Dynamic Bulging of Intervertebral Discs in the Degenerative Lumbar Spine
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.
Cervical segmental motion at levels adjacent to disc herniation as determined with kinetic magnetic resonance imaging
From: Spine (Phila Pa 1976). 2009 Oct 15;34(22):2389-94
This article investigates the effects of cervical disc herniation on kinematics at adjacent vertebral motion segments. Kinetic magnetic resonance imaging is an alternative method to conventional MRI, which allows evaluation of the cervical spine in a more physiologic, weight-bearing position, and acquisition of images in flexion, extension, and neutral alignment. Kinetic magnetic resonance imaging has previously been used to evaluate the effects of disc degeneration on cervical kinematics. A total of 407 patients with neck pain without prior history of surgery were evaluated using kinetic magnetic resonance imaging. Translational motion, angular variation, and disc height were measured at each segment from C2-C3 through C7-T1. Other factors including the degree of disc degeneration, age, gender, and vertebral segment location were analyzed in order to determine any predisposing risk factors for segmental instability adjacent to disc herniations.
Spinal levels above the disc herniation exhibited, on average, a 7.2% decrease in translational motion per mm of disc herniation, without significant change in angular motion. Levels below the herniation demonstrated a 5.2% decrease in angular motion per mm of disc herniation without significant change in translational motion. The degree of disc degeneration had no significant effect on adjacent level motion. Disc herniation had no significant impact on disc height at adjacent levels, although disc degeneration correlated with decreased disc height above and increased disc height below.
Although disc height, translational motion, and angular variation are significantly affected at the level of a disc herniation, no significant changes are apparent in adjacent segments. This study indicates that herniated discs have no effect on ROM at adjacent levels regardless of the degree of disc degeneration or the size of disc herniation, suggesting that the natural progression of disc degeneration and adjacent segment disease may be separate, unrelated processes within the cervical spine.
Muscone Protects Vertebral End plate Degeneration by Antiinflammatory Property
From: Clin Orthop Relat Res. 2009 Sep 18
Neck pain is one of the most common chronic conditions affecting quality of life and sometimes causing disability in adults. Most chronic neck pain is the result of degeneration of the intervertebral discs in the cervical spine. An intact end plate cartilage is critical for normal disc functions, as the major nutrient supply of the discs is diffused through the end plates. Pathological changes in end plate cartilage are closely related to disc degeneration and thus to cervical spondylopathy. Prevention and reduction of lesions to the vertebral end plate are high research priorities.
IL-1beta may play an important role in intervertebral disc degeneration. This being the case, inhibiting IL-1beta could provide a therapeutic approach for reducing or preventing disc degeneration. Muscone reportedly relieves pain and suppresses inflammation. Therefore, the authors asked whether muscone, a potent antiinflammatory agent, could reduce proinflammatory cytokines in vitro (end-plate cartilage cultures) and end-plate degeneration in vivo (a rat model that induces intervertebral disc degeneration). In vitro, muscone reversed IL-1beta-induced upregulation of IL-1beta, tumor necrosis factor alpha, cyclooxygenase 2, inducible nitric oxide synthase, matrix metalloproteinase 13, aggrecanase 2, and nitric oxide and downregulation of Col2alpha1 and aggrecan. Pretreatment with muscone (6.25, 12.5, 25 mumol/L) inhibited the IL-1beta-induced phosphorylation of extracellular signal-regulated kinases 1/2 and c-Jun N-terminal kinase in a dose-dependent manner. In vivo, muscone inhibited the expression of prostaglandin E2, 6-keto-prostaglandin F1alpha, IL-1beta, and tumor necrosis factor alpha and recovered the structural distortion of the degenerative disc. The findings suggest muscone is a promising agent for treating intervertebral disc degeneration through its antiinflammatory effects.
2009 ISSLS Prize Winner: What Influence Does Sustained Mechanical Load Have on Diffusion in the Human Intervertebral Disc?: An In Vivo Study Using Serial Postcontrast Magnetic Resonance
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.
Increased expression of matrix metalloproteinase-10, nerve growth factor and substance P in the painful degenerate intervertebral disc
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.
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Modic changes, possible causes and promotion to lumbar intervertebral disc degeneration
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.
The internal mechanical functioning of intervertebral discs and articular cartilage, and its relevance to matrix biology
From: Matrix Biol. 2009 Jul 5. [Epub ahead of print]
Degeneration of intervertebral discs and articular cartilage can cause pain and disability. Risk factors include genetic inheritance and age, but mechanical loading also is important. Its influence has been investigated using miniature pressure transducers to measure the distribution of compressive stress (force per unit area) within loaded tissue. The technique quantifies stress concentrations, and detects regions that behave in a fluid-like manner.
Intervertebral discs demonstrate a central fluid-like region which normally extends beyond the anatomical nucleus pulposus so that the whole disc functions like a “water bed”. With increasing age, the fluid region shrinks and pressure within it falls. Stress concentrations appear in the surrounding anulus fibrosus, with location depending on posture. Stress concentrations become large in degenerated discs, and are intensified by sustained loading or injury. Articular cartilage never exhibits an internal fluid pressure: stress gradients and concentrations normally occur within it, and are intensified by sustained loading.
Excessive matrix stresses can cause pain and progressive damage. They also inhibit matrix synthesis and stimulate production of matrix degrading enzymes. In this way, injury to chondroid tissues can initiate a ‘vicious circle’ of abnormal matrix stresses, abnormal metabolism, weakened matrix, and further injury, which explains many features of their degeneration.
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Changes in Spinal Height Following Sustained Lumbar Flexion and Extension Postures: A Clinical Measure of Intervertebral Disc Hydration Using Stadiometry
From: J Manipulative Physiol Ther. 2009 Jun;32(5):352-7
Throughout the course of the day, the spinal intervertebral discs display viscoelastic creep properties that determine an individual’s overall stature. These properties were demonstrated by Tyrrell et al who used in vivo stadiometry measurements to detect 19.3 mm (1.1% of stature) variation in height between first arising and the end of the day.
Contributions to the total diurnal stature loss from structures other than the intervertebral disc are minimal. Kanlayanaphotporn et al used stadiometer measurements to assess the contribution of soft tissue structures below the sacrum and concluded that these structures accounted for 19% of the height change during the first 5 minutes of sitting. Based on these findings, stadiometry is considered to provide an accurate measure of spinal height changes after various loading conditions.
The 2 primary methods of measuring spine height changes are magnetic resonance imaging (MRI) and stadiometry. Stadiometry has been shown to be a valid and reliable tool to assess spinal height when compared to objectifiable measures made from MRI. Stadiometry assessment has advantages over MRI in terms of costs, use in clinical setting, as well as the ability to measure subjects that simultaneously sustain compressive loads of the trunk.
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Comparison of the intervertebral disc spaces between axial and anterior lean cervical traction
From: Eur Spine J. 2009 Jun 16. [Epub ahead of print]
One of the main function of the intervertebral disc is to damp the compressive loadings during daily activities. Disc injury or degeneration could lead to mechanical compression or chemical irritation of the nerve root causing neurological deficits. Spinal traction is generally regarded as a conservative management in treating various types of neck or back disorders. Several mechanisms have been proposed for the possible therapeutic effects of neck traction. DeLacerda et al. reported that the axial traction reduced pain by improving circulation or preventing adhesions and contractures of spinal structures. Spinal traction could widen the intervertebral disc space reflecting a stretching of the posterior longitudinal ligaments. This condition might be associated with the suction effect of the negative intradiscal pressure and the pushing effect of the posterior longitudinal ligament.
The insufficient investigations on the changes of spinal structures during traction prevent further exploring the possible therapeutic mechanism of cervical traction. A blind randomized crossover-design study was conducted to quantitatively compare the intervertebral disc spaces between axial and anterior lean cervical traction in sitting position. A total of 96 radiographic images from the baseline measurements, axial and anterior lean tractions in 32 asymptomatic subjects were digitized for further analysis. The intra and inter examiner reliabilities for measuring the intervertebral disc spaces were in good ranges. With the application of anterior lean traction, the statistical increases were detected both in anterior and in posterior disc spaces compared to the baseline and axial traction.
The greater intervertebral disc spaces obtained during anterior lean traction might be associated with the more even distribution of traction forces over the anterior and posterior neck structures. The neck extension moment through mandible that generally occurred in the axial traction could be counteracted by the downward force of head weight during anterior lean traction. This study quantitatively demonstrated that anterior lean traction in sitting position provided more intervertebral disc space enlargements in both anterior and posterior aspects than axial traction did. These findings may serve as a therapeutic reference when cervical traction is suggested.
An earlier article in Spine. 1992 Feb;17(2):136-8 noted; The separation of facet joint surfaces was found after traction at 15 degrees extension, but not in the neutral or flexion positions.
