Cavitation – Practitioner Experience Best Indicator of Success

cavitation, spine, joints

Practitioner Experience Best Indicator of Success in Cervical Spine Manipulation Cavitation


Cervical spine studies have historically indicated that manipulation (and the generation of cavitation) by a qualified practitioner is the most effective means of treatment for neck pain, far exceeding placebos or exercise. Though there are various definitions and modalities of cervical manipulation, in general, treatment involves the use of applied force in a single direction perpendicular to the affected cervical joint surface. The widely-accepted indicator of the success of any manipulation is an audible “pop” or other sound produced by the joint’s cavitation, regardless of which technique is applied in the manipulation.

A recent study 1 compared the results of four practitioners’ spine manipulation therapies on the relative range of motion (ROM) in four control groups. The subjects of the study—students with no history of neck pain—were analyzed for relative ROM prior to, and after manipulation therapy. Practitioners involved in the study represented a range of experience (1,20, and 20 years) in cervical spine manipulative therapy. They employed “classic” HVLA technique (in which the patient is in an upright, seated position, with shoulders relaxed) on their subjects, who were fitted with spine motion analyzers attached to an adjustable helmet and harness prior to their manipulations. The volunteers—9 women and one man whose average age was 25 years—were manipulated one-to-four times by each of the four practitioners, who were instructed to discontinue the manipulations after achieving cavitation or after four attempts. An independent observer collected kinematics data during the experiment. This data was later analyzed to determine the rate of cavitation occurrence during each practitioner’s C3 and C5 thrust manipulations. The procedures used in the study employed a low magnitude of axial rotation to reduce the risk of potential cervical artery dissection.

The study concluded that there was little relevance in the direction of applied forces in the vertebral manipulation. Rather, the number of years a practitioner had been in practice was a more reliable indicator of kinematic impact on the subjects in the study. The most experienced practitioners most consistently achieved acceleration magnitude and produced cavitation. Their therapies consistently improved neck mobility and relative ROM in their subjects, suggesting that certain kinematics parameters are most likely linked with the occurrence of cavitation for thoracic manipulation.




  1. Assessment of in vivo 3D kinematics of cervical spine manipulation: Influence of practitioner experience and occurrence of cavitation noise

Fostering Postural Interoceptive Exercises to Help Reduce Neck Pain

posture, awareness, pain, spine model

In a recently accepted Level 1 evidence publication (Jan 31, 2017), a study looked at how postural awareness can make an impact on non-specific neck pain. Non-specific neck pain usually indicates that there isn’t  any pathological problems. Moreover, this usually indicates a degenerative problem associated with the intervertebral discs and/or facet joints.

In their study (Does Postural Awareness Contribute to Exercise-induced Improvements in Neck Pain Intensity? A Secondary Analysis of a Randomized Controlled Trial Evaluating Tai Chi and Neck Exercises) seventy-five subjects were randomly allocated to two groups: a Tai Chi group and conventional neck exercise group. After a period of 12 weeks, neck pain VAS measures decreased significantly in both groups.

The authors speculated that postural awareness played an important role in the positive outcomes.

Postural awareness can be a challenging concept to encourage especially when patients do not know the reason to do so. Dynamic Disc Designs models allow the practitioner to explain why posture is important. This fosters postural awareness through education rather than a dictatorship approach.

Interoceptive consciousness often begins with an understanding of how changing posture can change the stresses on the internal spinal structures.

Whether you are trying to motivate postural interoceptive awareness or explain why certain neck exercises are important to the patient, our models help connect the reasons at to why.

“ Your models have re-established the vital importance of the doctor / client communication relationship, dramatically bridging the gap for both to have a common understanding of the condition, the process ahead, and the targeted outcomes towards health and wellness for life. Simply perfect.” Barry Kluner DC

Postural awareness begins with an understanding of how the spine works. Our viscoelastic models show patients the effect of load and time dependent compression. Changing the angles of the endplates can significantly improve ones posture and the reduction of pressure on sensitive tissues. Teaching a patient as to WHY to improve their posture is a key to helping them reduce their pain.


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Migration of Nucleus Pulposus

Treatment strategies related to intervertebral disc displacement often involves extension. Robin McKenzie’s work on centralization of symptoms in the case of disc herniation has been used by many.  Most of the research on migration nucleus pulposus has been previously investigated in the lumbar spine. In a recent study published in PM&R 1 , researchers looked at the cervical spine and wondered if this was a similar case. They hypothesized that cervical extension would centralize and shift the nucleus anterior–away from the associated disc herniation.

They looked at 10 healthy young males with mean age of 22 yrs old and compared neutral to extension position of the cervical discs using MRI. They carefully mapped out the nucleus pulposus and found that in extension the migration nucleus pulposus was anterior and away from the posterior disc margin.

They concluded that moving the cervical spine into extension could be clinically valuable in the case of cervical disc problems.

At Dynamic Disc Designs, we have seen what these researchers have seen! When our handcrafted models (with an annulus and nucleus) are moved into extension, the nucleus can been seen to move anterior. In our lumbar models, the clear L4 vertebra of our Professional LxH Model allows full migration visibility of the nucleus pulposus. This is helpful in the clinical explanation of treatment targets for patients with intervertebral disc problems.

migration nucleus pulposus, lumbar model

Posterior nucleus migration in flexion.

  1.  Kim YH, Kim SI, Park S, Hong SH, Chung SG Effects of Cervical Extension on Deformation of Intervertebral Disk and Migration of Nucleus Pulposus. PM R. 2016 Sep 6. pii: S1934-1482(16)30905-4. doi: 10.1016/j.pmrj.2016.08.027. [Epub ahead of print

Posterior Annulus and the High Intensity Zone – Research looks to sub-classify this MRI finding

posterior annulus

Discogenic pain is quite common. A finding on MRI that has been hotly debated is a hyperintensity zone, often seen within the posterior annulus of the intervertebral discs.

In a recent study published in PLOS One 1 researchers conducted the first large scale study to identify subclassifications of high intensity zones (HIZ). They looked at a cross sectional study of 814 participants both using T1 and T2 weighted imaging and created a morphological and topographical classification system. Findings included HIZs on the posterior annulus and anterior annulus.

High Intensity Zone, HIZ, Lumbar Disc, posterior annulus

They believe the results could help in the standardization of MRI findings in clinical and research settings.

MRI has been thought to be not very helpful in the early management of back pain. However, more research (like this) to extract MRI findings should help localize pain generators and direct patient care and treatments. Even if imaging is thought to be less than optimal in the early management of back pain 2 it is still important to look carefully at MRI and correlate a patient’s symptoms to help direct patient care. Otherwise, it is a bit of guessing game which structures are inflamed.

Dynamic Disc Designs Corp. develops models that can help the clinician in the explanation of MRI findings. Visit us.

This is the best model lumbar spine I have seen. I am proud to possess one. It will be of great value when explaining to my patients as well as in my research using Upright MRI

Francis W. Smith MD Clinical Professor of Radiology Positional MRI Centre Woodend Hospital Aberdeen, Scotland


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Nuclear tracking spine model – helping explain research findings.

3D discogenic pain model

Nuclear tracking as a result of vibration for spine has been revealed in an ISSLS price winning study in Spine. In a microanatomical investigation titled : ” Vibration Really Does Disrupt the Disc ” 1 researchers looked at motion segments and the influence of vibration as it relates to intervertebral disc damage.

There has been background knowledge stating that whole body vibration can lead to back pain but no-one had studied the micro structure of the disc. Looking carefully how nuclear tracking disrupts the annulus and endplate, this study looked at sheep discs, with controls, and vibrated motion segments under 7 degrees of flexion. The forces used were 1300 plus or minus 500N and the frequency applied was 5hz. This equates to 5 vibration movements per second. They conducted the movement for 20,00 to 120,000 cycles to mimic lose does and high dose variation.

Nuclear Tracking in a Spine Model

nuclear tracking, flexion, motion segment, model, modeling

Flexion load causes posterior nuclear tracking.

They found there was no sharp significant drop in displacement revealing there was not one moment of catastophic failure. What they found was nuclear tracking and internal disruption of the inner and mid layers of the annulus fibrosus. They also saw delamination of the annular fibres where they attach to the endplate (aka, Sharpey’s Fibres)

In conclusion, these researchers revealed that vibration in a flexed spinal motion segment leads to inner and mid layer annular disruption rather than outer annular disruption that is seen with disc herniation. They believe this mechanism could lead to a better understanding of the initiation of the degenerative cascade of spine.

Dynamic Disc Designs tries to highlight important research and model the respective findings for spine professionals working with patients of back problems. Educating patients about the mechanisms  of back pain can be an empowering tool for both doctors and patients.

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Herniated Lumbar Disk – Review and Modeling

Published May 5th, 2o16 in the New England Journal of Medicine 1 is a review paper on herniated lumbar disk. Dr. Deyo opens the manuscript with a case presentation of  41-yr-old man. He develops progressive increasing lower back and leg pain from doing yard work. This involved pulling out large bushes. With a positive straight leg raise at 40 degrees, the most probable diagnosis is herniated lumbar disk.

About two-thirds of adults experience back pain some time in their life. Sciatica is often used to describe the result of a disk herniation as the sciatic nerve is the downstream nerve effected. A more appropriate term is lumbar radiculopathy. This is due to the proximal origin of the issue and the sensory and motor findings that presents along the sciatic nerve distribution.

Herniated Lumbar Disk

To help with patient education of a herniated lumbar disk, accurate modeling of the nucleus pulposus and annulus fibrosus is developed by Dynamic Disc Designs Corp. Now, a patient can understand the geometry and forces involved to create a disk herniation and may think twice about repeating the activity that causes the problem initially. Accurate patient education of herniated lumbar disk to reveal the mechanism of the injury is very helpful in the management of the condition. This is both in onset and rehabilitation as load with flexion causes the nucleus to push posteriorly.

herniated lumbar disk. lumbar, disk

Herniated lumbar intervertebral disk – important for patients to see how this happened

It is important for patients to understand what caused their symptoms as to change future behaviours. It is known that a herniated lumbar disk is caused by hydraulic compression of overloading the spine into a flexion moment as the posterior annulus is compromised causing radial fissures 2. And now, this never before seen event can be shown with a knowledge transfer to the patient in an easily understandable dynamic model to help improve outcomes.


  1. Richard A. Deyo, M.D., M.P.H., and Sohail K. Mirza, M.D., M.P.H. Herniated Lumbar Intervertebral Disk. The New England Journal of Medicine. May 5, 2016 1763-72
  2.  Samuel P. Veres, BEng, Peter A. Robertson, MD, Neil D. Broom, PhD The Morphology of Acute Disc Herniation. A Clinically Relevant Model Defining the Role of Flexion. SPINE 2009 Volume 34, Number 21, pp 2288–2296
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Intervertebral Disc – Stress Shielded by Facets – Dynamic Education

intervertebral disc, model, facets, stress shielded, dynamic, spine, patient education

The intervertebral disc annulus can be shielded by the facets. This is important for the patient to understand to help motivate exercise strategies to relieve their back pain.

Researchers have seen in studies that bending the spine backwards (extension) helps resist compression of the spine discs 1 especially when the disc has already lost some height. 2 3 When crafting exercises, and if the facets are not considered a pain generator, bending backwards, especially in the unloaded position, can be an effective strategy to help heal discogenic pain.

Several mechanisms have been proposed on why extension-based exercises aid in the reduction of back pain. One likely path is the direction the nucleus moves as the spine is bent backwards. It has been shown in several studies that the nucleus moves away from the posterior annulus in spinal extension 4 5 6 7 8 9

Dynamic Disc Designs Corp. is the only spine modeling company that demonstrates these findings in a dynamic spine education platform. The Professional and Academic LxH models allows clear visualization of the nucleus as the model moves through 6 degrees of freedom. Patient education that motivates and drives compliance through knowledge to improve clinic outcomes for spine.