Why do some intervertebral discs degenerate, when others (in the same spine) do not?

TNFR1-mediated senescence and lack of TNFR2-signaling limit human intervertebral disc cell repair in back pain conditions

Poor intervertebral disc (IVD) healing causes IVD degeneration (IVDD) and progression to herniation and back pain. This study identified distinct roles of TNFα-receptors (TNFRs) in contributing to poor healing in painful IVDD. We first isolated IVDD tissue of back pain subjects and determined the complex pro-inflammatory mixture contained many chemokines for recruiting inflammatory cells. Single-cell RNA-sequencing of human IVDD tissues revealed these pro-inflammatory cytokines were dominantly expressed by a small macrophage-population. Human annulus fibrosus (hAF) cells treated with IVDD-conditioned media (CM) underwent senescence with greatly reduced metabolic rates and limited inflammatory responses. TNFR1 inhibition partially restored hAF cell metabolism sufficiently to enable a robust chemokine and cytokine response to CM. We showed that the pro-reparative TNFR2 was very limited on hIVD cell membranes so that TNFR2 inhibition with blocking antibodies or activation using Atsttrin had no effect on hAF cells with CM challenge. However, TNFR2 was expressed in high levels on macrophages identified in scRNA-seq analyses, suggesting their role in repair responses. Results therefore point to therapeutic strategies for painful IVDD involving immunomodulation of TNFR1 signaling in IVD cells to enhance metabolism and enable a more robust inflammatory response including recruitment or delivery of TNFR2 expressing immune cells to enhance IVD repair.

Bioinformatics analysis and experimental validation of key genes associated with lumbar disc degeneration and biomechanics

Background

Lumbar disc degeneration (LDD) is an important pathological basis for the development of degenerative diseases of the lumbar spine. Most clinical patients have low back pain as their main symptom. The deterioration of the biomechanical environment is an important cause of LDD. Although there is a large amount of basic research on LDD, there are fewer reports that correlate biomechanical mechanisms with basic research. Our research aims to identify 304 key genes involved in LDD due to biomechanical deterioration, using a bioinformatics approach. We focus on SMAD3, CAV1, SMAD7, TGFB1 as hub genes, and screen for 30 potential target drugs, offering novel insights into LDD pathology and treatment options.

Methods

The Gene Cards, GenCLip3, OMIM and Drugbank databases were explored to obtain genes associated with biomechanics and LDD, followed by making veen plots to obtain both co-expressed genes. GO enrichment analysis and KEGG pathway analysis of the co-expressed genes were obtained using the DAVID online platform and visualised via a free online website. Protein interaction networks (PPI) were obtained through the STRING platform and visualised through Cytoscape 3.9.0. These genes were predicted for downstream interaction networks using the STITCH platform. Then, the GSE56081 dataset was used to validate the key genes. RT-PCR was used to detect mRNA expression of core genes in the degenerated nucleus pulposus (NP) samples and western bolt was used for protein expression. Lastly, the obtained hub genes were searched in the drug database (DGIdb) to find relevant drug candidates.

Results

From the perspective of biomechanics-induced LDD, we obtained a total of 304 genes, the GO functional enrichment and KEGG pathway enrichment analysis showed that the functions of these genes are mostly related to inflammation and apoptosis. The PPI network was constructed and four Hub genes were obtained through the plug-in of Cytoscape software, namely SMAD3, CAV1, SMAD7 and TGFB1. The analysis of key genes revealed that biomechanical involvement in LDD may be related to the TGF-β signaling pathway. Validation of the GSE56081 dataset revealed that SMAD3 and TGFB1 were highly expressed in degenerating NP samples. RT-PCR results showed that the mRNA expression of SMAD3 and TGFB1 was significantly increased in the severe degeneration group; Western blot results also showed that the protein expression of TGFB1 and P-SMAD3 was significantly increased. In addition, we identified 30 potential drugs.

Conclusion

This study presented a new approach to investigate the correlation between biomechanical mechanisms and LDD. The deterioration of the biomechanical environment may cause LDD through the TGF-β signaling pathway. TGFB1 and SMAD3 are important core targets. The important genes, pathways and drugs obtained in this study provided a new basis and direction for the study, diagnosis and treatment of LDD.

Dynamic segmental kinematics of the lumbar spine during diagnostic movements

Background: In vivo measurements of segmental-level kinematics are a promising avenue for better understanding the relationship between pain and its underlying, multi-factorial basis. To date, the bulk of the reported segmental-level motion has been restricted to single plane motions. Methods: The present work implemented a novel marker set used with an optical motion capture system to non-invasively measure dynamic, 3D in vivo segmental kinematics of the lower spine in a laboratory setting. Lumbar spinal kinematics were measured for 28 subjects during 17 diagnostic movements. Results: Overall regional range of motion data and lumbar angular velocity measurement were consistent with previously published studies. Key findings from the work included measurement of differences in ascending versus descending segmental velocities during functional movements and observations of motion coupling paradigms in the lumbar spinal segments. Conclusion: The work contributes to the task of establishing a baseline of segmental lumbar movement patterns in an asymptomatic cohort, which serves as a necessary pre-requisite for identifying pathological and symptomatic deviations from the baseline.

The association between vertebral endplate defects, subchondral bone marrow changes, and lumbar intervertebral disc degeneration: a retrospective, 3-year longitudinal study

PURPOSE

To investigate the influence of vertebral endplate defects and subchondral bone marrow changes on the development of lumbar intervertebral disc degeneration (DD).

METHODS

Patients > 18 y/o without any history of lumbar fusion who had repeat lumbar magnetic resonance imaging scans primarily for low back pain (LBP) performed at a minimum of 3 years apart at a single institution, and no spinal surgery in between scans were included. Total endplate score (TEPS), Modic changes (MC), and Pfirrmann grading (PFG) per lumbar disc level were assessed. DD was defined as PFG ≥ 4.

RESULTS

Three hundred and fifty-three patients (54.4% female) were included in the final analysis, comprising 1765 lumbar intervertebral discs. The patient population was 85.6% Caucasian with a median age of 60.1 years and a body mass index (BMI) of 25.8 kg/m2. A cutoff score of 5 was identified for the TEPS above which both the prevalence of DD and the odds of developing DD increased. The probability of developing DD did not differ significantly between lumbar disc levels (P = 0.419). In the multivariable analysis with adjustments for age, sex, race, body mass index (BMI), MC, TEPS cutoff > 5, and spinal level, only age (OR = 1.020; P = 0.002) was found to be an independent risk factor for developing intervertebral DD.

CONCLUSION

Our results suggest that TEPS does not unequivocally predict intervertebral DD in patients with LBP, since higher degrees of endplate defects might also develop secondarily to DD, and MC tend to occur late in the cascade of degeneration.

Why Are Some Intervertebral Discs More Prone to Degeneration?: Insights Into Isolated Thoracic "Dysgeneration"

STUDY DESIGN

Prospective observational study.

OBJECTIVE

To determine the prevalence of isolated thoracic degeneration on magnetic resonance imaging (MRI), demographic factors and imaging features, as well as the patient-reported quality of life outcomes associated with this condition.

SUMMARY OF BACKGROUND DATA

Thoracic intervertebral discs are least susceptible to disc degeneration (DD) and may represent a manifestation of "dysgeneration." These discs may never be hydrated from the beginning and seem hypointense on MRI.

PATIENTS AND METHODS

A population-based MRI study of 2007 volunteers was conducted. Each disc from C2/3 to L5/S1 was measured by Pfirrmann and Schneiderman grading. Disc herniation, Schmorl node (SN), high-intensity zones (HIZ), and Modic changes were studied. DD was defined by Pfirrmann 4 or 5. patient-reported quality of life scores, including a 36-item short-form questionnaire and visual analog scale for low back pain, were recorded. Subjects were divided into "isolated thoracic degeneration" (only thoracic segment) and "tandem thoracic degeneration" (thoracic with other segments). The association between imaging findings and isolated thoracic degeneration was determined using multivariate logistic regression.

RESULTS

The mean age of the subjects was 50.0 ± 0.5 and 61.4% were females (n = 1232). Isolated thoracic degeneration was identified in 2.3% of the cohort. Factors associated with isolated thoracic degeneration included lower age, C6/7 HIZ, T8/9 HIZ, and T8/9 SN. Factors associated with tandem thoracic degeneration included L4/5 posterior bulging. The thoracic and lumbar tandem degeneration group demonstrated higher bodily pain, despite a lower visual analog scale, and a higher physical component score of the 36-item short form.

CONCLUSIONS

Isolated thoracic degeneration demonstrated an earlier age of onset, mostly involving the mid-thoracic region (T5/6-T8/9), and in association with findings such as SN. Subjects with tandem thoracolumbar degeneration had less severe lumbar DD and low back pain as compared with those with isolated lumbar degeneration. This paints the picture of "dysgeneration" occurring in the thoracic and lumbar spine.

LEVEL OF EVIDENCE

1.

5-Year progression prediction of endplate defects: Utilizing the EDPP-Flow convolutional neural network based on unbalanced data

Background

Lumbar disc degeneration (LDD) is considered as one of the main causes of low back pain. For clinical diagnosis of LDD, magnetic resonance imaging (MRI) is commonly used. Schmorl's node, high intensity zone (HIZ), Modic changes, and other MRI biomarkers of intervertebral disc (IVD) degeneration are also associated with low back pain. However, the progression and natural history of these features are unclear and there is limited predictive capacity with MRI.

Purpose

We aim to establish and validate a deep learning pipeline, EDPP-Flow, for the 5-year progression prediction of Schmorl's node, HIZ, and Modic changes, based on clinical MRIs.

Materials and methods

An MRI dataset developed on 1152 volunteers was used in this study. For each volunteer, two MRI scans, at baseline and 5-year follow-up, were collected and pathology labels were annotated as present or absent (with/without pathology) by two specialists with over 10 years of clinical experience. Our pipeline contained the published MRI-SegFlow and state-of-the-art convolutional neural network for progression prediction of endplate defects. The label distribution of the dataset is unbalanced, where the number of present samples was much smaller than absent samples. The resampling and data augmentation strategies were adopted to increase the number of present samples in the training process and balance the influence of different samples on the model, which can improve the prediction accuracy.

Results

Our pipeline achieved high weighted accuracy, sensitivity, and specificity for progression prediction of Schmorl's node (89.46 ± 3.71%, 89.19 ± 2.70%, 89.72 ± 2.42%), HIZ (91.75 ± 2.48%, 93.07 ± 3.96%, 90.43 ± 2.51%), and Modic changes (87.51 ± 2.23%, 87.93 ± 1.72%, 87.10 ± 1.99%), on the unbalanced dataset (present sample's percentages of the 3 pathologies above were 4.3%, 11.7%, and 6.7%).

Conclusion

We developed and validated a deep learning pipeline, for the progression prediction of endplate defects, which showed high prediction accuracy on unbalanced data. The method has significant potential for clinical implementation.

Microgravity and the intervertebral disc: The impact of space conditions on the biomechanics of the spine

The environmental conditions to which astronauts and other military pilots are subjected represent a unique example for understanding and studying the biomechanical events that regulate the functioning of the human body. In particular, microgravity has shown a significant impact on various biological systems, such as the cardiovascular system, immune system, endocrine system, and, last but not least, musculoskeletal system. Among the potential risks of flying, low back pain (LBP) has a high incidence among astronauts and military pilots, and it is often associated with intervertebral disc degeneration events. The mechanisms of degeneration determine the loss of structural and functional integrity and are accompanied by the aberrant production of pro-inflammatory mediators that exacerbate the degenerative environment, contributing to the onset of pain. In the present work, the mechanisms of disc degeneration, the conditions of microgravity, and their association have been discussed in order to identify possible molecular mechanisms underlying disc degeneration and the related clinical manifestations in order to develop a model of prevention to maintain health and performance of air- and space-travelers. The focus on microgravity also allows the development of new proofs of concept with potential therapeutic implications.

MRI-based measurement of in vivo disc mechanics in a young population due to flexion, extension, and diurnal loading

Background

Intervertebral disc degeneration is often implicated in low back pain; however, discs with structural degeneration often do not cause pain. It may be that disc mechanics can provide better diagnosis and identification of the pain source. In cadaveric testing, the degenerated disc has altered mechanics, but in vivo, disc mechanics remain unknown. To measure in vivo disc mechanics, noninvasive methods must be developed to apply and measure physiological deformations.

Aim

Thus, this study aimed to develop methods to measure disc mechanical function via noninvasive MRI during flexion and extension and after diurnal loading in a young population. This data will serve as baseline disc mechanics to later compare across ages and in patients.

Materials & Methods

To accomplish this, subjects were imaged in the morning in a reference supine position, in flexion, in extension, and at the end of the day in a supine position. Disc deformations and vertebral motions were used to quantify disc axial strain, changes in wedge angle, and anterior-posterior (A-P) shear displacement. T2 weighted MRI was also used to evaluate disc degeneration via Pfirrmann grading and T2 time. All measures were then tested for effect of sex and disc level.

Results

We found that flexion and extension caused level-dependent strains in the anterior and posterior of the disc, changes in wedge angle, and A-P shear displacements. Flexion had higher magnitude changes overall. Diurnal loading did not cause level-dependent strains but did cause small level-dependent changes in wedge angle and A-P shear displacements.

Discussion

Correlations between disc degeneration and mechanics were largest in flexion, likely due to the smaller contribution of the facet joints in this condition.

Conclusion

In summary, this study established methods to measure in vivo disc mechanical function via noninvasive MRI and established a baseline in a young population that may be compared to older subjects and clinical disorders in the future.

Biomaterials delivery strategies to repair degenerated intervertebral discs by regulating the inflammatory microenvironment

Intervertebral disc degeneration (IVDD) is one of the leading causes of lower back pain. Although IVDD cannot directly cause death, it can cause pain, psychological burdens, and economic burdens to patients. Current conservative treatments for IVDD can relieve pain but cannot reverse the disease. Patients who cannot tolerate pain usually resort to a strategy of surgical resection of the degenerated disc. However, the surgical removal of IVDD can affect the stability of adjacent discs. Furthermore, the probability of the reherniation of the intervertebral disc (IVD) after surgery is as high as 21.2%. Strategies based on tissue engineering to deliver stem cells for the regeneration of nucleus purposes (NP) and annulus fibrosus (AF) have been extensively studied. The developed biomaterials not only locally withstand the pressure of the IVD but also lay the foundation for the survival of stem cells. However, the structure of IVDs does not provide sufficient nutrients for delivered stem cells. The role of immune mechanisms in IVDD has recently become clear. In IVDD, the IVD that was originally in immune privilege prevents the attack of immune cells (mainly effector T cells and macrophages) and aggravates the disease. Immune regulatory and inflammatory factors released by effector T cells, macrophages, and the IVD further aggravate IVDD. Reversing IVDD by regulating the inflammatory microenvironment is a potential approach for the treatment of the disease. However, the biological factors modulating the inflammatory microenvironment easily degrade in vivo. It makes it possible for different biomaterials to modulate the inflammatory microenvironment to repair IVDD. In this review, we have discussed the structures of IVDs and the immune mechanisms underlying IVDD. We have described the immune mechanisms elicited by different biological factors, including tumor necrosis factors, interleukins, transforming growth factors, hypoxia-inducible factors, and reactive oxygen species in IVDs. Finally, we have discussed the biomaterials used to modulate the inflammatory microenvironment to repair IVDD and their development.

Assessment of the correlation between clinical and radiological outcomes in patients suffering from mild to moderate cervical spine dysfunction symptoms: a prospective study

BACKGROUND

Neck pain and cervical disc degeneration (CDD) are common findings. Valid data on correlation between clinical scores and radiological grade of CDD in patients with mild to moderate clinical disability are not available. The study has been designed to investigate the correlation between clinical and radiological outcomes in these patients.

METHODS

A cohort of 150 patients who suffered from mild to moderate cervical spine dysfunction symptoms from September 2020 to May 2021 was enrolled. We evaluated functional status using Japanese Orthopaedic Association scores (JOA), the visual analog scale, and the Neck Disability Index. We assessed the CDD with magnetic resonance imaging-based grading systems. We analyzed relationships between radiological grades of CDD and clinical symptoms along with demographic data.

RESULTS

One hundred thirteen patients [mean age 44.78, 78 (69%) females] were finally included. CDD occurred most at the C5-C6 level, with 56.93% of higher grade III from Miyazaki. The grades of Miyazaki (P < 0.05) and the scores of Nakashima (P < 0.05) were positively correlated with the duration of symptoms, and the severity of the CDD increased with aging (P < 0.01). Moreover, we correlated patients' JOA scores with the current scoring and grading systems, especially the grades of Miyazaki (P < 0.01) and the scores of Nakashima (P < 0.01).

CONCLUSION

Increasing grades of CDD paralleled decreasing JOA scores in the population studied.

Correlation between Adrenoceptor Expression and Clinical Parameters in Degenerated Lumbar Intervertebral Discs

Despite advanced knowledge of the cellular and biomechanical processes of intervertebral disc degeneration (IVDD), the trigger and underlying mechanisms remain unclear. Since the sympathetic nervous system (SNS) has been shown to exhibit catabolic effects in osteoarthritis pathogenesis, it is attractive to speculate that it also influences IVDD. Therefore, we explored the adrenoceptor (AR) expression profile in human IVDs and correlated it with clinical parameters of patients. IVD samples were collected from n = 43 patients undergoing lumbar spinal fusion surgery. AR gene expression was analyzed by semi-quantitative polymerase chain reaction. Clinical parameters as well as radiological Pfirrmann and Modic classification were collected and correlated with AR expression levels. In total human IVD homogenates α1A-, α1B-, α2A-, α2B-, α2C-, β1- and β2-AR genes were expressed. Expression of α1A- (r = 0.439), α2A- (r = 0.346) and β2-AR (r = 0.409) showed a positive and significant correlation with Pfirrmann grade. α1A-AR expression was significantly decreased in IVD tissue of patients with adjacent segment disease (p = 0.041). The results of this study indicate that a relationship between IVDD and AR expression exists. Thus, the SNS and its neurotransmitters might play a role in IVDD pathogenesis. The knowledge of differential AR expression in different etiologies could contribute to the development of new therapeutic approaches for IVDD.

Application of mesenchymal stem cell-derived exosomes from different sources in intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is a main cause of lower back pain, leading to psychological and economic burdens to patients. Physical therapy only delays pain in patients but cannot eliminate the cause of IVDD. Surgery is required when the patient cannot tolerate pain or has severe neurological symptoms. Although surgical resection of IVD or decompression of the laminae eliminates the diseased segment, it damages adjacent normal IVD. There is also a risk of re-protrusion after IVD removal. Cell therapy has played a crucial role in the development of regenerative medicine. Cell transplantation promotes regeneration of degenerative tissue. However, owing to the lack of vascular structure in IVD, sufficient nutrients cannot be provided for transplanted mesenchymal stem cells (MSCs). In addition, dead cells release harmful substances that aggravate IVDD. Extracellular vesicles (EVs) have been extensively studied as an emerging therapeutic approach. EVs generated by paracrine MSCs retain the potential of MSCs and serve as carriers to deliver their contents to target cells to regulate target cell activity. Owing to their double-layered membrane structure, EVs have a low immunogenicity and no immune rejection. Therefore, EVs are considered an emerging therapeutic modality in IVDD. However, they are limited by mass production and low loading rates. In this review, the structure of IVD and advantages of EVs are introduced, and the application of MSC-EVs in IVDD is discussed. The current limitations of EVs and future applications are described.

Slanted slot was the most resistant to failure of ventral slot techniques tested in rabbit cervical vertebrae

The ventral slot technique is used to relieve neural compression secondary to intervertebral disc degeneration or disease. In the present study, the biomechanical properties of three different ventral surgical procedures in the rabbit C6–C7 vertebral motion unit (VMU) were assessed and compared with the intact C6–C7 VMU. The ventral slot procedure (slanted, full, or mini; n = 8/group) was performed on these cervical vertebrae. Normal spine torsion and flexion values were compared to those of spines subjected to slanted, full, and mini slot surgery. The slanted slot spines were the most stable, maintaining 70% of normal cervical spine strength, compared to 26% with the full slot and 30% with the mini slot. Regarding torsion, slanted slot spines showed 74% stability compared to the normal cervical spine, while the full slot and mini slot spines showed 58% and 62% stability, respectively. Flexion values were lower after all versions of the ventral slot procedure than in the normal spine, with the greatest flexion difference occurring after the full slot procedure (21% of the normal flexion value). The flexion values also differed significantly between the slanted and full spine groups, and all operated spines showing roughly 60% torsion rates compared with normal spines. The slanted slot maintains more stability in rabbit cervical spine than the other procedures. To our knowledge, this was the first study to examine biomechanical failure differences between the distinct versions of this ventral slot procedure.

Lumbar Intervertebral Disc Herniation: Annular Closure Devices and Key Design Requirements

Lumbar disc herniation is one of the most common degenerative spinal conditions resulting in lower back pain and sciatica. Surgical treatment options include microdiscectomy, lumbar fusion, total disc replacement, and other minimally invasive approaches. At present, microdiscectomy procedures are the most used technique; however, the annulus fibrosus is left with a defect that without treatment may contribute to high reherniation rates and changes in the biomechanics of the lumbar spine. This paper aims to review current commercially available products that mechanically close the annulus including the AnchorKnot® suture-passing device and the Barricaid® annular closure device. Previous studies and reviews have focused mainly on a biomimetic biomaterials approach and have described some mechanical and biological requirements for an active annular repair/regeneration strategy but are still far away from clinical implementation. Therefore, in this paper we aim to create a design specification for a mechanical annular closure strategy by identifying the most important mechanical and biological design parameters, including consideration of material selection, preclinical testing requirements, and requirements for clinical implementation.

The Multi-Modal Risk Analysis and Medical Prevention of Lumbar Degeneration, Fatigue, and Injury Based on FEM/BMD for Elderly Chinese Women Who Act as Stay-Home Grandchildren Sitters

Background: An increasing number of Chinese elderly women stay at home and act as grandchildren sitters. In consequence of the frequent load-bearing, chronic lumbar fatigue probably caused a higher risk of lumbar degeneration, fatigue, and injury which has become one of the most important aging and health problems in China. In this study, a multi-mode lumbar finite element model (FEM) with specific bone mineral density (BMD) were developed and validated for further spine injury prevention and control.

Methods: The material properties of lumbar vertebra were modified according to degenerated bone mineral density, and geometry was adjusted based on intervertebral disc height. The motion of lifting children was simulated by a 76 year-old Chinese women's FEM, and the stress distribution was calculated and predicted.

Results: The pressure of L5-S intervertebral disc in the bending 3-year-old dummy lifting posture was significantly higher than the same posture without lifting, the maximum effective stress of endplate cartilage in the upright child lifting posture was 1.6 times that of the bending without lifting posture. And the fatigue risk limitation frequency of the upright with dummy posture was predicted with the functional equation of fatigue and stress which was deduced by genetic algorithm, which combined with the effective stress of lumbar vertebrae spongy bone calculated from FEM.

Conclusions: The child-lifting motion could increase the risk of lumbar degeneration, fatigue, and injury in elderly women, and they should keep below the frequency limit of the motion of lifting children in their daily life. This study could put forward scientific injury prevention guidance to Chinese elderly women who lift children in daily life frequently.

Association and histological characteristics of endplate injury and intervertebral disc degeneration in a rat model

INTRODUCTION

The purpose of this study was to construct a rat caudal vertebral body fracture model and to analyze the association and histological characteristics of vertebral body fracture with endplate injury and adjacent intervertebral disc degeneration.

MATERIALS AND METHODS

This study included 144 clean-grade male Sprague-Dawley rats, which were randomly divided into a control, middle vertebral body injury (MI), and endplate injury (EI) groups. A vertebral body fracture with or without endplate injury was developed by either drilling a hole in the middle of a rat caudal vertebral body to create a fracture with an intact endplate or drilling a hole in the vertebral body near the intervertebral disc to create a vertebral body fracture with endplate injury. The histological differences in the adjacent intervertebral discs of vertebral body fractures with or without endplate injury were detected using imaging, non-specific histological staining, immunohistochemistry and TUNEL assay.

RESULTS

Imaging results revealed that the EI group showed a significant decrease in intervertebral space height and intervertebral disc T2 signal over time. Non-specific histological staining revealed that in the EI group, the intervertebral disc was degenerative. Immunohistochemistry indicated that Aggrecan and Collagen-II were decreased and inflammatory factors were increased in the EI group. The TUNEL detection found that apoptosis was significantly increased in the EI group as compared with the MI and control groups.

CONCLUSION

In rat caudal vertebral body fractures, a fracture with endplate injury is more likely to induce or accelerate degeneration of adjacent intervertebral discs.

Surgical Outcomes for Upper Lumbar Disc Herniations: A Systematic Review and Meta-analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

To conduct a literature review on outcomes of discectomy for upper lumbar disc herniations (ULDH), estimate pooled rates of satisfactory outcomes, compare open laminectomy/microdiscectomy (OLM) versus minimally invasive surgical (MIS) techniques, and compare results of disc herniations at L1-3 versus L3-4.

METHODS

A systematic review of articles reporting outcomes of nonfusion surgical treatment of L1-2, L2-3, and/or L3-4 disc herniations was performed. The inclusion and exclusion of studies was performed according to the latest version of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

RESULTS

A total of 20 articles were included in the quantitative meta-analysis. Pooled proportion of satisfactory outcome (95% CI) was 0.77 (0.70, 0.83) for MIS and 0.82 (0.78, 0.84) for OLM. There was no significant improvement with MIS techniques compared with standard OLM, odds ratio (OR) = 0.86, 95% CI (0.42, 1.74), P = .66. Separating results by levels revealed a trend of higher satisfaction with L3-4 versus L1-3 with OLM surgery, OR = 0.46, 95% CI (0.19, 1.12), P = .08.

CONCLUSION

Our analysis reveals that discectomy for ULDH has an overall success rate of approximately 80% and has not improved with MIS. Discectomy for herniations at L3-4 trends toward better outcomes compared with L1-2 and L2-3, but was not significant.

Analysis of the influence of species, intervertebral disc height and Pfirrmann classification on failure load of an injured disc using a novel disc herniation model

BACKGROUND CONTEXT

Annular repair devices offer a solution to recurrent disc herniations by closing an annular defect and lowering the risk of reherniation. Given the significant risk of neurologic injury from device failure it is imperative that a reliable preclinical model exists to demonstrate a high load to failure for the disc repair devices.

PURPOSE

To establish a preclinical model for disc herniation and demonstrate how changes in species, intervertebral disc height and Pfirrmann classification impacts failure load on an injured disc. We hypothesized that: (1) The force required for disc herniation would be variable across disc morphologies and species, and (2) for human discs the force to herniation would inversely correlate with the degree of disc degeneration.

STUDY DESIGN

Animal and human cadaveric biomechanical model of disc herniation.

METHODS

We tested calf lumbar spines, bovine tail segments and human lumbar spines. We first divided individual lumbar or tail segments to include the vertebral bodies and disc. We then hydrated the specimens by placing them in a saline bath overnight. A magnetic resonance images were acquired from human specimens and a Pfirrmann classification was made. A stab incision measuring 25% of the diameter of the disc was then done to each specimen along the posterior intervertebral disc space. Each specimen was placed in custom test fixtures on a servo-hydraulic test frame (MTS, Eden Prarie, MN) such that the superior body was attached to a 10,000 lb load cell and the inferior body was supported on the piston. A compressive ramping load was placed on the specimen in load control at 4 MPa/sec stopping at 75% of the disc height. Load was recorded throughout the test and failure load calculated. Once the test was completed each specimen was sliced through the center of the disc and photos were taken of the cut surface.

RESULTS

Fifteen each of calf, human, and bovine tail segments were tested. The failure load varied significantly between specimens (p<.001) with human specimens having the highest average failure load (8154±2049 N). Disc height was higher for lumbar/bovine tail segments as compared to calf specimens (p<.001) with bovine tails having the highest disc height (7.1±1.7 mm). Similarly, human lumbar discs had a cross sectional area that was greater than both bovine tail/calf lumbar spines (p<.001). There was no correlation between disc height and failure load within each individual species (p>.05). Cross sectional area and failure load did not correlate with failure load for human lumbar spine and bovine tails (p>.05) but did correlate with calf spine (r=0.53, p=.04). There was a statistically significant inverse correlation between disc height and Pfirrmann classification for human lumbar spines (r=-0.84, p<.001). There was also a statistically significant inverse relationship between Pfirrmann classification and failure load (r=-0.58, p=.02).

CONCLUSIONS

We have established a model for disc herniation and have shown how results of this model vary between species, disc morphology, and Pfirrmann classification. Both hypotheses were accepted: The force required for disc herniation was variable across species, and the force to herniation for human spines was inversely correlated with the degree of disc degeneration. We recommend that models using human intervertebral discs should include data on Pfirrmann classification, while biomechanical models using calf spines should report cross sectional area. Failure loads do not vary based on dimensions for bovine tails.

CLINICAL SIGNIFICANCE

Our analysis of models for disc herniation will allow for quicker, reliable comparisons of failure forces required to induce a disc herniation. Future work with these models may facilitate rapid testing of devices to repair a torn/ruptured annulus.

Increasing BMI increases lumbar intervertebral disc deformation following a treadmill walking stress test

High body mass index (BMI) and obesity have been implicated as risk factors for lumbar degenerative disc disease and low back pain. Despite this, there is limited in vivo data to quantify how obesity influences the mechanical function of intervertebral discs (IVD) in response to activities of daily living. Recently, our lab has developed methodologies to non-invasively measure in vivo IVD deformation resulting from activities of daily living using magnetic resonance (MR) imaging and solid modeling techniques. This pilot study expands on these methodologies to assess how BMI influences IVD deformation following treadmill walking in eight asymptomatic individuals. Ordinary least squares regression analyses revealed a statistically significant relationship between BMI and compressive deformation (strain (%)) in the L5-S1 IVD (R² = 0.61, p < 0.05). This relationship was weaker in the L3-L4 (R² = 0.28, p > 0.05) and L4-L5 IVDs (R² = 0.28, p > 0.05). Importantly, no relationship between pre-exercise disc height and BMI was identified (p > 0.05). Therefore, the results of this study suggest that BMI may alter the mechanical response of lumbar spine IVDs, particularly at the L5-S1 level. Furthermore, the observed relationship between increased BMI and IVD compressive deformation, in the absence of a detected relationship between pre-exercise disc height and BMI, suggests that changes in IVD mechanical function may be more sensitive to alterations in disc health than static clinical imaging alone. This finding highlights the importance of quantifying disc mechanical function when examining the relationship between BMI and IVD degeneration.

Recent advances of hydrogel-based biomaterials for intervertebral disc tissue treatment: A literature review

Low back pain is an increasingly prevalent symptom mainly associated with intervertebral disc (IVD) degeneration. It is highly correlated with aging, as the nucleus pulposus (NP) dehydrates and annulus fibrosus fissure formatting, which finally results in the IVD herniation and related clinical symptoms. Hydrogels have been drawing increasing attention as the ideal candidates for IVD degeneration because of their unique properties such as biocompatibility, highly tunable mechanical properties, and especially the water absorption and retention ability resembling the normal NP tissue. Numerous innovative hydrogel polymers have been generated in the most recent years. This review article will first briefly describe the anatomy and pathophysiology of IVDs and current therapies with their limitations. Following that, the article introduces the hydrogel materials in the classification of their origins. Next, it reviews the recent hydrogel polymers explored for IVD regeneration and analyses what efforts have been made to overcome the existing limitations. Finally, the challenges and prospects of hydrogel-based treatments for IVD tissue are also discussed. We believe that these novel hydrogel-based strategies may shed light on new possibilities in IVD degeneration disease.

In vivo intervertebral kinematics and disc deformations of the human cervical spine during walking

The kinematics of the cervical spine during various functional neck motions has been widely reported. However, no data has been reported on the cervical intervertebral kinematics during walking, the most frequently performed daily functional activity. In this study, we evaluated cervical kinematics and disc deformation of asymptomatic subjects during a gait cycle using a dual fluoroscopic imaging system. Our measurements showed that the vertical translation of the cervical spine (1.6 ± 0.1 Hz) occurred at twice the frequency of the gait cycle (0.8 ± 0.1 Hz). The overall ranges of motion (ROMs) of the entire (C2-T1) cervical spine were 5.0 ± 3.1° in the flexion-extension rotation, 3.4 ± 1.0° in the lateral-bending rotation, and 5.8 ± 2.1° in the axial-twisting rotation during walking. Each intervertebral disc (measured at the disc centre location) dynamically deformed in its axial direction in a range of 16.2 ± 5.7% ~ 23.7 ± 8.7% (without significant differences among different segment levels, p > 0.05), similar to the ranges of shear deformations of the same disc (p > 0.05, except for the C7-T1 disc, where p = 0.010). These data could be useful for improvements of diagnosis and treatment methods of cervical pathologies.

One strike loading organ culture model to investigate the post-traumatic disc degenerative condition

Background

Acute trauma on intervertebral discs (IVDs) is thought to be one of the risk factors for IVD degeneration. The pathophysiology of IVD degeneration induced by single high impact mechanical injury is not very well understood. The aim of this study was using a post-traumatic IVD model in a whole organ culture system to analyze the biological and biomechanical consequences of the single high-impact loading event on the cultured IVDs.

Methods

Isolated healthy bovine IVDs were loaded with a physiological loading protocol in the control group or with injurious loading (compression at 50% of IVD height) in the one strike loading (OSL) group. After another 1 day (short term) or 8 days (long term) of whole organ culture within a bioreactor, the samples were collected to analyze the cell viability, histological morphology and gene expression. The conditioned medium was collected daily to analyze the release of glycosaminoglycan (GAG) and nitric oxide (NO).

Results

The OSL IVD injury group showed signs of early degeneration including reduction of dynamic compressive stiffness, annulus fibrosus (AF) fissures and extracellular matrix degradation. Compared to the control group, the OSL model group showed more severe cell death (P ​< ​0.01) and higher GAG release in the culture medium (P ​< ​0.05). The MMP and ADAMTS families were up-regulated in both nucleus pulposus (NP) and AF tissues from the OSL model group (P ​< ​0.05). The OSL injury model induced a traumatic degenerative cascade in the whole organ cultured IVD.

Conclusions

The present study shows a single hyperphysiological mechanical compression applied to healthy bovine IVDs caused significant drop of cell viability, altered the mRNA expression in the IVD, and increased ECM degradation. The OSL IVD model could provide new insights into the mechanism of mechanical injury induced early IVD degeneration.

The translational potential of this article

This model has a high potential for investigation of the degeneration mechanism in post-traumatic IVD disease, identification of novel biomarkers and therapeutic targets, as well as screening of treatment therapies.

Positional changes in lumbar disc herniation during standing or lumbar extension: a cross-sectional weight-bearing MRI study

OBJECTIVES

To investigate biomechanical changes in lumbar disc herniations.

METHODS

Patients with lumbar disc herniation verified on a 1.5-3-T magnetic resonance imaging (MRI) scanner were imaged in a weight-bearing 0.25-T MRI scanner in (1) standing position, (2) conventional supine position with relative lumbar flexion, and (3) supine position with a forced lumbar extension by adding a lumbar pillow. The L2-S1 lordosis angle, the disc cross-sectional area, the disc cross-sectional diameter, and the spinal canal cross-sectional diameter were measured for each position. Disc degeneration and nerve root compression were graded, and the pain intensity was reported during each scan position.

RESULTS

Forty-three herniated discs in 37 patients (36.7 ± 11.9 years) were analyzed in each position. The L2-S1 lumbar angle increased in the standing position (mean difference [MD]: 5.61°, 95% confidence interval [95% CI]: 3.44 to 7.78) and with the lumbar pillow in the supine position (MD: 14.63°, 95% CI: 11.71 to 17.57), both compared with the conventional supine position. The herniated disc cross-sectional area and diameter increased during standing compared with during conventional supine position. No changes were found in the spinal canal cross-sectional diameter between positions. Higher nerve root compression grades for paracentral herniations were found during standing compared with during conventional supine position. This was neither found with a lumbar pillow nor for central herniations in any position compared with conventional supine.

CONCLUSION

Disc herniations displayed dynamic behavior with morphological changes in the standing position, leading to higher nerve root compression grades for paracentral herniated discs.

KEY POINTS

• Lumbar herniated discs increased in size in the axial plane during standing. • Increased nerve root compression grades for paracentral herniated discs were found during standing. • Weight-bearing MRI may increase the diagnostic sensitivity of nerve root compression in lumbar disc herniations.

Senotherapeutic drugs for human intervertebral disc degeneration and low back pain

Cellular senescence is a contributor to intervertebral disc (IVD) degeneration and low back pain. Here, we found that RG-7112, a potent mouse double-minute two protein inhibitor, selectively kills senescent IVD cells through apoptosis. Gene expression pathway analysis was used to compare the functional networks of genes affected by RG-7112, a pure synthetic senolytic with o-Vanillin a natural and anti-inflammatory senolytic. Both affected a functional gene network related to cell death and survival. O-Vanillin also affected networks related to cell cycle progression as well as connective tissue development and function. Both senolytics effectively decreased the senescence-associated secretory phenotype (SASP) of IVD cells. Furthermore, bioavailability and efficacy were verified ex vivo in the physiological environment of degenerating intact human discs where a single dose improved disc matrix homeostasis. Matrix improvement correlated with a reduction in senescent cells and SASP, supporting a translational potential of targeting senescent cells as a therapeutic intervention.

Pain in the lower back affects about four in five people during their lifetime. Over time, the discs that provide cushioning between the vertebrae of the spine can degenerate, which can be one of the major causes of lower back pain.

It has been shown that when the cells of these discs are exposed to different stress factors, they stop growing and become irreversibly dormant. Such ‘senescent’ cells release a range of proteins and small molecules that lead to painful inflammation and further degeneration of the discs. Moreover, it is thought that a high number of senescent cells may be linked to other degenerative diseases such as arthritis.

Current treatments can only reduce the severity of the symptoms, but they cannot prevent the degeneration from progressing. Now, Cherif et al. set out to test the effects of two different compounds on human disc cells grown in the laboratory. One of the molecules studied, RG-7112, is a synthetic drug that has been approved for safety by the US Food and Drug Administration and has been shown to remove senescent cells. The other, o-Vanillin, is a natural compound that has anti-inflammatory and anti-senescence properties.

The results showed that both compounds were able to trigger changes to that helped new, healthy cells to grow and at the same time kill senescent cells. They also reduced the production of molecules linked to inflammation and pain.

Further analyses revealed that the compounds were able to strengthen the fibrous matrix that surrounds and supports the discs. Cherif et al. hope that this could form the basis for a new family of drugs for back pain to slow the degeneration of the discs and reduce pain. This may also have benefits for other similar degenerative diseases caused by cell senescence, such as arthritis.

Alterations in the Geometry, Fiber Orientation, and Mechanical Behavior of the Lumbar Intervertebral Disc by Nucleus Swelling

Soft tissues observed in clinical medical images are often prestrained in tension by internal pressure or tissue hydration. For a native disc, nucleus swelling occurs in equilibrium with osmotic pressure induced by the high concentration of proteoglycan in the nucleus. The objective of this computational study was to investigate the effects of nucleus swelling on disc geometry, fiber orientation, and mechanical behavior by comparing those of prestrained and zero-pressure (unswelled) discs. Thermoelastic analysis techniques were repurposed in order to determine the zero-pressure disc geometry which, when pressurized, matches the prestrained disc geometry observed in clinical images. The zero-pressure geometry was then used in simulations to approximately represent a degenerated disc, which loses the ability of nucleus swelling but has not undergone distinct soft tissue remodeling/disruption. Our simulation results demonstrated that the loss of nucleus swelling caused a slight change in the disc geometry and fiber orientation, but a distinct deterioration in the resistance to intervertebral rotations including sagittal bending, lateral bending, and axial torsion. Different from rotational loading, in compression (with a displacement of 0.45 mm applied), a much larger stiffness (3.02 KN/mm) and a greater intradiscal pressure (IDP) (0.61 MPa) were measured in the zero-pressure disc, compared to the prestrained disc (1.41 KN/mm and 0.52 MPa). This computational study could be useful to understand mechanisms of disc degeneration, and guide the future design of disc tissue engineering material and biomimic disc implants.

Comparison of biomechanical studies of disc repair devices based on a systematic review

BACKGROUND CONTEXT

A variety of solutions have been suggested as candidates for the repair of the annulus fibrosis (AF), with the ability to withstand physiological loads of paramount importance.

PURPOSE

The objective of our study was to capture the scope of biomechanical test models of AF repairs. We hypothesized that common test parameters would emerge.

STUDY DESIGN

Systematic Review METHODS: PubMed and EMBASE databases were searched for studies in English including the keywords "disc repair AND animal models," "disc repair AND cadaver spines," "intervertebral disc AND biomechanics," and "disc repair AND biomechanics." This list was further limited to those studies which included biomechanical results from annular repair in animal or human spinal segments from the cervical, thoracic, lumbar and/or coccygeal (tail) segments. For each study, the method used to measure the biomechanical property and biomechanical test results were documented.

RESULTS

A total of 2,607 articles were included within our initial analysis. Twenty-two articles met our inclusion criteria. Significant variability in terms of species tested, measurements used to quantify annular repair strength, and the method/direction/magnitude that forces were applied to a repaired annulus were found. Bovine intervertebral disc was most commonly used model (6 of 22 studies) and the most common mechanical property reported was the force required for failure of the disc repair device (15 tests).

CONCLUSIONS

Our hypothesis was rejected; no common features were identified across AF biomechanical models and as a result it was not possible to compare results of preclinical testing of annular repair devices. Our analysis suggests that a standardized biomechanical model that can be repeatably executed across multiple laboratories is required for the mechanical screening of candidates for AF repair.

CLINICAL SIGNIFICANCE

This literature review provides a summary of preclinical testing of annular repair devices for clinicians to properly evaluate the safety/efficacy of developing technology designed to repair annular defects after disc herniations.

Hyperbaric oxygen treatment: A complementary treatment modality of Modic changes?

Modic changes (MCs) have attracted great interest in recent years. The complex process of MC development and progression seems to involve interplay between mechanical, infective, inflammatory, and degenerative processes that cannot be clearly differentiated. Based on signal intensity on T1- and T2-weighted MRI scans, MCs can be divided three types: Type 1, Type 2, and Type 3. Predominantly Type 1 MCs are commonly associated with chronic low back pain that is unresponsive to classic treatment options. Infection with low-virulent anaerobic microorganisms, most commonly Propionibacterium acnes, has been implicated in MC development following a disc herniation when a tear enables bacteria to enter the disc. Recent studies in patients with chronic low back pain following a lumbar disc herniation associated with Type 1 MCs have reported promising results following prolonged systemic antibiotic treatment with amoxicillin-clavulanate. Hyperbaric oxygen therapy, as primary or adjuvant treatment in association combination with systemic antibiotics or anti-inflammatory therapy, could offer important advantages in treating patients with suspected low-virulent disc infections due to anaerobic microorganisms associated with Type 1 MCs. We believe that hyperbaric oxygenation could contribute to faster resolution of Type 1 MCs and associated pain through multiple effects-including direct antimicrobial effects through formation of reactive oxygen species (ROS), altering the favorable low oxygen tension milieu such that it becomes unfavorable for bacterial growth and survival, and anti-biofilm effects. Additionally, hyperbaric oxygenation could contribute to faster pain resolution via direct and indirect anti-inflammatory effects. As an adjuvant treatment administered in combination with systemic antibiotics, HBOT could increase the sensitivity of Propionibacterium acnes to antimicrobial drugs under hyperoxic conditions, resulting in faster MC resolution. Overall, the faster infection resolution, diminished bacterial load, and anti-inflammatory effects due to reduced cytokine expression and levels of infectious by-products could lead to faster pain resolution following HBOT, and a significant improvement of quality of life in these patients.

Association of vertebral endplate microstructure with bone strength in men and women

Epidemiological and biomechanical evidence indicates that the risk of vertebral fracture differs between men and women, and that vertebral fracture frequently involves failure of the endplate region. The goal of this study was to compare the bone microstructure of the endplate region-defined as the (bony) vertebral endplate and underlying subchondral trabecular bone-between sexes and to determine whether any such sex differences are associated with vertebral strength. The bone density (volume fraction, apparent density and tissue mineral density) of the superior-most 2 mm of the vertebra, and the bone density and trabecular architecture of the next 5 mm were quantified using micro-computed tomography in human T8 (12 female, 16 male) and L1 (13 female, 12 male) vertebrae. Average density of the vertebra (integral bone mineral density (BMD)) was determined by quantitative computed tomography and compressive strength by mechanical testing. Few differences were found between male and female vertebrae in the density of the endplate region; none were found in trabecular architecture. However, whereas endplate volume fraction was positively correlated with integral BMD in male vertebrae (r = 0.654, p < .001), no correlation was found in the female vertebrae (r = 0.157, p = .455). Accounting for the density of the endplate region improved predictions of vertebral strength (p < .034) and eliminated sex-specificity in the strength prediction that was based on integral BMD alone. These results suggest that the density of the endplate region influences vertebral fracture and that non-invasive assessment of this region's density can contribute to predictions of vertebral strength in men and women.

Lumbar Disc Herniation Within Solid Fused Segments After Removal of Pedicle Screws: A Case Report

CASE

A 73-year-old man with instrumented fusion of L3-4-5 underwent the removal of previous pedicle screws and posterior instrumented fusion of L1-2-3. The solid dorsal fusion mass of L3-5 was identified intraoperatively and preoperatively. At 3 years after the second surgery, he presented with abrupt radiating pain in the left leg. Plain radiographs showed a collapse of the intervertebral disc space, and magnetic resonance imaging showed disc herniation of L3-4.

CONCLUSIONS

Disc herniation even in solid fused segments may occur. Removal of pedicle screws and cranial extension of interbody fusion may increase the intradiscal stress associated with physiologic cantilever motion of the disc.

Development and characterization of an immunomodulatory and injectable system composed of collagen modified with trifunctional oligourethanes and silica

Immunomodulatory biomaterials have emerged as a promising approach to engineer wound healing. To achieve this task, the bioactivity of the biomaterials and an easy application are two key desirable characteristics. This work reports an injectable gel system containing immune cells primed for wound healing. By combining the self-assembly of type I collagen, cross-linked with trifunctional oligourethanes, and silica particle entrapment, the structured collagen network acts as a delivery vehicle for macrophages. This structured collagen network primes the macrophages for an anti-inflammatory response. Rheological measurements suggest that the mixture of liquid precursors can be safely stored at low temperatures and low pH (4 °C, pH 3) for at least one month. After pH neutralization and injection, gels with a storage modulus of 50-80 Pa are obtained in five minutes. Several immunocytochemistry and ELISA tests strongly suggest that mouse and human macrophages are stimulated by the material to up-regulate the production of anti-inflammatory cytokines, while down-regulating the production of pro-inflammatory cytokines. The injection of gel in an ex vivo inflammation model of intervertebral discs demonstrated that it is possible to transit from a pro-inflammatory to an anti-inflammatory microenvironment. Altogether, the results suggest that this gel can polarize the macrophage response and promote a surrounding anti-inflammatory microenvironment ready for injection for wound healing applications.

Visualization of intervertebral disc degeneration in a cadaveric human lumbar spine using microcomputed tomography

Gross features of disc degeneration (DD) that are associated with back pain include tears in the anulus fibrosus, structural changes of the endplates, and a collapse of the anulus. The aim of this study is the detailed visualization and microstructural characterization of DD using microcomputed tomography (μCT) and a dedicated image post‐processing pipeline. In detail, we investigate a cadaveric spine that shows both types of DD between L1 and L2 and between L2 and L3, respectively. The lumbar spine was obtained from a male donor aged 74 years. The complete specimen was scanned using μCT with an isometric voxel size of 93 μm. Subsequently, regions of interest (ROI) were prepared featuring each complete intervertebral disc including the adjacent endplates. ROIs were then additionally scanned with a voxel size of 35 μm and by means of magnetic resonance imaging. The collapsed endplate of the superior L2 showed explicit signs of an endplate‐driven degeneration, including bony endplate failures. In contrast, the intervertebral disc between L2 and L3 showed indications of an annulus‐driven DD including severe disc height loss and concentric tears. Using μCT we were able to visualize and quantify bone and cartilage features in DD. We showed that in both cases a suite of structural changes accompanies cartilage degeneration, including microstructural bony adaptions to counteract changes in the biomechanical loading regimen.

[Back pain and intervertebral disc degeneration in the International Classification of Diseases 11th revision]

In 2018, the World Health Organization introduced a new version of the International Classification of Diseases (ICD-11), which is preliminary and introductory in nature and will come into force on 1 January 2022. One of the most changed sections compared to ICD-10 is the section characterizing the spine pain syndrome and other manifestations of discogenic pathology. The article describes the terms and codes for the degenerative lesion of the intervertebral disk (IVD) in accordance with the requirements of ICD-11, which also agree with the definitions of the 2nd revision of the nomenclature and classification of the pathology of the lumbar IVD from 2014. The basic concepts of IVD degenerative changes are also revealed. The need to create a new revision of the domestic clinical classification of vertebrogenic neurologic pathology adapted to ICD-11 codes is underlined.

Lessons learned from intervertebral disc pathophysiology to guide rational design of sequential delivery systems for therapeutic biological factors

Intervertebral disc (IVD) degeneration has been associated with low back pain, which is a major musculoskeletal disorder and socio-economic problem that affects as many as 600 million patients worldwide. Here, we first review the current knowledge of IVD physiology and physiopathological processes in terms of homeostasis regulation and consecutive events that lead to tissue degeneration. Recent progress with IVD restoration by anti-catabolic or pro-anabolic approaches are then analyzed, as are the design of macro-, micro-, and nano-platforms to control the delivery of such therapeutic agents. Finally, we hypothesize that a sequential delivery strategy that i) firstly targets the inflammatory, pro-catabolic microenvironment with release of anti-inflammatory or anti-catabolic cytokines; ii) secondly increases cell density in the less hostile microenvironment by endogenous cell recruitment or exogenous cell injection, and finally iii) enhances cellular synthesis of extracellular matrix with release of pro-anabolic factors, would constitute an innovative yet challenging approach to IVD 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.

Asymmetry between the superior and inferior endplates is a risk factor for lumbar disc degeneration

Endplate pathology plays an important role in the development of lumbar disc degeneration. Previous research paid little attention to differences between the superior and inferior endplates as a possible risk factor for disc degeneration. The purpose of this study was to test the hypothesis that asymmetry between the superior and inferior endplates is a risk factor for the development of lumbar disc degeneration. A total of 134 patients with lumbar disc herniation (LDH) and 100 healthy adults ("Controls") underwent magnetic resonance imaging scans. Each disc was categorized as non-degenerated (Pfirrmann grades I-II) or degenerated (Pfirrmann grades III-V) and get the following three groups: "Degenerated LDH" discs (n = 145), "Non-degenerated LDH" discs (n = 525) and "Non-degenerated Control" discs (n = 500). On mid-sagittal image, the lumbar endplate morphology could be categorized into three types: Flat, concave, and irregular. Superior and inferior endplates of a given disc were "symmetric" if both were of the same type, and "asymmetric" if they were of different types. The proportion of asymmetric endplates at L4-5 was higher in the "Degenerated LDH" discs group (47%) than in the "Non-degenerated LDH" discs group (21%) or "Non-degenerated Control" discs group (7%) (p < 0.05). At L5-S1 the proportions were 73%, 55%, and 38% (p < 0.05). Asymmetry of superior and inferior endplates in the mid-sagittal plane is a risk factor for lumbar disc degeneration. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2469-2475, 2018.

Unexpectedly decreased plasma cytokines in patients with chronic back pain

Introduction

Chronic back pain is one of the most important socioeconomic problems that affects the global population. Elevated levels of inflammatory mediators, such as cytokines, have been correlated with pain, but their role in chronic back pain remains unclear. The effectiveness of anti-inflammatory drugs seems to be limited for chronic back pain. The authors wanted to investigate the levels of inflammatory mediators in long-term medically treated patients with persistent chronic back pain.

Methods

Cytokine plasma levels of patients with chronic back pain (n=23), compared to pain-free healthy controls (n=30), were investigated by immunoassay. Patients with chronic back pain were exposed to long-term conservative medical therapy with physiotherapy and anti-inflammatories, also combined with antidepressants and/or muscle-relaxants.

Results

The patients with chronic back pain expressed lower levels of the chemokines MCP1, CCL5, and CXCL6 compared to pain-free healthy controls. Significantly lower concentrations of the anti-inflammatory cytokines, interleukin (IL)-4 and granulocyte-colony stimulating factor were also found. Interestingly, levels of proinflammatory cytokines (IL-2, IL-6, IL-1β, tumor necrosis factor alpha), IL-10, granulocyte-macrophage colony-stimulating factor, and stromal cell-derived factor 1 alpha showed no significant differences between both groups.

Conclusion

This decrease of inflammatory mediators in medically treated patients with chronic back pain is of unclear origin and might be either a long-term side effect of medical therapy or related to chronic pain. Further longitudinal research is necessary to elucidate the underlying cause of these findings.

VEGF vascularization pathway in human intervertebral disc does not change during the disc degeneration process

Objective

During degeneration of the intervertebral disc ingrowth of blood vessels and nerves into the disc are associated with back pain. Vascular endothelial growth factors promote vasculogenesis by binding to the membrane vascular endothelial growth factor receptor 1, while shorter soluble forms of this receptor can inhibit vascularization. We hypothesized that membrane and soluble receptor forms might change between stages of intervertebral disc degeneration.

Results

Expression of soluble and membrane forms of vascular endothelial growth factor receptor 1 in human degenerated intervertebral discs and healthy bovine caudal discs was assessed by qRT-PCR and immunoblot. Comparative microarray meta-analysis across disc degeneration grades showed that membrane and soluble forms of this receptor, together with other components of classic vascularization pathways, are constitutively expressed across human disc degeneration stages. Contrary to our hypothesis, we observed that expression of the classic vascularization pathway is stable across degeneration stages and we assume that soluble vascular endothelial growth factor receptor 1 does not contribute to prevent disc degeneration. However, we observed increased expression levels of genes involved in alternative vascularization signalling pathways in severely degenerated discs, suggesting that abnormal vascularization is part of the pathological progression of disc degeneration.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3441-3) contains supplementary material, which is available to authorized users.

Biologic therapies to enhance intervertebral disc repair

Degenerative disc disease is a progressive, chronic disorder with strong association to pain, where the dysregulated tissue environment signals disc cells, thereby leading to a low inflammatory process and slow extracellular matrix degradation and fibrosis in a perpetual vicious cycle, generating a structural and functional failure of intervertebral disc joint (IVDJ). Among current biologic therapies, there is an emerging minimally invasive strategy that consists of infiltrating plasma rich in growth factors, a safe and efficacious therapeutic approach for other musculoskeletal degenerative conditions. This review summarizes the homeostasis and degeneration of IVDJ, discusses some results on basic science and therapeutic use of platelet-rich plasma products and advances an alternative minimally invasive biologic therapy in IVDJ degeneration and chronic back pain.

The effect of gigantomasty on vertebral degeneration: A computed tomography study

The main reason for waist and back pain in patients with gigantomasty is increased thoracic kyphosis and lumber lordosis. These symptoms and abnormal spinal angulations regress after reduction mammoplasty operations. However, the effect of chronic mechanical stress caused by gigantomasty on the spinal degenerative process is not clear yet. In this study with computed tomography it is shown that degenerative spondylosis is more widespread and severe in patients with large breasts.

Adult Apical Ligament of the Dens Lacks Notochordal Tissue: Application to Better Understanding the Origins of Skull Base Chordomas

INTRODUCTION

The apical ligament has long been reported to contain notochord remnants and thus might serve as a site of origin of chordoma formation at the skull base. However, to our knowledge, the histologic study of the apical ligament using histologic staining specific for notochordal tissue has not been previously performed. Therefore the current study was undertaken.

METHODS

Fifteen apical ligament samples underwent histologic examination with specific markers for notochordal differentiation.

RESULTS

Across all samples, there was no indication of any notochordal remnants.

CONCLUSIONS

On the basis of our cadaveric study, the apical ligament does not contain notochord tissue and in adults should not be considered a remnant of this structure. Moreover, it is unlikely that the apical ligament gives rise to chordomas at the craniocervical junction under normal circumstances.

Single Nucleotide Variants of Candidate Genes in Aggrecan Metabolic Pathway Are Associated with Lumbar Disc Degeneration and Modic Changes

Introduction

Lumbar disc degeneration (LDD) is genetically determined and severity of LDD is associated with Modic changes. Aggrecan is a major proteoglycan in the intervertebral disc and end plate. Progressive reduction of aggrecan is a main feature of LDD and Modic changes.

Objectives

The study investigated the associations of single nucleotide variants (SNVs) of candidate genes in the aggrecan metabolic pathway with the severity of LDD and Modic changes. In-silico functional analysis of significant SNVs was also assessed.

Methods

A descriptive cross sectional study was carried out on 106 patients with chronic mechanical low back pain. T1, T2 sagittal lumbar MRI scans were used to assess the severity of LDD and Modic changes. 62 SNVs in ten candidate genes (ACAN, IL1A, IL1B, IL6, MMP3, ADAMTS4, ADAMTS5, TIMP1, TIMP2 and TIMP3) were genotyped on Sequenom MassARRAY iPLEX platform. Multiple linear regression analysis was carried out using PLINK 1.9 in accordance with additive genetic model. In-silico functional analysis was carried out using Provean, SIFT, PolyPhen and Mutation Taster.

Results

Mean age was 52.42±9.42 years. 74 (69.8%) were females. The rs2856836, rs1304037, rs17561 and rs1800587 variants of the IL1A gene were associated with the severity of LDD and Modic changes. The rs41270041 variant of the ADAMTS4 gene and the rs226794 variant of the ADAMTS5 gene were associated with severity of LDD while the rs34884997 variant of the ADAMTS4 gene, the rs55933916 variant of the ADAMTS5 gene and the rs9862 variant of the TIMP3 gene were associated with severity of Modic changes. The rs17561 variant of the IL1A gene was predicted as pathogenic by the PolyPhen prediction tool.

Conclusions

SNVs of candidate genes in ACAN metabolic pathway are associated with severity of LDD and Modic changes in patients with chronic mechanical low back pain. Predictions of in-silico functional analysis of significant SNVs are inconsistent.