spinal mobility

Goal of the Study?

The goal of this study [1.Spinal mobility in radiographic axial spondyloarthritis: criterion concurrent validity of classic and novel measurements] is to evaluate spine range of motion (ROM) measured by tri-axial accelerometers compared to both current clinical tests and radiography in radiographic Axial spondyloarthritis (AxSpA) patients. 


Why are they doing this study?

AxSpa is a chronic and progressive form of inflammatory arthritis. To measure progression and plan treatment, there is a need to measure indicators for spinal mobility in forward and lateral bending. Currently, this is often done using a clinical tape measure. However, research has illustrated that there is poor validity using a tape measure to assess spine mobility compared to the images and RoM from radiographs. However, with the risks associated with repeated exposure to radiation for radiographs, and the lack of validity in using clinical tape measures, there is a need for better alternatives. To that end, research has illustrated the value of devices that incorporate strain gauges and/or accelerometers to measure spinal curvature.

spinal mobility

A novel measuring approach to minimize radiation exposure.


What was done?

This study recruited fifteen radiographic Spondyloarthritis patients. First, each participant had lateral and posterior-anterior radiographs taken standing upright. Following this, each participant completed three RoM trials in forward flexion, right lateral and left lateral bending. In total, five lumbar radiographs were taken. For each participant, three measurements were collected: tape, synchronized radiograph and accelerometer measurements at the end range of forward and bilateral lateral flexion. The researchers then used statistical software to determine reliability.


What did they find?

The findings of this research support using accelerometers as a replacement for sagittal spine mobility, but not lateral. The accelerometer measure of the sagittal spine had a stronger correlation to the radiographic measure than all tape measures. They argue that this approach can overcome some of the inherent challenges with tape, such as skin stretching. In lateral bending, the Lateral Spinal Flexion tape (LSFT) correlated stronger than the accelerometer method. Furthermore, an accelerometer-derived measure of frontal plane spine mobility underestimated lateral bend angles from the radiographs. It demonstrated a moderate correlation to the radiographic gold standard lower than either the LSFT or DT.


Why do these findings matter?

The use of accelerometers can limit patients’ exposure to ionizing radiation through repeated radiographs in the AxSpA population. Improved ability to measure spinal changes is important to evaluating and managing disease progression and treatment. 


degenerative joint disease

Goal of the Study?

In this study 1, the authors investigate degenerative joint disease in the spine and major peripheral joints (shoulder, elbow, hip and knee) in chimpanzees, lowland gorillas and bonobos.


Why are they doing this study?

Degenerative joint disease is one of the most common pathological musculoskeletal conditions in human populations. It has also been observed in a variety of nonhuman animals, including nonhuman primates. Existing research has illustrated degenerative disease in chimpanzees, gorillas, orangutans, gibbons, macaques, baboons and probosci’s monkeys. Overall, prevalence has been reported as quite low in wild monkeys (with some exceptions) compared to colony-reared Old-World monkeys. 

The authors want better to understand the evolutionary basis of degenerative joint disease. 


What was done?

This investigation’s skeletal materials are drawn from two samples of chimpanzees, a sample of lowland gorillas and a small sample of bonobos. The samples from the chimpanzees are from Gombe National Park, Tanzania, while the other materials are from museum materials originally collected in west/central Africa. In total, 5807 sample surfaces for vertebral osteophytosis (VOP), 12,479 surfaces for spinal osteoarthritis (OA) and 1211 joints for evaluation of peripheral joint OA.

The human osteological samples are from two areas, Central California and a group of Inuit from Alaska.

The presence of VOP was based on a determination of osteophyte development. OA presence was based on hypertrophic development and changes to joint spacing. The severity of VOP and OA was scored based on slight, moderate or severe.


What did they find?

All apes display significantly less spinal disease compared to humans. The authors suggest that this is most likely related to movement on two legs. Among the African apes, gorillas are slightly more involved in the spine than chimpanzees with almost no spinal degeneration. Both bonobos and gorillas have significantly more involvement than chimpanzees in the cervical and thoracic regions (but the sample size for bonobos is so small that it is hard to say there is any significance).  As with previous research, the authors found that colony reared Old World monkeys, such as macaques, have higher OA levels than other free-ranging apes. The authors argue that the variation between humans and African apes in VOP and OA prevalence may be explained by human longevity.


Why do these findings matter?

This study can help understand basic processes in degenerative joint disease among humans and our closest relatives in a broader evolutionary context. 



Goal of the Study?

In this study 1, the authors use a rat model to examine the time-course development of pathological joint changes and correlate them with pain-related behaviour in OA. 

Why are they doing this study?

There is a very high incidence of Osteoarthritis (OA) in the elderly population, and it is a leading cause of disability and pain. However, there is a lack of knowledge of OA’s pain mechanisms, particularly the role that neuropathic pain (NP) plays in OA.

OA has been described as a degenerative rather than an inflammatory disease. However, in recent years research has identified the many inflammatory processes that take place in OA.  Existing OA models have shown how this inflammation is supported by overexpression of nerve growth factors causing nociceptive fibres to grow into inflamed joints. This inflammatory process helps explain why there is a poor correlation between radiographic changes and pain levels in OA patients. Moreover, some patients continue to experience pain after a total joint replacement, suggesting that OA can result in neuropathic pain (NP). 

What was done?

The researchers used a rat monoiodoacetate (MIA) model of the ankle joint. MIA results in pathological changes and pain-like behaviour common with those observed in human OA. This model has been used extensively in research and is well validated.

They injected MIA or saline into a total of 126 male rats. For this study, they used the rat ankle joint as it receives most of its nerve supply from the sciatic nerve, which is used most commonly in NP models. From this, they assessed a variety of changes, including pain-related behaviour, hypersensitivity, reaction to cold and heat, changes to normal movement, cartilage degeneration, bone degeneration, and the effects of drug treatments.

What did they find?

 Overall, the study provided a time-course view of the development of pathological changes to the joint and the associated pain-related behaviours. 

The researchers found significant innervation increases at specific periods of time that coincided with mechanical hypersensitivity at 4 weeks and pain in response to cold at 5 weeks. X-ray findings showed significant cartilage and bone degeneration and joint space narrowing at 5 and 10 weeks. 

The study also illustrated changes in sensory and sympathetic innervation of joints in the subchondral bone and synovial membrane at 5 and 10 weeks.  This increased concentration of sensory and sympathetic fibres was associated with pain-related behaviour and similar to those observed in NP models. Furthermore, they found that pain-related behaviour and extensive joint damage were associated with the expression of activating transcription factor 3 (ATF3) in the dorsal root ganglia (DRG), as well as the microglia and astrocyte changes in the dorsal horn. Using various pharmacological treatments to inhibit or block sympathetic fibres and glial could suppress pain-related behaviour. They argue that these findings suggest that multiple factors contribute to OA pain, including inflammatory changes in the joints, supporting the theory of a neuropathic component in OA.

Why do these findings matter?

As pain is the main reason patients seek medical help, effective pain management is critical to improving life quality. Therefore, understanding what causes pain will help in the development of pain management protocols and treatments. 


vacuum sign

Vacuum sign is a common radiological finding. It is also referred to as a vacuum phenomenon and often associated with degenerative spinal discs, knee joints, hip joints, and shoulder joints.  Degenerative spondylolisthesis is a spinal condition whereby one vertebra slips on another. However, it is sometimes difficult to ascertain whether this slippage is stable or not. A more than 4mm movement defines instability, but some have indicated only 2mm as clinically significant.

degenerative spondylolisthesis model

Degenerative Spondylolisthesis Dynamic Disc Model

In a research paper published in World Surgery, 1 a group of authors looked at the vacuum sign in the facet joint as an indication of degenerative instability of the spine. They wanted to investigate the relationship between the vacuum facet phenomenon and lumbar instability. Why, you may ask? More and more research is directing spine researchers to the cause of pain and disability to the imbalance of motion of the individual vertebral segments of the spine. Some have coined this motion sharing.

Each vertebral motion segment consists of two vertebrae, and a disc should have a certain stiffness level. That is, it should move similar to its adjacent segment above and below in the spinal column. For this study, they looked at L4 on L5 (which is a prevalent spinal level to degenerate with age) and used flexion/ extension X-rays in both the fully bent forward (flexion) and the fully bending backwards (extension) with degenerative spondylolisthesis. Additionally, when available, they also looked at CAT scans of these same patients. To determine the slippage degree, they used a dynamic motion index to measure the degree of slippage.

In a total of 67 patients examined, 35 patients had vacuum signs on their CAT scan, and 32 patients did not. The degree of slippage appeared to correlate with the vacuum sign as well. That is, the more the vertebrae had slipped forward, the more likelihood of the presence of the vacuum sign. With this, the authors concluded a linear correlation between the degree of slippage and the presence of vacuum sign.

Vacuum sign

Vacuum phenomenon or vacuum sign and mobility

Commentary by Jerome Fryer

Vacuum sign or vacuum phenomenon is often considered an incidental finding. However, based on the modelling research I’ve done, I believe that the vacuum sign can be a clue into joint mechanics’ stiffness. In 2017 I published an article related to the cracking event we are familiar with, and in there, I believe in having revealed the vacuum phenomenon. In the presence of cavitation, a joint will have less stiffness, and in time I hope we can collectively use these radiographic findings to help us determine which joint requires more stability in the treatment of them. JF

facet osteoarthritis, facet joint pain

Facet osteoarthritis pain is common and thought to be a significant contributor to back pain in the US. Within the United States, it costs 100 Billion dollars annually to combat this endemic problem. However, back pain can originate from many anatomical structures, and the facet joint is only one of them but thought by many as significant. Other common pain structures are the intervertebral discs in the case of disc bulges, disc extrusions, disc protrusions and frank nuclear sequestration. There are also more severe causes of back pain like aneurysm and other organ pathology, so it is crucial to have a professional look carefully at the diagnostics of each case.

In the case of mechanical lower back pain (others use the term non-specific lower back pain), the facet joint garners good attention. The word ‘facet’ comes from the French facette (12c., Old French facete), diminutive of face “face, appearance” and are two anatomical structures that reside behind the intervertebral disc.

Facet osteoarthritis

Modeling facet osteoarthritis is tricky because of the complexity of motion at the spinal level. The intervertebral disc height plays a role with respective facet compression because it resides on the front of the spinal motion segment. It is this compression thought to be contributing to back pain.

Clincally, facet osteoarthritis pain is often unilateral in nature

In a study conducted recently 1, researchers worked to induce facet joint arthritis by creating compression with a spring. Over time the researchers found the increased expression of interleukin‑1β and tumour necrosis factor‑α expression. In other words, with more compression elapsing over time, the more the expression of the molecules related to many low back pain patients.

This is an important study linking the mechanics of compression and the associated physiology of molecules, which are thought to be markers of back pain patients.

At Dynamic Disc Designs, we have developed models to help explain the associated compression of facet joints as it relates to disc height loss and gains. We are committed to bringing the best in modelling. Explore our website for more.


A very recent study 1 published in the ‘Journal of Biomechanics’ analyzed the dynamic interactions present between the human lumbar intervertebral motion segments during flexion and return. It wanted to help further understand the components linked to disability and pain.

What Was the Context?

Low back pain or LBP causes millions of people (around the globe) to experience physical, psychological, and economic stress. That’s why research continues to develop a more efficient means of LBP management.

Understanding of the biomechanics involved in back pain has increased due to continuous dynamic multi-segmental studies of the human lumbar motion. Such knowledge is required before attempting in vivo studies of loading during bending tasks.

However, the readings collected during bending tasks tend to be variable, and establishing normative values is challenging. That’s why, during bending tasks, there’s a need to further explore the interactions present between motion segments.

If one wants to model contemporaneous kinematics and loading for estimating relative intersegmental stresses occurring during bending motion, certain factors need to be studied. These factors include continuously measuring the proportions of the flexion as well as return motion that’s accepted by individual levels. The dynamic interactions between them, during bending, needs to be measured, too.

The current study set out to analyze the adjacent lumbar level’s motion contributions during flexion (active weight-bearing) and the return protocol while using quantitative fluoroscopy or QF.


Demonstrate flexion using LxH Dynamic Disc Model

What Was the Methodology?

The study involved a total of 8 patients (5 males and 3 females). Each of them had chronic non-specific LBP. An obvious mechanical disruption wasn’t present in the patients. All of them went through QF during the flexion as well as return motion. The patients were matched with 8 healthy controls. The same tasks had been performed by the controls, too.

The dynamic motion sharing of segments were calculated throughout the person’s bend and return. The segments were from L2 to S1.

Furthermore, the statistical analysis included the SPSS’s Shapiro Wilk test, independent t-tests, and the Mann-Whitney U.

What Was Concluded?

The results revealed that there were no significant differences between the groups with regards to age, weight, height, or BMI. However, the asymptomatic controls did show higher ranges of intervertebral motion with the only significant reading being at the L5-S1 level. The patient population showcased a significantly less range of motion at the L2-S1 level.

In simple terms, the results revealed that the patient and control groups displayed consistent yet non-significant differences in motion sharing patterns.

According to this study, the results could offer an advantage to help identify components that have a link to disability and pain. For example, this study shared that patients and controls have significant differences in their Average Motion Share or AvMS at the L3-L4 level. Take note; the IV-RoM data was unable to reveal these differences.

The said differences could be due to involuntary muscle activity, bending strategy, or passive tissue restraint.

Hopefully, the current data could help others conduct further research while also covering the muscle’s electrical activity, oxygenation, kinematics, and loading.

cartilage damage and osteoarthritis

A very recent study 1 in the journal ‘Osteoarthritis and Cartilage’ has offered some helpful results. It focused on OA-induced pain in relation to mechanical joint loading and cartilage damage.

Why Conduct Such a Study?

Osteoarthritis or OA is defined as a degenerate joint disease that involves cartilage damage and the loss of cartilage. It tends to physically, emotionally, and economically impact numerous people around the world. And even though a lot still remains to be understood, progress has been made to look at osteoarthritis with a multifactorial lens.

Due to multiple joint tissues having identified pathologies as well as their relationship with OA, many have questioned the role pathologies play with regards to the clinical presentation of pain associated with OA.

When it comes to patients, the clinical presentation of their pain happens to be the most problematic oesteoarthritis symptom. And much remains unknown about knee pathology’s link with OA-related pain.

The current study’s primary objective was to better understand the complexities of the pain-structure relationship. The team used MJL or the mechanical joint loading model of OA for investigating knee pathology as well as nociceptive behavior.

What Was the Methodology?

The study used the MLJ model for inducing OA in the right knees of male mice. These mice were 12-weeks-old. A two-week loading regime was administered through an electronic testing machine.

A total of 36 mice had OA induced. Another batch of 36 mice (with no induced OA) acted as non-loaded controls. The team sacrificed separate groups of non-loaded and loaded mice during the one, three, and six-weeks points of post-loading for post-mortem analysis.

The study conducted behavior analysis before loading. At weeks one, three as well as six post-loading, nociception was verified (a day before the mentioned sacrifice points).

Coming to the post-mortem samples, half were used for µCT analysis, OA as well as synovitis grading. The other half ended up being used for nerve analysis.

The collected data was analyzed using the GraphPad Prism. Statistical analysis also included repeated two-way ANOVA, parametric two-way ANOVA, and Levene’s test.

Early cartilage damage

The Professional LxH Dynamic Disc Model can be used to show early cartilage damage.

What Were the Results?

According to the results, increased mechanical hypersensitivity paired with altered weight-bearing was shown by loaded mice. The initial ipsilateral cartilage lesions (that were at the one-week post-loading point) grew worse at the three and six-week points. The observed increase in lesion severity correlated with the development of mechanical hypersensitivity.

Furthermore, loaded mice also showed increased synovitis when compared to the control mice at the one-week post-loading points. However, the said increase returned to normal during the third and sixth week. Also, cortisol levels increased only during the one-week post-loading timeline.

Take note; there was no change in the subchondral bone integrity and nerve volume.

What was Concluded?

The study indicated that even though initial stress reaction, as well as local inflammation, was induced by loading, the said processes aren’t directly deemed responsible for the observed nociceptive phenotype.

However, allodynia induced by MJL is mainly associated with the cartilage lesions’ OA-like progression.

The team also noted that more still needs to be done to improve the understanding of how nociceptive behavior is induced by cartilage damage as well as which types of tissue pathologies could potentially play a role in pain associated with OA.

The current study’s team hopes that their current research might help others analyzing the MJL model’s pain-structure relationship.