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

Does Spinal Posture Act as a Trigger for an Episodic Headache

A review 1, found in Current Pain and Headache Reports was conducted to see if there was indeed a valid link between spinal posture acting as a trigger for an episodic headache. While the review concluded more research is required, it did present some interesting results.

The Global Issue of Headaches

According to the WHO (World Health Organization), headaches are one of the ten most disabling conditions for human beings. Numerous factors have been studied to contribute to or give rise to the development of a headache. Secondary headaches have been observed to be due to an underlying etiology, for example, trauma, infections, and dysfunctional or abnormal cervical structures. Take note, primary as well as certain secondary headaches arise from complex multi-dimensional interactions between lifestyle, psychosocial, cognitive, biological, and environmental factors. Due to several triggers, identifying underlying mechanisms of headaches continues to be challenging.

Headaches and Spinal Positions

The current world encourages people to remain seated. According to studies, when daily computer use exceeds 3 hours, there’s a higher prevalence of musculoskeletal complaints. Such complaints include experiencing pain in the neck, head, or upper extremity. These complaints are suspected to be linked to slumped sitting postures.

A slumped sitting position involves an increased posterior pelvic rotation, forward head posture, and thoracic flexion. Such postures (if sustained) tend to increase the biomechanical momentum and torque, decrease proprioception, cause creep of spinal tissue, and limit postural variability.



Headaches and posture

Why do such a Review?

While an extensive framework for headache classification is provided by The International Classification of Headache Disorder, outcomes following physiotherapy do vary. Such variability might be explained due to the absence of protocol studies for identifying the role of spinal posture in headaches. That’s why conducting multi-dimensional profiling of patients (suffering from a headache) based on the interactions present between spinal posture, lifestyle, and psychosocial factors may be essential.

The current review had the objective to find support about whether spinal posture could trigger an episodic headache. The review considered a multi-dimensional view on tension-type and cervicogenic headache (this included modern pain neuroscience).

What Did It Find?

The current review described several pathways to support how spinal postures acted as a trigger for an episodic headache. Psychosocial factors could also act as a catalyst for the development of a headache through a maladaptive spinal posture.

However, further research is still required to determine the exact level of contribution of spinal postural dysfunctions and their ability to trigger a headache.

Analyzing the Sensorimotor Control of the Spine

A review 1 was conducted to analyze the sensorimotor control of the spine. The overall conclusion of the review was that spinal structures were capable of monitoring sensory information and can control spinal muscles. They could likely offer kinesthetic perception to the sensory cortex.

Why Conduct such a Review?

One of the most common medical ailments affecting the middle-age population is low back pain or LBP. According to reports, LBP is an expensive musculoskeletal ailment. It’s multi-faceted and needs to be covered under sociological and psychological parameters. Trying to find the origin of LBP still requires a lot of research. Studies have speculated LBP being the cause of intervertebral disc damage. It has been linked to the damage of zygapophysial joints as well. The damage can be due to disc prolapse or traumatic injuries. It can be due to a degenerative process, too (particularly loading patterns).

sensorimotor control spine

The mechanics behind numerous spinal disorders can act in combination or single variables. Direct and referred pain can be caused by the derangement in the zygapophysial joints and lumbar intervertebral disc. The point being that we are yet to fully understand the link between structural alignment and pain.

What did this Review Do?

The current review went over the spinal viscoelastic structures. These structures included capsule, ligaments, and disc. The review gave particular focus to the structures’ sensory motor functions. The review shared that electrical stimulation of the lumbar afferents in the capsules, discs, and ligaments showed elicit reflex contraction of the longissimus and the multifidus muscles. Furthermore, the mechanical stimulation of the spinal viscoelastic tissues was able to excite the muscles with a higher excitation intensity. This occurred when more than one tissue was stimulated.

The review covered reflexes from different lumbosacral structures, the neuromuscular interaction between the spinal structures, and the reflexes from spinal ligaments. It also looked at the clinical implications of reflexes from the passive structures in the spine.

What did the Review Conclude?

The current review concluded that spinal structures were capable of monitoring sensory information in humans. They were also able to control spinal muscles.

Spinal manipulation, DDD

A follow-up MRI study 1 of how non-specific lower back pain (LBP) patients responded to spinal manipulative therapy (SMT) showed that, while there were no significant differences in spinal degenerative features across responding and non-responding groups studied, the non-responding patient group appeared to have more severe degenerative features and lower baseline ADC values in their MRI scans than those who responded well to SMT. The study indicates that patients who respond well to SMT have fewer degenerative changes in posterior joints and disc diffusion than those who do not respond positively to SMT. The study suggests that treatment for patients with extreme degenerative changes should be tailored to address their LBP, as SMT may not provide a desired outcome for their condition.

What’s at Stake?

LBP –in particular, non-specific LBP—is one of the leading causes of disability and lost income potential across the world. Though SMT has been proven an effective form of treatment for many patients with non-specific forms of LBP, not all patients respond favorably to spinal adjustments or report satisfaction with their levels of pain relief and physical comfort, post-SMT. While many patients demonstrate measurable clinical improvements after 1 -3 SMT treatments, a subset of non-specific LBP patients do not respond to SMT. A previous study demonstrated a reduction in spinal stiffness, improvements in modality and an increase in lumbar multifidus contraction, and water diffusion at the L4-L5 disc level in a group of SMT responders after one week of treatment, while these benefits did not manifest in a group of non-responders or a control group. The current study was conducted to use MRI to look for significant differences between responders and non-responders that might account for the discrepancy in SMT outcomes.

The Review

A secondary analysis of the original non-randomized clinical trial involving subjects between 18 and 60 years of age who experienced non-specific LBP with an intensity of at least 2 on an 11-point scale and at least 20 percent on the modified Oswestry Disability Index (mODI) was conducted. Exclusion criteria included prior lumbar surgery, scoliosis, pregnancy, SMT within the past four weeks, and spinal tumors, fractures, or any issues that might exclude the subject from MRI scanning.

The 32 subjects attended three sessions—the first, with an MRI scan and standardized SMT, the second, with SMT only, and the third, where an evaluation of their mODI score, spinal stiffness, and multifidus function was analyzed. No SMT was performed at the last session. Subjects with greater than 30 percent improvement at the third session within one week were deemed “responders.” Those with less than 30 percent improvement were considered “non-responders.”

MRI findings were graded on a 4-point scale of joint degeneration and clinical value. Considerations included space between joints, osteophyte presence, hypertrophy of the articular process, subchondral cysts, and subarticular erosion. Other spinal irregularities were also analyzed and graded on subsequent rating scales.


Baseline spinal structure demographics were similar across the board for all subject groups. A total of 15 subjects were labeled as “responders” based on the mODI scores, and 17 were considered to be “non-responders” to the SMT. The non-responders had more disc degeneration in their facet joints, as seen in the MRI scans. IVD and MC grading was similar in both groups. There was a higher prevalence of degeneration in the L4-L5 and L5-S1 levels in those with disc degeneration. Modic endplate changes were more prevalent in the non-responder group, at 58 percent (46.7 percent in the responder group).

Baseline ADC mean measurements and post-SMT disc diffusion responses varied between the two groups, with the lower scores of non-responders suggestive of higher rates of L4-L5 disc degeneration—a potential source of pre-and-post-treatment pain. The limited mobility of the degenerated discs could also be a factor in the non-responder group’s outcomes. The authors of the review suggest further studies with a larger sample size be conducted in the future to investigate the relationship between spinal degeneration, SMT response, and lower back pain.

The review did find beneficial post-SMT ADC level increases in the group of responders with LBP that suggests the therapeutic value of spinal manipulation in improving disc diffusion in and around painful spinal segments. However, 26 percent of the responders with LBP had no significant change in the ADC levels, so the beneficial effects of SMT may have more to do with mechanical or neurophysiological alterations, rather than diffusion.

Pathologies that are not biomechanical in nature, including bone inflammation, are unlikely to respond to SMT, according to the study. The findings highlight that non-specific LBP is treatment-specific, since its origin may be caused by a number of different conditions. Therefore, the review’s authors caution against using a single SMT approach in treating all non-specific LBP.