ISSLS prize winner: A study of diffusion in human lumbar discs: a serial magnetic resonance imaging study documenting the influence of the endplate on diffusion in normal and degenerate discs

Different Load-Induced Alterations in Intervertebral Discs Between Low Back Pain Patients and Controls: A T2-map Study

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

Investigate load-induced effects in lumbar intervertebral discs (IVDs) and differences between low back pain (LBP) patients and controls.

SUMMARY OF BACKGROUND DATA

T2-map values, obtained from quantitative MRI sequences, reflect IVD tissue composition and integrity. Feasibility studies with T2-mapping indicate different load-induced effects in entire IVDs and posterior IVD parts between LBP patients and controls. Larger studies are required to confirm these findings and increase the understanding of specific characteristics distinguishing IVD changes in LBP patients compared with controls.

MATERIALS AND METHODS

Lumbar IVDs of 178 patients (mean age: 43.8 yr; range: 20-60 yr) with >3 months of LBP and 74 controls (mean age: 40.3 yr; range: 20-60 yr) were imaged with T2-map sequence in a 3T scanner in supine position without axial load, immediately followed by a repeated examination, using the same sequence, with axial load. On both examinations, mean T2-map values were obtained from entire IVDs and from central/posterior IVD parts on the three midsagittal slices in 855 patient IVDs and 366 control IVDs. Load-induced effect was compared with Fold-change ratio and adjusted for IVD-degeneration grade.

RESULTS

Loading induced an increase in T2-map values in both patients and controls. Excluding most extreme values, the ranges varied between -15% and +35% in patients and -11% and +36% in controls (first to 99th percentile). Compared with controls, the T2-map value increase in patients was 2% smaller in entire IVDs (Fold-change: 0.98, P =0.031), and for central and posterior IVD parts 3% (Fold-change: 0.98, P =0.005), respectively, 2% (Fold-change: 0.9, P =0.015) smaller.

CONCLUSIONS

This quantitative study confirmed diverse load-induced behaviors between LBP patients and controls, suggesting deviant biomechanical characteristics between IVDs in patients and controls not only attributed to the global grade of degeneration. These findings are an important step in the continuous work of identifying specific IVD phenotypes for LBP patients.

LEVEL OF EVIDENCE

Level II.

"Does the Gut microbiome influence disc health and disease?-the interplay between dysbiosis, pathobionts, and disc inflammation: a Pilot Study"

BACKGROUND CONTEXT

Gut microbiome alterations resulting in inflammatory responses have been implicated in many distant effects on different organs. However, its influence on disc health is still not fully investigated.

PURPOSE

Our objective was to document the gut biome in healthy volunteers and patients with disc degeneration and to understand the role of gut dysbiosis on human disc health.

STUDY DESIGN

Experimental case-control study.

PATIENT SAMPLE

We included 40 patients with disc degeneration (DG) and 20 healthy volunteers (HV). HV comprised of age groups 30 to 60 years with no known record of back pain and no clinical comorbidities, with normal MRI. Diseased group (DG) were patients in the same age group undergoing surgery for disc disease (disc herniation-25; discogenic stenosis-15) and without instability (with Modic-20; and non-Modic-20).

OUTCOME MEASURES

N/A.

METHODS

We analyzed 16S V3-V4 rDNA gut metagenome from 20 healthy volunteers (HV) and compared the top signature genera from 40 patients with disc degeneration (DG) across Modic and non-Modic groups. Norgen Stool DNA Kit was used for DNA extraction from ∼200 mg of each faecal sample collected using the Norgen Stool Collection Kit.16S V3-V4 rDNA amplicons were generated with universal bacterial primers 341F and 806R and amplified with Q5 High-Fidelity DNA Polymerase. Libraries were sequenced with 250×2 PE to an average of 0.1 million raw reads per sample (Illumina Novaseq 6000). Demultiplexed raw data was assessed with FastQC, and adapter trimmed reads >Q30 reads were processed in the QIME2 pipeline. Serum C-reactive protein (CRP) was measured by the immunoturbimetry method and Fatty acid-binding protein 5 (FABP5) was measured in albumin-globulin-depleted plasma through global proteome analysis.

RESULTS

We observed significant gut dysbiosis between HV and DG and also between the Modic and non-Modic groups. In the Modic group, commensals Bifidobacterium and Ruminococcus were significantly depleted, while pathobionts Streptococcus, Prevotella, and Butryvibrio were enriched. Firmicutes/Bacteroidetes ratio was decreased in DG (Modic-0.62, non-Modic-0.43) compared to HV (0.70). Bacteria-producing beneficial short-chain fatty acids were also depleted in DG. Elevated serum CRP and increased FABP5 were observed in DG.

CONCLUSION

The study revealed gut dysbiosis, an altered Firmicutes/Bacteroidetes ratio, reduced SCFA-producing bacteria, and increased systemic and local inflammation in association with disc disease, especially in Modic changes. The findings have considerable importance for our understanding and prevention of disc degeneration.

The role of sirtuins in intervertebral disc degeneration: Mechanisms and therapeutic potential

Intervertebral disc degeneration (IDD) is one of the main causes of low back pain, which affects the patients' quality of life and health and imposes a significant socioeconomic burden. Despite great efforts made by researchers to understand the pathogenesis of IDD, effective strategies for preventing and treating this disease remain very limited. Sirtuins are a highly conserved family of (NAD+)-dependent deacetylases in mammals that are involved in a variety of metabolic processes in vivo. In recent years, sirtuins have attracted much attention owing to their regulatory roles in IDD on physiological activities such as inflammation, apoptosis, autophagy, aging, oxidative stress, and mitochondrial function. At the same time, many studies have explored the therapeutic effects of sirtuins-targeting activators or micro-RNA in IDD. This review summarizes the molecular pathways of sirtuins involved in IDD, and summarizes the therapeutic role of activators or micro-RNA targeting Sirtuins in IDD, as well as the current limitations and challenges, with a view to provide possible solutions for the treatment of IDD.

Role of End Plate Changes and Paraspinal Muscle Pathology in Lower Back Pain: A Narrative Review

Degenerative changes of the lumbar intervertebral disc are the most significant causes of enduring lower back pain. The possibility of the diagnosis is limited in people with this low back pain. Therefore, it is essential to identify the relevant back pain subgroups. The paraspinal muscles, that is, the muscles that attach to the spine, are necessary for the proper functioning of the spine and the body; insufficiency can result in back pain. Lower back pain disorders are strongly associated with altered function or structure of these paraspinal muscles, especially fibrosis and fatty infiltration. Modic changes are the bone marrow changes of the end plate in the vertebral body seen on MRI. These are strongly related to degeneration of the disc and are common in individuals with back pain symptoms. Articles were selected from Google Scholar using the terms 'Modic changes,' 'end plate changes,' 'paraspinal muscles,' and 'lower back pain. ' This article compiled different studies aiming to enhance the comprehension of biochemical processes resulting in the development of lumbar pain. Search using the keywords 'Modic changes,'' end plate changes lower back pain,' 'paraspinal muscles lower back pain,' and 'Modic changes lower back pain' on Google Scholar yielded 33000, 41000, 49400, and 17,800 results, and 958, 118, 890 and 560 results on Pubmed respectively.

ISSLS prize in clinical/bioengineering science 2024: How standing and supine positions influence nutrient transport in human lumbar discs?-A serial post-contrast MRI study evaluating interplay between convection and diffusion

PURPOSE

The intervertebral disc being avascular depends on diffusion and load-based convection for essential nutrient supply and waste removal. There are no reliable methods to simultaneously investigate them in humans under natural loads. For the first time, present study aims to investigate this by strategically employing positional MRI and post-contrast studies in three physiological positions: supine, standing and post-standing recovery.

METHODS

A total of 100 healthy intervertebral discs from 20 volunteers were subjected to a serial post-contrast MR study after injecting 0.3 mmol/kg gadodiamide and T1-weighted MR images were obtained at 0, 2, 6, 12 and 24 h. At each time interval, images were obtained in three positions, i.e. supine, standing and post-standing recovery supine. The signal intensity values at endplate zone and nucleus pulposus were measured. Enhancement percentages were calculated and analysed comparing three positions.

RESULTS

During unloaded supine position, there was slow gradual increase in enhancement reaching peak at 6 h. When the subjects assumed standing position, there was immediate loss of enhancement at nucleus pulposus which resulted in reciprocal increase in enhancement at endplate zone (washout phenomenon). Interestingly, when subjects assumed the post-standing recovery position, the nucleus pulposus regained the enhancement and endplate zone showed reciprocal loss (pumping-in phenomenon).

CONCLUSIONS

For the first time, present study documented acute effects of physiological loading and unloading on nutrition of human discs in vivo. While during rest, solutes diffused gradually into disc, the diurnal short loading and unloading redistribute small solutes by convection. Standing caused rapid solute depletion but promptly regained by assuming resting supine position.

Late/delayed gadolinium enhancement in MRI after intravenous administration of extracellular gadolinium-based contrast agents: is it worth waiting?

The acquisition of images minutes or even hours after intravenous extracellular gadolinium-based contrast agents (GBCA) administration ("Late/Delayed Gadolinium Enhancement" imaging; in this review, further termed LGE) has gained significant prominence in recent years in magnetic resonance imaging. The major limitation of LGE is the long examination time; thus, it becomes necessary to understand when it is worth waiting time after the intravenous injection of GBCA and which additional information comes from LGE. LGE can potentially be applied to various anatomical sites, such as heart, arterial vessels, lung, brain, abdomen, breast, and the musculoskeletal system, with different pathophysiological mechanisms. One of the most popular clinical applications of LGE regards the assessment of myocardial tissue thanks to its ability to highlight areas of acute myocardial damage and fibrotic tissues. Other frequently applied clinical contexts involve the study of the urinary tract with magnetic resonance urography and identifying pathological abdominal processes characterized by high fibrous stroma, such as biliary tract tumors, autoimmune pancreatitis, or intestinal fibrosis in Crohn's disease. One of the current areas of heightened research interest revolves around the possibility of non-invasively studying the dynamics of neurofluids in the brain (the glymphatic system), the disruption of which could underlie many neurological disorders.

No evidence of association between either Modic change or disc degeneration and five circulating inflammatory proteins

Introduction

Intervertebral disc degeneration and Modic change are the main spinal structural changes associated with chronic low back pain (LBP). Both conditions are thought to manifest local inflammation and if inflammatory proteins translocate to the blood circulation could be detected systemically. The work here assesses whether the presence of disc degeneration is associated with detectable blood level changes of five inflammatory markers and whether chronic LBP is associated with these changes.

Materials and Methods

Two hundred and forty TwinsUK cohort participants with both MRI disc degeneration grade and Modic change extent, and IL-6, IL-8, IL-8 TNF, and CX3CL1 protein blood concentration measurements were included in this work. Linear mixed effects models were used to test the association of blood cytokine concentration with disc degeneration score and Modic change volumetric score. Association of chronic LBP status from questionnaires with disc degeneration, Modic change, and cytokine blood concentration was also tested.

Results

No statistically significant association between disc degeneration or Modic change with cytokine blood concentration was found. Instead, regression analysis pointed strong association between cytokine blood concentration with body mass index for IL-6 and with age for IL-6 and TNF. Mild association was found between IL-8 blood concentration and body mass index. Additionally, LBP status was associated with Modic change volumetric score but not associated with any cytokine concentration.

Conclusions

We found no evidence that Modic change and disc degeneration are able to produce changes in tested blood cytokine concentration. However, age and body mass index have strong influence on cytokine concentration and both are associated with the conditions studied which may confound associations found in the literature. It is then unlikely that cytokines produced in the disc or vertebral bone marrow induce chronic LBP.

The role of the complement system in disc degeneration and Modic changes

Disc degeneration and vertebral endplate bone marrow lesions called Modic changes are prevalent spinal pathologies found in chronic low back pain patients. Their pathomechanisms are complex and not fully understood. Recent studies have revealed that complement system proteins and interactors are dysregulated in disc degeneration and Modic changes. The complement system is part of the innate immune system and plays a critical role in tissue homeostasis. However, its dysregulation has also been associated with various pathological conditions such as rheumatoid arthritis and osteoarthritis. Here, we review the evidence for the involvement of the complement system in intervertebral disc degeneration and Modic changes. We found that only a handful of studies reported on complement factors in Modic changes and disc degeneration. Therefore, the level of evidence for the involvement of the complement system is currently low. Nevertheless, the complement system is tightly intertwined with processes known to occur during disc degeneration and Modic changes, such as increased cell death, autoantibody production, bacterial defense processes, neutrophil activation, and osteoclast formation, indicating a contribution of the complement system to these spinal pathologies. Based on these mechanisms, we propose a model how the complement system could contribute to the vicious cycle of tissue damage and chronic inflammation in disc degeneration and Modic changes. With this review, we aim to highlight a currently understudied but potentially important inflammatory pathomechanism of disc degeneration and Modic changes that may be a novel therapeutic target.

Therapeutic factors and biomaterial-based delivery tools for degenerative intervertebral disc repair

Intervertebral disc degeneration (IDD) is the main cause of low back pain (LBP), which significantly impacts global wellbeing and contributes to global productivity declines. Conventional treatment approaches, encompassing conservative and surgical interventions, merely serve to postpone the advancement of IDD without offering a fundamental reversal. Consequently, there is an urgent demand for an effective approach to prevent the progression of IDD. Recent investigations focusing on the treatment of IDD utilizing diverse bioactive substances integrated within various biomaterials have exhibited promising outcomes. Various bioactive substances, encompassing conventional small molecule drugs, small molecule nucleic acids, and cell therapies, exhibit distinct capacities for repairing IDD. Additionally, various biological material delivery systems, such as nano micelles, microspheres, and hydrogels, possess diverse biological and release characteristics. Consequently, these diverse materials and drugs hold promise for advancing the treatment of IDD. This article aims to provide a concise overview of the IDD process and investigate the research advancements in biomaterials and bioactive substances for IDD treatment, delving into their mechanisms.

The disc-endplate-bone-marrow complex classification: progress in our understanding of Modic vertebral endplate changes and their clinical relevance

BACKGROUND CONTEXT

The disc, endplate (EP), and bone marrow region of the spine form a single anatomical and functional interdependent unit; isolated degeneration of any one structure is rare. Modic changes (MC), however, are restricted to the subchondral bone alone and based on only T1 and T2 sequences of MRI. This results in poor reliability in differentiating fat from edema and hence may give a false impression of disease inactivity.

PURPOSE

To study the changes in disc, endplate, and bone marrow as a whole in degeneration and propose a classification based on the activity status of this complex with the addition of STIR MRI sequences.

STUDY DESIGN

Observational cohort.

PATIENT SAMPLE

Patients with isolated brain, cervical, or thoracic spine injury and patients with low back pain (LBP) who underwent MRI formed the control and study groups, respectively.

OUTCOME MEASURES

Demographic data, the prevalence of MC and disc-endplate-bone marrow classification (DEBC) changes, EPs undergoing reclassification based on DEBC, and comparison of the prevalence of MC, DEBC, H+modifier and DEBC with H+concordance between control and LBP group. The study determined the risk of LBP patients undergoing surgery as well as the incidence of postoperative infection based on DEBC changes. Significance was calculated by binomial test and chi-square test with the effect size of 0.3 to 0.5. Prevalence and association of outcome were calculated by Altman's odds ratio with the 95% CI and the scoring of z statistics. Logistic expression was plotted for independent variables associated with each class of both Modic and DEBC against dependent variables surgery and nonsurgery.

METHODS

Lumbar segments in both groups were assessed for MC types. The DEBC classification was developed with the addition of STIR images and studying the interdependent complex as a whole: type-A: acute inflammation; type-B: chronic persistence; type-C: latent and type-D: inactive. Modifier H+ was added if there was disc herniation. The classification was compared with MC and correlated to clinical outcomes.

RESULTS

A total of 3,560 EPs of 445 controls and 8,680 EPs in 1,085 patients with LBP were assessed. Four nonMC, 560 MC-II, and 22 MC-III EPs were found to have previously undetected edema in STIR (n=542) or hyperintensity in discs (n=44) needing reclassification. The formerly undescribed type-B of DEBC, representing a chronic persistent activity state was the most common (51.8%) type. The difference between the control and LBP of H+(12% vs 28.8%) and its co-occurrence with DEBC type 1.1% vs 23.3%) was significant (p<.0001). The odds ratio for the need for surgery was highest (OR=5.2) when H+ and DEBC type change co-occurred. Postoperative deep infection (as determined by CDC criteria) was 0.47% in nonDEBC, compared with 2.4% in patients with DEBC (p=.002), with maximum occurrence in type-B.

CONCLUSION

Classification based on the classic MC was found to need a reclassification in 586 EPs showing the shortcomings of results of previous studies. Considering the DEBC allowed better classification and better predictability for the need for surgical intervention and incidence of postoperative infection rate than MC.

Abdominal aortic calcification is independently associated with lumbar endplate degeneration

BACKGROUND

Abdominal aortic calcification (AAC) is associated with lower back pain, reduced bone mineral density of the spine. Vascular changes could also affect the already sparsely perfused intervertebral endplate and intervertebral disc.

METHODS

Lumbar MRIs and lateral radiographs of patients with lower back pain were retrospectively analyzed. AAC was assessed on lateral lumbar radiographs according to the Kauppila score, with a maximum score of 24. Patients were grouped into no (AAC = 0), moderate (AAC 1 to ≤ 4), and severe AAC (AAC ≥ 5). Endplate and disc degeneration were classified according to the total endplate score (TEPS) and Pfirrmann classification. The associations between AAC and degenerative changes was analyzed with a generalized mixed model and was adjusted for age, sex, body mass index as well as diabetes mellitus, and smoking status.

RESULTS

A total of 217 patients (47.9% female) were included in the analysis, totaling 1085 intervertebral levels. Of those, 45 (20.7%) patients had moderate, and 39 (18%) had severe AAC. The results of the generalized mixed model showed no significant association between AAC and disc degeneration (p > 0.05). In contrast, a significant positive association between AAC and the severity of TEPS (β: 0.51, 95% CI: 1.92-2.12, p = 0.004) was observed in the multivariable analysis.

CONCLUSIONS

This study demonstrates an independent association between AAC and endplate degeneration. These findings expand our knowledge about the degenerative cascade of the lumbar spine and suggest that AAC might be a modifiable risk factor for endplate changes.

Lumbar endplate microfracture injury induces Modic-like changes, intervertebral disc degeneration and spinal cord sensitization - an in vivo rat model

BACKGROUND CONTEXT

Endplate (EP) injury plays critical roles in painful IVD degeneration since Modic changes (MCs) are highly associated with pain. Models of EP microfracture that progress to painful conditions are needed to better understand pathophysiological mechanisms and screen therapeutics.

PURPOSE

Establish in vivo rat lumbar EP microfracture model and assess crosstalk between IVD, vertebra and spinal cord.

STUDY DESIGN/SETTING

In vivo rat EP microfracture injury model with characterization of IVD degeneration, vertebral remodeling, spinal cord substance P (SubP), and pain-related behaviors.

METHODS

EP-injury was induced in 5 month-old male Sprague-Dawley rats L4-5 and L5-6 IVDs by puncturing through the cephalad vertebral body and EP into the NP of the IVDs followed by intradiscal injections of TNFα (n=7) or PBS (n=6), compared with Sham (surgery without EP-injury, n=6). The EP-injury model was assessed for IVD height, histological degeneration, pain-like behaviors (hindpaw von Frey and forepaw grip test), lumbar spine MRI and μCT, and spinal cord SubP.

RESULTS

Surgically-induced EP microfracture with PBS and TNFα injection induced IVD degeneration with decreased IVD height and MRI T2 signal, vertebral remodeling, and secondary damage to cartilage EP adjacent to the injury. Both EP injury groups showed MC-like changes around defects with hypointensity on T1-weighted and hyperintensity on T2-weighted MRI, suggestive of MC type 1. EP injuries caused significantly decreased paw withdrawal threshold, reduced axial grip, and increased spinal cord SubP, suggesting axial spinal discomfort and mechanical hypersensitivity and with spinal cord sensitization.

CONCLUSIONS

Surgically-induced EP microfracture can cause crosstalk between IVD, vertebra, and spinal cord with chronic pain-like conditions.

CLINICAL SIGNIFICANCE

This rat EP microfracture model was validated to induce broad spinal degenerative changes that may be useful to improve understanding of MC-like changes and for therapeutic screening.

Role of non‑coding RNAs in cartilage endplate (Review)

Cartilage endplate (CEP) degeneration is considered one of the major causes of intervertebral disc degeneration (IDD), which causes non-specific neck and lower back pain. In addition, several non-coding RNAs (ncRNAs), including long ncRNAs, microRNAs and circular RNAs have been shown to be involved in the regulation of various diseases. However, the particular role of ncRNAs in CEP remains unclear. Identifying these ncRNAs and their interactions may prove to be is useful for the understanding of CEP health and disease. These RNA molecules regulate signaling pathways and biological processes that are critical for a healthy CEP. When dysregulated, they can contribute to the development disease. Herein, studies related to ncRNAs interactions and regulatory functions in CEP are reviewed. In addition, a summary of the current knowledge regarding the deregulation of ncRNAs in IDD in relation to their actions on CEP cell functions, including cell proliferation, apoptosis and extracellular matrix synthesis/degradation is presented. The present review provides novel insight into the pathogenesis of IDD and may shed light on future therapeutic approaches.

ISSLS PRIZE in basic science 2023: Lactate in lumbar discs-metabolic waste or energy biofuel? Insights from in vivo MRS and T2r analysis following exercise and nimodipine in healthy volunteers

PURPOSE

To quantitatively assess the dynamic changes of Lactate in lumbar discs under different physiological conditions using MRS and T2r.

METHODS

In step1, MRS and T2r sequences were standardized in 10 volunteers. Step2, analysed effects of high cellular demand. 66 discs of 20 volunteers with no back pain were evaluated pre-exercise (EX-0), immediately after targeted short-time low back exercises (EX-1) and 60 min after (EX-2). In Step 3, to study effects of high glucose and oxygen concentration, 50 lumbar discs in 10 volunteers were analysed before (D0) and after 10 days intake of the calcium channel blocker, nimodipine (D1).

RESULTS

Lactate showed a distinctly different response to exercise in that Grade 1 discs with a significant decrease in EX-1 and a trend for normalization in Ex-2. In contrast, Pfirrmann grade 2 and 3 and discs above 40 years showed a higher lactate relative to proteoglycan in EX-0, an increase in lactate EX-1 and mild dip in Ex-2. Similarly, following nimodipine, grade 1 discs showed an increase in lactate which was absent in grade 2 and 3 discs. In contrast, exercise and Nimodipine had no significant change in T2r values and MRS spectrum of proteoglycan, N-acetyl aspartate, carbohydrate, choline, creatine, and glutathione across age groups and Pfirrmann grades.

CONCLUSION

MRS documented changes in lactate response to cellular demand which suggested a 'Lactate Symbiotic metabolic Pathway'. The differences in lactate response preceded changes in Proteoglycan/hydration and thus could be a dynamic radiological biomarker of early degeneration.

Clinical outcome and MRI appearance in a group of chronic low back pain patients more than 10 years after discography evaluation and consideration for surgery

BACKGROUND

It is an ongoing debate whether fusion surgery is superior to non-operative treatment for non-specific low back pain (LBP) in terms of patient outcome. Further, the evidence for how signs of intervertebral disc (IVD) degeneration on magnetic resonance imaging (MRI) correlate with patient outcome is insufficient. Longitudinal studies of low back pain (LBP) patients are thus of interest for increased knowledge. The aim of this study was to investigate long-term MRI appearance in LBP patients 11-14 years after discography.

METHODS

In 2021, 30 LBP patients who had same-day discography and MRI in 2007-2010 were asked to undergo MRI (Th12/L1-L5/S1), complete visual analog scale (VAS), Oswestry Disability Index (ODI) and EuroQol-5 Dimension (EQ5D) questionnaires. Patients who had fusion surgery before the follow-up were compared with those without such surgery. MRIs were evaluated on Pfirrmann grade, endplate classification score (EPS), and High Intensity Zones (HIZ). For each disk it was noted if injected at baseline or not.

RESULTS

Of 17 participants (6 male;mean age 58.5 years, range 49-72), 10 (27 disks) had undergone fusion surgery before the follow-up. No differences in VAS, ODI, or EQ5D scores were found between patients with and without surgery (mean 51/32/0.54 vs. 50/37/0.40, respectively; 0.77 > p < 0.65). Other than more segments with EPS ≥ 4 in the surgery group (p < 0.05), no between-group differences were found in longitudinal change in MRI parameters. Of 75 non-fused disks, 30 were injected at baseline. Differences were found between injected and non-injected disks at both baseline and follow-up for Pfirrmann grade and HIZ, and at follow-up for EPS (0.04 > p < 0.001), but none for progression over time (0.09 > p < 0.82).

CONCLUSIONS

Other than more endplate changes in the surgery group, no differences in longitudinal change of MRI parameters were established between LBP patients treated with or without fusion surgery in the studied cohort. The study also highlights the limited progress of degenerative changes, which may be seen over a decade, despite needle puncture and chronic LBP.

Lumbar endplate microfracture injury induces Modic-like changes, intervertebral disc degeneration and spinal cord sensitization - An In Vivo Rat Model

BACKGROUND CONTEXT : Endplate (EP) injury plays critical roles in painful IVD degeneration since Modic changes (MCs) are highly associated with pain. Models of EP microfracture that progress to painful conditions are needed to better understand pathophysiological mechanisms and screen therapeutics. PURPOSE : Establish in vivo rat lumbar EP microfracture model with painful phenotype. STUDY DESIGN/SETTING : In vivo rat study to characterize EP-injury model with characterization of IVD degeneration, vertebral bone marrow remodeling, spinal cord sensitization, and pain-related behaviors. METHODS : EP-driven degeneration was induced in 5-month-old male Sprague-Dawley rats L4-5 and L5-6 IVDs through the proximal vertebral body injury with intradiscal injections of TNFα (n=7) or PBS (n=6), compared to Sham (surgery without EP-injury, n=6). The EP-driven model was assessed for IVD height, histological degeneration, pain-like behaviors (hindpaw von Frey and forepaw grip test), lumbar spine MRI and μCT analyses, and spinal cord substance P (SubP). RESULTS : EP injuries induced IVD degeneration with decreased IVD height and MRI T2 values. EP injury with PBS and TNFα both showed MC type1-like changes on T1 and T2-weighted MRI, trabecular bone remodeling on μCT, and damage in cartilage EP adjacent to the injury. EP injuries caused significantly decreased paw withdrawal threshold and reduced grip forces, suggesting increased pain sensitivity and axial spinal discomfort. Spinal cord dorsal horn SubP was significantly increased, indicating spinal cord sensitization. CONCLUSIONS : EP microfracture can induce crosstalk between vertebral bone marrow, IVD and spinal cord with chronic pain-like conditions. CLINICAL SIGNIFICANCE : This rat EP microfracture model of IVD degeneration was validated to induce MC-like changes and pain-like behaviors that we hope will be useful to screen therapies and improve treatment for EP-drive pain.

Translucent Zone Between Autograft and Endplate Two Months Postoperatively Is an Independent Predictor of Delayed Osseous Union in Elderly Patients With Posterior Lumbar Interbody Fusion Surgery

Background Delayed union or pseudoarthrosis after posterior lumbar interbody fusion (PLIF) is associated with poor outcomes in health-related quality of life. Therefore, it is important to achieve earlier solid fusion for a successful clinical outcome after PLIF. A few authors reported that biomechanical factors may influence spinal fusion rates. The purpose of our retrospective study was to evaluate the independent predictors of delayed osseous union related to intraoperative procedures of PLIF, and to find ways to reduce delayed osseous union. Methods This was a retrospective study of a completed trial. We reviewed 66 elderly patients with osteoporosis after PLIF (all female, mean age 71 years, follow-up period over 6 months). Lumbar computed tomography scans at 2 months postoperatively were examined for the presence of a translucent zone between autograft and endplate (more than 50% of vertebral diameter), and autograft position with bone bridging (anterior, central, or posterior). Osseous union was assessed by using computed tomography 6 months postoperatively. Results Thirty-three patients (50%) showed complete osseous union, while 33 did not. A translucent zone between autograft and endplate two months postoperatively was observed in nine patients (27%) in the union group and in 23 (70%) in the nonunion group (p<0.01). Autograft position with bone bridging two months postoperatively was anterior, central, and posterior in 17 (52%), 30 (91%), and 20 patients (61%) in the union group, and in 12 (36%), 20 (61%), and seven patients (21%) in the nonunion group (p=0.22, p<0.01, and p<0.01), respectively. Multivariate logistic regression analysis showed that the presence of a translucent zone between autograft and endplate (odds ratio, 0.101; 95% confidence interval: 0.026-0.398; p<0.01) and teriparatide administration (odds ratio, 8.810; 95% confidence interval: 2.222-34.936; p<0.01) were independently associated with osseous union after PLIF. Conclusions A translucent zone between autograft and endplate at two months postoperatively independently predicted delayed osseous union within six months after PLIF. Complete osseous union rates were higher in patients with posterior bone bridging two months postoperatively than in those without. These findings apart from preoperative predictors of osseous union might serve as indicators of how intraoperative techniques affects osseous union enhancement.

Loading of the Spine in Low Back Pain Patients Does Not Induce MRI Changes in Modic Lesions: A Prospective Clinical Study

Modic changes (MCs) are gaining increased interest as potential generators of low back pain (LBP). The current aim was to investigate possible spinal loading effects on the MRI signal in MCs in patients with LBP. Supine lumbar MRIs were performed and immediately repeated with axial loading in 100 LBP patients. A total of 43 patients (23 male, mean age 45.7 years) had MCs. Each Modic was outlined on all sagittal T2-weighted images (>25% affected vertebrae). For reference, regions of interest were placed in both vertebrae without Modic and in Modic-free tissue in vertebrae with Modic. The Modic signal intensity, normalized to cerebrospinal fluid, and Modic volume were compared between MRIs with and without spinal loading. Of the 94 MCs, 36.2% (n = 34) were type I, 58.5% (n = 55) were type II, and 5.3% (n = 5) were type III. No differences in Modic volume (mean 0.046 cm3; p = 0.25) between the MRIs with and without spinal loading were found. In addition, no significant changes in Modic signal were induced by loading (mean 1.5% difference; p = 0.308). Loading increased the signal in the reference regions of interest in vertebrae both with Modic (mean 5.5%; p = 0.002) and without (mean 3.5%; SD 0.09; p = 0.02). To conclude, MRIs performed with and without spinal loading showed no change in either volume or signal of MCs, suggesting that most MCs are not instantaneously influenced by biomechanical load.

In vivo fluid transport in human intervertebral discs varies by spinal level and disc region

Background

The lumbar discs are large, dense tissues that are primarily avascular, and cells residing in the central region of the disc are up to 6-8 mm from the nearest blood vessel in adults. To maintain homeostasis, disc cells rely on nutrient transport between the discs and adjacent vertebrae. Thus, diminished transport has been proposed as a factor in age-related disc degeneration.

Methods

In this study, we used magnetic resonance imaging (MRI) to quantify diurnal changes in T2 relaxation time, an MRI biomarker related to disc hydration, to generate 3D models of disc fluid distribution and determine how diurnal changes in fluid varied by spinal level. We recruited 10 participants (five males/five females; age: 21-30 years; BMI: 19.1-29.0 kg/m2) and evaluated the T2 relaxation time of each disc at 8:00 AM and 7:00 PM, as well as degeneration grade (Pfirrmann). We also measured disc height, volume, and perimeter in a subset of individuals as a preliminary comparison of geometry and transport properties.

Results

We found that the baseline (AM) T2 relaxation time and the diurnal change in T2 relaxation time were greatest in the cranial lumbar discs, decreasing along the lumbar spine from cranial to caudal. In cranial discs, T2 relaxation times decreased in each disc region (nucleus pulposus [NP], inner annulus fibrosus [IAF], and outer annulus fibrosus [OAF]), whereas in caudal discs, T2 relaxation times decreased in the NP but increased in the AF.

Conclusions

Fluid transport varied by spinal level, where transport was greatest in the most cranial lumbar discs and decreased from cranial to caudal along the lumbar spine. Future work should evaluate what level-dependent factors affect transport.

Traumatic vertebra and endplate fractures promote adjacent disc degeneration: evidence from a clinical MR follow-up study

OBJECTIVES

The integrity of endplate is important for maintaining the health of adjacent disc and trabeculae. Yet, pathological impacts of traumatic vertebra and endplate fractures were less studied using clinical approaches. This study aims to investigate their effects on the development of adjacent disc degeneration, segmental kyphosis, Modic changes (MCs), and high-intensity zones (HIZs).

MATERIALS AND METHODS

Magnetic resonance (MR) images of patients with acute traumatic vertebral compression fractures (T11-L5) were studied. On MR images, endplate fractures were evaluated as present or absent. Disc signal, height, bulging area, sagittal Cobb angle, MCs, and HIZs were measured on baseline and follow-up MR images to study the changes of the disc in relation to vertebra fractures and endplate fractures.

RESULTS

Ninety-seven patients were followed up for 15.4 ± 14.0 months. There were 123 fractured vertebrae, including 79 (64.2%) with endplate fractures and 44 (35.8%) without. Both the adjacent and control discs decreased in signal and height over time (p < 0.001), and the disc adjacent to vertebral fractures had greater signal and height loss than the control disc (p < 0.05). In the presence of endplate fractures, the adjacent discs had greater signal decrease in follow-up (p < 0.05), as compared to those without endplate fractures. Sagittal Cobb angle significantly increased in segments with endplate fractures (p < 0.05). Vertebra fractures were associated with new occurrence of MCs in the fractured vertebra (p < 0.001) but not HIZs in the adjacent disc.

CONCLUSIONS

Traumatic vertebral fractures were associated with accelerated adjacent disc degeneration, which appears to be further promoted by concomitant endplate fractures. Endplate fractures were associated with progression of segmental kyphosis.

Single-Cell RNA-Seq Analysis of Cells from Degenerating and Non-Degenerating Intervertebral Discs from the Same Individual Reveals New Biomarkers for Intervertebral Disc Degeneration

In this study, we used single-cell transcriptomic analysis to identify new specific biomarkers for nucleus pulposus (NP) and inner annulus fibrosis (iAF) cells, and to define cell populations within non-degenerating (nD) and degenerating (D) human intervertebral discs (IVD) of the same individual. Cluster analysis based on differential gene expression delineated 14 cell clusters. Gene expression profiles at single-cell resolution revealed the potential functional differences linked to degeneration, and among NP and iAF subpopulations. GO and KEGG analyses discovered molecular functions, biological processes, and transcription factors linked to cell type and degeneration state. We propose two lists of biomarkers, one as specific cell type, including C2orf40, MGP, MSMP, CD44, EIF1, LGALS1, RGCC, EPYC, HILPDA, ACAN, MT1F, CHI3L1, ID1, ID3 and TMED2. The second list proposes predictive IVD degeneration genes, including MT1G, SPP1, HMGA1, FN1, FBXO2, SPARC, VIM, CTGF, MGST1, TAF1D, CAPS, SPTSSB, S100A1, CHI3L2, PLA2G2A, TNRSF11B, FGFBP2, MGP, SLPI, DCN, MT-ND2, MTCYB, ADIRF, FRZB, CLEC3A, UPP1, S100A2, PRG4, COL2A1, SOD2 and MT2A. Protein and mRNA expression of MGST1, vimentin, SOD2 and SYF2 (p29) genes validated our scRNA-seq findings. Our data provide new insights into disc cells phenotypes and biomarkers of IVD degeneration that could improve diagnostic and therapeutic options.

Development, Pathogenesis, and Regeneration of the Intervertebral Disc: Current and Future Insights Spanning Traditional to Omics Methods

The intervertebral disc (IVD) is the fibrocartilaginous joint located between each vertebral body that confers flexibility and weight bearing capabilities to the spine. The IVD plays an important role in absorbing shock and stress applied to the spine, which helps to protect not only the vertebral bones, but also the brain and the rest of the central nervous system. Degeneration of the IVD is correlated with back pain, which can be debilitating and severely affects quality of life. Indeed, back pain results in substantial socioeconomic losses and healthcare costs globally each year, with about 85% of the world population experiencing back pain at some point in their lifetimes. Currently, therapeutic strategies for treating IVD degeneration are limited, and as such, there is great interest in advancing treatments for back pain. Ideally, treatments for back pain would restore native structure and thereby function to the degenerated IVD. However, the complex developmental origin and tissue composition of the IVD along with the avascular nature of the mature disc makes regeneration of the IVD a uniquely challenging task. Investigators across the field of IVD research have been working to elucidate the mechanisms behind the formation of this multifaceted structure, which may identify new therapeutic targets and inform development of novel regenerative strategies. This review summarizes current knowledge base on IVD development, degeneration, and regenerative strategies taken from traditional genetic approaches and omics studies and discusses the future landscape of investigations in IVD research and advancement of clinical therapies.

Next-generation sequencing (NGS) to determine microbiome of herniated intervertebral disc

BACKGROUND CONTEXT

There is apparent causality between chronic infection of the intervertebral disc and its degenerative process. Although disc is considered a sterile tissue, collected samples of uninfected patients sent to culture testing resulted positive.

PURPOSE

The purpose of this study was to analyze the microbiome of the intervertebral disc by using and validating the next-generation sequencing (NGS) molecular test, controlled with tissue culture and clinical presentation of patients.

STUDY DESIGN/SETTING

Prospective study of consecutive patients in a hospital.

PATIENT SAMPLE

Patients with lumbar disc herniation undergoing open microdiscectomy aging 18 to 65 years.

OUTCOME MEASURES

NGS, tissue culture METHODS: Subjects undergoing open decompression surgery for lumbar disc herniation were consecutively included and clinically followed for one year. Three samples of the excised herniated disc fragment were sent to tissue culture and another sample of the disc was sent to NGS test for microbiome analysis. Control samples of the ligamentum flavum and deep muscle were collected and sent to culture.

RESULTS

A total of 17 patients were included. All patients presented negative cultures of the removed disc samples, as well as negative cultures of muscle and yellow ligament. None of the patients evolved to clinical infection one year after surgery, nor presented significant alteration of laboratory markers. NGS mapped a mean of 14,645 (range 6,540 to 27,176) DNA sequences for each disc sample of each patient. There were a total of 45 different bacteria genera remnants with different amount of DNA sequences detected. There was a mean of 8 (range 3-17) different bacterial elements in each sample of intervertebral disc. Three bacteria were present in all disc samples (Herbaspirillum, Ralstonia, and Burkolderia). Although there were a considerable mean number of bacterial sequences mapped in each disc sample, the amount of sequences related to bacteria was low. Cutibacterium acnes elements was not found in any disc microbiome analysis.

CONCLUSIONS

NGS has been proven to adequately determine bacterial DNA presence within the intervertebral disc. C. acnes was not isolated in culture neither in microbiome analysis of patients with lumbar disc herniation. We cannot confirm disc sterility since, even if it does not cause infection, there is bacterial or remnant DNA in herniated discs.

Should Degenerated Intervertebral Discs of Patients with Modic Type 1 Changes Be Treated with Mesenchymal Stem Cells?

Low back pain (LBP) has been among the leading causes of disability for the past 30 years. This highlights the need for improvement in LBP management. Many clinical trials focus on developing treatments against degenerative disc disease (DDD). The multifactorial etiology of DDD and associated risk factors lead to a heterogeneous patient population. It comes as no surprise that the outcomes of clinical trials on intradiscal mesenchymal stem cell (MSC) injections for patients with DDD are inconsistent. Intradiscal MSC injections have demonstrated substantial pain relief and significant disability-related improvements, yet they have failed to regenerate the intervertebral disc (IVD). Increasing evidence suggests that the positive outcomes in clinical trials might be attributed to the immunomodulatory potential of MSCs rather than to their regenerative properties. Therefore, patient stratification for inflammatory DDD phenotypes may (i) better serve the mechanisms of action of MSCs and (ii) increase the treatment effect. Modic type 1 changes—pathologic inflammatory, fibrotic changes in the vertebral bone marrow—are frequently observed adjacent to degenerated IVDs in chronic LBP patients and represent a clinically distinct subpopulation of patients with DDD. This review discusses whether degenerated IVDs of patients with Modic type 1 changes should be treated with an intradiscal MSC injection.

Modic Change: An Emerging Complication in the Aging Population

STUDY DESIGN

This was a literature review.

OBJECTIVE

The objective of this study was to review the pathogenesis, prevalence, clinical associations, diagnostic modalities, and treatment options for patients with lower back pain (LBP) associated with Modic change (MC).

SUMMARY OF BACKGROUND DATA

Vertebral body endplates are located between the intervertebral disk and adjacent vertebral body. Despite their crucial roles in nutrition and biomechanical stability, vertebral endplates are extremely susceptible to mechanical failure. Studies examining the events leading to disk degeneration have shown that failure often begins at the endplates. Endplate degeneration with subchondral bone marrow changes were originally noticed on magnetic resonance imaging. These magnetic resonance imaging signal changes were classified as MC.

METHODS

A literature review was conducted on the history, etiology, risk factors, diagnostic modalities, and treatment of LBP with MC.

RESULTS

Type 1 MC refers to the presence of increased vascularization and bone marrow edema within the vertebral body. Type 2 MC involves fatty marrow replacement within the vertebral body. Type 3 MC reflects subchondral bone sclerosis. Despite the original classification, research has supported the notion that MCs possess a transitional nature. Furthermore, type 1 MCs have been strongly associated with inflammation and severe LBP, while types 2 and 3 tend to be more stable and demonstrate less refractory pain. With a strong association to LBP, understanding the etiology of MC is crucial to optimal treatment planning. Various etiologic theories have been proposed including autoimmunity, mechanics, infection, and genetic factors.

CONCLUSIONS

With the aging nature of the population, MC has emerged as an extremely prevalent issue. Research into the pathogenesis of MC is important for planning preventative and therapeutic strategies. Such strategies may include rehabilitation, surgical fixation, stabilization, steroid or cement injection, or antibiotics. Improved diagnostic methods in clinical practice are thus critical to properly identify patients suffering from MC, plan early intervention, and hasten return to functioning.

A definition and clinical grading of Modic changes

To provide an up-to-date description of knowledge and pitfalls related to the classification, definition and grading of Modic changes (MC) visualized on magnetic resonance imaging (MRI). State-of-the-art review of current knowledge regarding the definition and grading of MC on MRI. MC on MRI have been reported to be associated with low back pain and disability. However, previous studies have shown heterogeneous results in regards to the impact of MC and its clinical relevance in patients with back pain. MC is a term used with considerable variation in the literature. No strict definition has been provided previously, this has contributed to varying diagnostic inclusion criteria, heterogeneous study populations, and discrepancy in results. A definition of MC and a proposal for grading is provided in this state-of-the-art review. MC are important, clinically relevant findings. However, issues with the nomenclature, definition and grading of these changes need to be addressed. Our current review highlights relevant issues related to MC, and provides a definition and grading score for the term MC that includes the Modic type and the extent of vertebral body involvement. Future studies should seek to validate the MC grading score in clinically relevant populations.

The Role of Oxidative Stress in Intervertebral Disc Degeneration

Intervertebral disc degeneration is a very common type of degenerative disease causing severe socioeconomic impact, as well as a major cause of discogenic low back pain and herniated discs, placing a heavy burden on patients and the clinicians who treat them. IDD is known to be associating with a complex process involving in extracellular matrix and cellular damage, and in recent years, there is increasing evidence that oxidative stress is an important activation mechanism of IDD and that reactive oxygen and reactive nitrogen species regulate matrix metabolism, proinflammatory phenotype, autophagy and senescence in intervertebral disc cells, apoptosis, autophagy, and senescence. Despite the tremendous efforts of researchers within the field of IDD pathogenesis, the proven strategies to prevent and treat this disease are still very limited. Up to now, several antioxidants have been proved to be effective for alleviating IDD. In this article, we discussed that oxidative stress accelerates disc degeneration by influencing aging, inflammation, autophagy, and DNA methylation, and summarize some antioxidant therapeutic measures for IDD, indicating that antioxidant therapy for disc degeneration holds excellent promise.

The role of oxidative stress in intervertebral disc cellular senescence

With the aggravation of social aging and the increase in work intensity, the prevalence of spinal degenerative diseases caused by intervertebral disc degeneration(IDD)has increased yearly, which has driven a heavy economic burden on patients and society. It is well known that IDD is associated with cell damage and degradation of the extracellular matrix. In recent years, it has been found that IDD is induced by various mechanisms (e.g., genetic, mechanical, and exposure). Increasing evidence shows that oxidative stress is a vital activation mechanism of IDD. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) could regulate matrix metabolism, proinflammatory phenotype, apoptosis, autophagy, and aging of intervertebral disc cells. However, up to now, our understanding of a series of pathophysiological mechanisms of oxidative stress involved in the occurrence, development, and treatment of IDD is still limited. In this review, we discussed the oxidative stress through its mechanisms in accelerating IDD and some antioxidant treatment measures for IDD.

Fundamentals of Intervertebral Disc Degeneration

Lumbar disc degeneration is one of the leading causes of chronic low back pain. The degenerative cascade is often initiated by an imbalance between catabolic and anabolic processes in the intervertebral discs. As a consequence of extracellular matrix degradation, neoinnervation and neovascularization take place. Ultimately, this degenerative process results in disc bulging and loss of nucleus pulposus and water content and subsequent loss of disc height. Most patients respond to conservative management and surgical interventions well initially, yet a significant number of patients continue to suffer from chronic low back pain. Because of the high prevalence of long-term discogenic pain, regenerative biological therapies, including gene therapies, growth factors, cellular-based injections, and tissue-engineered constructs, have attracted significant attention in light of their potential to directly address the degenerative process. Understanding the pathophysiology of degenerative disc disease is important in both refining existing technologies and developing innovative techniques to reverse the degenerative processes in the discs. In this review, we aimed to cover the underlying pathophysiology of degenerative disc disease as well as its associated risk factors and give a comprehensive summary about the developmental, structural, radiological, and biomechanical properties of human intervertebral discs.

Personalized multitarget biologic injection in the spine: prospective case series of multitarget platelet-rich plasma for low back pain

Aim: To evaluate the use of a multitarget platelet-rich plasma (PRP) injection approach for the treatment of chronic low back pain (LBP). Materials & Methods: Forty-six patients with more than 12 weeks of LBP who failed conservative treatments were injected with PRP into the facet joints, intervertebral discs, epidural space and/or paravertebral muscles. Visual analog pain scale and Roland-Morris Disability Questionnaire scores were measured at baseline and predefined intervals. Results: Mean visual analog pain scale was reduced from 8.48 to 5.17 and mean Roland-Morris Disability Questionnaire from 18.0 to 10.98 at 12 weeks (p < 0.001). These statistically significant improvements were sustained over 52 weeks. No adverse effects were observed. Conclusion: Our PRP approach demonstrated clinically favorable results and may be a promising treatment for chronic LBP.

Intervertebral disc repair and regeneration: Insights from the notochord

The vertebrate notochord plays an essential role in patterning multiple structures during embryonic development. In the early 2000s, descendants of notochord cells were demonstrated to form the entire nucleus pulposus of the intervertebral disc in addition to their key role in embryonic patterning. The nucleus pulposus undergoes degeneration during postnatal life, which can lead to back pain. Recently, gene and protein profiles of notochord and nucleus pulposus cells have been identified. These datasets, coupled with the ability to differentiate human induced pluripotent stem cells (iPSCs) into cells that resemble nucleus pulposus cells, provide the possibility of generating a cell-based therapy to halt and/or reverse disc degeneration.

Diagnostic Role of Magnetic Resonance Imaging in Low Back Pain Caused by Vertebral Endplate Degeneration

Low back pain (LBP) is a common health issue worldwide with a huge economic burden on healthcare systems. In the United States alone, the cost is estimated to be $100 billion each year. Intervertebral disc degeneration is considered one of the primary causes of LBP. Moreover, the critical role of the vertebral endplates in disc degeneration and LBP is becoming apparent. Endplate abnormalities are closely correlated with disc degeneration and pain in the lumbar spine. Imaging modalities such as plain film radiography, computed tomography, and fluoroscopy are helpful but not very effective in detecting the causes behind LBP. Magnetic resonance imaging (MRI) can be used to acquire high-quality three-dimensional images of the lumbar spine without using ionizing radiation. Therefore, it is increasingly being used to diagnose spinal disorders. However, according to the American College of Radiology, current referral and justification guidelines for MRI are not sufficiently clear to guide clinical practice. This review aimed to evaluate the role of MRI in diagnosing LBP by considering the correlative contributions of vertebral endplates. The findings of the review indicate that MRI allows for fine evaluations of endplate morphology, endplate defects, diffusion and perfusion properties of the endplate, and Modic changes. Changes in these characteristics of the endplate were found to be closely correlated with disc degeneration and LBP. The collective evidence from the literature suggests that MRI may be the imaging modality of choice for patients suffering from LBP. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 3.

TELD with limited foraminoplasty has potential biomechanical advantages over TELD with large annuloplasty: an in-silico study

Background

Facetectomy, an important procedure in the in–out and out–in techniques of transforaminal endoscopic lumbar discectomy (TELD), is related to the deterioration of the postoperative biomechanical environment and poor prognosis. Facetectomy may be avoided in TELD with large annuloplasty, but iatrogenic injury of the annulus and a high grade of nucleotomy have been reported as risk factors influencing poor prognosis. These risk factors may be alleviated in TELD with limited foraminoplasty, and the grade of facetectomy in this surgery can be reduced by using an endoscopic dynamic drill.

Methods

An intact lumbo-sacral finite element (FE) model and the corresponding model with adjacent segment degeneration were constructed and validated to evaluate the risk of biomechanical deterioration and related postoperative complications of TELD with large annuloplasty and TELD with limited foraminoplasty. Changes in various biomechanical indicators were then computed to evaluate the risk of postoperative complications in the surgical segment.

Results

Compared with the intact FE models, the model of TELD with limited foraminoplasty demonstrated slight biomechanical deterioration, whereas the model of TELD with large annuloplasty revealed obvious biomechanical deterioration. Degenerative changes in adjacent segments magnified, rather than altered, the overall trends of biomechanical change.

Conclusions

TELD with limited foraminoplasty presents potential biomechanical advantages over TELD with large annuloplasty. Iatrogenic injury of the annulus and a high grade of nucleotomy are risk factors for postoperative biomechanical deterioration and complications of the surgical segment.

Melatonin Attenuates Intervertebral Disk Degeneration via Maintaining Cartilaginous Endplate Integrity in Rats

Objective

The aim of this study is to verify whether melatonin (Mel) could mitigate intervertebral disk degeneration (IVDD) in rats and to investigate the potential mechanism of it.

Method

A rat acupuncture model of IVDD was established with intraperitoneal injection of Mel. The effect of Mel on IVDD was analyzed via radiologic and histological evaluations. The specific Mel receptors were investigated in both the nucleus pulposus (NP) and cartilaginous endplates (EPs). In vitro, EP cartilaginous cells (EPCs) were treated by different concentrations of Mel under lipopolysaccharide (LPS) and Luzindole conditions. In addition, LPS-induced inflammatory response and matrix degradation following nuclear factor kappa-B (NF-κB) pathway activation were investigated to confirm the potential mechanism of Mel on EPCs.

Results

The percent disk height index (%DHI) and MRI signal decreased after initial puncture in the degeneration group compared with the control group, while Mel treatment protected disk height from decline and prevented the loss of water during the degeneration process. In the meantime, the histological staining of the Mel groups showed more integrity and well-ordered construction of the NP and EPs in both low and high concentration than that of the degeneration group. In addition, more deep-brown staining of type II collagen (Coll-II) was shown in the Mel groups compared with the degeneration group. Furthermore, in rat samples, immunohistochemical staining showed more positive cells of Mel receptors 1a and 1b in the EPs, instead of in the NP. Moreover, evident osteochondral lacuna formation was observed in rat EPs in the degeneration group; after Mel treatment, the osteochondral destruction alleviated accompanying fewer receptor activator for nuclear factor-κB ligand (RANKL) and tartrate-resistant acid phosphatase (TRAP)-stained positive cells expressed in the EPs. In vitro, Mel could promote the proliferation of EPCs, which protected EPCs from degeneration under LPS treatment. What is more, Mel downregulated the inflammatory response and matrix degradation of EPCs activated by NF-κB pathway through binding to its specific receptors.

Conclusion

These results indicate that Mel protects the integrity of the EPs and attenuates IVDD by binding to the Mel receptors in the EPs. It may alleviate the inflammatory response and matrix degradation of EPCs activated by NF-κB pathway.

Multiscale Regulation of the Intervertebral Disc: Achievements in Experimental, In Silico, and Regenerative Research

Intervertebral disc (IVD) degeneration is a major risk factor of low back pain. It is defined by a progressive loss of the IVD structure and functionality, leading to severe impairments with restricted treatment options due to the highly demanding mechanical exposure of the IVD. Degenerative changes in the IVD usually increase with age but at an accelerated rate in some individuals. To understand the initiation and progression of this disease, it is crucial to identify key top-down and bottom-up regulations' processes, across the cell, tissue, and organ levels, in health and disease. Owing to unremitting investigation of experimental research, the comprehension of detailed cell signaling pathways and their effect on matrix turnover significantly rose. Likewise, in silico research substantially contributed to a holistic understanding of spatiotemporal effects and complex, multifactorial interactions within the IVD. Together with important achievements in the research of biomaterials, manifold promising approaches for regenerative treatment options were presented over the last years. This review provides an integrative analysis of the current knowledge about (1) the multiscale function and regulation of the IVD in health and disease, (2) the possible regenerative strategies, and (3) the in silico models that shall eventually support the development of advanced therapies.

In vivo intervertebral disc deformation: intratissue strain patterns within adjacent discs during flexion-extension

The biomechanical function of the intervertebral disc (IVD) is a critical indicator of tissue health and pathology. The mechanical responses (displacements, strain) of the IVD to physiologic movement can be spatially complex and depend on tissue architecture, consisting of distinct compositional regions and integrity; however, IVD biomechanics are predominately uncharacterized in vivo. Here, we measured voxel-level displacement and strain patterns in adjacent IVDs in vivo by coupling magnetic resonance imaging (MRI) with cyclic motion of the cervical spine. Across adjacent disc segments, cervical flexion-extension of 10° resulted in first principal and maximum shear strains approaching 10%. Intratissue spatial analysis of the cervical IVDs, not possible with conventional techniques, revealed elevated maximum shear strains located in the posterior disc (nucleus pulposus) regions. IVD structure, based on relaxometric patterns of T₂ and T_1ρ images, did not correlate spatially with functional metrics of strain. Our approach enables a comprehensive IVD biomechanical analysis of voxel-level, intratissue strain patterns in adjacent discs in vivo, which are largely independent of MRI relaxometry. The spatial mapping of IVD biomechanics in vivo provides a functional assessment of adjacent IVDs in subjects, and provides foundational biomarkers for elastography, differentiation of disease state, and evaluation of treatment efficacy.

Tissue physiology revolving around the clock: circadian rhythms as exemplified by the intervertebral disc

Circadian clocks in the brain and peripheral tissues temporally coordinate local physiology to align with the 24 hours rhythmic environment through light/darkness, rest/activity and feeding/fasting cycles. Circadian disruptions (during ageing, shift work and jet-lag) have been proposed as a risk factor for degeneration and disease of tissues, including the musculoskeletal system. The intervertebral disc (IVD) in the spine separates the bony vertebrae and permits movement of the spinal column. IVD degeneration is highly prevalent among the ageing population and is a leading cause of lower back pain. The IVD is known to experience diurnal changes in loading patterns driven by the circadian rhythm in rest/activity cycles. In recent years, emerging evidence indicates the existence of molecular circadian clocks within the IVD, disruption to which accelerates tissue ageing and predispose animals to IVD degeneration. The cell-intrinsic circadian clocks in the IVD control key aspects of physiology and pathophysiology by rhythmically regulating the expression of ~3.5% of the IVD transcriptome, allowing cells to cope with the drastic biomechanical and chemical changes that occur throughout the day. Indeed, epidemiological studies on long-term shift workers have shown an increased incidence of lower back pain. In this review, we summarise recent findings of circadian rhythms in health and disease, with the IVD as an exemplar tissue system. We focus on rhythmic IVD functions and discuss implications of utilising biological timing mechanisms to improve tissue health and mitigate degeneration. These findings may have broader implications in chronic rheumatic conditions, given the recent findings of musculoskeletal circadian clocks.

[Modern concepts of intervertebral disc degeneration]

The widespread prevalence of degenerative spine diseases and achievements in the treatment of these lesions have not yet led to an answer the main question: «What is the etiology of spine degeneration?» Treatment will remain symptomatic if primary cause of disease will be unclear. However, improvement of genetic and molecular survey gradually clarifies the mechanisms underlying degenerative processes. The latest knowledge in regenerative medicine seem promising. Nevertheless, further advances in understanding the fundamental processes in human organism are followed by additional questions and unsolved problems. The authors analyzed the best-studied modern theories of degeneration in this brief review devoted to current concepts of intervertebral disc degeneration.

MRI evaluation of the hydration status of non-pathological lumbar intervertebral discs in a pediatric population

INTRODUCTION

The intervertebral disc (IVD) is made up of the annulus fibrosus (AF) and the nucleus pulposus (NP) - an inert hydrated complex. The ability of the IVD to deform is correlated to that of the NP and depends on its hydration. As the IVD ages, its hydration decreases along with its ability to deform. In adolescent idiopathic scoliosis, one of the etiological hypotheses pertains to the IVD, thus making its condition relevant for the diagnosis and monitoring of this pathology.

HYPOTHESIS

IVD hydration depends on sex, age and spine level in an asymptomatic pediatric population. The corollary is data on a control group of healthy subjects.

MATERIAL AND METHODS

A cohort of 98 subjects with normal spine MRI was enrolled; their mean age was 13.3 years. The disc volume and hydration of each IVD was evaluated on T2-weighted MRI sequences, using previously validated image processing software. This evaluation focused on the lumbar spine, from the thoracolumbar junction to the lumbosacral junction. It was assumed that IVD hydration was related to the ratio of NP and AF volumes. A mixed multivariate linear analysis was used to explore the impact of age, sex and spinal level on disc hydration.

RESULTS

Disc hydration was higher overall in boys than in girls, but this difference was not significant. Hydration increased with age by +0.005 for each additional year (p=0.0213). Disc hydration appears to be higher at the thoracolumbar junction than the lumbar spine, although this difference was not significant.

CONCLUSION

Through this MRI study, we established a database of non-pathological lumbar disc hydration as a function of age, sex and spinal segment along with 95% confidence intervals.

LEVEL OF EVIDENCE

IV.

Drug delivery in intervertebral disc degeneration and osteoarthritis: Selecting the optimal platform for the delivery of disease-modifying agents

Osteoarthritis (OA) and intervertebral disc degeneration (IVDD) as major cause of chronic low back pain represent the most common degenerative joint pathologies and are leading causes of pain and disability in adults. Articular cartilage (AC) and intervertebral discs are cartilaginous tissues with a similar biochemical composition and pathophysiological aspects of degeneration. Although treatments directed at reversing these conditions are yet to be developed, many promising disease-modifying drug candidates are currently under investigation. Given the localized nature of these chronic diseases, drug delivery systems have the potential to enhance therapeutic outcomes by providing controlled and targeted release of bioactives, minimizing the number of injections needed and increasing drug concentration in the affected areas. This review provides a comprehensive overview of the currently most promising disease-modifying drugs as well as potential drug delivery systems for OA and IVDD therapy.

Impact of sufficient contact between the autograft and endplate soon after surgery to prevent nonunion at 12 months following posterior lumbar interbody fusion

OBJECTIVE

Nonunion after posterior lumbar interbody fusion (PLIF) is associated with poor long-term outcomes in terms of health-related quality of life. Biomechanical factors in the fusion segment may influence spinal fusion rates. There are no reports on the relationship between intervertebral union and the absorption of autografts or vertebral endplates. Therefore, the purpose of this retrospective study was to evaluate the risk factors of nonunion after PLIF and identify preventive measures.

METHODS

The authors analyzed 138 patients who underwent 1-level PLIF between 2016 and 2018 (75 males, 63 females; mean age 67 years; minimum follow-up period 12 months). Lumbar CT images obtained soon after the surgery and at 6 and 12 months of follow-up were examined for the mean total occupancy rate of the autograft, presence of a translucent zone between the autograft and endplate (more than 50% of vertebral diameter), cage subsidence, and screw loosening. Complete intervertebral union was defined as the presence of both upper and lower complete fusion in the center cage regions on coronal and sagittal CT slices at 12 months postoperatively. Patients were classified into either union or nonunion groups.

RESULTS

Complete union after PLIF was observed in 62 patients (45%), while nonunion was observed in 76 patients (55%). The mean total occupancy rate of the autograft immediately after the surgery was higher in the union group than in the nonunion group (59% vs 53%; p = 0.046). At 12 months postoperatively, the total occupancy rate of the autograft had decreased by 5.4% in the union group and by 11.9% in the nonunion group (p = 0.020). A translucent zone between the autograft and endplate immediately after the surgery was observed in 14 and 38 patients (23% and 50%) in the union and nonunion groups, respectively (p = 0.001). The nonunion group had a significantly higher proportion of cases with cage subsidence and screw loosening at 12 months postoperatively in comparison to the union group (p = 0.010 and p = 0.009, respectively).

CONCLUSIONS

A lower occupancy rate of the autograft and the presence of a translucent zone between the autograft and endplate immediately after the surgery were associated with nonunion at 12 months after PLIF. It may be important to achieve sufficient contact between the autograft and endplate intraoperatively for osseous union enhancement and to avoid excessive absorption of the autograft. The achievement of complete intervertebral union may decrease the incidence of cage subsidence or screw loosening.

Intervertebral Disc Degeneration Is Associated With Aberrant Endplate Remodeling and Reduced Small Molecule Transport

The intervertebral disc is the largest avascular structure in the body, and cells within the disc rely on diffusive transport via vasculature located within the vertebral endplate to receive nutrients, eliminate waste products, and maintain disc health. However, the mechanisms by which small molecule transport into the disc occurs in vivo and how these parameters change with disc degeneration remain understudied. Here, we utilize an in vivo rabbit puncture disc degeneration model to study these interactions and provide evidence that remodeling of the endplate adjacent to the disc occurs concomitant with degeneration. Our results identify significant increases in endplate bone volume fraction, increases in microscale stiffness of the soft tissue interfaces between the disc and vertebral bone, and reductions in endplate vascularity and small molecule transport into the disc as a function of degenerative state. A neural network model identified changes in diffusion into the disc as the most significant predictor of disc degeneration. These findings support the critical role of trans-endplate transport in disease progression and will improve patient selection to direct appropriate surgical intervention and inform new therapeutic approaches to improve disc health. © 2020 American Society for Bone and Mineral Research. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

The role of estrogen in intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is a main contributor to low back and radicular pain, which imposes heavy economic burdens on society. However, the etiology and mechanism of IVDD are complex and still not completely clear. In particular, the role of estrogen in IVDD has not received much attention in recent research, although estrogen plays a crucial role in the metabolic dysfunction of others musculoskeletal structures, such as bone, muscle, and tendon. In this review, we attempt to describe the role of estrogen in IVDD and to summarize the proposed mechanisms in vivo and in vitro, as well as, to outline several interesting questions in this field.

Modic changes - An evidence-based, narrative review on its patho-physiology, clinical significance and role in chronic low back pain

OBJECTIVE

Lumbar degenerative spinal ailments are the most important causes for chronic low back pain. Modic changes (MC) are vertebral bone marrow signal intensity changes seen on MRI, commonly in association with degenerative disc disease (DDD). Despite being widely studied, majority of issues concerning MC are still controversial. The current narrative, evidence-based review comprehensively discusses the various aspects related to MC.

LITERATURE SEARCH

An elaborate search was made using keywords "Modic changes", "lumbar Modic changes", "Modic changes in lumbar spine", and "vertebral Endplate Spinal Changes", on pubmed and google (scholar.google.com) databases on the 3rd of March 2020. We identified crucial questions regarding Modic changes and included relevant articles pertaining to these topics for this narrative review.

RESULTS

The initial search using the keywords "Modic changes", "lumbar Modic changes", "Modic changes in lumbar spine", and "vertebral Endplate Spinal Changes" on pubmed yielded a total of 568, 412, 394 and 216 articles on "pubmed" database, respectively. A similar search using the aforementioned keywords yielded a total of 3650, 3548, 3726 and 21570 articles on "google scholar" database. The initial screening involved exclusion of duplicate articles, articles unrelated to MC, animal or other non-clinical studies, and articles in non-English literature based on abstracts or the titles of articles. This initial screening resulted in the identification of 405 articles. Full manuscripts were obtained for all these selected articles and thoroughly scrutinised at the second stage of article selection. All articles not concerning Modic changes, not pertaining to concerned questions, articles concerning other degenerative phenomena, articles discussing cervical or thoracic MC, case reports or animal studies, articles in non-English language and duplicate articles were excluded. Review articles, randomised controlled trials and level 1 studies were given preference. Overall, 69 articles were included in this review.

CONCLUSION

Modic change (MC) is a dynamic phenomenon and its true etiology is still not definitely known. Disc/end plate injury, occult discitis and autoimmune reactions seem to trigger an inflammatory cascade, which leads to their development. Male sex, older age, diabetes mellitus, genetic factors, smoking, obesity, spinal deformities, higher occupational loads and DDD are known risk factors. There is no conclusive evidence on the causative role of MC in chronic low back pain (LBP) or any influence on the long term outcome in patients with LBP or lumbar disc herniations (LDH). Patients with MC have been reported to have less satisfactory outcome following conservative treatment or discectomy, although the evidence is still unclear.

APOE-knockout in rabbits causes loss of cells in nucleus pulposus and enhances the levels of inflammatory catabolic cytokines damaging the intervertebral disc matrix

Rabbits with naturally high levels of cholesterol ester transfer protein (CETP), unlike rodents, have become an interesting animal model for the study of lipid metabolism and atherosclerosis, as they have similarities to humans in lipid metabolism, cardiovascular physiology and susceptibility to develop atherosclerosis. Rodents, such as mice, are not prone to atherosclerosis as they lack the mass and activity of CETP, as a key player in lipoprotein metabolism. Recently, APOE-knockout in rabbits has been shown to promote atherosclerosis and associated premature IVD degeneration that mimic the symptoms of atherosclerosis and structural changes of IVDs in humans. Here we examined whether APOE-knockout promoted IVD degeneration in rabbits is associated with imbalanced inflammatory catabolic activities, as the underlying problem of biological deterioration that mimic the symptoms of advanced IVD degeneration in humans. We analysed in lumbar nucleus pulposus (NP) of APOE-knockout rabbits the cell viabilities and the intracellular levels of inflammatory, catabolic, anti-catabolic and anabolic proteins derogating IVD matrix. Grades of IVD degeneration were evaluated by magnetic resonance imaging. NP cells were isolated from homozygous APOE-knockout and wild-type New Zealand White rabbits of similar age. Three-dimensional cell culture with low-glucose was completed in alginate hydrogel. Cell proliferation and intracellular levels of target proteins were examined by MTT and ELISA assays. Alike human NP cells of different disc degeneration grades, NP cells of APOE-knockout and wild-type rabbits showed significantly different in vivo cell population densities (p<0.0001) and similar in vitro proliferation rates. Furthermore, they showed differences in overexpression of selective inflammatory and catabolic proteins (p<0.0001) similar to those found in human NP cells of different disc degeneration grades, such as IL-1β, TNF-α, ADAMTS-4, ADAMTS-5 and MMP-3. This study showed that premature IVD degeneration in APOE-knockout rabbits was promoted by the accumulation of selective inflammatory catabolic factors that enhanced imbalances between catabolic and anabolic factors mimicking the symptoms of advanced IVD degeneration in humans. Thus, APOE-knockout rabbits could be used as a promising model for therapeutic approaches of degenerative disc disorders.

An MRI study of solute transport in the intervertebral disc

Objective

Quantitative magnetic resonance imaging was used to determine partition coefficients and characteristic time constants for diffusion of MRI contrast agents in disc tissue.

Materials and methods

Twenty-two excised equine intervertebral discs were exposed to a range of contrast agents: six to manganese chloride, eight to Magnevist (gadopentetate dimeglumine) and eight to Gadovist (gadobutrol), and uptake into the disc was quantified in T₁-weighted images.

Results

Diffusion for all contrast agents was approximately 25% faster in the nucleus than in the outer annulus; disc-average time constants ranged from (2.28 ± 0.23) × 10⁴ s for Gadovist (uncharged, molecular mass 605 g/mol) to (5.07 ± 0.75) × 10⁴ s for the manganese cation (charge + 2). Disc-average partition coefficients ranged from 0.77 ± 0.04 for the anion in Magnevist (charge − 2, molecular mass 548 g/mol) to 5.14 ± 0.43 for the manganese cation.

Conclusion

The MRI technique provides high-quality quantitative data which correspond well to theoretical predictions, allowing values for partition coefficient and time constant to be readily determined. These measurements provide information to underpin similar studies in vivo and may be used as a model for the transport of nutrients and pharmaceutical agents in the disc.

Reducing the extent of facetectomy may decrease morbidity in failed back surgery syndrome

Background

Percutaneous transforaminal endoscopic discectomy (PTED) is widely used for the treatment of lumbar disc herniation. Facetectomy in PTED is necessary for accessing the intraspinal region and for decompressing the exiting nerve roots in patients who suffer from hypertrophy of the facet joints. However, this may increase morbidity in failed back surgery syndrome (FBSS) and has not been clearly elucidated.

Methods

A three-dimensional lumbosacral model was reconstructed and validated. And corresponding models after PTED with one-quarter and one-half excisions of the superior articular process were reconstructed. The maximum shear stress on the annulus in L5, von Mises stress of the facet cartilage, maximum principle capsular strain and deformation of the lumbosacral model were calculated using finite element methods.

Results

Calculated results show no significant differences in the complete model and the model with one-quarter excision of the superior articular process, but all biomechanical indexes have been deteriorated under most of the loading conditions tested in the model with one-half excision of the superior articular process.

Conclusions

Less facetectomy is better because it may reduce the risk of biomechanical deterioration and consequently, that of FBSS.

Roles of large aggregating proteoglycans in human intervertebral disc degeneration

Degeneration of the intervertebral discs, a natural progression of the aging process, is strongly implicated as a cause of low back pain. Aggrecan is the major structural proteoglycan in the extracellular matrix of the intervertebral disc. It is large, possessing numerous glycosaminoglycan chains and the ability to form aggregates in association with hyaluronan. The negatively charged glycosaminoglycan side chains in aggrecan in the nucleus pulposus of the intervertebral discs can bind electrostatically to polar water molecules, which are crucial for maintaining the well-hydrated state that enables the discs to undergo reversible deformation under compressive loading. A more in-depth understanding of the molecular basis of disc degeneration is essential to the design of therapeutic solutions to treat degenerative discs. Within this scope, we discuss the current knowledge concerning the structure and function of aggrecan in intervertebral disc degeneration. These data suggest that aggrecan plays a central role in the function and degeneration of the intervertebral disc, which may suggest potential aggrecan-based therapies for disc regeneration.

New insights link low-virulent disc infections to the etiology of severe disc degeneration and Modic changes

Within the last 5 years, international research collaborations including those of several research groups skilled in microbiology, immunology and pathophysiology, have identified a low-virulent intradiscal infection with the ability to provoke gradual and progressive disc degeneration, end-plate disruption, Modic changes and persistent clinical lower-back pain. Certain strains of the Propionibacterium acne bacterium seem able to invade, colonize and develop a protective biofilm inside the disc. The interaction of P. acne, disc tissues and mononuclear cells of the bone marrow are shown to trigger a relevant immunological response and an ensuing destructive inflammation of the disc and adjacent vertebrae. This process presents on MRI as Modic changes. Recent proof-of-concept data provide compelling evidence for this bacterial disc infection hypothesis.