Background. Intervertebral disc degeneration (DD) is a complex age-related condition that constitutes the main risk factor for disabling back pain. DD is assessed using different traits extracted from MR imaging (MRI), normally combined to give summary measures (e.g. Pfirmann score). The aetiology of DD is poorly understood and despite its high heritability (75%), the precise genetic predisposition is yet to be defined. Genome wide association study (GWAS) is used to discover genetic variants associated with a disease or phenotype. It tests variants across the whole genome. It requires large samples to provide adequate but unfortunately there is poor availability of spine imaging data due to the high cost of MRI. We have adopted new methods to examine different MRI traits independently and use the information of those traits to boost GWAS power using specialized statistical software for jointly analyse correlated traits. Methods/Results. We examined DD MRI features disc narrowing, disc bulge, disc signal intensity and osteophyte formation in the TwinsUK cohort who had undergone T2-weighted sagittal spine MRI. GWAS were performed on the four traits. MTAG software was used to boost single trait GWAS power using the information in the other trait GWAS. 9 different loci were identified. Conclusions. Preliminary results suggest genes GDF6, SP1/SP7 are associated with individual trait signal intensity. In addition, novel associated genes with potential for shedding new light on pathogenic mechanisms are identified. Additional cohorts will be included in the design as a replication to test reproducibility of the results. Conflicts of interest: No conflicts of interest. Sources of funding: Funded by Disc4All, EU Horizon 2020, MSCA-2020-ITN-ETN GA: 955735

Introduction. Vertebral compression fractures are the most common type of osteoporotic fracture. Though 89% of clinical fractures occur anteriorly, it is challenging to replicate these ex vivo with the underlying intervertebral discs (IVDs) present. Furthermore, the role of disc degeneration in this mechanism is poorly understood. Understanding how disc morphology alters vertebral strain distributions may lead to the utilisation of IVD metrics in fracture prediction, or inform surgical decision-making regarding instrumentation type and placement. Aim. To determine the effect of disc degeneration on the vertebral trabecular bone strain distributions in axial compression and flexion loading. Methods. Eight cadaveric thoracolumbar segments (T11-L3) were prepared (N=4 axial compression, N=4 flexion). µCT-based digital volume correlation was used to quantify trabecular strains. A bespoke loading device fixed specimens at the resultant displacement when loaded to 50N and 800N. Flexion was achieved by adding 6° wedges. Disc degeneration was quantified with Pfirrmann grading and T2 relaxation times. Results. Anterior axial strains were 80.9±39% higher than the posterior region in flexion (p<0.01), the ratio of which was correlated with T2 relaxation time (R. 2. =0.80, p<0.05). In flexion, the central-to-peripheral axial strain ratio in the endplate region was significantly higher when the underlying IVDs were non-degenerated relative to degenerated (+38.1±12%, p<0.05). No significant differences were observed in axial compression. Conclusion. Disc degeneration is a stronger determinant of the trabecular strain distribution when flexion is applied. Load transfer through non-degenerate IVDs under flexion appears to be more centralised, suggesting that disc degeneration predisposes flexion-type compression fractures by shifting high strains anteriorly. Conflicts of interest. The authors declare none. Sources of funding. This work was funded by the Engineering & Physical Sciences Research Council (EP/V029452/1), and Back-to-Back

Aims. This study aimed, through bioinformatics analysis and in vitro experiment validation, to identify the key extracellular proteins of intervertebral disc degeneration (IDD). Methods. The gene expression profile of GSE23130 was downloaded from the Gene Expression Omnibus (GEO) database. Extracellular protein-differentially expressed genes (EP-DEGs) were screened by protein annotation databases, and we used Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) to analyze the functions and pathways of EP-DEGs. STRING and Cytoscape were used to construct protein-protein interaction (PPI) networks and identify hub EP-DEGs. NetworkAnalyst was used to analyze transcription factors (TFs) and microRNAs (miRNAs) that regulate hub EP-DEGs. A search of the Drug Signatures Database (DSigDB) for hub EP-DEGs revealed multiple drug molecules and drug-target interactions. Results. A total of 56 EP-DEGs were identified in the differential expression analysis. EP-DEGs were enriched in the extracellular structure organization, ageing, collagen-activated signalling pathway, PI3K-Akt signalling pathway, and AGE-RAGE signalling pathway. PPI network analysis showed that the top ten hub EP-DEGs are closely related to IDD. Correlation analysis also demonstrated a significant correlation between the ten hub EP-DEGs (p＜0.05), which were selected to construct TF–gene interaction and TF–miRNA coregulatory networks. In addition, ten candidate drugs were screened for the treatment of IDD. Conclusion. The findings clarify the roles of extracellular proteins in IDD and highlight their potential as promising novel therapeutic targets. Cite this article: Bone Joint Res 2023;12(9):522–535

Purpose of study and background. Degeneration of the intervertebral disc is a strong contributor of low back pain. Studies have shown that both, mechanical unloading and overloading, lead to disc degeneration. This is intuitively clear if one considers that an intervertebral disc essentially is a poro-elastic material embedded with cells, which depend on fluid flow for the transport of nutrients and waste products. As such, mechanical loading is also required for regeneration. It is unclear, however, how much loading is beneficial or detrimental for the healthy or degenerated disc. Methods and Results. We developed a loaded disc culture system for the long-term study of disc physiology. This way we could control both the mechanical and biochemical conditions. If no loading was applied, about half of the cells died within a week. Cells died under a low dynamic loading regime after three weeks. A diurnal loading regime rescued cell viability, gene expression profile and mechanical behavior of the discs. Both static and dynamic overloading induced damage to the discs and led to catabolic and inflammatory gene expressions. Conclusion. Intervertebral discs need a certain dosage of mechanical loading to remain viable. Under overloading, cells deform, change gene expression and become degenerative. The matrix is also remodeled, thereby further decreasing the hydrostatic pressure on the cells and increasing their deformation. This induces a vicious circle of disc degeneration, which needs to be reversed in order to repair the disc. The loaded disc culture system also allows evaluating new therapies for disc degeneration. There are no conflicts of interest. Funded by ZonMW program “Alternatives for live animal testing”, grant #11400090;. BioMedical Materials Program, grant # P2.01 IDiDas; Dutch Arthritis Funds, personal grant KSE

The belief that an intervertebral disc must degenerate before it can herniate has clinical and medicolegal significance, but lacks scientific validity. We hypothesised that tissue changes in herniated discs differ from those in discs that degenerate without herniation. Tissues were obtained at surgery from 21 herniated discs and 11 non-herniated discs of similar degeneration as assessed by the Pfirrmann grade. Thin sections were graded histologically, and certain features were quantified using immunofluorescence combined with confocal microscopy and image analysis. Herniated and degenerated tissues were compared separately for each tissue type: nucleus, inner annulus and outer annulus. Herniated tissues showed significantly greater proteoglycan loss (outer annulus), neovascularisation (annulus), innervation (annulus), cellularity/inflammation (annulus) and expression of matrix-degrading enzymes (inner annulus) than degenerated discs. No significant differences were seen in the nucleus tissue from herniated and degenerated discs. Degenerative changes start in the nucleus, so it seems unlikely that advanced degeneration caused herniation in 21 of these 32 discs. On the contrary, specific changes in the annulus can be interpreted as the consequences of herniation, when disruption allows local swelling, proteoglycan loss, and the ingrowth of blood vessels, nerves and inflammatory cells. In conclusion, it should not be assumed that degenerative changes always precede disc herniation. Cite this article: Bone Joint J 2013;95-B:1127–33

Objectives. Low back pain is strongly associated with degeneration of the intervertebral disc (IVD). During degeneration, altered matrix synthesis and increased matrix degradation, together with accompanied cell loss is seen particularly in the nucleus pulposus (NP). It has been proposed that notochordal (NC) cells, embryonic precursors for the cells within the NP, could be utilized for mediating IVD regeneration. However, injectable biomaterials are likely to be required to support their phenotype and viability within the degenerate IVD. Therefore, viability and phenotype of NC cells were analysed and compared within biomaterial carriers subjected to physiological oxygen conditions over a four-week period were investigated. Methodology. Porcine NC cells were incorporated into three injectable hydrogels: NPgel (a L-pNIPAM-co-DMAc hydrogel), NPgel with decellularized NC-matrix powder (dNCM) and Albugel (an albumin/ hyaluronan hydrogel). The NCs and biomaterials constructs were cultured for up to four weeks under 5% oxygen (n=3 biological repeats). Histological, immunohistochemical and glycosaminoglycans (GAG) analysis were performed to investigate NC viability, phenotype and extracellular matrix synthesis and deposition. Results. Histological analysis revealed that NCs survive in the biomaterials after four weeks and maintained cell clustering in NPgel, Albugel and dNCM/NPgel. NPgel and Albugel maintained NC cell markers and extracellular matrix. NC containing constructs excreted more GAGs over the four weeks than the acellular controls. Conclusion. NC cells maintain their phenotype and characteristic features in vitro when encapsulated into biomaterials. NC cells and biomaterial construct could potentially become a therapy to treat and regenerate the IVD. Conflicts of interest: No conflicts of interest. Sources of funding: This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 825925

Purpose of study and background. Low back pain affects 80% of the population at some point in their lives with 40% of cases attributed to intervertebral disc (IVD) degeneration. A number of potential regenerative approaches are under investigation worldwide, however their translation to clinic is currently hampered by an appropriate model for testing prior to clinical trials. Therefore, a more representative large animal model for IVD degeneration is needed to mimic human degeneration. Here we investigate a caprine IVD degeneration model in a loaded disc culture system which can mimic the native loading environment of the disc. Methods and Results. Goat discs were excised and cultured in a bioreactor under diurnal, simulated-physiological loading (SPL) conditions, following 3 days pre load, IVDs were degenerated enzymatically for 2hrs and subsequently loaded for 10 days under physiological loading. A PBS injected group was used as controls. Disc deformation was continuously monitored and changes in disc height recovery quantified using stretched-exponential fitting. Histological staining was performed on caprine discs to assess extracellular matrix production and immunohistochemistry performed to determine expression of catabolic protein expression. The injection of collagenase and cABC induced mechanical behavior akin to that seen in human degeneration. A decrease in collagens and glycosaminoglycans (GAGs) was seen in enzyme injected discs, which was accompanied by increased cellular expression for degradative enzymes and catabolic cytokines. Conclusion. This model provides a reproducible model of IVD degeneration which mimics human degeneration. This model allows the testing of biomaterials and other potential treatments of IVD degeneration on a scale more representative of the human disc. There are no conflicts of interest. Funded by MRC and Versus Arthritis

Aims. In this investigation, we administered oxidative stress to nucleus pulposus cells (NPCs), recognized DNA-damage-inducible transcript 4 (DDIT4) as a component in intervertebral disc degeneration (IVDD), and devised a hydrogel capable of conveying small interfering RNA (siRNA) to IVDD. Methods. An in vitro model for oxidative stress-induced injury in NPCs was developed to elucidate the mechanisms underlying the upregulation of DDIT4 expression, activation of the reactive oxygen species (ROS)-thioredoxin-interacting protein (TXNIP)-NLRP3 signalling pathway, and nucleus pulposus pyroptosis. Furthermore, the mechanism of action of small interfering DDIT4 (siDDIT4) on NPCs in vitro was validated. A triplex hydrogel named siDDIT4@G5-P-HA was created by adsorbing siDDIT4 onto fifth-generation polyamidoamine (PAMAM) dendrimer using van der Waals interactions, and then coating it with hyaluronic acid (HA). In addition, we established a rat puncture IVDD model to decipher the hydrogel’s mechanism in IVDD. Results. A correlation between DDIT4 expression levels and disc degeneration was shown with human nucleus pulposus and needle-punctured rat disc specimens. We confirmed that DDIT4 was responsible for activating the ROS-TXNIP-NLRP3 axis during oxidative stress-induced pyroptosis in rat nucleus pulposus in vitro. Mitochondria were damaged during oxidative stress, and DDIT4 contributed to mitochondrial damage and ROS production. In addition, siDDIT4@G5-P-HA hydrogels showed good delivery activity of siDDIT4 to NPCs. In vitro studies illustrated the potential of the siDDIT4@G5-P-HA hydrogel for alleviating IVDD in rats. Conclusion. DDIT4 is a key player in mediating pyroptosis and IVDD in NPCs through the ROS-TXNIP-NLRP3 axis. Additionally, siDDIT4@G5-P-HA hydrogel has been found to relieve IVDD in rats. Our research offers an innovative treatment option for IVDD. Cite this article: Bone Joint Res 2024;13(5):247–260

Purpose of study and background. Clinical researchers use Pfirrmann classification for grading intervertebral disc degeneration radiologically. Basic researchers have access to morphology and instead use the Thompson score. The aim of this study was to assess the inter-observer reliability of both classifications, along with their correlation. Methods and Results. We obtained T2-weighted MR images of 80 human lumbar intervertebral discs with various stages of degeneration to assess the Pfirrmann-score. Then the discs were dissected midsagittally to obtain the Thompson-score. The observers were typical users of both grading systems: a spine surgeon, radiology resident, orthopaedic resident, and a basic scientist, all experts on intervertebral disc degeneration. Cohen's kappa (CK) was used to determine inter-observer reliability, and intra-class correlation (ICC) as a measure for the variation between the outcomes. For the Thompson score, the average CK was 0.366 and ICC score 0.873. The average inter-observer reliability for the Pfirrmann score was 0.214 (CK) and 0.790 (ICC). Comparing the grading systems, the intra-observer agreement was 0.240 (CK) and 0.685 (ICC). Conclusion. With substantial variation between observers, the inter-observer agreements for the Pfirrmann and Thompson grading systems were moderate. This may explain the poor relationship between radiological and clinical observations in patients and raises questions about the validity of the Pfirrmann score. The mediocre intra-observer agreement between the Pfirrmann and Thompson score shows that there is no clear definition of intervertebral disc degeneration. The field is in need for a new, objective and quantitative classification system to better define and evaluate disc degeneration. There are no conflicts of interest. Funded in part by Annafonds Netherlands and Dutch Spine Society

Purpose of study and background. Mechanical overloading initiates intervertebral disc degeneration, presumably because cells break down the extracellular matrix (ECM). We used Fourier Transform Infrared Spectroscopy (FTIR) imaging to identify, visualize and quantify the ECM and aimed to identify spectroscopic markers for early disc degeneration. Methods and Results. In seven goats, one disc was injected with chondroitinase ABC (mild degeneration) and after three months compared to control. Ex vivo, 50 caprine discs received physiological loading (50–150N) or overloading (50–400N) in a loaded disc culture system. To determine whether ECM degeneration is due to cell activity, half of the discs was subjected to freeze-thaw cycles. Spectroscopic images were collected at 1000–1300 cm. −1. and analyzed using multivariate curve resolution analysis. In vivo, less proteoglycan was found in the degenerated group (p<0.05), especially in the nucleus. Collagen content was increased in the nucleus and anterior annulus, and had higher entropy (p<0.01), indicating matrix disorganization. In the ex vivo experiment, the proteoglycan/collagen ratio was decreased (p<0.05) in the vital group and there was an increase in collagen entropy (p<0.05). A significant interaction between loading and vitality was found in the amount of collagen (p<0.05), but not in the entropy. Conclusion. Three weeks of mild overloading causes measurable changes in the extracellular matrix. Increased collagen entropy indicates that remodeling of collagen is a first step into disc degeneration. We could not confirm, however, that increase in entropy was due to cell activity. FTIR imaging allows more detailed investigation of early disc degeneration than traditional measures. There are no conflicts of interest. Partially funded by Dutch Arthritis Funds, personal grant KSE

Background. Intervertebral disc (IVD) degeneration is a major cause of low back pain (LBP). Degenerate discs are associated with accelerated cellular senescence. Cell senescence is associated with a secretory phenotype characterised by increased production of catabolic enzymes and cytokines. However to date, the mechanism of cell senescence within disc degeneration is unclear. Senescence can be induced by increased replication or induced by stress such as reactive oxygen species or cytokines. This study investigated the association of cellular senescence with markers of DNA damage and presence of cytoplasmic DNA (which in cancer cells has been shown to be a key regulator of the secretory phenotype), to determine mechanisms of senescence in disc degeneration. Methods and Results. Immunohistochemistry for the senescence marker: p16. INK4A. was firstly utilised to screen human intervertebral discs for discs displaying at least 30% immunopostivity. These discs were then subsequently analysed for immunopostivity for DNA damage markers γH2AX and cGAS and the presence of cytoplasmic DNA. The number of immunopositive cells for p16. INK4A. positively correlated with the expression of γH2AX and cGAS. Senescent cells were also associated with the presence of cytoplasmic DNA. Conclusions. These new findings elucidated a role of cGAS and γH2AX as a link from genotoxic stress to cytokine expression, which is associated with senescent cells. The findings indicate that cellular senescence in vivo is associated with DNA damage and presence of cytoplasmic DNA. Whether this DNA damage is a result of replicative senescence or stress induced is currently being investigated in vitro. No conflicts of interest. Sources of funding: Funded by ARUK and MRC

Background. The association between lumbar intervertebral disc degeneration (LDD) and low back pain (LBP) is modest. We have recently shown that genetic propensity to pain is an effect modifier of the LDD-LBP relationship when LDD is defined as a summary score of LDD (LSUM), suggesting the association may be driven by individuals with the greatest genetic predisposition to pain. This study examined the association between individual spine magnetic resonance imaging (MRI)-determined LDD features and LBP in subgroups defined by genetic predisposition to pain. Method. We developed a polygenic risk score (PRS) for “genetic propensity to pain” defined as the number of non-back pain locations (head, face, neck/shoulder, stomach/abdomen, hip, and knee) with duration ≥3 months in 377,538 UK Biobank participants of European ancestry. This PRS was used to stratify TwinsUK MRI samples (n=645) into four strata of genetic propensity to pain. We examined the association between LBP and MRI features of lumbar disc height, disc signal intensity, disc bulge, and osteophytes with adjustments for age, sex, PRS strata, interaction terms for each MRI feature x PRS strata, and twin status. Results. We found significant effect modification of the LDD-LBP relationship by genetic propensity to pain for the lumbar MRI features of disc height (p=0.03 for the interaction term with highest quartile of genetically-predicted propensity to pain) and disc signal intensity (p=0.001), but not for disc bulge and osteophytes. Conclusion. Genetic propensity to pain modifies the association between individual LDD features and LBP and should be considered in LBP clinical studies. Conflicts of interest. No conflicts of interest. Sources of funding. No funding obtained. Acknowledgement. UKBB data were obtained under the project #18219. This paper is submitted to the Spine journal and is under review

We studied 52 patients, each with a lumbosacral transitional vertebra. Using MRI we found that the lumbar discs immediately above the transitional vertebra were significantly more degenerative and those between the transitional vertebrae and the sacrum were significantly less degenerative compared with discs at other levels. We also performed an anatomical study using 70 cadavers. We found that the iliolumbar ligament at the level immediately above the transitional vertebra was thinner and weaker than it was in cadavers without a lumbosacral transitional vertebra. Instability of the vertebral segment above the transitional vertebra because of a weak iliolumbar ligament could lead to subsequent disc degeneration which may occur earlier than at other disc levels. Some stability between the transitional vertebra and the sacrum could be preserved by the formation of either an articulation or by bony union between the vertebra and the sacrum through its transverse process. This may protect the disc from further degeneration in the long term

Objectives. A single degenerate intervertebral disc is suggested to promote rapid degeneration in its adjacent discs. We validated this hypothesis using discordant co-twin case-control design. Methods. 185 pairs of twins were selected from the TwinsUK database having cervical MRI scans at baseline and at follow-up, after 10 years. Isolated disc degeneration (IDD) was diagnosed in subjects having severe loss in disc height (graded 3/3) in a single disc, whilst discs immediately adjacent manifested little or no degeneration (graded 0 or 1). The controls' ‘adjacent discs’ were considered at the same levels as their affected co-twins. Results. Eight twin pairs fulfilled case/control criteria. At follow-up, no significant difference in adjacent disc degeneration between IDD cases and controls remained (p=0.69). Conclusions. Using a highly matched case-control design we did not find evidence that lone IDD has an adverse effect on the natural rate of adjacent disc degeneration in the cervical spine. No conflicts of interest. Acknowledgements. This study was supported by a grant from Globus Inc. Arthritis Research UK supported the imaging costs. TwinsUK. The study was funded by the Wellcome Trust; European Community's Seventh Framework Programme (FP7/2007–2013). The study also receives support from the National Institute for Health Research (NIHR)- funded BioResource, Clinical Research Facility and Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust in partnership with King's College London

We investigated the relationship between spinopelvic parameters and disc degeneration in young adult patients with spondylolytic spondylolisthesis. A total of 229 men with a mean age of 21 years (18 to 26) with spondylolytic spondylolisthesis were identified. All radiological measurements, including pelvic incidence, sacral slope, pelvic tilt, lumbar lordosis, sacral inclination, lumbosacral angle (LSA), and sacrofemoral distance, were calculated from standing lateral lumbosacral radiographs. The degree of intervertebral disc degeneration was classified using a modified Pfirrmann scale. We analysed the spinopelvic parameters according to disc level, degree of slip and disc degeneration. There were significant positive correlations between the degree of slip and pelvic incidence (p = 0.009), sacral slope (p = 0.003) and lumbar lordosis (p = 0.010). The degree of slip and the LSA were correlated with disc degeneration (p < 0.001 and p = 0.003, respectively). There was also a significant difference between the degree of slip (p < 0.001) and LSA (p = 0.006) according to the segmental level of disc degeneration. Cite this article: Bone Joint J 2013;95-B:1239–43

Introduction. Primary cilia are singular structures containing a microtubule-based axoneme which are believed to not only be mechanosensitive but also to co-ordinate many cell functions via signalling pathways including Hedgehog and Wnt. Primary cilia have previously been described on cells of mouse intervertebral discs (IVDs), but not in bovine or human IVDs. Our aim was to examine primary cilia in these species. Methods. Nucleus pulposus cells were obtained from cows with no overt disc degeneration and patients following spine surgery (for herniations and/or degenerative disc disease) and cultured until confluent before maintaining with or without serum for 24h. Primary cilia were visualised with antibodies to the axoneme (acetylated α-tubulin and Arl13b) and/or the basal body (pericentrin) using fluorescent secondary antibodies and ≥200 cells per sample were counted. Results. Primary cilia were detected in the majority of disc cells (81.2±4.1% and 54.8±28.7% with and without serum depletion, respectively, in bovine and 78.9±0.3% and 89.8±7.4% in human cells). Some cilia demonstrated abnormalities, such as bulbous tips or breaks in the axonome. Conclusion. This is the first report of primary cilia being present on human and bovine IVD cells. There remain many other aspects to be investigated, for example, their length has been shown to alter in osteoarthritic chondrocytes. If this, or the incidence of abnormalities, differs in cells from normal and abnormal discs, it could suggest new pathways of disc degeneration, as these organelles are key to so many cell functions. Conflicts of interest: None. Supported by the Orthopaedic Institute Ltd

This article reviews the current knowledge of the intervertebral disc (IVD) and its association with low back pain (LBP). The normal IVD is a largely avascular and aneural structure with a high water content, its nutrients mainly diffusing through the end plates. IVD degeneration occurs when its cells die or become dysfunctional, notably in an acidic environment. In the process of degeneration, the IVD becomes dehydrated and vascularised, and there is an ingrowth of nerves. Although not universally the case, the altered physiology of the IVD is believed to precede or be associated with many clinical symptoms or conditions including low back and/or lower limb pain, paraesthesia, spinal stenosis and disc herniation. New treatment options have been developed in recent years. These include biological therapies and novel surgical techniques (such as total disc replacement), although many of these are still in their experimental phase. Central to developing further methods of treatment is the need for effective ways in which to assess patients and measure their outcomes. However, significant difficulties remain and it is therefore an appropriate time to be further investigating the scientific basis of and treatment of LBP

Background. Endplate defect is an MRI trait, found to be associated with intervertebral disc degeneration. There is a lack of understanding regarding the mechanism underlying lumbar disc degeneration (LDD). This large-scale longitudinal population-based study aimed to determine the order of appearance of degenerative change in the vertebral body and intervertebral disc, the influence of endplate degeneration on LBP and whether there is a genetic influence on endplate damage. Methods. Individuals from the TwinsUK spine study having longitudinal T2-weighted lumbar MRI scans at baseline (n=996) and a decade later (n=438) were included. LDD, vertebral endplate defect expressed as a total endplate (TEP) score and Modic change (MC) were assessed using standard techniques. Mixed-effects models were used to determine the association between spine pathology features adjusted for covariates. Endplate defect heritability was estimated using variance component analysis. Results. Significant association between endplate defect, LDD, MRI features of LDD and MC was observed. Endplate defect was independently associated with severe disabling LBP episodes. An association between LDD at baseline and MC at follow-up was shown at upper lumbar levels. TEP score was heritable with estimated additive genetic component A = 55.3% (95% CI 43.0–65.4). Conclusion. Endplate defect, LDD and MC are all independent risk factors for episodes of severe and disabling LBP. Longitudinal analysis showed LDD is followed by MC. Endplate defect has significant heritability. However, whether endplate defect triggers LDD or these pathological changes occur concurrently could not be determined conclusively. Conflicts of interest: none. Sources of Funding: This work was funded by the EU FP7 project Pain_Omics

This short contribution aims to explain how intervertebral disc ‘degeneration’ differs from normal ageing, and to suggest how mechanical loading and constitutional factors interact to cause disc degeneration and prolapse. We suggest that disagreement on these matters in medico-legal practice often arises from a misunderstanding of the nature of ‘soft-tissue injuries’

Introduction. Disc degeneration is often scored using macroscopic and microscopic scoring systems. Although reproducible, these scores may not accurately reflect declining function in a degenerated disc. Accordingly, we compared macroscopic and microscopic degeneration scores with measurements of disc function. Methods. Thirteen cadaveric motion segments (62–93 yrs) were compressed to 1kN while a pressure-transducer was pulled across the mid-sagittal diameter of the disc. Resulting stress profiles indicated intradiscal pressure (IDP), and maximum stress in the anterior (MaxStress_Ant) and posterior (MaxStress_Post) annulus. Macroscopic grade (1–4) of disc degeneration was based on visual examination of mid-sagittal sections, using subscales that yielded a maximum score of 48. Microscopic grade (1–4) was based on histological sections of the disc + vertebral body taken from anterior annulus, nucleus pulposus and posterior annulus, using subscale scores that totalled 108. Cartilage endplate thickness (CEP_thickness) was measured histologically, and porosity of the bony endplates was measured using micro-CT. ANOVA was used to compare between grades, and regression was used to establish dependence on scores. Results. IDP and CEP_thickness both decreased with increasing macroscopic grade (1–4) of degeneration (P= 0.021 & 0.022 respectively). Also, IDP, CEP_thickness and MaxStress_Ant decreased with increasing macroscopic score (1–48) (R. 2. = 0.39, P = 0.022; R. 2. = 0.36, P = 0.03; R. 2. = 0.30, P = 0.04 respectively). IDP and MaxStress_Ant decreased with increasing microscopic grade (1–4) of degeneration (P=0.05 & 0.005 respectively) and increasing microscopic score (1–108) (R. 2. = 0.36, P = 0.02; R. 2. = 0.47, P = 0.009 respectively) whereas inferior endplate porosity increased with increasing microscopic grade (P = 0.05) and score (R. 2. = 0.36, P = 0.03). Conclusion. Macroscopic and microscopic ‘degeneration’ scores both reflect changes in disc function and endplate integrity