Burned-out discs stop hurting: fact or fiction?

Quantifying internal intervertebral disc strains to assess nucleus replacement device designs: a digital volume correlation and ultra-high-resolution MRI study

Introduction: Nucleus replacement has been proposed as a treatment to restore biomechanics and relieve pain in degenerate intervertebral discs (IVDs). Multiple nucleus replacement devices (NRDs) have been developed, however, none are currently used routinely in clinic. A better understanding of the interactions between NRDs and surrounding tissues may provide insight into the causes of implant failure and provide target properties for future NRD designs. The aim of this study was to non-invasively quantify 3D strains within the IVD through three stages of nucleus replacement surgery: intact, post-nuclectomy, and post-treatment. Methods: Digital volume correlation (DVC) combined with 9.4T MRI was used to measure strains in seven human cadaveric specimens (42 ± 18 years) when axially compressed to 1 kN. Nucleus material was removed from each specimen creating a cavity that was filled with a hydrogel-based NRD. Results: Nucleus removal led to loss of disc height (12.6 ± 4.4%, p = 0.004) which was restored post-treatment (within 5.3 ± 3.1% of the intact state, p > 0.05). Nuclectomy led to increased circumferential strains in the lateral annulus region compared to the intact state (-4.0 ± 3.4% vs. 1.7 ± 6.0%, p = 0.013), and increased maximum shear strains in the posterior annulus region (14.6 ± 1.7% vs. 19.4 ± 2.6%, p = 0.021). In both cases, the NRD was able to restore these strain values to their intact levels (p ≥ 0.192). Discussion: The ability of the NRD to restore IVD biomechanics and some strain types to intact state levels supports nucleus replacement surgery as a viable treatment option. The DVC-MRI method used in the present study could serve as a useful tool to assess future NRD designs to help improve performance in future clinical trials.

MRI Characteristics at a Mean of Thirteen Years After Lumbar Disc Herniation Surgery in Adolescents: A Case-Control Study

The purpose of this study was to describe the prevalence of lumbar spine degeneration in adult individuals who had undergone lumbar disc herniation surgery during adolescence.

An exploratory study of different definitions and thresholds for lumbar disc degeneration assessed by MRI and their associations with low back pain using data from a cohort study of a general population

BACKGROUND

Lumbar disc degeneration seen on magnetic resonance imaging (MRI) is defined as loss of signal intensity and/or disc height, alone or in combination with other MRI findings. The MRI findings and thresholds used to define disc degeneration vary in the literature, and their associations with low back pain (LBP) remain uncertain.

OBJECTIVE

To explore how various thresholds of lumbar disc degeneration alter the association between disc degeneration and self-reported LBP.

METHODS

An exploratory, cross-sectional cohort study of a general population. Participants in the cohort 'Backs-on-Funen' had MRI scans and completed questionnaires about LBP at ages 41, 45 and 49 years. The MRI variables, signal intensity (Grades 0-3) and disc height (Grades 0-3), were dichotomised at different thresholds. Logistic regression analyses were used to determine associations. Arbitrarily, a difference in odds ratio (OR) of > 0.5 between thresholds was considered clinically relevant. Receiver Operating Characteristic curves were used to investigate differences between diagnostic values at each threshold.

RESULTS

At age 41, the difference in ORs between signal loss and LBP exceeded 0.5 between the thresholds of ≥2 (OR = 2.02) and = 3 (OR = 2.57). Difference in area under the curves (AUC) was statistically significant (p = 0.02). At ages 45 and 49, the difference in ORs exceeded 0.5 between the thresholds of ≥2 and = 3, but the differences between AUC were not statistically significant. At age 41, the difference in ORs between disc height loss and LBP at the thresholds of ≥1 (OR = 1.44) and ≥ 2 (OR = 2.53) exceeded 0.5. Differences in AUC were statistically significant (p = 0.004). At age 49, differences in ORs exceeded 0.5 (OR = 2.49 at the ≥1 threshold, 1.84 at ≥2 and 0.89 at =3). Differences between AUC were not statistically significant.

CONCLUSION

The results suggest that the thresholds used to define the presence of lumbar disc degeneration influence how strongly it is associated with LBP. Thresholds at more severe grades of disc signal and disc height loss were more strongly associated with LBP at age 41, but thresholds at moderate grades of disc degeneration were most strongly associated with LBP at ages 45 and 49.

Significance of the Association between Disc Degeneration Changes on Imaging and Low Back Pain: A Review Article

Low back pain (LBP) is a major health issue resulting in a huge economic burden on the community. It not only increases the medical costs directly, but also raises the disability and loss of productivity in the general population. Symptoms include local pain over the spinal area, pain radiating to the lower leg, stiffness, and muscle tension. LBP is strongly linked with intervertebral disc degeneration that is further associated with the disruption of the complex anatomy of nucleus pulposus, annulus fibrosus, and adjacent supporting structures of the spine. Change in the shape and intensity of nucleus pulposus, decreased disc height, disc herniation, vertebral endplate changes, presence of osteophyte, and posterior high intensity zones are degenerative changes found in imaging studies. Every feature is considered while grading the severity score. Modic changes, DEBIT (disc extension beyond interspace) score, and Pfirrmann criteria are some of the scoring criteria used for evaluating disc degeneration severity. Moreover, the total number and contiguous pattern of affected discs play a crucial role in symptom generation of back pain. Many studies have reported asymptomatic patients. Thus, the correlation between degeneration severity found in imaging study and symptom severity of LBP remain unclear. This review discusses and summarizes the available literature on the significance of the association between the severity of degenerative changes found in imaging study with the presence and intensity of LBP.

MRI identifies biochemical alterations of intervertebral discs in patients with low back pain and radiculopathy

KEY POINTS

• Molecular intervertebral disc damage was associated with LBP and radiculopathy.• Patients with radiculopathy and LBP demonstrated a depletion of gagCEST values compared with healthy controls.• GagCEST imaging may be a non-invasive tool for investigation of degeneration processes of lumbar intervertebral discs (IVDs). GagCEST imaging may be an imaging biomarker for biochemical IVD alterations.

Vertebral Endplate Defect as Initiating Factor in Intervertebral Disc Degeneration: Strong Association Between Endplate Defect and Disc Degeneration in the General Population

STUDY DESIGN

Cross-sectional study of spine magnetic resonance in a population, predominantly female, sample.

OBJECTIVE

To determine the relationship between vertebral endplate defect and intervertebral disc degeneration (DD) in general population.

SUMMARY OF BACKGROUND DATA

Precise understanding of the mechanisms leading to DD development is lacking. In a degenerating disc, mechanical and structural changes lead to further worsening of disc integrity. Increasing attention has been paid to vertebral endplate defects as having a possible role in the etiopathogenesis of DD.

METHODS

The study population comprised 831 twin volunteers from TwinsUK (mean age 54 ± 8 yr, 95.8% female). Lumbar T2-weighted magnetic resonance images were coded for endplate defects from 8310 endplates into six grades. Total endplate score (TEP score) was achieved by summing both endplate defect grades from the same disc level. DD was evaluated using two different classifications; Pfirrmann grading, and a quantitative trait for DD based on a 4-point grading system. Multivariable regression analysis was used to determine relationships between the traits of interest and the known risk factors for DD, age, and body mass index (BMI). A receiver operator curve for TEP score predicting DD was generated, and survival analysis paired with Cox proportional hazards models analysis performed.

RESULTS

There was statistically significant association between DD and age and BMI. These associations lost significance when TEP score was included as predictor in multivariable model. TEP score was strongly and independently associated at every lumbar disc level with DD (Pfirmann P≤0.001; 4-point grading systems P < 1e-16). A cut-off point score of 5 for TEP score was found above which there was a higher DD prevalence. Across all age subgroups, probabilities of having DD were significantly increased in those considered TEP score positive (≥5).

CONCLUSION

Our large, population-based study has shown that endplate defect was strongly and independently associated with DD at every lumbar disc level. These results provide a mechanism by which increasing age and BMI predispose to DD.

LEVEL OF EVIDENCE

2.

Catabolic effects of endothelial cell-derived microparticles on disc cells: Implications in intervertebral disc neovascularization and degeneration

Neovascularization of intervertebral discs, a phenomenon considered pathological since normal discs are primarily avascular structures, occurs most frequently in annulus fibrosus (AF) of degenerated discs. Endothelial cells (ECs) are involved in this process, but the mechanism of the interaction between AF and endothelial cells is unclear. In this study, we evaluated the effects on matrix catabolic activity of AF cells by the extracellular endothelial microparticles (EMPs) and soluble protein factors (SUP fraction) produced from ECs. Passage 1 human AF cells grown in monolayer cultures were treated for 72 h with 250 µg of EMPs or SUP fraction isolated from culture of the microvascular endothelial cell line, HEMC-I. Live-cell imaging revealed uptake of EMPs by AF cells. RT-PCR analysis demonstrated increased mRNA expression of MMP-1 (50.3-fold), MMP-3 (4.5-fold) and MMP-13 (5.5-fold) in AF cell cultures treated with EMPs compared to untreated control. Western analysis also demonstrated increased MMP protein expression in EMP-treated AF cells. AF cells treated with the SUP fraction also exhibited a dramatic increase in MMP mRNA and protein expression. Increased MMP expression is primarily due to EMP or SUP stimulation of AF cells since EMPs or SUP fraction alone contained negligible amount of MMPs. Interestingly, MMP activity was elevated in AF cell cultures treated with EMPs but not with SUP. This study revealed enhanced matrix catabolism as a molecular consequence of action of ECs on AF cells via EMPs, which might be expected during neo-angiogenesis of degenerating disc. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1466-1474, 2016.

The Involvement of Protease Nexin-1 (PN1) in the Pathogenesis of Intervertebral Disc (IVD) Degeneration

Protease nexin-1 (PN-1) is a serine protease inhibitor belonging to the serpin superfamily. This study was undertaken to investigate the regulatory role of PN-1 in the pathogenesis of intervertebral disk (IVD) degeneration. Expression of PN-1 was detected in human IVD tissue of varying grades. Expression of both PN-1 mRNA and protein was significantly decreased in degenerated IVD, and the expression levels of PN-1 were correlated with the grade of disc degeneration. Moreover, a decrease in PN-1 expression in primary NP cells was confirmed. On induction by IL-1β, the expression of PN-1 in NP cells was decreased at day 7, 14, and 21, as shown by western blot analysis and immunofluorescence staining. PN-1 administration decreased IL-1β-induced MMPs and ADAMTS production and the loss of Agg and Col II in NP cell cultures through the ERK1/2/NF-kB signaling pathway. The changes in PN-1 expression are involved in the pathogenesis of IVD degeneration. Our findings indicate that PN-1 administration could antagonize IL-1β-induced MMPs and ADAMTS, potentially preventing degeneration of IVD tissue. This study also revealed new insights into the regulation of PN-1 expression via the ERK1/2/NF-kB signaling pathway and the role of PN-1 in the pathogenesis of IVD degeneration.

Expression of matrix factors in the process of neovascularization of intervertebral disc

<sec><title>OBJECTIVE:</title><p> To investigate the effects of proteins products of endothelial cells (ECs) on the annulus fibrosus (AF) cell metabolism in an in vitro culture.</p></sec><sec><title>METHODS:</title><p>Human AF cells were expanded in monolayer cultures and treated with proteins from the medium of cell line HMEC-1 (Human Microvascular Endothelial Cells) (125µg/ml). After 72h of treatment RNA was isolated from AF cells for analysis of gene expression and the culture medium was collected for protein expression analysis.</p></sec><sec><title>RESULTS:</title><p> The qRT-PCR analysis demonstrated increased gene expression of matrix metalloproteinases (MMPs) in AF cells treated with protein products of endothelial cells compared with cells from control group of AF cells: MMP-1 243.10 times (p<0.05), MMP-2 1.37 time (p<0.05), MMP-3 39.83 times (p<0.05) and MMP-13 5.70 times (p<0.05). In contrast, tissue inhibitors of metalloproteinases (TIMPs) were suppressed; TIMP-2 (0.55 time) (p<0.05) and TIMP-3 (0.60 time) (p<0.05) in the exposed groups. The expression of aggrecan gene (0.83 time) (p<0.05), an important extracellular matrix component, was also reduced. MMP-1 and MMP-3 detection was performed, confirming the results of PCR by Western Blot technique.</p></sec><sec><title>CONCLUSIONS:</title><p> In this study, we observed that the proteins produced by ECs induced the MMPs expression and suppressed the TIMPs as well as the aggrecan in primary cells of the human intervertebral disc, targeting the development of potential treatments for intervertebral disc degeneration and associated discogenic pain.</p></sec>

Associations between serum biomarkers and pain and pain-related function in older adults with low back pain: a pilot study

OBJECTIVES

To examine the relationship between serum biomarkers and self-reported pain intensity and pain-related function, in addition to the contribution of magnetic resonance imaging (MRI) findings of lumbar spine degenerative changes, in older adults with chronic low back pain.

DESIGN

Single-center cross-sectional cohort study.

SETTING

Academic medical center.

PARTICIPANTS

Individuals aged 60 and older with axial low back pain without radiculopathy or previously diagnosed osteoarthritis of the knee or hip or pain outside the low back that is more severe than the back pain (n = 43).

MEASUREMENTS

To examine pain-related impairment, pain was measured on a pain thermometer and the McGill Pain Questionnaire Short Form was administered. To examine pain-related function or activity limitation, the Roland Morris Disability Questionnaire, Short Physical Performance Battery (SPPB), and repetitive trunk rotation were used. Single plasma samples were obtained before and after physical performance tests and analyzed for inflammatory markers (E-selectin and regulated on activation, normal T cell expressed and secreted (RANTES)), inhibitors of catabolic enzymes (tissue inhibitor of metalloproteinases-1 (TIMP-1)), markers of matrix turnover (C- telopeptide of type II collagen (CTX-II) and aggrecan chondroitin sulfate 846 (CS846)), and stress biomarkers (neuropeptide Y (NPY)). Conventional nongadolinium lumbar MRI was performed and analyzed quantitatively and clinically.

RESULTS

Composite MRI measurements did not show significant correlation with pain or pain-related function. Basal levels and changes in serum biomarkers in response to activity, particularly NPY and RANTES, demonstrated associations with pain and pain-related function in addition to the explanatory power of MRI-based results.

CONCLUSION

Serum biomarkers may be a metric for assessment of active disease in older adults, in whom imaging changes are ubiquitous. In addition, changing levels of biomarkers in response to activity suggests that they may be useful as metrics to measure treatment responses in future studies and may reflect potential targets for use in designing personalized treatment for older adults with low back pain.

Presence and extent of severe facet joint osteoarthritis are associated with back pain in older adults

OBJECTIVE

To determine whether the presence and extent of severe lumbar facet joint osteoarthritis (OA) are associated with back pain in older adults, accounting for disc height narrowing and other covariates.

DESIGN

Two hundred and fifty-two older adults from the Framingham Offspring Cohort (mean age 67 years) were studied. Participants received standardized computed tomography (CT) assessments of lumbar facet joint OA and disc height narrowing at the L2-S1 interspaces using four-grade semi-quantitative scales. Severe facet joint OA was defined according to the presence and/or degree of joint space narrowing, osteophytosis, articular process hypertrophy, articular erosions, subchondral cysts, and intraarticular vacuum phenomenon. Severe disc height narrowing was defined as marked narrowing with endplates almost in contact. Back pain was defined as participant report of pain on most days or all days in the past 12 months. We used multivariable logistic regression to examine associations between severe facet joint OA and back pain, adjusting for key covariates including disc height narrowing, sociodemographics, anthropometrics, and health factors.

RESULTS

Severe facet joint OA was more common in participants with back pain than those without (63.2% vs 46.7%; P = 0.03). In multivariable analyses, presence of any severe facet joint OA remained significantly associated with back pain (odds ratio (OR) 2.15 [95% confidence interval (CI) 1.13-4.08]). Each additional joint with severe OA conferred greater odds of back pain [OR per joint 1.20 (95% CI 1.02-1.41)].

CONCLUSIONS

The presence and extent of severe facet joint OA on CT imaging are associated with back pain in community-based older adults, independent of sociodemographics, health factors, and disc height narrowing.

Degenerative joint disease of the spine

Degenerative changes are the manifestations of metabolic disturbances in the matrix of intervertebral disks and zygapophysial joints. Genetic factors and physical loading contribute, but the strongest correlation is with age. Degenerative changes lack any significant correlation with spinal pain. Therefore, they do not constitute a diagnosis. Internal disk disruption is a distinctive condition that is independent of degeneration and age. Its biophysical and morphologic features correlate with back pain, as do its manifestations on magnetic resonance imaging.

Intervertebral disc degeneration: evidence for two distinct phenotypes

We review the evidence that there are two types of disc degeneration. 'Endplate-driven' disc degeneration involves endplate defects and inwards collapse of the annulus, has a high heritability, mostly affects discs in the upper lumbar and thoracic spine, often starts to develop before age 30 years, usually leads to moderate back pain, and is associated with compressive injuries such as a fall on the buttocks. 'Annulus-driven' disc degeneration involves a radial fissure and/or a disc prolapse, has a low heritability, mostly affects discs in the lower lumbar spine, develops progressively after age 30 years, usually leads to severe back pain and sciatica, and is associated with repetitive bending and lifting. The structural defects which initiate the two processes both act to decompress the disc nucleus, making it less likely that the other defect could occur subsequently, and in this sense the two disc degeneration phenotypes can be viewed as distinct.

The association of lumbar intervertebral disc degeneration on magnetic resonance imaging with body mass index in overweight and obese adults: a population-based study

OBJECTIVE

To investigate the association of being overweight or obese with the presence, extent, and severity of lumbar disc degeneration on magnetic resonance imaging (MRI) in adults.

METHODS

A population-based cross-sectional study of 2,599 southern Chinese volunteers was conducted. Subjects underwent radiographic and clinical assessment, and weight and height were measured. Sagittal T2-weighted MRIs of the lumbar spine were obtained. The presence, extent, and severity of disc degeneration and additional radiographic and clinical parameters were assessed. Asian-modified body mass index (BMI) (kg/m(2) ) categories were used. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

The study included 1,040 men and 1,559 women (mean age 41.9 years). Disc degeneration was noted in 1,890 subjects (72.7%). BMI was significantly higher in subjects with disc degeneration (mean 23.3 kg/m(2) ) than in subjects without degeneration (mean 21.7 kg/m(2) ) (P < 0.001). A significant increase in the number of degenerated levels (P < 0.001), global severity of disc degeneration (P < 0.001), and end-stage disc degeneration with disc space narrowing (P < 0.001) was noted with elevated BMI, in particular in overweight and obese subjects. In the adjusted multivariate logistic regression model, there was a positive linear trend (r(2) = 0.99) between BMI and the overall presence of disc degeneration in overweight (OR 1.30 [95% CI 1.03-1.62]) and obese (OR 1.79 [95% CI 1.17-2.74]) subjects. End-stage disc degeneration with disc space narrowing was significantly more pronounced in obese subjects (adjusted OR 1.72 [95% CI 1.23-2.41] [reference normal weight]).

CONCLUSION

Our findings, in one of the largest studies to systematically assess lumbar disc degeneration on MRI, indicated a significant association between the presence, extent, and global severity of disc degeneration with weight in overweight and obese adults.

Influence of lumbar intervertebral disc degeneration on the outcome of total lumbar disc replacement: a prospective clinical, histological, X-ray and MRI investigation

INTRODUCTION

The role of fusion of lumbar motion segments for the treatment of axial low back pain (LBP) from lumbar degenerative disc disease (DDD) without any true deformities or instabilities remains controversially debated. In an attempt to avoid previously published and fusion-related negative side effects, motion preserving technologies such as total lumbar disc replacement (TDR) have been introduced. The adequate extent of preoperative DDD for TDR remains unknown, the number of previously published studies is scarce and the limited data available reveal contradictory results. The goal of this current analysis was to perform a prospective histological, X-ray and MRI investigation of the index-segment's degree of DDD and to correlate these data with each patient's pre- and postoperative clinical outcome parameters from an ongoing prospective clinical trial with ProDisc II (Synthes, Paoli, U.S.A.).

MATERIALS AND METHODS

Nucleus pulposus (NP) and annulus fibrosus (AF) changes were evaluated according to a previously validated quantitative histological degeneration score (HDS). X-ray evaluation included assessment of the mean, anterior and posterior disc space height (DSH). MRI investigation of DDD was performed on a 5-scale grading system. The prospective clinical outcome assessment included visual analogue scale (VAS), Oswestry Disability Index (ODI) scores as well as the patient's subjective satisfaction rates.

RESULTS

Data from 51 patients with an average follow-up of 50.5 months (range 6.1-91.9 months) were included in the study. Postoperative VAS and ODI scores improved significantly in comparison to preoperative levels (p < 0.002). A significant correlation and interdependence was established between various parameters of DDD preoperatively (p < 0.05). Degenerative changes of NP tissue samples were significantly more pronounced in comparison to those of AF material (p < 0.001) with no significant correlation between each other (p > 0.05). Preoperatively, the extent of DDD was not significantly correlated with the patient's symptomatology (p > 0.05). No negative influence was associated with increasing stages of DDD on the postoperative clinical outcome parameters following TDR (p > 0.05). Increasing stages of DDD in terms of lower DSH scores were not associated with inferior clinical results as outlined by postoperative VAS or ODI scores or the patient's subjective outcome evaluation at the last FU examination (p > 0.05). Conversely, some potential positive effects on the postoperative outcome were observed in patients with advanced stages of preoperative DDD. Patients with more severe preoperative HDS scores of NP samples demonstrated significantly lower VAS scores during the early postoperative course (p = 0.02).

CONCLUSION

Increasing stages of DDD did not negatively impact on the outcome following TDR in a highly selected patient population. In particular, no preoperative DDD threshold value was identified from which an inferior postoperative outcome could have been deduced. Conversely, some positive effects on the postoperative outcome were detected in patients with advanced stages of DDD. Combined advantageous effects of progressive morphological structural rigidity of the index segment and restabilizing effects from larger distraction in degenerated segments may compensate for increasing axial rotational instability, one of TDR's perceived disadvantages. Our data reveal a "therapeutic window" for TDR in a cohort of patients with various stages of DDD as long as preoperative facet joint complaints or degenerative facet arthropathies can be excluded and stringent preoperative decision making criteria are adhered to. Previously published absolute DSH values as contraindication against TDR should be reconsidered.

Evaluation of intervertebral disk degeneration in chondrodystrophic and nonchondrodystrophic dogs by use of Pfirrmann grading of images obtained with low-field magnetic resonance imaging

OBJECTIVE

To assess whether the Pfirrmann system for grading lumbar intervertebral disk (IVD) degeneration in humans can also be used in dogs.

ANIMALS

202 dogs.

PROCEDURES

Magnetic resonance imaging was used to obtain images of vertebral segments from dogs, which were reviewed separately by 3 observers who graded the extent of degeneration in each visible IVD by use of the Pfirrmann classification system used for grading lumbar IVD degeneration in humans. Grading was validated against 2 factors associated with the extent of disk degeneration: type of dog (chondrodystrophic or nonchondrodystrophic breeds) and age.

RESULTS

Interobserver and intraobserver agreement for Pfirrmann grading of IVD degeneration were good (κ scores, 0.81 to 0.93). An increase in the extent of disk degeneration was positively correlated with increases in age and with chondrodystrophic breed.

CONCLUSIONS AND CLINICAL RELEVANCE

The Pfirrmann system was reliably used to grade IVD degeneration in dogs of various breeds and ages. An increase in the extent of IVD degeneration was positively correlated with increases in age and with chondrodystrophic-type dogs.

Management of degenerative disk disease and chronic low back pain

Degenerative disk disease is a strong etiologic risk factor of chronic low back pain (LBP). A multidisciplinary approach to treatment is often warranted. Patient education, medication, and cognitive behavioral therapies are essential in the treatment of chronic LBP sufferers. Surgical intervention with a rehabilitation regime is sometimes advocated. Prognostic factors related to the outcome of different treatments include maladaptive pain coping and genetics. The identification of pain genes may assist in determining individuals susceptible to pain and in patient selection for appropriate therapy. Biologic therapies show promise, but clinical trials are needed before advocating their use in humans.