, , , , , , ,

Diurnal Disc Shape and Height Changes – Basic Science and Natural Variations to Understand Back Pain

Diurnal Disc Shape

The spine undergoes natural shape and fluid changes over the course of 24 hours. Often, back pain symptoms vary as well over the day and night cycle.  But the small changes and the links to pain have not been researched thoroughly. Here, a group of researchers from Duke University looked at the reliability of measuring intervertebral disc shape with recumbent MRI. This large avascular structure is linked to back pain and has significant diurnal variation in the human body. It would seem wise to further understand its diurnal disc shape changes.

Some people feel pain in the mornings and others feel things more so at the end of the day. Yet others feel pain more so when they lie down.

The intervertebral disc hydraulically keeps vertebrae separated. Water is squeezed out throughout the day as the human frame is vertical, and this water gets resorbed when an individual lays down. During the process, the disc changes shape and height. And when pain is involved, these shape and height changes can bear increased ( or decreased ) physical stress on structures that may be inflammatory. These can include annular fissures, disc bulges, disc herniations, disc protrusions, encroaching nerve or rootlets of nerves and the shingling of facet joints, just to name a few.

The purpose of this study was to determine intra and inter-rater reliability using MRI to measure diurnal changes of the intervertebral discs.

They did find excellent reliability, and interestingly they saw the most significant change in the posterior annulus region of L5-1. The diurnal variations were in line with what others had seen in previous work. Boos at al. in 1996 saw a 1-2mm change over the course of an 8h workday while Hutton et al. in 2003 saw a volume change of 1-2 cm3.

This research is essential if we are to fully understand back pain origins. Often pain syndromes related to the lower back present with symptoms that are diurnal. At Dynamic Disc Designs, we have models to help explain these subtle but significant changes to the discs, assisting patients to understand the onset of their pains and the diurnal disc shape and the natural variations.

 

, , , , ,

Exploring the Link Between Lower Back Pain, Disc Degeneration and Intradiscal Pressure

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.

Observations

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.

 

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

, ,

Study Finds Evidence Asymmetrical Postures During Loading Contribute to Disc Failure

disc failure and nerves in the intervertebral disc graphic

A microstructural analysis of how healthy discs respond to compression and complex loading postures—specifically those incorporating flexion and facet-constrained shear—found evidence that the required load contributing to disc failure was reduced when complex postures, rather than simple flexion, were utilized in load-bearing situations. In addition, when asymmetric postures were used during lifting, rather than simple compression or flexion, there occurred more infiltration of the nucleus material as it made its way to the annular periphery. The results of the study indicate that asymmetric postures during lifting are more likely to contribute to disc degeneration and lower back pain and should therefore be avoided.

The Study

The study 1 involved 30 motion segments from 10 sheep spines that had no previous signs of disc degeneration. The discs were frozen, thawed, and then rehydrated fully prior to the compression experiments to be in agreement with previous similar experiments and maximize the annular load. Researchers created a bending, twisting, lifting scenario that involved axial rotation, lateral, anterior, and posterior shear, and flexion, adapting the mechanical rig to compress and rotate the disc segments to failure using compressive force.

The typical failure was lower under complex loading conditions than in conditions of simple flexion. Microstructural damage included fractures of the vertebrae and three variations of annular damage, including mid-span direct tearing, non-continuous mid-span tearing, and annular-endplate tearing. Combinations of all three types of damage occurred, as well as circumferential failure, in all 30 discs.

The complex postures utilized in the study lessened the discs abilities to withstand compressive loading and contributed to failures. The complex loading conditions contributed to instances of dual modes of failure, including the circumferential (circuitous tracking of nuclear materials towards the annular periphery) evident in all study samples. This suggests that the lateral parts of the disc may be especially vulnerable during flexion because of shear loading in the area. Circumferential damage was evident in all 30 discs involved in this study, which suggests that it is likely an important type of damage involved in disc failure under complex loading conditions.

Conclusion

Complex postures during load-lifting may contribute to herniation and disc failure. Asymmetrical postures (in addition to flexion) should be avoided during lifting to reduce the likelihood of sustaining a lower back injury.

, , , ,

sciatica – coughing, sneezing and straining

Sciatica, disc, model

Sciatica is often worsened by coughing, sneezing and straining. It is a sign that patients complain about in the case of back pain. In some, the act of coughing or sneezing can actually cause a disc herniation.

In a recent study in The European Spine Journal, researchers wanted to find out if the act of coughing, sneezing or straining is important in the assessment of nerve root compression or disc herniation on MRI.

In “A diagnostic study in patients with sciatica establishing the importance of localization of worsening of pain during coughing, sneezing and straining to assess nerve root compression on MRI” 1 they found that the worsening of leg pain with these actions which includes increasing intradiscal pressure 2 has good diagnostic value for nerve root compression and disc herniation with MRI.

The research revealed the importance of asking whether the patient has these symptoms in the history taking.

At Dynamic Disc Designs, our models showcase how compression will extrude the nucleus….helping patient’s understand their pain.

Quote by the famous Karel Lewit:

“The first task for the physician is to show the patient the cause of their pain”.

  1.  Eur Spine J. 2016 May;25(5):1389-92. doi: 10.1007/s00586-016-4393-8. Epub 2016 Feb 2.
  2.  Spine (Phila Pa 1976). 1999 Apr 15;24(8):755-62. New in vivo measurements of pressures in the intervertebral disc in daily life. Wilke HJ1, Neef P, Caimi M, Hoogland T, Claes LE.
, , ,

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.

, , , , ,

Dynamic Degenerative Disc Model

Degenerated Disc Model - Dynamic Disc Designs

Coming this fall, a Dynamic Degenerative Disc Model with the ability to show innervation of the nucleus pulposus dynamically.

Dynamic Disc Designs strives to showcase important research in a dynamic platform so spine doctors can effectively educate their patients. This new design includes many new features including:

  1. dynamic two-part disc that is easier to squeeze
  2. neoinnervation into the dynamically mobile and fully visible nucleus pulposus
  3. facetogenic arthropathy narrowing the lateral recess
  4. dynamic disc bulge vs. herniation
  5. degenerative specimen chosen to copy
  6. much much more…

Subscribe on Youtube channel

With these features, spine professionals can quickly demonstrate pain generators and the solutions related to mechanical back pain. Help patients understand how to centralize the nucleus during movements in the teaching of lumbar lordosis with load, for example.

Centralization of pain is an important goal in the treatment/management of back and leg pain as well as neck and arm pain. Patients often think in terms of muscles but the core of the issue is often more central. With this new model, a greater understanding of how the nucleus moves can be a huge benefit as patients can work to minimize annular stress and disruption. If patients understand the mechanical forces responsible for their pain, they are better equipped to work as a team player in the management of back pain. Teaching containment of the nucleus will now be an asset with this new model design.

Degenerated Centralizer

This new Degenerative Centralizer Lumbar Model will change the way doctors and physiotherapists talk to their patients. We expect those that use this model for education will have better outcomes. Pre-orders being accepted now with discount offered to those early on the list.

, ,

Disc Herniation on Earth – Learning from Astronauts

Disc Herniation - Dynamic Disc Designs

Disc herniation on Earth are common.

The most common age of disc herniation presentation is thought to be between 31-40 years and is found more common in people from rural areas, moderate and heavy workers and vehicle drivers on bad roads (https://ispub.com/IJNS/3/1/5615). In a recent narrative review article in the European Spine Journal, a team of powerful researchers looked at why astronauts get disc herniations when they return to Earth. This was in response to National Aeronautics and Space Administration (NASA) showed an increased risk of intervertebral disc (IVD) herniations in US astronauts (research).

In Disc herniations in astronauts: What causes them, and what does it tell us about herniation on earth? the authors looked at the common themes seen here on Earth in the better understanding why people get disc herniations in general.

We have known for quite some time that astronauts often suffer from back pain. Why is that? Simply it is because of hyperhydration and flexion.

Over the course of the day on Earth the spine undergoes an accordion-like height change losing as much as 20 percent of fluid loss. When astronauts are in space, their discs over-inflate. And when they return to Earth and bend forward in flexion, the posterior annulus is under increased stress and is susceptible to rupture. This is in line with some research showing disc morning pressures are a risk factor of disc herniations (research).

On the other hand, when we lie down (or go to space) the discs swell up to recharge the fluid loss to prepare for more load the following day.

Teaching patients about avoiding flexion first thing in the morning when putting on socks, for example, is important in the management of back pain. ddd models help with this conversation.

Subscribe on Youtube channel

Quick Clinical Tip:

Teach patients anterior and posterior structures in the spine. Discs are on the front, the facet joints are on the back. Bending forward compresses the discs. Teach posture tips to maintain neutral posture, especially first thing in the morning to help minimize the risk of disc herniation.

So what can we learn about this research?

It is important to keep the discs balanced with regard to compression and decompression. If discs are over-inflated, they are susceptible to disc herniation injury. On the other hand, if the discs are under-inflated, other problems can develop like degenerated disc disease. Most people fall into the latter category and require more off-loading.

Follow us on Google+