From: Curr Rheumatol Rep. 2009 Dec;11(6):433-436

Chronic widespread pain is very prevalent in the general population (5%-10%) and is characterized by pain in all four body quadrants, the neck, and back. Chronic widespread pain differs from localized pain not only in its distribution but also in the way it affects lives. Multiple pain sites are associated with higher pain intensity, longer pain duration, and greater disability. Anxiety and depression are more common in chronic widespread pain patients than among those with localized pain and pain-free controls. Fibromyalgia has been classified as chronic widespread pain of more than a 3 month duration, with mechanical hyperalgesia at greater than or equal to 11 tender point sites. Fibromyalgia has been found in 2% to 4% of community subjects and represents the extreme of chronic widespread pain. This article compares pain characteristics, quality of life, consequences for daily living, and psychosocial status between fibromyalgia patients and individuals with chronic widespread pain. Available evidence shows that fibromyalgia is associated with more severe symptoms and consequences for daily life and higher pain severity compared with chronic widespread pain.

Tags: chronic, widespread, pain,, localized, pain,, fibromyalgia

From: Yonsei Med J. 2009 Oct 31;50(5):624-9

Facet tropism is defined as asymmetry in both the facet joint angles of the lumbar and lumbosacral regions. For many years, the effect of facet tropism on the development of intervertebral disc degeneration has been debated. However, the specific details regarding the effects of facet tropism on the development of degenerative disc disease remains as the subject of debate. Most of the previous facet tropism studies have focused on the relationship between facet tropism and lumbar disc herniation.

The role of facet tropism in the pathogenesis of lumbar degenerative disc disease is not fully understood Currently, controversy exists surrounding the question of whether or not any significant relationship exists between facet tropism and the development of disc or facet joint degeneration. Additionally, the relationship between facet tropism and degenerative spondylolisthesis and translational segmental motion is highly controversial.

In the current study, the authors attempted to evaluate the effect of facet tropism on disc and facet joint degeneration. Additionally, the relationship between facet tropism and changes in translational segmental motion was investigated.

Facet tropism is defined as asymmetry between the left and right facet joint angles of the lumbar spine. Asymmetry in the orientation of the zygapophyseal joint surfaces is not uncommon, with estimates of its occurrence at 10-70.5% of the population. Our study revealed an incidence of facet tropism in 35% of the spinal units which were taken into consideration. Facet tropism is most common at L5-S1, followed by L4-L5.

The criteria for determining facet tropism have varied greatly, although the actual definition of facet tropism is asymmetry between the right and left facet joints. In the lumbar spine, the majority of facet joints vary by less than 7° in orientation between the two sides. Noren et al. defined facet asymmetry as a bilateral angle difference greater than 5°. In other biomechanical studies, facet asymmetry was defined as a difference in facet angles greater than 1-10° or one SD. Grogan, et al. divided facet joint tropism into three distinct classifications. When the orientation differed from one side to another by more than 7°, the facet joints at that level were defined as having tropism. Moderate tropism was defined as a difference of 7° to 15° between the orientation of the joints (one SD from the mean difference) and severe tropism was defined as a difference of more than 15° (two SDs from the mean) between the two sides. For the current study, the authors defined facet tropism to be bilateral angular asymmetry greater than 7°.

The angular difference inherent to facet joint tropism causes biomechanical issues. By definition, facet joint degeneration exists when one joint has more coronal orientation than the other. Farfan and Sullivan emphasized the importance of coronally facing facet joints upon the development of lumbar disc herniations. Coronally facing facet joints offer little resistance to shear intervertebral force, so that the joints tend to rotate toward the side of the more coronary facing facet joint, possibly leading to additional rotational stress on the annulus fibrosus. Loback, et al. showed that facet joint asymmetry is found more likely on the side of the coronally facing facet joint. When tropism was present, the motion segment was found to have a tendency to rotate towards the more oblique joint when axial loads were applied. This asymmetric axial rotation caused by tropism can place additional torsional loads on the intervertebral discs which can lead to intervertebral disc injury and degeneration. This biomechanical mechanism was used to describe the development of lumbar disc herniation, disc degeneration, and degenerative spondylolisthesis associated with facet tropism. Some studies have claimed that lumbar facet joint tropism does not accelerate degeneration of the facet joints. For the current study, the authors chose to investigate facet tropism and some of the findings associated with lumbar degenerative disc disease, including disc degeneration, facet joint degeneration, and spondylolisthesis (translational segmental motion).

The role of facet tropism in the pathogenesis of disc degeneration is a contested issue. Boden, et al. and Vanharanta, et al. reported no significant correlation between facet tropism and disc degeneration. However, Noren, et al. concluded that the existence of facet tropism can increase the risk of disc degeneration. Additionally, Dai reported that a significant correlation existed between facet joint tropism and the degree of disc degeneration in patients with degenerative spondylolisthesis. In the present study, no significant correlation was observed between facet joint tropism and disc degeneration at L3-L4, L4-L5, or L5-S1. However, a higher (but not statistically significant) incidence of highly degenerated discs at L4-L5 was observed within the facet tropism group.

Grogan, et al. concluded that lumbar facet joint tropism does not accelerate facet joint degeneration. They reported no significant differences in facet joint degeneration between facet joints with and without tropism. However, there are many limitations associated with this study. It was based on a small number of specimens (21 cadavers) and an even smaller number of lumbar facet joints exhibiting facet tropism (10 out of 104 lumbar facet joints). Additionally, this study did not take the level, where the tropism occurred, into consideration. Our current study included L3-L4, L4-L5, and L5-S1 facet joints belonging to 300 living participants and our findings were found to be similar to Grogan et al.’s at L3-L4 and L5-S1. However, at L4-L5, a significant correlation between facet joint tropism and facet joint degeneration was observed. Based on the fact that L4-L5 experiences the most segmental flexion and extension within the lower lumbar spine, this result suggests that the existence of facet tropism within highly mobile lumbar segments could affect the development of facet joint degeneration.

Berlemann, et al. reported that facet joint asymmetry does not seem to play a major role in the development of degenerative spondylolisthesis. However, Dai found that facet joint tropism was a predisposing factor for the development of degenerative spondylolisthesis. The present study found no association between facet tropism and translational segmental motion (such as vertebral slippage) within the lumbar spine. Our results indicate that facet tropism has no major association with the development of degenerative spondylolisthesis.

Previous reports have shown that facet orientation has a significant association with degenerative spondylolisthesis. Additionally, some of these studies reported that, in patients with degenerative spondylolisthesis, the transverse plane of facet joints was more sagittally oriented. All of these studies found that individuals with larger facetjoint angles, relative to the coronal plane (more sagittal orientation of facet joint), exhibited a higher incidence of degenerative spondylolisthesis. Although facet orientation was not taken into consideration for this study, the authors believe that it is an important element for understanding all of the factors that lead to the development of spondylolisthesis, and that this topic should be investigated further.

Another interesting factor to take into consideration is the existence of facet joint tropism within normal spines. This raises questions as to the root causality of facet joint tropism. Facet joint tropism could be caused by an inborn characteristic of the human spine, as a result of mechanical stresses on the spine (i.e., asymmetric loading of the human spine) or as a consequence of existing spinal deformities (i.e., scoliosis). Noren, et al. documented that subjects with lumbar degenerative disc disease had a higher incidence of facet joint tropism than the normal population. The nature of the relationship between facet joint tropism and degenerative changes within the lumbar spine remains a controversial topic. Essentially, there are two sides to this debate, one advocating that facet tropism leads to degeneration and the other claiming that certain degenerative statuses (i.e., degenerative spondylolisthesis) lead to facet tropism. Our results show that, at active functional spine units, facet tropism partially influences the development of facet joint degeneration. This seems to give legitimacy to the theory that facet tropism can lead to facet joint degeneration, although further investigation into the relationship between facet tropism and facet joint degeneration is necessary.

From: Spine (Phila Pa 1976). 2009 Oct 16

The effect of postural change on degenerative lumbar discs was quantified using novel kinematic magnetic resonance imaging. The purpose is to describe the bulging of degenerative intervertebral lumbar discs in vivo subjected to different postural loads using a novel kinematic magnetic resonance imaging.

Symptomatic lumbar disc degeneration is a leading cause of pain and disability throughout the world. Over 70% of US citizens will experience a debilitating episode of low back pain. Earlier reports of degenerative disc changes are cadaver studies or are performed with recumbent MRI that eliminates the functional effects of gravity and muscle power. Little data are available on the behavior of degenerative intervertebral discs in vivo under physiologic loads.

A total of 513 patients obtained kMRI. Disc bulging beyond the intervertebral space was quantified during upright neutral, flexion, and extension imaging. The degree of intervertebral disc degeneration was correlated using the Pfirrmann Classification. Moderately degenerated intervertebral discs (grade III and IV) demonstrated greater bulging than mildly degenerated discs (grade II). Severely degenerated discs (grade V) also showed a trend toward greater bulging, but this was not significant. Grade I discs at all levels moved posteriorly in flexion and anteriorly in extension when compared to neutral posture. However, mild to severe (grade II-V) degenerative discs behaved differently in response to postural loads. Extension resulted in significant posterior bulging, while flexion did not demonstrate obvious anterior derangement.

Disc bulging increases with the severity of disc degeneration. Grade I discs demonstrate the expected sagittal migration in response to postural load. However, more degenerative discs behave less predictably, and spine extension may result in significant posterior disc bulging. Degenerative changes in the intervertebral disc significantly affect the kinematic patterns under postural load in vivo. Kinematic magnetic resonance imaging is a useful tool to quantify the kinematic behavior of degenerative intervertertebral discs.

Tags: degenerative, lumbar, discs,, symptomatic, lumbar, disc, degeneration,, postural, load

From: Clin Invest Med. 2009 Oct 1;32(5):E360-7

Chronic low back pain is one of the main causes of disability in the community. Although there have been studies suggesting an association between smoking and chronic low back pain, these studies were limited by the small numbers of patients, and they did not control for confounders. The objective of this study was to determine whether cigarette smoking is associated with an increased risk of chronic low back pain among adults.

Using Canadian Community Health Survey (cycle 3.1) data, 73,507 Canadians aged 20 to 59 yr were identified. Self-reported chronic low back pain status, smoking habits, sex, age, height, weight, level of activity and level of education were identified as well. Back pain secondary to fibromyalgia was excluded. Multivariate logistic regression analysis was used to detect effect modification and to adjust for covariates. Design effects associated with complex survey design were taken into consideration.

The prevalence of chronic low back pain was 23.3% in daily smokers and only 15.7% in non smokers. Age and sex were found to be effect modifiers, and the relationship between smoking and chronic low back pain risk was dependent on sex and age. The association between daily smoking and the risk of chronic low back pain was stronger among younger individuals. Occasional smoking slightly increased the odds of having chronic low back pain.

Daily smoking increases the risk of chronic low back pain among young adults, and this effect seems to be dose dependent. Back pain treatment programs may benefit from integrating smoking habit modification. Further research is required to develop effective prevention strategies.

From: Spine (Phila Pa 1976). 2009 Sep 14

An in vivo study of the effects of mechanical loading on transport of small solutes into normal human lumbar intervertebral discs using serial postcontrast magnetic resonance imaging (MRI) to investigate the influence of a sustained mechanical load on diffusion of small solutes in and out of the normal intervertebral disc.

Diffusion is an important source of disc nutrition and the in vivo effects of load on diffusion in human intervertebral disc remains unknown. Forty normal lumbar discs (on MRI) in 8 healthy volunteers were subjected to serial post contrast (Gadoteridol) 3 Tesla MRI in 2 phases. In phase 1 (control), volunteers were scanned at different time points – precontrast and 1.5, 3, 4.5, 6, and 7.5 hours postcontrast injection. In phase 2, 1 month later, the same volunteers were subjected to sustained supine loading for 4.5 hours. MRI scans were performed precontrast (preload) and postcontrast (postloading) at 1.5, 3, and 4.5 hours. Their spines were then unloaded and recovery scans performed at 6 and 7.5 hours postcontrast. In house software was used to analyze images.

Repeated-measures ANOVA and pairwise comparisons at different time points in the central region of the loaded disc compared to the unloaded discs revealed significantly lower signal intensity ratios indicating reduction in transport rates for the loaded discs. Signal intensity ratioscontinued to rise in loaded disc for 3 hours into recovery phase, whereas unloaded discs at the same time point showed a decrease.

Sustained supine creep loading (50% body weight) for 4.5 hours retards transport of small solutes into the center of human IVD and it required 3 hours of accelerated diffusion in recovery state for loaded disc to catch-up with diffusion in unloaded discs. The study supports the theory that sustained mechanical loading impairs diffusion of nutrients entering the disc and quite possibly accelerates disc degeneration.

From: J Manipulative Physiol Ther. 2009 Sep;32(7):521-6

Low back pain is one of the leading causes of disability, contributing to 40% of all workdays lost in the United States of America. Because of the cost associated with work-related low back pain disabilities, most published studies have focused on the working-aged population. However, back pain and neck pain are also common musculoskeletal disorders affecting, each month, approximately one third of adults older than 70 years. The annual prevalence of chronic low back pain ranges from 44% to 84% in adults older than 65 years. In Canada, chronic low back pain is the third and fourth most important chronic health problem in women and men, respectively, older than 65 years. Women with severe chronic low back pain are 3 to 4 times more likely than other women to have difficulty with light housework tasks and 2 times more likely to encounter problems with mobility tasks, such as climbing stairs, walking, or lifting. In Canada, it is estimated that approximately 25% of the population will be older than 65 years by 2031. Anticipating the growing impact of the ageing population, a better understanding of chronic low back pain’s impact on physical capabilities in elderly people is important.

In working aged adults, chronic low back pain has been associated with increased fatigability of the lumbopelvic extensor muscles, as demonstrated by shorter back endurance test duration. In all back endurance protocols reported in the literature, isometric testing procedures with the trunk positioned in a weight-dependent position, such as the Sorensen test, may be most suitable in clinical settings. Weight dependent position tests of muscle endurance are cost-effective, easy to perform in a clinical context, and require no special equipment. The Sorensen test is conducted with subjects lying prone, the upper body unsupported in a horizontal position relative to the ground, and the lower limbs fixed by straps. This procedure has been found to be a reliable measure of position-holding time and can discriminate between subjects with and without low back pain.

Ageing has been related to changes in the neuromuscular system. Among these changes, loss of muscle force generation capacity, a slower firing rate of motor units, and a reduction in motor unit and muscle fiber number have been observed. Together with the loss of muscle fibers, a selective decrease in fast twitch fibers has been demonstrated with advancing age, leading to alteration of muscle fiber type proportion. This shift in fiber-type proportion appears to contribute to changes in muscle fatigability in healthy elderly individuals.

Very few studies have assessed back muscle endurance in elderly subjects. The current investigation aims to evaluate back extensor muscle fatigability in healthy elderly adults by quantifying endurance time during a clinical isometric back endurance test and the posttest decrease of lumbopelvic extensor maximal force. We hypothesized that elderly subjects will experience greater fatigability of lumbopelvic extensor muscles than young subjects.

The endurance time of back extensor muscles has become an important outcome in clinical decision making to guide exercise therapy interventions, particularly in chronic low back pain patients. Indeed, reduced back muscle endurance has been identified as a potential personal risk factor for developing low back pain. However, identifying endurance deficits requires normative values and an understanding of related psychophysical mechanisms. Very few databases on back muscle endurance time in elderly subjects are available. Furthermore, there is very limited information regarding the psychophysical aspects of performance during isometric back extensor testing in young adults and the elderly.

The experimental data provided in this study support the Sorensen test to evaluate back and hip extensor muscle endurance in elderly subjects. All the elderly participants in our study were able to perform the Sorensen test until exhaustion. One could consider that they had not achieved their endurance time limit to exhaustion because they may have underestimated their physical capabilities or have altered perceptive physical exertion. We tried to account for this with other measures, such as force reduction occurring with fatigue and effort perception on the Borg scale. Force was decreased after prolonged exertion and was an indicator of muscle fatigue. Both the elderly and young adult groups presented a significant decline of maximal isometric lifting force values after the Sorensen protocol. In addition, our results demonstrated that the amount of postfatigue reduction of isometric lifting force was similar between young adults and elderly subjects. The perceived exertion during the Sorensen test increased similarly in the elderly subjects and young adults, and we did not find any difference in Borg scores during the Sorenson test. All these results support the hypothesis that the elderly subjects achieved their endurance time limit during the Sorensen test.

The authors initially hypothesized that lumbopelvic extensor muscle endurance in the elderly subjects would be decreased during the weight-dependent isometric test due to age-associated muscle strength reduction. Although strength diminution was observed with age, we did not see a significant age effect on performance during the Sorensen test. McGill et al argued that age could impact the endurance time of torso muscles. Indeed, this study sample was composed of community-dwelling, nonsymptomatic, physically active elderly subjects that could have contributed to decrease the between-group difference. Maximal isometric lifting force was associated with back extensor endurance time in the young subjects, but no such relationship was clearly established for the elderly study participants. Thus, factors other than back muscle strength may have modulated endurance time for the elderly subjects during the fatiguing protocol in our study. Yassierli et al also found lower correlations between torso extension torque and back endurance time in elderly subjects compared to young adults, using a dynamometer in an upright position. Age-related adaptations, such as decreased muscle mass and increased type I muscle fiber proportion in elderly subjects, may limit maximal force-generation capacity in elderly subjects. These neurophysiologic factors may cause a reduction of the force-endurance relationship. In the study by Yassierli et al, back extension torque explained 74% to 78% and 46% to 63% of the endurance time variance in young and elderly subjects, respectively. In the present investigation, much lower correlation values between maximal isometric lift force and endurance time were obtained during the Sorenson test. The isometric lift task involves synergistic muscle activation of knee extensor muscles and lumbopelvic extensor muscles. Motor control strategies of multiple joints and muscles during isometric lifting may also explain the low correlation observed in elderly subjects.

This study is the first to assess lumbopelvic extensor muscle endurance in a clinical isometric back extension test in elderly subjects. Lumbopelvic extensor muscle endurance seems to be modulated by different neurophysiologic or mechanical factors with age, and in light of the present findings, normative data gathered from young adults should be interpreted with caution in elderly subjects. Future studies will be needed to assess lumbopelvic extensor muscle endurance in elderly male and female subjects with or without low back pain.

From: Iowa Orthop J. 2009;29:97-9

This cross-sectional study examines whether there is an association between gluteus medius weakness in the presence of low back pain in pregnant women at any stage of gestation. Prevalence of low back pain during pregnancy is high, and identifying potential etiologies and targeted interventions is lacking. Thus, identification of an association between specific muscle weakness and pain would have clinical relevance. Initial pilot data suggests that weakness of the gluteus medius is strongly associated with the presence of low back pain during pregnancy.

Low back pain during pregnancy is considered a significant public health issue due to its high prevalence and associated health care costs. Prevalence ranges between 49-68.5% with up to one third of these women having pain that limits their ability to perform basic activities of daily living. Ten percent of women with chronic low back pain link the onset of their pain to pregnancy. Physical therapy literature and physical therapy clinical practice relating to low back pain in pregnancy has historically involved discussion of postural dysfunction, sacroiliac joint dysfunction, and “sciatica.” The authors of this proposal offer another possible correlation explaining back pain during pregnancy relating to gluteus medius performance.

It is the experience of the authors of this proposal that pregnant women routinely present to their physical therapy clinic with “radiculopathy” or “sciatica.” In fact, the incidence of herniated disc in pregnancy is actually quite rare (1%). Often, the physical exam does not reveal any neurologic findings indicative of radiculopathy, but instead reveals weakness and/or strain of the gluteus medius. Gluteus medius strain can present as low back pain either due to facet joint irritation relating to Trendelenburg gait, or can be referred pain from the gluteus medius itself. If a true neurologic weakness were present, one would expect to find both tensor fascia lata and posterior gluteus medius weak as they are commonly innervated (L5). Rather, in the authors experience weakness is specific to the gluteus medius. Foti et al. performed 3-dimensional gait analysis on 15 pregnant women during the second half of their pregnancy and again one year post-partum. Gait analysis includes both kinetic and kinematic parameters. The authors found significant changes in kinetic gait parameters during pregnancy, and offer this as an explanation for how
gait motion overall remains relatively unchanged. They found increased demand on the ankle plantar flexors, hip abductors, and hip extensors. Atrophied tissues, or weak muscles, are less tolerant of physical stresses applied. Pregnant women with weakness of the gluteus medius are therefore vulnerable for tissue injury—both because of the increased magnitude of stress applied (weight gain), and a decrease in stress tolerated before injury/strain.

Thus, the primary aim of this pilot study was to determine the association between weakness of the gluteus medius and the presence of low back pain during pregnancy.

As mentioned, prevalence of low back pain in pregnant women is high. Yet our knowledge is limited to descriptions of natural history. Unfortunately, most clinicians are limited in both work-up and treatment options due to the pregnancy. Often, women are advised to wait until after delivery for appropriate tests and treatment.

The rationale for postural change as a contributor to back pain during pregnancy involves increased lumbar lordosis with subsequent extension-related facet pain. Treatment is then guided toward improving posture, abdominal strengthening, and improved lumbopelvic stability. Lengthening of the abdominal muscles is a known consequence of a growing uterus, causing possible weakness of this musculature. It is thought that this lengthening and weakness contributes to poor lumbar stabilization and pain. Few studies exist showing a correlation between abdominal weakness and back pain in pregnant women. Fast et al. looked at rectus abdominus function in terms of ability to perform a sit-up. They found no significant difference between performance of a sit-up and incidence of back pain. Moore et al. performed a longitudinal study of 30 pregnant women and found the line of gravity, measured using special markers along the spinous processes, to be unaffected for the majority of women. Those who did experience a change, tended toward flattening of the lumbar spine. Other studies have found no correlation between postural patterns and the presence of low back pain.

Sacroiliac joint dysfunction is a much debated issue in the physical therapy literature. There is disagreement relating to whether the sacroiliac joints are mobile, and if so, to what extent. An excellent review by Walker documents review of multiple articles citing greater tendency toward fracture than joint displacement with high impact injury. This review also notes motion of the sacroiliac joint averaging about four degrees or three millimeters.
This brings into question whether this small amount of movement can be detected through physical exam alone. The discussion changes somewhat in the context of pregnancy, as there is known joint laxity around the pelvis. As the sacroiliac joint joint is not crossed by any muscle, we assume that stability is achieved through bony morphology and ligaments. During pregnancy, it is thought that the hormone relaxin contributes to the decreased strength
of collagen. There appears to be conflicting evidence relating to whether a correlation exists between relaxin levels, pain, and sacroiliac joint ovement/sympheseal distension. Specific provocative maneuvers to detect sacroiliac joint pain, as well as tests to determine symmetry/joint motion exist. However, at this time, reliability and validity of these tests does not appear sound, particularly in the case of detecting symmetry/abnormal joint motion.

Pregnant women with gluteus medius weakness were roughly 6 to 8 times more likely to have low back pain than those without weakness. There were no neurologic findings indicative of radiculopathy. This pilot data encourages us to continue this study with larger numbers. The authors also will consider a treatment trial looking to see if strengthening exercises prescribed at the first OB visit can reduce incidence of low back pain.

From: Public Health. 2009 Aug 24

Examination of the prevalence, correlates and prospective impact of musculoskeletal pain on physical and psychological function in a population health survey of elderly Chinese men and women. Four thousand men and women, aged 65 years and over, living in the community in Hong Kong took part in this study. A questionnaire to determine demographics, socio-economic status, medical history, smoking, alcohol intake and level of physical activity was administered by an interviewer. Participants were asked about the presence of pain in the back, neck, hip and knee in the past 12 months. They were re-interviewed after 4 years of follow-up to document physical performance measures, psychological function and occurrence of falls, fractures and mortality.

Overall, back pain was most prevalent (48%), followed by knee (31%), neck (22.5%) and hip (8.9%) pain; the values was nearly twice as high in women compared with men for all sites. The presence of pain was not correlated with age, but was associated with various measures of socio-economic status as well as comorbidities. Baseline prevalence of pain was related to physical performance and quality-of-life measures, and fracture incidence after 4 years of follow-up.

Musculoskeletal pain is prevalent among elderly men and women, being much higher in the latter, giving rise to considerable functional and psychological impairments. Osteoporosis and osteoarthritis are likely to be the main underlying causes. The condition may be considered part of the frailty syndrome, and in this context, prevention and management represent major public health challenges.

From: Arthritis Res Ther. 2009 Aug 20;11(4):R126. [Epub ahead of print]

The human intervertebral disc is an avascular and aneural tissue comprising a central gelatinous region (the nucleus pulposus), surrounded by a fibrous ring of highly organised collagen fibres (the annulus fibrosus). The extracellular matrix of the nucleus pulposus is rich in type II collagen and proteoglycans, predominantly aggrecan, which produces a highly hydrated matrix capable of withstanding the loads experienced within the spine. This extracellular matrix is constantly being remodelled in a process driven by the constituent nucleus pulposus cells.

During intervertebral disc degeneration there is an imbalance in the normal homeostatic mechanisms, which favours matrix catabolism and leads to a loss of disc height,
coupled with ingrowth of both nerves and blood vessels into both the annulus fibrosus and nucleus pulposus. The authors have previously demonstrated that this ingrowth of nerves into the degenerate intervertebral disc is associated with low back pain. While low back pain is multifactorial, studies have shown that this debilitating condition affecting around 80% of adults at some stage of life is associated with intervertebral disc degeneration in approximately 40% of cases. Indeed in a recent study by Cheung et al (2009) it has been shown that there is a significant association of lumber disc degeneration imaged by MRI with low back pain.

The nucleus pulposus of the normal human intervertebral disc is an avascular and aneural environment, comprising of chondrocyte like cells embedded within an extracellular matrix rich in proteoglycans and collagens. This matrix is continuously remodelled in a process controlled by the nucleus pulposus cells and closely regulated by anabolic growth factors and catabolic cytokines. In intervertebral disc degeneration there is disregulation in this finely balanced homeostatic matrix turnover mechanism, leading to an increase in catabolic processes over anabolic matrix formation. Over time this results in breakdown of matrix, until the disc loses both height and function and in a large proportion of cases there is innervation and initiation of the pain response which leads to low back pain.

Matrix metalloproteinases (MMPs) are known to be involved in the degradation of the nucleus pulposus during intervertebral disc degeneration. This study investigated MMP-10 (stromelysin-2) expression in the nucleus pulposus during intervertebral disc degeneration and correlated its expression with proinflammatory cytokines and molecules involved in innervation and nociception during degeneration which results in low back pain.

Human nucleus pulposus tissue was obtained at post-mortem from patients without a history of back pain and graded as histologically normal or degenerate. Symptomatic degenerate nucleus pulposus samples were also obtained at surgery for low back pain. Expression of MMP-10 mRNA and protein was analysed using real time PCR and immunohistochemistry. Gene expression for proinflammatory cytokines IL-1 and TNF-alpha, nerve growth factor and the pain associated neuropeptide Substance P were also analysed. Correlations between MMP-10 and IL-1, TNF-alpha and nerve growth factor were assessed along with nerve growth factor with Substance P.

MMP-10 mRNA was significantly increased in surgical degenerate nucleus pulposus when compared to post-mortem normal and post-mortem degenerate samples. MMP-10 protein was also significantly higher in degenerate surgical nucleus pulposus samples compared to post-mortem normal. IL-1 and MMP-10 mRNA demonstrated a significant correlation in surgical degenerate samples, while TNF-alpha was not correlated with MMP-10 mRNA. Nerve growth factor was significantly correlated with both MMP-10 and Substance P mRNA in surgical degenerate nucleus pulposus samples.

MMP-10 expression is increased in the symptomatic degenerate intervertebral disc, where it may contribute to matrix degradation and initiation of nociception. Importantly, this study suggests differences in the pathways involved in matrix degradation between painful and pain free intervertebral disc degeneration.

This study has demonstrated, for the first time, increased MMP-10 expression in the symptomatic degenerate intervertebral disc when compared to non-degenerate or asymptomatic degenerate intervertebral disc . The correlation of MMP-10 with IL-1 and nerve growth factor, combined with the correlation between nerve growth factor and Substance P in symptomatic degenerate intervertebral disc’s suggests differences in the catabolic pathways between painful and pain free intervertebral disc degeneration. While this study focused on gene and protein expression profiling, it emphasizes the importance of MMP-10 in symptomatic intervertebral disc degeneration and highlights that a more detailed investigation into these pathways, including analysis of enzyme activities is required to better understand the underlying pathogenesis.

From: Med Hypotheses. 2009 Jul 23. [Epub ahead of print]

Modic changes are bone marrow and endplate lesions visible in magnetic resonance imaging (MRI). They are regarded as a part of degenerative disc disease and associated with low back pain. And severe disc degeneration was occurred more in the patients with Modic changes. But there is still no study to analyze the relationship between Modic changes and intervertebral disc degeneration. The authors hypothesize that Modic changes are the possible causes and promotion of lumbar intervertebral disc degeneration. And there are three possible mechanisms for this hypothesis:

A structural cause: Modic changes make cartilaginous material easier in extruded disc herniations, to destroy the structure of intervertebral disc and inhibit the absorption of the disc.

A biomechanical cause: Modic changes alter the mechanical loading distribution on disc, to initiate a series of disc disruption and inhibit the self-recovery of the disc.

A nutritional cause: Modic changes destroy the vascular architecture in vertebral endplate and block the most important metabolism pathway between vertebrae and disc.

Perspectives:

(1) Find out procedures to cure Modic changes may be an important breakthrough for disc degenerative disease.

(2) Treatment of Modic changes may be a critical step of biotherapy for disc degeneration disease.