At Dynamic Disc Designs, we believe research to be the foundation of our spine models so practitioners in musculoskeletal health feel confident in the use of an accurate model while they educate patients about their findings.  Historically, models have been inaccurate and most critically, static, making it very difficult for the doctor to be convincing to the patient in the accuracy of diagnosis.

Research is at the roots of any practice. It fuels practice guidelines and directs both the patient and practitioner down the best path of care. Our models help support that voyage. We have worked hard to bring the best to practitioners of musculoskeletal science by scouring databases of spine science, to arrive at the most accurate model for teaching possible.

With over 1000 papers read in full text, Dr. Jerome Fryer leads the way by making sure our models are keeping up to the standards of best evidence. Weekly literature searches on keywords that surround musculoskeletal health are at the core roots of Dynamic Disc Designs.

Sagittal

Goal of the Study?

In this study 1, the authors investigated the flexion-extension range of motion (ROM) and centre of rotation (COR) of lumbar motion segments in a large population, as well as the relationship between lumbar movement and sex, age and intervertebral disc degeneration (IVD).

 

Why are they doing this study?

Research on the in vivo motion of the spine has a long history. However, many of these studies have used non-invasive technologies with inherent limitations impacting their accuracy and precision. Moreover, many studies have included a lower number of subjects, preventing the ability of the data to represent the general population.

The authors argue that radiographic techniques in this study help overcome these limitations as the images allow for better visualization of each vertebra and movement of the lumbar segments. Additionally, the use of a large sample size for this study addresses the issue of representation and is the largest study to date looking at in vivo lumbar motion. 

 

What was done?

The researchers did a retrospective study looking at the radiographs of the lumbar spine in full flexion and extension for 602 patients, with the age and sex documented for each one.  Additionally, they used MRI scans of 354 patients. 

All spinal levels between T12-L1 and L5 – S1 were analyzed, resulting in 3612 lumbar motion segments from the radiographic images. They also examined 2124 images from the MRI scans looking at disc degeneration. ROM and COR were calculated for all lumbosacral segments using the software. They then examined the associations between motion and age, sex, spinal level and disc degeneration.

 

What did they find?

The median ROM in this study was 6.6 °. The researchers found an association between age and ROM, with older individuals, have lower ROMS. They argue these findings clearly demonstrate a relationship between age and lumbar spine flexibility independent of any signs of spinal degeneration. They also found that lower ROMS were associated with disc degeneration. However, they did not find any association between sex and ROM.   

In this study, they did not find an association between the position of the COR and the spinal segment. The most common COR was at the centre of the lower endplate of the IVD or slightly lower. With degeneration, particularly severe degeneration, they found the location of the COR spread randomly around the centre of the intervertebral space.

 

Limitations?

One of the main limitations of this study was the sole focus on the flexion-extension motion of the lumbar spine rather than including information on movements of different areas of the back. 

 

Why do these findings matter?

This study comprises the largest examination of the in vivo lumbar spine in flexion-extension, paying attention to age and spinal degeneration issues. Understanding the relationship between age and spinal mobility provides patients and doctors with information to better treat back pain and instability.

Facet angle

Goal of the Study? 

In this study 1 the authors use MRI to measure changes in the facet angles of the lumbar spine and analyze the relationship between angle changes and the herniated lumbar intervertebral disc. 

 

Why are they doing this study?

The incidence of lower back pain (LBP) is prevalent in today’s society and can place an enormous burden on individuals and health systems. There are many causes of LBP, including lumbar facet joint (LFJ) degeneration, lumbar disc herniation (LDH), compression of nerve roots, and others. There is currently little understanding of the role of lumbar facet joint angle changes and lumbar disc herniation play in LBP. The authors comment that there is a lack of knowledge on whether the structural abnormality of the spine resulting from LFJ degeneration causes the abnormal force of the lumbar intervertebral disc herniation. Additionally, there is a need to understand whether lumbar facet joint angle changes are common in patients with lumbar disc herniation.

 

Professional LxH Model (L4-5) with asymmetric facet angles

 

What was done?

First, the authors review both direct and indirect signs of lumbar disc herniation as seen on MRI. They state that MRI provides an advantage to obtain horizontal and sagittal three-dimensional scanning of the spinal cord, subarachnoid space, vertebral body and intervertebral discs. They review the various signs of the nucleus pulposus, schmorl nodules, lumbar dural sac, lumbar spinal cord and nerve root compression.

The authors used cross-sectional images of the MRI to measure angles of the articular processes on both sides. They included 500 cases of patients with a clinical diagnosis of lumbar disc herniation and concurrent lumbar disc MRI examination. This included 227 males and 273 females with an average age of 41. This was broken down into 137 cases in the central LDH group, 140 cases in the left paralateral LDH group, 127 cases in the right-side LDH group and 75 cases in the control group. The cases were based on those who met the diagnostic criteria over 18 and relevant imaging and clinical data. Statistical software was used for statistical analysis.

 

What did they find?

The authors found no statistically significant relationship between age, gender, height and weight of the groups and LDH. They found no statistically significant relationship between MRI and CT measurements of the facet joint angle. They argue a correlation between the changes illustrated in MRI images of lumbar disc herniation and the TCM syndromes of lumbar intervertebral disc herniation. They found that the L4/5 and L5/S1 segments of the lesion in the central LDH group and the left paralateral LDH and right-side LDH were all significantly different from the control group.  Facet joint asymmetry is closely related to lateral lumbar disc herniation. However, the asymmetry of the facet joints is not related to the central lumbar disc herniation. They argue that MRI has a high sensitivity concerning measuring angles of the facet joint and changes to those angles and how they correlate with herniated discs. 

 

Why do these findings matter?

Understanding the relationship between lumbar facet joint angle changes and lumbar disc herniation is useful for preventing and treating LBP

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. 

 

loading

Goal of the Study?

In this preliminary study, 1 the authors compared the effects of loading compression and traction on lumbar disc measurements, particularly the magnitude and distribution pattern of fluid within lumbar discs, in relation to intervertebral disc degeneration.

 

Why are they doing this study?

Intervertebral disc degeneration (IVDD) is associated with many biochemical and morphological changes in the disc that contribute to degeneration and negatively impact normal function. With degeneration, there are changes to the amount of fluid and the distribution pattern of this fluid within the disc. The authors argue that this may provide unique biomarkers that can help with diagnosing and classifying degeneration. The authors hypothesize that using T2- weighted MR images will enable better insight into disc degeneration. It only changes in response to variations in fluid distribution and these potential degeneration biomarkers. 

 

What was done?

A total of 35 volunteers between the ages of 18-65 were recruited: 20 with and 15 without low back pain (LBP). Using a custom MRI compatible loading table, the participants spent 20 minutes in the supine, unloaded position; then they spent 20 minutes loaded in axial compression and then 20 minutes with axial traction. A compressive load equal to 50% of each subjects’ body weight was applied to simulate loading and traction. For lumbar discs, the height, angle, width, mean-T2 and T2 weighted centroid (T2WC) locations were calculated. Disc degeneration was measured using the 5-point scale by Pfirrmann et al.

 

What did they find?

Most of the effect size (ES) differences the authors found in response to loading were seen from compression to traction. They observed small but statistically significant changes with an inferior and posterior shift in L4-5 (ES: 0.4, 0.14) and L5-S1 (ES: 0.25, 0.33) T2 weighted centroid. More degeneration was associated with larger anterior displacement and more superior displacement of the disc T2WC. Moreover, degeneration was not associated with changes in disc width, but with greater degeneration, there were larger decreases in an extension of segmental angles.

From unloaded to compression, they found statistically significant small posterior shifts for the disc T2WC at the L1-2 level (ES: 0.39). They also saw an increase in L5-S1 width (ES: 0.22), an anterior shift in L1-2 T2WC (ES: 0.39), and L3-4 (mean 2.1˚) and L4-5 (1.8˚) extension angle. Additionally, with more degeneration, there were larger inferior movements of the disc T2WC, but not changes in disc width. 

Overall, their findings on compression to traction demonstrated the most significant findings in the lower lumbar levels. They also found a magnitude difference associated with the severity of disc degeneration. This supported their hypothesis that fluid distribution-related measurements illustrating the effects of degeneration and lumbar disc loading.

 

Why do these findings matter?

Biomarkers can help to illustrate how the lumbar spine responds to different loading conditions and can be used to monitor degenerative changes in the lumbar spine.

 


At Dynamic Disc Designs, we appreciate the dynamics of the discs and how professionals can communicate these small changes to patients as it relates to their dynamic symptoms and the solutions of back pain.

GAG content

Goal of the Study?

In this study 1, the authors’ goal was to assess the GAG contents of lumbar IVDs in disorders of the spine, including non-specific lower back pain (nsLBP) and radiculopathy, against asymptomatic volunteers to determine the potential influence of IVD protrusions on the GAG contents of adjacent IVDs.

 

Why are they doing this study?

Low back pain (LBP) is a common health burden that has significant implications for individuals and society. Most LBP is non-specific (nsLBP) and without a known cause. One potential factor contributing to nsLBP is lumbar degenerative disk disease (LDDD). A common structural disorder that leads to LBP is lumbar IVD extrusion with radiculopathy. While MRI for diagnosis of LBP is controversial, it is the most commonly used technique for looking at the morphological changes in LDDD, such as IVD dehydration and loss of IVD height. However, to detect early structural changes to cartilage, the use of the non-invasive compositional MRI technique GAG Chemical Exchange Saturation Transfer (gagCEST) is preferred. Existing research has demonstrated how gagCEST images can help to differentiate degenerative and non-degenerative IVDs based on their respective GAG contents. To that end, the authors hypothesized that the GAG contents in patients with nsLBP and radiculopathy are significantly lower than in asymptomatic volunteers and that the GAG content of lumbar IVDs adjacent to extruded IVDs is markedly lower than that of non-adjacent IVDs.

 

What was done?

In total, they recruited 18 patients with radiculopathy and IVD extrusion, 16 age-matched patients with chronic nsLBP and 20 age-matched volunteers. All of these participants underwent morphologic and compositional gagCEST MRI. Patients were assessed by an orthopedic surgeon and underwent a neurologic exam, with a focus on radicular pain, distal sensation and muscle strength. All participants’ lumbar IVDs were graded individually and independently using the Pfirrmann classification (non-degeneration) grades 1 and 2; degenerative IVDs (grades 3-5). Statistical software was used to determine statistical significance.

 

What did they find?

Patients with radiculopathy demonstrated IVD extrusions at the IVD segments L4/5 and L5/S1, compared to patients with nsLBP or asymptomatic volunteers who showed none. No differences in Pfirrmann grades were found between patients with nsLBP and patients with radiculopathy and patients with radiculopathy and asymptomatic volunteers. Regarding gagCEST values, the authors found that patients with nsLBP demonstrated lower gagCEST values in their IVDs than those of volunteers, with 1.3% and 1.9%, respectively. However, there were no differences in gagCEST values between patients with radiculopathy and asymptomatic volunteers or female and male participants. Finally, in patients with radiculopathy, IVDs directly adjacent to IVD extrusions showed lower gagCEST values than distant IVDs. The authors argue that GAG depletion in nsLBP and IVDs adjacent to extrusions in radiculopathy demonstrates close interrelatedness between clinical pathology and the compositional and structural changes to IVDs in the degeneration of the lumbar spine. 

 

Why do these findings matter?

Non-invasive gagCEST imaging provides potential diagnostic value to detect early changes to tissue composition and pre-morphological IVD degeneration. It serves to differentiate patterns of IVD degeneration in disorders of the lumbar spine. Early detection can lead to better diagnosis, care and treatment of lumbar spine disorders in patients.

Lower Extremity Arterial Occlusive Disease

Goal of the Study?

In this study, 1 the aim is to understand the risk factors and symptoms that contribute to patients with Lower Extremity Arterial Occlusive Disease (LEAOD) being misdiagnosed with lumbar disc herniation (LDH).

 

Why are they doing this study?

The authors argue that patients who should be diagnosed with lower extremity arterial occlusive disease are being diagnosed with LDH as there are similar symptoms. They argue it is important to understand what factors contribute to this misdiagnosis so that there is no delay in treatment and an increased economic burden to patients and society.

 

What was done?

This was a clinical study with a total of 148 patients. Group A had 126 patients who had LDH with lower extremity symptoms and whose symptoms had been relieved after lumbar surgery of posterior lumbar interbody fusion (PLIF). Group B had 22 patients with LDH with lower extremity symptoms but who had no relief after PLIF. In this group, they were diagnosed with LEOAD and their symptoms recovered after vascular treatment. The Japanese Orthopedic Association and Oswestry disability index scores were collected before surgery, six months after PLIF and sex months after vascular treatment. An evaluation of symptom relief between patients in groups A and B was then used. For each group, the researchers also collected gender, age, HBP, diabetes, smoking, coronary, pulse pressure (PP), LDH, segment and type, ankle-brachial index (ABI) and straight leg raising test (SLRT). They then used statistical software to determine the relationship between the various factors.

 

What did they find?

They found a statistical difference between the two groups in PP, ABI, central disc herniation and SLRT. The researchers found that higher PP, lower ABI, central disc herniation and negative SLRT led to an increased risk of misdiagnosis for LDH, even though these are all associated with LEAOD. Moreover, they found patients were misdiagnosed as having LDH as a way to explain lower limb symptoms even though MRI images displayed only a mild herniation. The authors argue it is important to consider other imaging exams such as CTA and MRA and sufficient patient history and physical exam to determine a diagnosis for LEAOD.  For example, skin temperature and abnormal skin colour are common in patients with LEAOD, but not LDH.

 

Why do these findings matter?

 Appropriate diagnosis is key to appropriate and timely treatment. Understanding how to differentiate LEAOD from LDH is important for good patient care.

 

minimal damage

Goal of the Study?

In this study 1, the authors evaluate the scientific validity of using the biomechanical approach to assess injury causation from minimal damage traffic crashes.

 

Why are they doing this study?

A major point of contention in civil litigation cases following traffic injury claims is related to causation. Claimants generally rely on their doctor’s expertise to explain the cause of a persistent injury following a crash. In contrast, insurers often rely on a biomechanical approach as a basis for denying any link between the crash and ongoing injuries. The theoretical basis of the biomechanical approach is that the risk of injury from a crash is the same as the forces of activities of daily living (ADLs). However, the authors argue that the literature does not support this approach. Findings of large epidemiologic studies indicate that the injury rate is significantly greater in minimal and no damage crashes than ADLs.

 

What was done?

For this review, the authors included literature from three categories: volunteer rear-impact crash testing studies, ADL studies that describe linear and angular head acceleration for various ADL activities, and observational studies of real-world impacts. They compared the occupant accelerations of minimal or no damage (3-11kph speed change or delta-V) rear-impact crash tests to the accelerations described in 6 of the most commonly reported ADLs in the reviewed studies. The injury risk observed in real-world crashes compared to the results of the pooled crash test and ADL analyses, controlling for delta-V and adjusting for test subject age and sex. 

 

What did they find?

The authors argue that the biomechanical injury causation approach is scientifically invalid. Research illustrates that both crash testing results and epidemiologic data from real-world rear crashes show that there is a substantial risk of injury even at the lowest levels of impact severity. This stands in contrast to ADLs that have virtually no risk. They found that the average acceleration forces of the head during rear-impact crash tests were several times greater than average forces experienced during ADLs. Moreover, the injury risk of real-world minimal damage rear-impact crashes was estimated to be at least 2000 times greater than for any ADL. For example, research has indicated a 54% risk of any cervical spine injury and a 6% risk of any injury lasting for more than 6 months in an 11km/h rear impact delta-V crash. For this reason, they argue that the basis underlying the biomechanical injury causation approach, which uses occupant acceleration as a proxy for injury risk, vastly underestimates the actual risk of such crashes and should not be used in practice. 

 

Why do these findings matter?

The results of this review challenge the use of the biomechanical approach and illustrate how it underestimates the risk of minimal damage crashes on those involved.