Degenerative disc disease (DDD) is very common and is not always related to pain. However, if a patient is experiencing back pain, it is more likely the patient does have DDD or is in the process of acquiring it. Our models help explain that DDD is often a process and often intertwined with aging and spinal pain conditions.

Degenerative disc disease (DDD) is at the roots of Dynamic Disc Designs (ddd). Learning and teaching the underlying mechanisms of pain and the strategies to relieve and live with this common condition is what we strive to do. Bringing the research to the forefront, in front of the patient and doctor with a dynamic teaching tool.

facet, lumbar spinal stenosis model

A retrospective CT scan and medical record review [ 1. The Prevalence of Asymptomatic Cervical and Lumbar Facet Arthropathy: A Computed Tomography Study] of 50 patients with no history of spinal pathology used a four-point scale to grade the severity of evident arthritis and found that arthritic spinal changes were frequently evident—even in asymptomatic patients. The incidence of these changes corresponded positively with aging and was more prevalent in scans of the lower lumbar spine.

What’s at Stake?

Chronic neck and lower back pain affect between 66 and 84 percent of the U.S. population and is responsible for approximately 87 billion dollars of lost income and medical expenses annually—a figure that is only surpassed by the yearly wage loss and expenditures on diabetes and heart disease.

Diagnosing CNP and LBP is problematic due to the number of possible factors—including dysfunction of the intervertebral discs (IVD’s), facet joints, spinal nerve roots, ligaments, and muscles surrounding the spine— that can contribute to these disorders.

Some studies have indicated that facet arthropathy, rather than nerve root irritation, cause axial neck and back pain. The increase of CNP and chronic LBP in aging populations may be associated with a progressive degeneration of the IVDs that subsequently increases facet joint loading and creates favorable conditions for the development of facet arthritis. Facet joint blocks by injection have been shown to be ineffective in providing symptomatic relief in up to 90 percent of patients diagnosed via CT scan in previous studies. This suggests that scan observations alone may provide prevalent false positive results and therefore cannot be a reliable diagnostic tool.

Disc replacement may alleviate pain and restore spinal fluidity of motion, but the presence of facet joint arthritis is considered a contraindication to this surgical procedure. Understanding more about facet joint arthritis can assist practitioners in developing effective treatment plans for LBP and CBP patients—including the determination of which patients may be ill-suited for IVD replacement. This study of asymptomatic patients was conducted with the aim of understanding the prevalence of facet joint arthritis to help quantify the percentage of patients for whom facet injections are ineffective.

The Study

An approved review of archived CT scans of 100 total non-spinal patients was conducted using scans of 500 cervical facet joints from 50 subjects and 500 lumbar facet joints from an additional 50 subjects. All of the patient subjects’ medical records and scans were previously analyzed and evaluated as spinally asymptomatic for the purpose of this study.

The images were each graded and evaluated by an orthopedic spinal surgeon, neuroradiologist, and trained medical student on an independent basis. An additional three observers with separate clinical backgrounds also conducted a review of the facet joints to ensure no bias existed due to training backgrounds of the first group. The severity of facet joint arthritis symptoms were graded and statistical analysis was applied across different subject age groups. An average of all groups was then calculated using a coefficient.

The Results

Cervical Data

Of the 500 cervical facet joints from 50 patient subjects studied, asymptomatic cervical facet joint arthritis was evident in more than 33 percent of the scans. Nearly 60 percent of these patients showed only mild narrowing of the joint space and irregularities. About half of the subjects over the age of 40 demonstrated signs of arthritic changes. There were fewer “normal” or non-degenerated facet joints in patients in the aging (over 45) subject population. The prevalence of degenerative changes increased at all cervical levels in the aging subjects.

In all age groups, greater changes occurred more prevalently in the caudal spine area. At the C6-C7 spinal level, 78 percent of patients over-40 demonstrated facet joint arthritis. At the C2-C3 level, however, only 29 percent of the patients of the over-40 age group showed arthritic changes.

Lumbar Data

Thirty-seven percent of the patient subjects in the lumbar data group demonstrated asymptomatic lumbar facet joint arthritis, and up to 2/3 of these subjects showed grade 1 changes. As with the cervical data set, the lumbar set demonstrated a positive correlation with aging (over 45) and arthritic changes and degeneration of the facet joints. Caudal levels (L5-S1, for example) were more likely to show increased arthritic degeneration compared to cephalad levels. Only 12 percent of the patients over 50 years old showed changes at the L1-L2 levels, while 54 percent demonstrated these changes at the L5-S1 level.

Lumbar Spinal Stenosis Model

Conclusion

This study found a statistically significant positive correlation between aging and asymptomatic arthritic changes and degeneration of the facet joints of patients over the age of 45. These changes were evident at all spinal levels but were most prevalent in the lumbar facet joints and the C2-C3 and C6-C7 levels of the caudal spine. Approximately one third of the patient population in this study were found to have evident facet joint arthritic changes that were asymptomatic and associated with aging. When considering motion-preserving spinal implants, the age of the patient should be considered, as the treatment may not be as effective in patients over the age of 45, who are more likely to have or develop asymptomatic facet joint arthritis—a contraindication of the implant procedure.

 

 

 

 

Radiculopathy

A study 1 compared different treatment efficacies in two groups of patients with degenerative spinal disease-related buttock pain and found that the group receiving a selective nerve root block had clinically-significant improvement outcomes at post-procedure through 6-weeks, compared to the group that were treated with a facet joint block. This suggests that the cause of spinal-related buttocks pain is most likely radiculopathy, rather than facet joint degeneration.

What’s at Stake?

Many patients with spinal stenosis complain of back pain, buttock pain, or pain radiating from the buttock to the lower legs. As it is assumed that nerve root inflammation can contribute to lumbar and lower leg pain radiating from the spine, a common and frequently effective treatment may involve steroid or procaine injections. Selective nerve root block is used effectively in the treatment of degenerative scoliosis and has been demonstrated to be a successful form of short-and-long-term treatment for the pain. Similarly, a facet joint block has been used as an effective treatment for buttock pain, post-procedural lumbar pain, and morning stiffness associated with spinal degeneration.

Though various treatments have proven effective in alleviating or reducing pain in a percentage of the spinal patients receiving injections and blocks, the exact etiology of spinal-related buttock pain and radiating pain remains unclear. Because of this, uniform diagnostic and treatment guidelines for buttock pain—especially without concurrent radiating lower leg involvement—have been difficult to establish. This study links positive treatment outcomes with a more definitive diagnostic cause of buttock pain and seeks to contribute to the diagnostic and treatment criteria of buttock pain discussion.

The Study

Researchers treated 146 male and female patients presenting with spinal-related buttock pain without lower leg radiation by one of two methods—a) selective nerve root block (76 patients), or b) facet joint block (70 patients). The mean age of patients in both groups was 65 years. Both groups shared similar demographics when it came to age, sex, and health. Each of the patients was evaluated prior to their procedure and on day one, week 2, week 6, and at 12 weeks post-procedure. Their evaluation results were compared by their group injection method, and the results were then analyzed.

Results

On the DAY 1 post-procedure analysis, 7 percent of the patients in the nerve block group (GROUP A) were shown to have experienced an “excellent” response, and 6 percent of those in the facet joint block group (GROUP B) had an “excellent” response. In GROUP A, 46 percent of the patients treated showed a “good” response to the treatment, while only 13 percent of the patients in GROUP B had a “good” response.

At the two-week post-procedure follow up, 11 percent of the GROUP A patients demonstrated an “excellent” response, with only 4 percent of the patients from GROUP B had an “excellent” response. Similarly, 41 percent of the GROUP A patients were classified as having experienced a “good” response, compared with only 20 percent of those in GROUP B.

At the six-week post-procedural follow up, 11 percent of the GROUP A patients were classified in the “excellent” response group, while only 7 percent from GROUP B had this distinction. Forty-one percent of the patients from GROUP A demonstrated a “good” response, and only 20 percent of the GROUP B patients had a “good” response.

At 12-weeks, 47 percent of the GROUP A patients were classified in the “good” response category, and 46 percent of those in GROUP B experienced a “good” response to the treatment.

Conclusion

Researchers in this study sought to identify the cause of buttock pain associated with spinal stenosis. Specifically, they used a retrograde methodology to discover if the buttock pain was radiating pain or caused by facet joint degeneration. They treated two groups of patients using either selective nerve root block or facet joint block, and the data collected and analyzed indicates that the selected nerve root block was more effective through post-treatment follow ups through 6 weeks. The implication of this data suggests that spinal-related buttock pain is most likely caused by radiculopathy, rather than facet joint degeneration.

IVD Problems, Disc Degeneration

A study 1 of how dietary advanced glycation end-products (AGEs) effect the structure and function of intervertebral discs (IVDs) in male and female mice concluded that high dietary AGEs impaired IVD collagen quality, altered annulus fibrosus (AF) organization and changed the biomechanical properties of female IVDs, while having no clinically-significant effect on male mice subjects. The results of the study suggest the importance of targeting AGEs in spinal health assessments and treatments of female patients—particularly those at risk for, or suffering from, Diabetes Mellitus (DM).

What’s at Stake?

Structural disruption and chronic inflammation of the IVD is one of the leading causes of back pain, disability, and lost work wages worldwide. The many contributors to IVD damage and degeneration include DM and obesity, conditions that are increasing rapidly across the globe. Obesity increases the risk of IVD herniation, spinal stenosis, chronic inflammation, and other complications of the spine. It is also associated with an increased risk of cardiovascular disease, stroke mortality, and heart attacks–particularly in women. Since AGE accumulation is known to cause complications in populations with DM, this study investigates the effects of a high AGE diet on the IVD and how sex-differences may play a role in sex-specific IVD changes and disruption.

The Study

The subjects of the study were 21 male and 23 female recently-weaned mice, separated by sex and assigned to two groups. One group received a low-AGE diet (chow), and another group was fed only high AGE chow, which had been subjected to high-temperature heating. Each subject represented a third-generation off-spring of maternal mice fed only the respective diet used in the study groups, to exclude any effects of maternal AGES on the newly-weaned experiment mice.

The high AGE chow was representative of the typical Western human diet, with 80 percent higher AGE values than those of the low AGE chow. An increased AGE content is typically caused by thermally processing (extreme heating) the foods prior to ingesting. Examples of this include microwaving or deep-frying foods.

The feeding study lasted for 6 months, after which time the mice were sacrificed, dissected, and prepared for biomechanical IVD testing through Western blot analysis. Fasting glucose and total serum AGE levels were measured and quantified, and proteins were extracted, buffered, and sonicated. A single freeze-thaw cycle was used prior to biomechanical testing to avoid the process influencing the IVD mechanics. Axial compression-tension and torsional tests were performed on caudal motion segments, and the IVD diameter measurements were taken using a caliper. Assessments of IVD morphology, collagen molecular properties, and fiber orientation were created, measured, compared, and analyzed.

Results

The Western blot data showed a significant accumulation of AGEs accumulation of the IVD problems of the female mice fed the high AGE (H-AGE) diet compared to those fed the low AGE (L-AGE) diet. There were no changes in the IVD AGE levels or serum samples of the male mice in either feeding group. The results indicate that even without the presence of DM or obesity, dietary AGEs are likely to systemically accumulate in the IVDs of female mice—but not in males.

Further, the H-AGE female mice IVDs showed increase stiffness and torque-range, while the date on the L-AGE female mice showed no such correlation, and the male mice IVDs of both feeding groups were unaffected. This indicates that motion segment behaviors of female mouse IVDs—but not male mouse IVDs— are negatively affected by the H-AGE diet.

In addition, the AF organization and collagen fibers of H-AGE diet female mouse IVDs—but not male mouse IVDs— appeared compromised, particularly in the anterior AF. The H-AGE diet also appears to have contributed substantially to AGE accumulation and collagen damage in the AF of the female mice subjects but not the male mice subjects.

Conclusion

The results of this study, combined with previous study literature, suggests that female mice are negatively affected by a H-AGE diet, which appears to increase glycation within the AF collagen matrix and damage collagen and molecules in the IVD. High IVD crosslinking and collagen damage can contribute to biomechanical changes in the IVD and disrupt form and function in the unit. It appears that high AGE diets may increase these risks in female spinal tissues. Future research is needed to investigate ways to promote spinal health through dietary interventions to lower AGE levels, particularly in at-risk populations. This includes patients suffering from obesity and DM, especially females.

 

 

 

 

 

intradiscal, endplate

A study 1 on the efficacy of intradiscal biologic therapy, where new cells or genes are implanted into the degenerated disc matrix to reduce inflammation and increase matrix cell production, found that degenerated discs may not have the necessary nutrient transport capabilities to ensure proper disc nutrition during this form of therapy. The authors of the study emphasize the importance of research into the determining factors influencing disc cell nutrient transport in informing targeted treatments and strategies to improve disc nutrition in degenerated discs.

What’s at Stake?

Disc degeneration (DD) is a chronic condition that causes spinal pain in aging adults worldwide. The process of DD involves biomechanical modeling of the entire disc matrix and frequently leads to surgical intervention to remove the offending disc and restore functionality to the spine. For many patients, surgical procedures are unsuccessful, however. A noninvasive treatment that has demonstrated recent promise involves regenerating the DD by injecting it with genes, growth factors, small molecules, or implanted cells. These procedures are intended to reduce inflammation and catabolism and assist in the creation of a new disc matrix. But a cell-rich disc requires increased nutrients, and the cartilage endplate (CEP) of the DD may not have the capacity to deliver these nutrients to the matrix. In this study, researchers examined the effects of CEP transport properties in DD on nutrient diffusion and cell function and survival.

The Study

In order to isolate the variable of how nutrient supply affects the nucleus pulposus (NP) cell function, the researchers involved in this study mimicked the in vivo, diffusion-poor disc environment by creating diffusion chambers with similar parameters to isolate the NP nutrient supply mechanics. The cells of the NP receive nutrients that are diffused through the CEP matrix. Cells at the center of the lumbar discs can be up to 10mm from a capillary, while other cells can be just beside a CEP.

Researchers provided glucose and oxygen to cultured NP cells within the chambers. These nutrients were delivered through diffusion from human CEP’s from the open sides of the chamber. Metabolites were expelled into the culture medium by CEP diffusion. The functioning and survival of the cells require a balance between CEP transport properties and cell density, allowing for the request and supply of nutrients. The researchers reproduced the disc matrix environment and physiologic transport conditions in their CEP tissue cultures and diffusion chambers to monitor the effects of NP cell viability and gene expression across the different conditions of nutrient transport.

Specifically, intact human CEP’s from human cadaveric lumbar spines were used for the study. Full-thickness samples of the CEP’s and surrounding calcified cartilage were frozen and sectioned. The researchers calculated the diffusivity of each full-thickness CEP sample through fluorescence and photo-bleaching and using the Axelrod method. They measured each CEP’s biochemical composition spatially via imaging. They created special maps of the collagen, aggrecan, and mineral-to-matrix ratio of the CEP samples with the highest and lowest diffusivities. They measured CEP thickness with photomicrographs and then determined the average measurement across the five chambers.

Bovine NP cells were used in the study (similar to human NP cells). Post-incubation cell viability was determined using a cytotoxicity assay involving gel-stains and low-magnification imagery. Each L4-L5 donor CEP was analyzed for cell density and the anabolic and catabolic gene expressions were examined after chamber incubation. A regression model of fluorescence intensity was used to determine the NP cell gene expression and distance from the CEP. Spatial fluctuations of the CEP composition were described based upon regression models.

Results

The diffusive transport of nutrients varied widely between the CEP samples, affecting the function, health, and survival potential of the NP cells. In fact, there was a four-fold variation in small solute diffusivity in our human CEP sample array. Those allowing less diffusive transport reduced the supply of nutrients to the NP and shortened the viable distance within the diffusion chambers up to 51 percent with typical cell density. Those permitting poor diffusion seemed to downregulate anabolic and catabolic NP cell gene expression. This may mean that a reduced number of disc cells are capable of being sustained through low nutrient CEP diffusion, and the cell’s ability to retain its matrix homeostatic condition is hindered.

When we increased cell density, there was a reduction in cell viability caused by the CEP transport properties, though increasing cell density should raise nutritional demands and shorten the viable distance.  The CEP’s in our study that exhibited low diffusive transport were unresponsive to doubling the cell density, perhaps because they did not provide enough nutrient diffusion to nurture the cell.

We imaged the CEP’s to identify any differences between those with low or high intradiscal diffusivity. Our data found that those with low-diffusivity (and shortened viable distance) contained more collagen and aggrecan, mineral, and lower cross-link maturity. This could explain the blockage of solute penetration and diffusion. At any rate, there appears to be a strong correlation between NP cell survival or function and the availability and mobility of the nutrient supply in the CEP. Compositional defects with the CEP matrix can inhibit nutrient diffusion and undermine biologic therapies that depend upon an increased supply of nutrients to the cell matrix to succeed.

Summary

Our findings suggest that the composition of CEP can contribute to or detract from the function and viability of NP cells. Deficits within the CEP matrix can cause poor nutrient diffusion and block solute passages. This can cause an abundance of collagen and aggrecan, as well as mineral, and lower cross-link maturity. When cell density is increased, CEP’s developed transport deficits, decreasing the cell’s viability. It appears NP function and survival are dependent on the proper CEP composition, as an imbalance in this makeup can reduce the supply of nutrients to the cells, reducing the success rates of biologic therapies.

 

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.

Results

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.

 

 

degenerative, MRI, low back pain

A retrospective magnetic resonance imaging (MRI) analysis 1 of lumbar degenerative changes in 283 patients with chronic low back pain (CLBP) found more severe disc degeneration (DD), lower disc height, and more extreme disc displacement at the L4–L5 and L5-S1 of patients with work-related CLBP. The results of the study help to elucidate MRI-visible changes and clinical attributes of work-related CLBP.

What’s at Stake

Lower back pain (LBP) affects up to 84 percent of the world population at some point in life and can contribute to acute or chronic disability in up to 12 percent of those affected. As of 2016, LBP was the leading cause of years lived with a disability, and the U.S. economic burden of LBP is estimated to be somewhere between 84.1 billion to 624.8 billion dollars. Understanding the various stages and degenerative characteristics of LBP can help with appropriate and timely treatment, which may help to reduce cases of CLBP. MRI allows physicians to recognize pathologies, so they can appropriately plan treatment for their LBP patients.

Study Design

The study involved the retrospective review of medical records of adults who had sought treatment for CLBP that had lasted for a period of greater than three months. Inclusion requirements included MRI scans of the entire lumbar spine and clinical lumbar evaluations. Excluded were patients under 18, or those whose LBP was intermittent or had not occurred every day for at least three months. Those experiencing pain that outranked their LBP elsewhere in their body were also excluded from the study, as were patients who could not have an MRI, who had a lumbar infection, spinal trauma, tumor, deformities, or spontaneous septic spondylodiscitis or epidural abscess, previous back surgery, osteoarthritis of the hip, and significant psychological disturbances.

Subject demographics were collected and analyzed, including their occupations, how many hours per week they worked, heavy lifting or lengthy desk sitting involved in their jobs, and the age, sex, body mass index, education level, smoking history, and duration of their LBP. Their LBP scores were recorded using a Visual Analog Scale (VAS) from 0 to 10 (no pain to worst pain). The Oswestry Disability Index (ODI) was used to rank each subject’s functional capacity, where those with a lower percentage were rated healthier.

Imaging Analysis Results

Pre-treatment MRIs of three positions—neutral, flexion, and extension—were performed on each subject by two experienced radiologists and then independently evaluated by an orthopedic surgeon. The subjects were grouped according to their MRI results. The four groups included: normal disc (ND), degenerative disc (DD), bulging disc (BD), and herniated disc (HD). Statistical analysis was performed using special software, and clinically-significant value was assigned. Of the 283 patients with CLBP taking part in the study, 110 were women, and 173 were men, and they ranged in age from 18 to 80, with a mean age of 41.8. The post-MRI groups included 37 subjects in the ND group, 85 in the DD group, 123 in the BD group, and 38 in the HD group. The mean age of the patients in the ND group was significantly lower (31.9) than that of the DD group patients (42.8), HD group (39.3), and the BD group (44.9). The ratio of male to female across all groups was 6:4, but the ratio in the HD group was 84.2 % male to 15.8 % female. The duration of CLBP across all groups was roughly 25 months, but when analyzed group-to-group, it progressively ranged from 15 to 25 months, with the ND group at the lowest range, followed by the DD, BD, and HD groups. The duration of pain was significantly increased from the ND group to the BD group. There were few differences in age, smoking history, or education levels across the groups.

The subjects were further categorized into 10 groups based on their occupations. The three groups that were most prominently represented in the ND, DD, BD, and HD groups were manual workers, desk workers, and technicians. They were similarly represented within their groups. Working hours were also similar across these groups, between 59.7 and 63.2 hours per week. The percentage of subjects who were required to manually handle weighty objects at work was significantly lower than those with no manual handling. The number of working hours spent sitting at a desk was much higher in the DD group, as compared to the other three groups.

When comparing clinical CLBP, the VAS pain scores in the DD, BD, and HD groups were much higher than those of the ND group members. The ODI scores of these three groups were also higher than those of the ND group, and those in the HD group were significantly higher than subjects in the DD and BD groups, indicating less functionality.

The MRI looked for the degree of DD in the neutral, flexion, and extension positions, as well as the vertebral height (anterior and posterior), slipping distance of spondylolisthesis in all three positions, height of the L1-S1 discs, disc bulge or herniation distance, AP diameter of the spinal canal, and translational motion. The data was analyzed and classified indicating the severity of disfunction or damage. The worst degeneration was at the L-4/L-5 and L-5/S-1 level, followed in severity by L-3/L-4.

The disc bulge distances of L-3/L-4 and L-4/L-5 were higher in the BD and HD subject groups. Also, the distance of L-4/L-5 was much higher in the HD group than in the BD group in the neutral position. The distances of L-4/L-5 were much higher in the BD and HD groups than in the ND and DD groups during flexion position, and that of L-3/L-4 was much higher in the HD group than in the ND and DD groups. The distances of L-4/L-5 and L-5/S-1 were much higher in the BD and HD groups during extension MRIs.

Conclusion

This study used MRI to analyze and compare four types of lumbar disc degeneration in patients with CLBP and found that the ND group represented a significantly younger demographic than that of the other three group members. This suggests that age is a likely contributor to DD in CLBP. The subjects in the BD group had a much longer mean pain duration than those in the ND group, suggesting a less successful clinical future outcome for those patients. There appeared to be little-to-no association between BMI and smoking history and CLBP in any of the subjects involved in this study.

There was a positive correlation between hours worked sitting at a desk—with those in the BD and HD groups working on average more than 60 hours per week and those in the ND and DD groups working fewer hours. Interestingly, the data collected indicated that most CLBP patients did not perform heavy manual labor at work and were highly educated—suggesting a strong connection between office work and CLBP. The MRI scans showed that lower lumbar disc segments (L-4/L-5 and L-5/S-1) were the most significantly degenerated in the CLBP patients, with lower disc height and displacement.

 

 

 

properties of the annulus, shear force

An in vivo study 1 of the effects of shear force loading applied to the L5-L6 spinal segment of lab rats revealed histological evidence of IVD degeneration in the unit and surrounding discs of sacrificed study rats that had been exposed to shear force via a custom-designed loading device, while no such evidence was evident in the post-mortem rat control group. The results of the study showed that shear force, applied at .33 MPa (a lower level of compressive stress than previously shown to cause IVD degeneration in rat tail discs), creates degeneration of rat IVDs. This information may be instrumental in providing preventative and treatment-oriented care for people who may be at risk of developing IVD degeneration.

The Study of Shear Force

Researchers tested the hypothesis that sustained shear force on a spinal segment would create IVD degeneration in rat lumbar spines. They used 15 young male rats divided into three groups—one sham control group, and two experimental loading groups that would be exposed to loading for one, and two weeks. The shear loading device used was created especially for the experiment and was made of stainless steel. It was applied to the L5 and L6 vertebral rat bones and delivered a static shear load of up to 4 N.

When the shear loading experiment was completed (1 week, and 2 weeks), the rats were sacrificed. The lumbar segments were removed, viewed microscopically, and tested histologically. A degenerative score from 0 to 3 was assigned each sample, with “0” representing no changes, “1” showing minimal changes, “2” representative of samples with moderate changes, and “3” assigned to those samples showing severe changes, including some with NP disappearance. The slides were blinded and randomized to prevent observer bias.

Results

All the rats involved in the study survived the surgery and post-op period, with no signs of distress. Each of the rats that underwent shear loading had IVD degeneration in most of their lumbar discs, across all levels. The sham control rats, however, demonstrated no degeneration after the experiment.

There were differing levels of degeneration in the IVDs of the shear stress-exposed rats. After the shear loading, the posterior annulus of the exposed rats curved into the dorsal area of the NP, creating a reduction in demarcation in these samples and a disappearance of notochordal cells. The anterior NP remnants were disaggregated, collapsing into smaller sections composed of multiple cells, which, along with the NP, later disappeared. There was also a blending of NP, AF, and CE, and it was difficult to see where one began and another ended. The lamellar wall of the inner and middle annulus dissolved, creating disorganization in the AF.

Discussion

Isolating the effects of different loading modes on IVD degeneration and response is helpful in developing a more complete understanding of IVD biomechanics. Understanding the consequences of shear force applied during compressive spinal loads through in vitro studies can elucidate how shear applied during bending and torsion loading can cause damage to the IVD at the microstructural level and contribute to AF degeneration and failure.

The results of this in vivo study on the disc segments of rats undergoing shear force stress on the L5-L6 IVD segment demonstrated evidence of degenerative changes in all the rats exposed to shear force, while no degeneration occurred in the rat sham control group. The disc damage noted in the experiment groups occurred not only at the L5-L6 levels, but was also evident at adjacent levels (L3-L4, L4-L5, L6-S1). This is further confirmation that the effects of shear force can create damage, proteoglycan depletion, NP content loss and/or collapse, and severe degeneration to disc segments within one week of exposure.