorer performance on the craniocervical flexion test (median pressure achieved, 24 mmHg) when compared with those in the asymptomatic group (median pressure achieved, 28 mmHg). The results of this study demonstrated that patients with chronic neck pain had a poorer ability to perform the craniocervical flexion test when compared with asymptomatic subjects. The study adds to the evidence that poor ability to perform the craniocervical flexion test may be clinical evidence of an impairment that characterizes neck pain, regardless of origin.
Heritability of neck pain: a population-based study of 33,794 Danish twins
From: Rheumatology (Oxford). 2006 May;45(5):589-94. Epub 2005 Dec 6
Neck pain is very common in Western countries, where more than one in two adults have had neck pain during their lifetime. Neck pain is a great socio-economic burden in terms of sick leave, disability and workers’ compensation benefits, and it is therefore important to study what causes neck pain in order to identify possible preventive measures. Studies on the aetiology of neck pain have largely focused on occupational and psychosocial risk factors. Also, comorbidities and a previous history of neck injury have been associated with neck pain, but much confusion exists regarding the true causes of this very common symptom.
Recently, a few studies have focused on whether genes play a role in relation to neck pain. Sambrook et al. found an important genetic influence in degenerative changes of the cervical intervertebral discs based on MRI. However, in women such changes are probably not associated with neck pain. In a recent study, MacGregor et al. showed a genetic influence on neck pain in women. Unfortunately, the analysis was based on a non-population-based sample of volunteer twins and is therefore probably subject to selection bias. Hartvigsen et al. studied neck pain in Danish twins aged 70 and older, and found that genes play only a minor role in the liability to neck pain in seniors. However, these results cannot be extrapolated to a younger twin cohort and so the heritability of neck pain in a population of young and middle-aged twins remains to be investigated.
The aim of this study was to determine the genetic and environmental contributions to neck pain in men and women aged between 20 and 71 yr. Population-based twin registries offer a valuable tool for investigating the effect of genes and environment in complex diseases such as neck pain. This paper will therefore add to the understanding of the aetiology of neck pain.
Risk factors for neck pain: a longitudinal study in the general population
From: Pain. 2001 Sep;93(3):317-25
The objective of the study was to examine the 1-year cumulative incidence of episodic neck pain and to explore its associations with individual risk factors, including a history of previous neck injury. A baseline cross-sectional survey of an adult general population sample made up of all 7669 adults aged 18-75 years, registered with two family practices in South Manchester, United Kingdom, identified the study population of adults with no current neck pain. This study population was surveyed again 12 months later to identify all those who had experienced neck pain during the follow-up period. At follow-up, cumulative 1-year episode incidence of neck pain was estimated at 17.9% (95% confidence interval 16.0-19.7%). Incidence was independent of age, but was more common in women.
A history of previous neck injury at baseline was a significant risk factor for subsequent neck pain in the follow-up year, independent of gender and psychological status. Other independent baseline risk factors for subsequent neck pain included number of children, poor self-assessed health, poor psychological status and a past history of low back pain. We have carried out a prospective study in a general population sample and demonstrated that established risk factors for chronic pain predict future episodes of neck pain, and shown that in addition a history of neck injury is an independent and distinct risk factor. This finding may have major public health and medicolegal implications.
Electromyographic analysis of neck muscle fatigue in patients with osteoarthritis of the cervical spine
From: Spine. 1994 Mar 1;19(5):502-6
Median frequency parameters of myoelectric signals were studied in 25 patients with osteoarthritis of the cervical spine and in 25 normal subjects. The median frequency parameters included initial median frequency and slope of the median frequency during 20%, 50%, 80%, and 100% of maximum voluntary contractions. The subjects performed sustained, isometric constant-force contractions of forward and backward bend of the cervical spine. The median frequency signals were obtained from the anterior (sternocleidomastoid) and posterior (upper trapezius) neck muscles. The results showed that at moderate and high forces (i.e., 50%, 80%, and 100% maximum voluntary contractions ) the anterior neck muscles in patients with osteoarthritis of the cervical spine fatigued faster than those of normal subjects. The posterior neck muscles in patients fatigued faster compared to normal subjects at high force levels (i.e., 80% and 100% maximum voluntary contractions ). This indicates a higher fatigue of the anterior and posterior neck muscles associated with arthritic changes of the cervical spine. Rehabilitation programs must consider these muscular changes to obtain optimal outcomes.
Prognosis in patients with recent onset low back pain in Australian primary care
From: BMJ 2008;337:a171
In this study of patients with acute low back pain in primary care, prognosis was not as favourable as claimed in clinical practice guidelines. Recovery was slow for most patients. Nearly a third of patients did not recover from the presenting episode within a year.
There is evidence that the type of advice given to patients can alter the course of an episode of low back pain. For this reason, most management guidelines recommend that patients should be reassured that they have a favourable prognosis. This recommendation is commonly supported with the statement that 90% of patients recover within six weeks. Such statements, however, might be too optimistic. While patients typically improve rapidly, the risk of developing chronic low back pain (that is, pain persisting for more than three months) is uncertain. Estimates of this risk vary from 2% to 56%.
To provide individualised advice, it is also necessary to consider prognostic factors. All guidelines for low back pain recommend identification of adverse prognostic factors, commonly described as “yellow flags.” Examples of yellow flags include fear of re-injury, leg pain, or low job satisfaction. While all guidelines endorse screening for prognostic factors, there is considerable uncertainty regarding the choice of these factors and their predictive value.
MRI follow-up of subchondral signal abnormalities in a selected group of chronic low back pain patients
From: Eur Spine J. 2008 Jul 22; [Epub ahead of print]
Subchondral signal abnormalities have been suggested to play an important role in chronic low back pain syndromes. Their natural course is not well known. In this study the morphology and natural course of isolated subchondral signal abnormalities in the lumbosacral spine were analyzed with MRI. Twenty-four chronic low back pain patients with a subchondral hypointensity on T1-weighted image (hyperintense on T2), indicating edema, were selected from a base population of 1,015 consecutive low back pain patients to a follow-up MRI study within 18-72 months. Exclusion criteria were age >60 years, nerve root compression, a more specific back disease or a recent or major spine operation. The size and location of each subchondral signal abnormality and endplate lesion and the degree of degenerative disc changes were evaluated and compared between the baseline and follow-up studies. Most subchondral hypointensities were found at the L4/L5 or L5/S1 disc space, anteriorly and in both adjacent endplates. Almost all (53/54) hypointensities were associated with an endplate lesion. Twelve of the 54 subchondral hypointensities enlarged, six remained constant and 36 decreased or disappeared while five new ones appeared. Twenty-two (41%) hypointensities changed totally to hyperintensities or to mixed lesions. If the hypointensity increased, decreased or changed into hyperintensity, a change tended to develop in the adjacent endplate. If the hypointensity was absent or unchanged, endplate lesions did not tend to progress. In the absence of disc herniation or other specific spinal disease, subchondral hypointensities indicating edema are uncommon. They seem to have a highly variable course. There appears to be a link between endplate lesions and subchondral signal abnormalities. Further study is needed to explain the contribution of these findings to low back symptoms.
Mechanical traction for neck pain with or without radiculopathy
From: Cochrane Database Syst Rev. 2008 Jul 16;(3):CD006408
Neck pain is a frequently reported complaint of the musculoskeletal system which can be disabling and costly to society. Mechanical traction is often used as an adjunct therapy in outpatient rehabilitation. To assess the effects of mechanical traction for neck disorders, a research librarian searched computerized bibliographic databases without language restrictions up to March 2008 for randomized controlled trials from the medical, chiropractic, and allied health literature. The randomized controlled trials we selected examined adults with neck disorders who received mechanical traction alone or in combination with other treatments compared to a placebo or another treatment. Our outcomes of interest were pain, function, disability, global perceived effect, patient satisfaction, and quality of life measures. Two review authors with different backgrounds in medicine, physiotherapy, massage therapy and chiropractics independently conducted study selection, risk of bias assessment and data abstraction using pre-piloted forms. We resolved disagreement through consensus.
Of the seven selected randomized controlled trials (total participants = 958), only one (N = 100) had a low risk of bias. It found no statistically significant difference between continuous traction and placebo traction in reducing pain or improving function for chronic neck disorders with radicular symptoms. Our review found no evidence from randomized controlled trials with a low potential for bias that clearly supports or refutes the use of either continuous or intermittent traction for neck disorders. The current literature does not support or refute the efficacy or effectiveness of continuous or intermittent traction for pain reduction, improved function or global perceived effect when compared to placebo traction, tablet or heat or other conservative treatments in patients with chronic neck disorders. Large, well conducted randomized controlled trials are needed to first determine the efficacy of traction, then the effectiveness, for individuals with neck disorders with radicular symptoms.
The fear avoidance model in whiplash injuries
From: Eur J Pain. 2008 Jul 18; [Epub ahead of print]
The aim of this work was to study whether fear of movement, and pain catastrophizing predict pain related disability and depression in subacute whiplash patients. Moreover, we wanted to test if fear of movement is a mediator in the relation between catastrophizing and pain related disability and/or depression as has been suggested by the fear avoidance model. Fear of movement and/or re-injury in chronic low back pain and its relation to behavioral performance. Pain 1995;62:363-72]. The convenience sample used was of 147 subacute whiplash patients (pain duration less than 3 months). Two stepwise regression analyses were performed using fear of movement and catastrophizing as the independent variables, and disability and depression as the dependent variables. After controlling for descriptive variables and pain characteristics, catastrophizing and fear of movement were found to be predictors of disability and depression. Pain intensity was a predictor of disability but not of depression. The mediation effect of fear of movement in the relationships between catastrophizing and disability, and between catastrophizing and depression was also supported. The results of this study are in accordance with the fear avoidance model, and support a biopsychosocial perspective for whiplash disorders.