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Study Finds Strong Correlation Between LBP, Age-related Degeneration, and Spinal Instability

Instability

A study examined the relationship between lumbar disc degeneration and instability in spinal segments of three groups of volunteers and found that factors of spinal instability were closely related to disc height and the age of the study subjects and that disc height was intimately associated with age and spinal instability and was the most consistently affiliated parameter of those examined.

Patients with lower back pain (LBP) and/or sciatica often have evident disc degeneration in MRI their images, especially elderly patients. Because these patients may demonstrate no other neurological symptoms, it is commonly assumed specific evidence of LBP –aside from degeneration and the age of the patient—may not exist. Excessive motion surrounding the affected disc segment can cause LBP and spinal instability, and previous studies on the relationship between instability and LBP have been inconsistent in their findings—in part, because imaging of the subjects was performed while the patients were in the static supine position.

Study Design Utilized Flexion-Extension Standing Postured Imaging Reviews

The authors of the current study were building upon their previous research utilizing images that had been performed on patients during flexion-extension standing postures to examine the relationship between spinal instability and disc degeneration of the L4/L5 motion segment. Because disc degeneration may not be associated with LBP at all stages, the authors of the study devised a method of measurement to examine different types of segmental degeneration and any relationship it may have with spinal instability.

The subjects of the study were LBP or leg pain outpatients who had received radiologic and MRI imaging within a two-month interval during the past three years. Of the 447 patients included in the study, 268 were men, and 179 were women. Their ages ranged from 10 to 86 years, with an average age of roughly 54 years-old.

Instability was measured at the L4/L5 spinal segments during neutral, extension, and flexion postured images and was then analyzed and categorized into three variable types: Anterior slip at L4 onto L5 while in neutral position (SN), sagittal translation (ST), and segmental angulation (SA). Measurements were taken of each slip, and the results were evaluated and noted to determine the degree of apparent instability.

The disc segments were evaluated radiologically for degeneration by looking at and comparing disc height, spur formation of the anterior vertebral edges, endplate sclerosis, and evidence of vacuum phenomenon in the films taken during flexion-extension. Sixty-eight of the subjects had high disc height (HDH), 212 patients were considered to have medium disc height (MDH), and 67 patients were categorized as having low disc height (LDH). Bony spur measurements were taken, and the presence of endplate sclerosis and vacuum phenomenon were noted as either being present or not. The level of disc degeneration was evaluated by MRI and graded from 1 to 5, as “normal,” to “severe” degeneration. The patients were divided into eight groups based upon the severity of their spinal instability, and the relationship between disc height, spur size, endplate sclerosis, vacuum phenomenon, and degeneration in the MRI’s was noted in relation to the types of instability present.

The compared data indicated a link between instability, age, and a reduction in disc height. Though increased age and a loss of disc height have long been suspected to be linked to degeneration and instability of the spine, this study uses MRI to evaluate that relationship more closely, demonstrating that a lower disc height was associated at least a 3mm slippage and a higher disc height was associated with subjects who were younger in age, with larger angulation in the spinal segments. Instability was prevalent in older patients with prominent anterior spur formation and/or vacuum phenomenon.

Age and relative spinal stability were intimately related to disc height, and this instability was progressive in nature and occurred over decades.

 

KEYWORDS: Correlation Between LBP, Age-related Degeneration, and Spinal Instability, relationship between lumbar disc degeneration and instability, comparing disc height, spur formation of the anterior vertebral edges, endplate sclerosis, and evidence of vacuum phenomenon, link between instability, age, and a reduction in disc height, degeneration and instability of the spine

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Increasing Gradients of Compressive Stress Can Lead to Annular Delamination, Collapse, and IVD Degeneration

delamination, annulus

A ISSLS Prize-winning study 1 examined how increasing gradients of compressive stress within the intervertebral disc (IVD) contributed to the progress of dis degeneration. The research findings suggest that an increased grade of disc degeneration created decreased nucleus pressure and compressive annulus stress, but anterior annular stress gradients increased by approximately 75 percent, and by 108 percent in the posterior annulus—findings that are clinically significant.

The neural arch may provide a stress-shield for the degenerating disc during mechanical loading, but delamination and collapse of the annulus are most likely caused not by loading, but by increasing gradients of compressive stress, leading to advanced disc degeneration, despite the stress-shield.

The Study

Using 191 motion segments from 42 cadavers of varied ages, researchers measured the intradiscal stresses under 1 kN of compression. A pressure transducer was pulled along the midsagittal diameter of the disc to measure the intradiscal stresses. Stress gradients in the annulus were quantified using a formula that averaged the rate of increase in compressive stress between the area of maximum stress in the anterior or posterior annuls, and the nucleus. Measurements were compared before and after applied creep-loading, as well as in flexed or erect postures. A scale of 1to 4 was used to describe the amount of macroscopic disc degeneration observed.

Results

An increase of disc degeneration from 2 to 4 decreased by 68 percent the amount of pressure in the nucleus, and compressive stress in the annulus was decreased by 48-64 percent, depending on the simulated posture of the segment and the location of the disc. However, anterior annular stress gradients showed an average 75 percent increase in the flexion position, and posterior annular stress gradients increased 108 percent in upright posture.

Conclusion

The neural-arch provides stress-shielding, but compressive stress gradients are significantly increased with an increasing grade of disc degeneration. Adjacent lamellae are sheared by the stress gradients, which may contribute to the delamination and collapse of the annulus.

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Low back pain and modic markers of cytokines

A L4-L5 Modic Model midsagittal cut demonstrating Type 1 Modic changes and the basivertebral nerve

Low back pain is very common and the markers to indicate why some people hurt and others do not, has been of a recent investigation. In The Spine Journal 1, just this month, researchers looked closer at modic changes and the chemicals that generate as a result. Modic changes were first identified by Michael Modic 2 in 1988 as unique findings on MR.

There is no doubt that disk degeneration appears to be related to low back pain, even if many asymptomatic people do have degenerative findings on MRI. 3 What seems to be the difference is the degree of inflammation in those that suffer with low back pain and those that don’t suffer.

Cytokines are inflammation markers, and in this study, these researchers found that Type 2 modic changes where associated with these markers and concluded:

“These results further strengthen the link between Modic Changes and low back pain”

The location of inflammation is something that is important to share with patients. Whether it is inflammation from the annulus within the disc itself, or whether MRI findings show intravertebral inflammation due to irritation to the basivertebral nerve, Dynamic Disc Designs develops models to help with spine education.

In a recent poll,

Do you know what patients really care about when choosing a spine surgeon?

Patients ranked Communicates well / Explains medical condition, symptoms, surgical, and non-surgical treatment options @ 17.7%.

3D discogenic pain model

modic, basivertebral

Modic and basivertebral nerve

 

  1.  Are modic changes associated with intervertebral disc cytokine profiles? Schroeder, Gregory D. et al. The Spine Journal IN PRINT
  2. Modic MT, Steinberg PM, Ross JS, Masaryk TJ, Carter JR. Degenerative disk disease: assessment of changes in vertebral body marrow with MR imaging. Radiology. 1988;166(1 Pt 1):193-9
  3.  Boden SD, Davis DO, Dina TS, Patronas NJ, Wiesel SW. Abnormal magnetic- resonance scans of the lumbar spine in asymptomatic subjects. A prospective investigation. The Journal of bone and joint surgery American volume. 26 1990;72(3):403-8
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Bending or twisting – Which predisposes low back pain?

bending or twisting

Bending or twisting?

In a recent bending study in Clinical Biomechanics, researchers looked at how the nucleus pulposus deformed as the vertebrae rotated at two lumbar levels: L1-2 and L4-5. They were curious about how the nucleus pulposus behaved as this hydraulic tissue has an important role in resisting compression with bending and twisting of the spine.

Rotation is often described as a body position to predispose low back injury but there is not much research on the topic to demonstrate this is actually the case.

There has also been mounting evidence that flexion bending is thought to be a mechanism for disc injury and this Flexion load is thought to be more important.

Coupling movements of both flexion AND rotation has historically been thought to be the worst.

These researchers led by Fazey, P. used MRI to look at 10 asymptomatic subjects of an average age of 29 yrs.

What these researchers determined was that side-ways bending demonstrated greater nuclear deformation compared to rotation. They also showed that the nucleus moves backwards when one bends forwards and moves forwards when one bends backwards. Opposite.

One of the take home messages from this study is that lateral flexion (or side-ways movement) of the spine causes the nucleus structure to deform more than twisting. Therefore, patients should be instructed to minimize sideways bending to help reduce the deformation of the nucleus pulposus.

This study is one example of why Dynamic Disc Designs has worked to showcase the anatomy and inner workings of human discs. Our latest is the Centralizer. Degeneration is as a result of annular fissures and understanding how to minimize annular stress will likely lead to better outcomes for pain practitioners.

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Degeneration vs. Disc Prolapse

Degeneration

Disc degeneration has been a topic of discussion in its mechanism of back pain for decades.

It is believed to be related but a causal link has been difficult to pin down. Researchers believe it to be related while others still question its role in back pain because of asymptomatic individuals with it as seen in MRI.

In order to continue to reveal the mechanisms related to back pain, a discernment between disc degeneration and prolapse was the topic of this outstanding runner up study in The Spine Journal.

Kanna et al. opened this research paper by stating that the pathogenesis, management, symptom presentation, etiology and prevention of lumbar disc degeneration has been elusive and how it is important to sub-classify and investigate degeneration and prolapse. These researchers wanted to analyze the patterns of degenerative disc disease with chronic low back pain and compare it to acute disc prolapse.

This study was conducted using a prospective MRI imaging approach.

In conclusion they found that back pain and degenerative disc disease (ddd) were radiologically and clinically different when compared to those with back pain and disc prolapse. These researchers found that in those with disc prolapse, there was less degeneration and more endplate disruption. This fits with other findings of endplate failure to be more common with disc herniation. Subjects in this study who had back pain were found to have more numbers of degenerative discs with primarily upper lumbar involvement.

Dynamic Disc Designs develops spine models to help patients understand more clearly their own pain generators….helping to reduce psychosocial factors involved with back pain.