properties of the annulus, disc model

Researchers examined the effects of endplate fractures  1 on the mechanical properties of the annulus fibrosis (AF) in porcine spinal segments and found that laminate adhesion strength was significantly compromised in the fractured spines. The findings suggest that microdamage may occur beyond the vertebra, into the interlamellar matrix of the AF—information that could be helpful in the diagnosis and treatment of adolescent spinal growth-plate fractures.

The Study

The authors of this study wished to examine the effects of high-intensity pressurization on the intervertebral discs (IVD) to see how it effected the mechanical and physiological properties of the posterior AF. They used 28 fresh, recently-thawed functional porcine spinal units from 14 porcine specimens that were approximately six months old.  Control units were also used as a comparative measure against the units subjected to pressure.

A hydraulic pump and high-pressure inflation needle were used to pump hydraulic fluid into the IVD of specimens. The researchers were careful not to pierce the AF in the samples. Pressure in the needle was measured by a pressure transducer and converted from analogue to digital at 2048 Hz. The needle was subsequently removed, and the vertebral bodies were assessed for damage. Although fractured endplates created an audible ‘pop,’ the condition was only confirmed after dissection of the IVD. The control-group segments were not tested for fractures. Measurements were taken following the dissection, and the end-plate area was quantified. Bilayer AF samples were then dissected and tested for tensile endurance in the circumferential direction. A second multi-layered sample was then dissected and subjected to delamination and a peel test. Mathematical ratios were then plotted to mark the variable results for each sample.


End-plate size measurements remained consistent across the control and fracture group samples. Bilayer stiffness, toe-region stretch ratio and stress, and stress at 30% stretch were consistent in the control and fracture group samples. However, there was a clinically-significant variance in peel strength—but not peel strength variability— between the two groups. In the fracture group, the peel strength was 31 percent lower than in the control group. Dissection and manual delamination were significantly easier in the fracture group of samples, as well.


The results of this study indicate that growth-plate fracture damage may not be limited to the vertebra and may cause microdamage in the nearby AF. This was indicated by the reduction of laminate adhesion strength in the posterior AF of the fracture IVD samples subjected to pressure in the tests. This information should be taken into account when practitioners are examining and treating adolescent or childhood vertebral fractures involving the endplates.


KEYWORDS: damage during spinal growth-plate fractures, effects of endplate fractures on the mechanical properties of the annulus fibrosis, effects of high-intensity pressurization on the intervertebral discs, mechanical and physiological properties of the posterior AF, delamination and a peel test, Bilayer stiffness, toe-region stretch ratio and stress


A recent study  1 mapped the rate of water diffusion in intervertebral discs (IVD) of lower back pain (LBP) patients using MRI and a software program to develop an apparent diffusion coefficient (ADC), or in vivo water proton measurement, shortly after spinal manipulation on the subjects. The results of the study indicate a short-term increase in apparent diffusion could be responsible for the immediate improvements in pain and mobility after a spinal manipulation, though chronic LBP sufferers, whose fissured and ruptured discs allow for more diffusion than typical healthy discs, may be less likely to experience the immediate benefits of mobilization than their acute LBP-suffering counterparts.


The Study

Eleven women and five men diagnosed with acute idiopathic LBP were recruited from a physical therapy practice over a six-month period. Their average age was 46 years-old, and they were included in the study based upon a shared complaint of acute LBP or stiffness of a duration less than six weeks, less pain days than non-pain days, with at least one asymptomatic month between the current and previous LBP episodes. Patients were excluded from the study if they suffered from chronic LBP, were resistant to spinal manipulation, had suffered a spinal fracture, felt pain radiating below the knee, previous spinal surgery, had osteoporosis, were pregnant, had any sort of metal implants that might interfere with the MRI machine, suffered from mental health problems, obesity, claustrophobia, substance abuse or cognitive disability.

The subjects received an explanation of the procedure and completed questionnaires about their levels of neuropathy and LBP prior to having their lumbar region scanned via MRI. After the initial scan, a spinal mobilization by an Orthopedic Manual Physical Therapist (OMPT) was performed in an adjacent room, with a scale beneath the OMPT’s feet measuring the weight change during the PA mobilization. Within the hour, another MRI scan was taken of the patients, and they were asked to answer a series of questions to rate their pain and mobility levels, post-treatment. The entire process took roughly 90 minutes per patient.

The images were analyzed visually and through a data software program in relation to each participant’s rate of a water molecule and nutrient diffusion and the sequences of diffusion pre-and post-manipulation. The images were interpreted by a single investigator and radiologist, and the ADC was calculated and verified. Clinical pain and mobility changes were noted and combined with the MRI changes before and after the PA mobilization computations were achieved.


There was a clinically-significant increase in ADC values across all anatomical levels, except for L2-S1 and L2-L3. The biggest changes occurred at L3-L4, and L4-L5. The pain ratings also saw a significant reduction post-mobilization across the subjects after mobilization. These results agree with previous similar study findings, but they offer new insights into acute LBP diffusion and that of older study subjects than in previous studies. Dr. Fryer’s research was referenced in this paper. Click To Tweet The findings of this study may indicate that the phenomenon of mobilization may not be responsible for the improvement of discogenic pain and increased water diffusion, but it is clear that pain, mobility, and diffusion are linked, and mobilization during the acute phases of LBP can temporarily provide increased flow to the IVD, allowing it to expand and decrease pressure and stress on the surrounding nerves. The improved fluid-flow may also help to remove obstructions, irritants, and debris from the IVD, which could also improve function and pain levels, post-manipulation.

Mobilization during the acute phases of LBP can temporarily provide increased flow to the IVD, allowing it to expand and decrease pressure and stress on the surrounding nerves. Click To Tweet

Though there was an overall four percent reduction in ADC between typical and slightly degenerated IVDs, the subjects with more severe degeneration had five percent higher levels of diffusion—probably due to fluids collecting in the fissures in the nucleus, created by the disc degeneration. Thus, spinal thrust significantly increased ADC values for those with mild or no degeneration but was less effective in those with more degeneration.

KEYWORDS: Spinal Mobilization Credited to Increased Apparent Diffusion, in vivo water proton measurement, shortly after spinal manipulation, short-term increase in apparent diffusion could be responsible for the immediate improvements in pain and mobility after a spinal manipulation, mobilization during the acute phases of LBP can temporarily provide increased flow to the IVD

cervical hydraulic recovery with recumbancy

A retrospective study 1. [Clinical Relationship of Degenerative Changes between the Cervical and Lumbar Spine] reviewing MRIs of 152 back patients showed a positive correlation between cervical and lumbar intervertebral disc degeneration (IDD) in patients presenting with lumbar spondylosis. The results suggest the necessity of screening LBP patients for evidence of cervical IDD.


The diagnosis of IDD may be complicated by the patient’s pain patterns and the tendency of practitioners to focus only on the area of discomfort. Studies have demonstrated the interrelatedness of spinal kinematics, reflexes, and complex neurogenic responses in IVD degeneration, but few studies have examined the connection between degenerative changes in the lumbar and cervical spine, as it relates to diagnosis. This study’s aim was to quantify the possible correlation, which could lead to better diagnostic and treatment outcomes for future IDD patients.



Positional MRIs of 152 patients presenting with cervical or lumbar spondylosis were reviewed and assessed and graded on a scale of 1 to 5 for every spinal segment. A degenerative disc score (DDS) was achieved by summing the grades across all segments, after which, the subjects were divided into two groups based upon their IDD for each spinal segment. The “normal” group received a grade of 1 to 2; the “degenerative” group had grades of between 3 and 5. The groups were then compared for evidence of a positive correlation.


A review of the two groups showed a positive correlation between DDS of the cervical and lumbar spine, with higher cervical DDSs at the upper lumber segments than at the lower degenerative segments. This indicates that patients demonstrating degenerations in the upper lumbar spinal segments are likely to suffer from some cervical spondylosis on further examination, regardless of whether they are currently symptomatic.


Patients with lumbar degeneration should also be screened for cervical spondylosis, particularly if their lumbar degeneration is present in the L1 to L3, to reduce the likelihood of a missed cervical degeneration diagnosis. Click To Tweet

KEYWORDS: positive correlation between cervical and lumbar intervertebral disc degeneration, better diagnostic and treatment outcomes for future IDD patients, the interrelatedness of spinal kinematics, reflexes, and complex neurogenic responses, patients demonstrating degenerations in the upper lumbar spinal segments are likely to suffer from some cervical spondylosis

intradiscal pressure, model

A study of in vivo intradiscal pressure in subjects with and without lower back pain (LBP) sought to find out how disc degeneration affects intradiscal pressure, measure the loading capacity of the L4/L5 IVD segment, and determine any relationship between movement in that disc segment and the spinal loading capacity. The researchers found that there was a significant relationship between spinal loading and the angle of the motion segment in healthy discs in vivo. In degenerated discs, the intradiscal pressure was much lower than that measured in healthy discs. Further study with wider parameters is suggested to fully understand the phenomenon and the problems associated with it.

Study Motivation and Design

The only way to directly measure spinal loading in humans is via the measurement of intradiscal pressure—a complex in vivo task. Most current knowledge about loading capacities were derived from pioneering studies in the 1960’s and 1970’s by Nachemson, but little corroborating evidence has been published on the topic since. These early studies utilized an inefficient means of evaluating intradiscal pressure—the polyethylene coated disc pressure needle until 1965, and after that, another needle designed specifically for intradiscal pressure measurements. This new needle was not without its deficits and required special handling and was prone to destroying structural defects on insertion. The current study’s authors utilized a newly designed silicone-based needle to measure the pressure and spinal load in 28 patients suffering from LBP, sciatica, or both at the L4/L5 segment, and in eight healthy volunteers with an average age of 25 years-old.

Magnetic resonance imaging (MRI) was performed on the healthy subjects prior to the beginning of the study to ensure no disc degeneration in the volunteers. The 28 LBP patients (10 women and 18 men with a mean age 45 years) were also imaged prior to pressure measurements being taken to visualize the amount of water content in their discs. These patients were diagnosed with disc herniation (16 patients) or spondylosis (12 patients).

The subjects were measured while in the prone position, without sedation but with a “local” dose of anesthesia. A guiding needle was used to position the pressure sensor needle into the nucleus pulposus of the L4/L5 IVD discs. Fluoroscopy was used to confirm correct placement of the needle had been achieved. The subjects were measured in eight positions: prone, upright standing, lateral decubitus, flexion and extension standing, and upright, flexion, and extension sitting positions. Radiograms of the lateral view were also taken of each of the subjects during their testing.


Pressure measurements in this study indicate that respiration creates a fluctuation in intradiscal pressure even when subjects are in the prone position and utilizing no other muscle activities. An IVD that is healthy is also elastic, with an intradiscal pressure that fluctuates in correspondence to muscle activities and respiration. It is possible that the normal pressure changes involved with respiration could be associated with the maintenance of the nutritional content inside the nucleus pulposus. There was a slight difference between horizontal and vertical pressures in healthy and degenerated discs and in the silicon gel, which may indicate that the nucleus pulposus has a similar pressure tropism to silicon gel. Normal discs had high water content, which explains the small difference between the horizontal and vertical pressure measurements. There was, however, a significant difference between the pressures of the total value (horizontal and vertical and whole posture) of healthy and degenerated discs. These values may not have been significant enough to measure in previous studies utilizing the less efficient needle-types. The information obtained in this study through the use of the sensitive silicone pressure needle will help in developing a better understanding of degenerative disc disease.

Professional LxH Model

Our Professional LxH Model


KEYWORDS: Link Between Lower Back Pain, Disc Degeneration and Intradiscal Pressure, relationship between spinal loading and the angle of the motion segment in healthy discs, respiration creates a fluctuation in intradiscal pressure, degenerative disc disease


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

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.


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.


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.

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