Our lumbar models are identical in size and geometry to a real cadaveric specimen. With careful construction of the soft tissues including a flexible intervertebral disc including an annulus fibrosus and a nucleus puplosus,  each model is meticulously hand-crafted to provide the most accurate modeling to help the musculoskeletal practitioner to engage with patients in a convincing way.

Lumbar models have historically been static and immobile, but at Dynamic Disc Designs, we have developed flexible lumbar models to help relay essential movements to the patient related to their pain triggers. Having a patient genuinely understand their body mechanics empowers the patient and improves outcomes.

Patient-centered care must include translational strategies to help a pain sufferer understand their origins. A dynamic lumbar model helps execute efficient and accurate patient education.

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Effect of overload on changes in mechanical and structural properties of disc biomechanics

disc biomechanics

Goal of the Study?

In this primary research study from the Biomechanics and Modeling in Mechanobiology Journal1 the authors analyzed structural and mechanical properties in the Intervertebral Disc (IVD) of 10 lumbar spine regions collected post mortem from domestic pigs.  The goal was to analyze the effects of long-term cyclic loading in the hope of determining the actual mechanism of disc biomechanics and injury.

 

Why are they doing this study?

Spinal degeneration is one of the most frequently mentioned changes and over 80% of those are in degeneration with the IVD.  The problem of degeneration and subsequent changes in the mechanical and structural properties of the IVD is a fundamental issue in the pathomechanical formation of spinal injuries. Among the numerous factors contributing to these changes, the greatest impact comes from long-term cycle loading.  This study was aimed to analyze the overload change occurring in the IVD caused by long-term compression loads, especially the impact of degenerative changes on the posterior column of the spine.  

 

 

What was done?

Fourteen Functional Spine Units (FSU) of the ten lumbar regions were removed from post mortem domestic pigs and cleaned of soft tissue.  The junctions between the vertebral bodies and the IVD and within the zygapophysial joint were left intact.  Eight lumbar regions were subjected to a series of cyclic compression loading. The other two lumbar regions of each FSU constituted the control group.  The non-control lumbar regions of the 14 FSU’s were divided into 2 equal groups. The first seven consisted of the segments with an Intact Posterior Column (IPC).  The second group had the articular processes removed to obtain segments Without a Posterior Column (facets), but with an intact anterior column (disc), a junction between the vertebral bodies and the IVD.  The impact of cyclic compression loads on the structural changes of disc biomechanics was analyzed macroscopically both in the control group and the two test groups.   

 

What did they find?

The test results show a significant decrease in the disc height after prolonged compression cyclic loading.  They also found that the posterior column does not significantly influence the change in this value in the form of support on the articular processes, but it does affect how fast this change happens.  

 

Why do these findings matter?

Investigating and understanding the processes of degenerative changes in the IVD will facilitate the direction and help shed light on future clinical treatments of patients with early diagnosis of spinal pain conditions.  The obtained results of this research may also be useful when selecting boundary conditions and validating numerical models of the IVD. 

 

At Dynamic Disc Designs, we have worked to develop a model that can show the time dependent height loss of the intervertbral disc under load. Often symptoms of back pain relate to load and time. Teaching the nociceptive drivers to patients can be empowering when the source(s) are clearly understood. We like to call it “patient-centred education”.

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Low Back-related Leg Pain and Axial Loading with MRI – Using the Visual Analog Scale and Pain Drawings

Low back-related leg pain

Goal of the Study?

Low back-related leg pain is thought to be neuropathic in origin due to compromise of a nerve root(s) and is also commonly known as sciatica. In a study published in the Journal of Clinical Medicine 1 a group of authors looked to see if loading the spine during MRI imaging (axial loaded MRI) would help discern more specificity to the anatomical cause of the low back-related leg pain. These leg pain sufferers will often undergo recumbent MRI while their symptoms are in the vertical or axially loading posture. 

 

Why are they doing this study?

Many cases of sciatica can be challenging to diagnose because of the complexity of the disc mechanics and physiology. There are many nuances of sciatica, and each case can bring its own set of complexities. Learning to determine the source(s) of sciatica more accurately can be helpful in its therapeutic management.

 

What was done?

Ninety patients were recruited for this retrospective observational study. The participant’ ages ranged from 21-89 years and were screened by an orthopedic surgeon to exclude those with hip and knee problems from the study. Participants were asked to fill out a self-evaluation including the visual analog scale along with a pain drawing. Each participant was evaluated by an attending physician and underwent an axial-loaded 1.5T MRI with added weight. As a comparison, each participant.

The investigators looked for these variables:

 Cross-section of the dural sac
 Lumbar spinal stenosis grade with axial loading
 Disk herniation with axial loading
 Size of herniated disc with axial loading
 Size of hyperintensity zone with axial loading
 Ligamentum flavum ‘type’ with axial loading
 Intervertebral foraminal size with axial loading
 Foraminal stenosis
 Degenerative disc classification
 Degenerative facet arthropathy
 Edema of facet joint and effusion with axial loading
 Synovial cyst area with axial loading

 

What did they find?

The authors found that axial-loading subjects played a significant role in extracting findings that would otherwise not be seen with conventional recumbent MRI. Specifically, they found facet joint edema, atypical ligamentum flavum, was associated with low back-related leg pain.

 

Why do these findings matter?

Often, sciatica patients undergo MRI to identify a cause. However, recumbent MRI does not tell the whole picture as patients often report a worsening of symptoms when they are axially loaded. This study helped reveal the changes in the loaded state and can help clinicians make informed decisions about the symptoms patients express in a clinical setting. Understanding that the facets are under more load and the ligamentum flavum can buckle inwards towards the spinal canal can help the clinician understand the anatomy when assessing patients. Notably, the authors summarized that these axial-loaded findings could offer a dynamic picture of the instability contributing to sciatica.

 

At Dynamic Disc Designs we have developed models to help demonstrate load related changes to the spine. We believe that our models not only help the patients understand their symptoms better so they can make the appropriate adjustments to improve their sciatica, but they also help in the context of the education of spine pain in general.

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Sensory mapping of lumbar facet joint pain: a feasibility study

facet osteoarthritis, facet joint pain

Goal of the Study?

The objective of this study 1 evaluates the feasibility of sensory mapping of lumbar facet joint pain in patients scheduled to undergo radiofrequency (RF) denervation. 

 

Why are they doing this study?

Lower back pain (LBP) is a widespread condition that can result in chronic pain.  While there are many treatment approaches, one of the most established interventions uses diagnostic blocks to identify the source of nociception. Though many parts of the back can be involved in LBP, facet joints are among the most common sources contributing to back pain. Most often, for treatment in clinical practice, the medial branches are anesthetized to establish the diagnosis of facet joint pain. RF denervation of these nerves, which is a process to stop nerves from transmitting pain, is used as pain management. 

The authors argue that while this approach has been well established, the use in a clinical setting has been questioned due to the high rates of false-positive (30%), cost-effectiveness and lack of standardization and anatomical variation. For this reason, the authors hope to develop a strategy for a more precise identification of the nerves involved in LBP.

facet capsule nerves, facet joint pain

 

What was done?

In total, they had 15 participants for this study. After written consent, participants completed a pre-procedure pain diagram and rated their pain on a scale of 1-10. The researchers used a standard procedure for RF denervation, including a single diagnostic block and imaging in determining cannula placement. To reproduce the pain in patients with chronic back pain, medial branches were stimulated using 50Hz electrical stimulation to determine the threshold. This was then increased threefold to achieve the suprathreshold stimulation, after which participants were asked to map their pain and compare this against the initial pre-procedure pain diagram.

 

What did they find?

A total of 71 nerves were scheduled for RF denervation. Sensory stimulation was successful in 68 out of 71 nerves using 50Hz electrical stimuli. All 15 participants reported either pain or paraesthesia (tingling or prickling) during suprathreshold stimulation, and 14 (93%) reported complete coverage of their usual painful area. In one participant, the upper lumbar pain was not covered by suprathreshold stimulation. For 60% of the participants, they reported pain/paraesthesia outside of their normal pain area during suprathreshold. Overall, in their population, 7.5% of the denervated nerves did not contribute to pain transmission. The average sensory detection threshold was 0.3V, with the suprathreshold was 0.6V.

 

Why do these findings matter?

Using suprathreshold stimulation, lumbar facet joint pain can be mapped and offers objectivity by reproducing patients’ back pain. This approach can also improve patient safety and experience by limiting RF denervation to nerves involved in pain transmission. This can improve patient safety and experience. 

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ISSLS Prize in Bioengineering Science 2021: in vivo sagittal motion of the lumbar spine in low back pain patients – a radiological big data study

Centre of Rotation

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 data’s ability to represent the general population.

The authors argue that the use of radiographic techniques in this study helps to overcome these limitations as the images allow for better visualization of each vertebra and movements 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 lumbar spine radiographs 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 COR and the spinal segment’s position. 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 COR location spread randomly around the centre of the intervertebral space.

Limitations?

One of the main limitations of this study was the sole focus on the lumbar spine’s flexion-extension motion 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.

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Studying the bulging of a Lumbar Intervertebral Disc: A Finite Element Analysis

Dynamic Disc Model

Goal of the Study?

In this study 1, the authors attempt to build a three-dimensional finite element (FE) model to investigate how changes to the nucleus pulposus (NP) under axial compression loads influences bulging in the lumbar disc. 

 

Why are they doing this study?

The intervertebral disc provides cushioning between vertebrae and absorbs pressure on the spine. A disc herniation happens when the annulus fibers are weakened or torn, and the NP pushes through the annulus fibrosus (AF). This bulging can generate pressure on the adjacent nerve roots causing lower back pain (LBP) and may even lead to paralysis. 

Existing research suggests that under the same compression the extent of the bulging differs by area, with the posterior region experiencing the least amount of bulging. Taking this knowledge into consideration, the authors argue that it is important to understand the behaviour of bulging in the disc to prevent severe damage and provide a path to more effective treatment. 

 

What was done?

The researchers created a 3D FEA model that simulates a functional human spinal unit of the lumbar region under axial compression loads. The material properties of the AN and NP are assumed to be linear elastic and the structure of the AF is modeled as a homogeneous material without fibrin. 

To validate the model, the authors looked at the axial and bulging displacements under axial compression load and compared that to existing data. They further validated their model by comparing the distribution of stress in the AF with and without the NP.

 

What did they find?

The researchers found that the condition of the disc (partial removal, full removal or intact) significantly affects how the disc bulges and where. For example, they found that for a disc without an NP the posterior region bulges inward. In contrast, for both an intact NP and with partial removal of the NP, the bulging occurs outward due to increasing pressure at the central part of the AF. 

 

Why do these findings matter?

The findings can help to improve treatment decisions of the degenerative disc and nucleus pulposus.

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Lesions of the Lumbar Region in Asymptomatic Young Soccer Players: A Cross-Sectional Study

Lumbar

NOTE: THIS PAPER IS STILL IN REVIEWS

 

Goal of the study?

 

To evaluate the frequency of lesions (injuries) in the lumbar region (lower back) of asymptomatic adolescent soccer players using MRI.

 

Why are they doing this study?

 

To date, there are very few studies that look at the frequency of spinal lesions in young athletes. Most of the research has focused on adult athletes and has shown that the lower back region is the most common site for problems. However, we know that the pediatric musculoskeletal system is particularly at risk to injury because adolescent bodies have not finished growing. Injuries at such a young age can result in an imbalance in bone tissue and muscles, which may cause an increased risk of injury, pain and limit young adolescents’ daily activities. These injuries can also get worse as we age. Therefore, it’s important to know if adolescent soccer players are getting lower back lesions that are not being identified and treated.

 

Lumbar

Modic Model

 

Who was involved?

 

The study 1 looked at two groups of asymptomatic male adolescents aged 13-18. 

 

  1. Soccer players who practiced the sport for at least two consecutive years, at least three times per week for 1-3 hours.
  2. Control group was made up of asymptomatic adolescents and was matched for age, gender, height and weight. They could not play soccer or any other sport more than once a week for more than 1 hour.

 

  • No one in the study could have any history of lesions, surgery, chronic disease or a high BMI score.
  • While they originally recruited 60 adolescents (30 in each group), because of exclusions the final sample size was 45.

 

What was done?

 

The researchers used MRI to evaluate the spine and look for the frequency of lesions in the lower back of adolescent soccer players. 

 

Two different radiologists examined the MRI images looking for the presence or absence of swelling, protrusions and disc extrusions (bulges). They also looked at stress reactions, cracks or stress fractures in the vertebras, vertebras slipped out of place, enlargements or growths, as well as swelling of the interspinal ligaments and muscles. 

 

What did they find?

 

Comparing the two groups, the researchers found that the proportion of spinal lesions was 76% in the soccer players compared to only 35% of the control group. In particular, they found that the percentage of lesions in the anterior and posterior of the spine was significantly higher in the soccer players than the control group. They did not find any significant differences between the age and BMI Z-scores between the two groups.

 

 

This study was able to show a high number of lesions in soccer players compared to other youth soccer studies that did not use MRI. However, research on young athletes playing other sports shows a similar frequency of spinal lesions.

 

What are the limitations?

 

This study had a very small number of participants. Also, all of the soccer players were studied during their championship season. This means it is likely that they are doing more intense training and playing than during regular season. As of Dec 28, 2020, the paper is still under review and going through the editorial process.

 

Why do these findings matter?

 

Lower back injuries in childhood and adolescence can lead to early degenerative changes. Therefore, the high number of lower back lesions in adolescent soccer players should be considered in the changing landscape of a person’s spinal health. Sport specific prevention efforts are important to reduce the occurrence and impact of lower back injuries on young adolescents. Better identification and management of spinal lesions may help to ensure that young people are able to continue playing sport and reduce the impact of these injuries in adulthood and into their senior years to avoid conditions like lumbar spinal stenosis. Learning recovery strategies show promise.

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Vertebral Osteophyte. Is it related to mechanics?

osteophyte

The patterns of vertebral osteophytosis (or the growth of bony projections from vertebrae) is a common study among researchers. The actual cause of these bony outgrowth projections has been questioned over the years, with some pointing to the abnormal movement patterns of motion segments. Others have questioned this and believe the cause to be related to age and genetics. In a 2014 paper, researchers sought to answer: Is vertebral body osteophytosis a reliable indicator of occupational stress1. A shallow dive into their findings will be shared here.

What we do know from the work of Kumareson et al. 2 and Adams & Roughley 3 is that osteophytosis looks to be linked to degeneration of the intervertebral disc which is defined by an aberrant, cell-mediated response to progressive structural failure. With this structural failure, inevitably, there must be physical stress and thought to influence the cells at the vertebral-disc interface margins to produce bony outgrowths.

Furthermore, others have looked at these bony outgrowths and tried to relate them to aberrant mechanical loading patterns along with physical age and genetics. 4 5 6. Archeologists that study biological remains have used this finding as a tool to measure historical population activity level and lifestyles 7 drawing speculative conclusions on the inter and intra-population differences. Two well documented skeletal population differences demonstrated that the women had more severe osteophytosis than the men and was thought to be caused by heavy lifting that the men did not do during this same time period.

However, other researchers believe that degeneration is not solely related to physical activity and more so related to genetic factors 8, ageing 9, and body mass 10. And with this, one can see the complexities underpinning the causative factors of these bony outgrowths that some call ‘bony spurs’ projecting from vertebrae.

The osteophytes’ anatomical margins are the entheses, which you can see in our Lumbar Spinal Stenosis Model. This is the region where a muscle, tendon or ligament attaches to the bone. It is the interface where force intersects with bony anatomy. This is often represented in the extremities but the same biological process is thought to be at the crux of these anatomical changes.

osteophyte

Osteophyte Projection in our Lumbar Spinal Stenosis Model

What did these researchers investigate?

A group of researchers 1 wanted to see if they could determine whether mechanical factors related to osteophyte formation. They looked at these entheseal margins in the lower and upper extremities and the spine to see if they were correlated. Their logic was to see if the bony osteophytes were similar in all anatomical regions and if so, they could speculate that there was a mechanical influence of the formation of them. They also wanted to see if age played a factor as they explored the relationship between vertebral osteophyte formation and entheseal changes in the extremities.

The samples that were used came from a burial site in Cedynia, Poland. 101 male skeletons were examined and divided into two age groups, 20-40 years old and 41-56 years old. To determine the vertebral osteophyte degree, they used a rating scale developed by Swedborg (1974) to measure the entheseal grade; they used Mysezka & Piontek (2012). The entheseal anatomical sites they measured included the humerus, radius, femur and the tibia.

What they found

Interestingly, the researchers found no significant age differences when comparing the presence and degree of both osteophytosis and enthesopathy in the spine and extremities, respectively. They did find a significant correlation between the lower extremity enthesopathy and the vertebral osteophytosis, however. In other words, if they saw bony spurs in the lower extremities of the specimens, there was a good chance they were going to find vertebral osteophytes of the spine.

 

Does this solve anything regarding whether mechanics plays a role in osteophyte presence?

No. But it does shed light on the possible mechanics. These researchers agreed that other factors, besides physical ones, could be at play and should be considered. In particular, like age, body mass and genetics.

 

Commentary by Jerome Fryer

From a clinical standpoint, we should be mindful of these anatomical changes. Do they cause pain and problems all the time? No. We have seen this time and time again with clinically abnormal imaging findings. However, in the case of vertebral osteophytosis, a projecting osteophyte into the foramen where an exiting nerve root needs room for its vascular geometry for nourishing itself, space is everything. Learning about how to prevent the progressive changes of these types of osteophytes that can encroach on the dorsal root ganglia is important. Ongoing facet arthropathy is an adaptable process, but if adaptation is too great and osteogenesis takes up space where the nerve needs it, pain and disability can present and often, there is no turning back. My hunch is if we can improve the spine’s mechanics and keep an eye on disc height changes over a lifetime, we can keep the spine healthier and avoid spinal conditions like lumbar spinal stenosis. However, this is purely speculative in nature, and much more research on the causes of osteophytosis must occur. JF

 

  1. Anthropol. Anz. 71/4 (2014), pp. 381–389 Notes J. Biol. Clinic. Anthropol. Stuttgart, November 2014 ↩
  2. Kumaresan, S., Yoganandan, N., Pintar, F.A., Maiman, D.J. & Goel, V.K. (2001): Contribution of disc degeneration to osteophyte formation in the cervical spine: a biomechanical investigation. – Journal of Orthopaedic Research 19, 977–984. DOI: 10.1016/S0736-0266(01)00 010-9. ↩
  3. Adams, M.A. & Roughley, P.J. (2006): What is intervertebral disc degeneration, and what causes it? – Spine 31, 2151–2161. DOI: 10.1097/01.brs.0000231761.73859.2c. ↩
  4. Sambrook, P.N., McGregor, A.J. & Spector,T.D. (1999): Genetic influences on cervical and lumbar disc degeneration: magnetic resonance imaging study in twins. – Arthritis and Rheumatism. 42, 366–372. DOI: 10.1002/1529-0131(199902)42:2<366::AIDANR20>3.0.CO;2-6. ↩
  5. Spector, T.D. & McGregor, A.J. (2004): Risk factors for osteoarthritis: genetics. Osteoarthritis and Cartilage 12, 39–44. DOI:org/10.1016/j.joca.2003.09.005. ↩
  6. Knüsel, C., Göggel, S. & Lucy, D. (1997): Comparative degenerative joint disease of the vertebral column in the medieval monastic cemetery of the Gilbertine Priory of St. Andrew, Fishergate, York, England. – American Journal of Physical Anthropology 103, 481–495. DOI: 10.1002/(SICI)1096-8644(199708)103:4<481::AID-AJPA6>3.0.CO;2-Q. ↩
  7. Novak, M. & ˇ Slaus, M. (2011): Vertebral pathologies in two Early Modern Period (16th–19th) century) populations from Croatia. – American Journal of Physical Anthropology 145, 270–281. DOI: 10.1002/ajpa.21491. ↩
  8. Sambrook, P.N., McGregor, A.J. & Spector,T.D. (1999): Genetic influences on cervical and lumbar disc degeneration: magnetic resonance imaging study in twins. – Arthritis and Rheumatism. 42, 366–372. DOI: 10.1002/1529-0131(199902)42:2<366::AIDANR20> 3.0.CO;2-6. , ageing and body mass index. ↩
  9. Snodgrass, J.J. (2004): Sex differences and ageing of the vertebral column. – Journal of Forensic Science 49 (3), 458–463. ↩
  10. Oishi, Y., Shimizu, K., Katoh, T., Nakao, H., Yamaura, M., Furuko, T., Narusawa, K. & Nakamura, T. (2003): Lack of association between lumbar disk degeneration and osteophyte formation in elderly Japanese women with back pain. – Bone 32, 405–411. DOI:10.1016/S8756-3282(03)00031-0. ↩
  11. Anthropol. Anz. 71/4 (2014), pp. 381–389 Notes J. Biol. Clinic. Anthropol. Stuttgart, November 2014 ↩
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