Dorsal root ganglion neurones with dichotomising axons are present in several species and are considered to play a role in referred pain. Clinically, patients with lesions in the lower lumbar discs occasionally complain of pain in the groin. We investigated the existence of dichotomising afferent neurones projecting axons both to the lumbar disc and to the groin skin, using the double fluorescent-labelling technique in rats. We observed neurones labelled with a tracer applied at the ventral portion of the L5-L6 disc and another tracer placed on the groin skin in L1 and L2 dorsal root ganglia. Our results showed that the double-labelled neurones had peripheral axons which dichotomised into both the L5-L6 disc and the groin skin, indicating the convergence of afferent sensory information from the disc and groin skin. Our findings provide a possible neuroanatomical mechanism for referred groin pain in patients with disc lesions

Based on a study using a retrograde neurotracer, we have previously found that the dorsal portion of the L5/6 disc in the rat is multisegmentally innervated by dorsal root ganglia (DRG) from the level of T13 to L6, and that sensory nerve fibres from DRG of T13, L1 and L2 pass through the paravertebral sympathetic trunks. In this study in newborn rats, we injected crystals of 1,1′-dioctadecyl-3,3,3′,3′-tetramethylinedocarbocyanine perchlorate (DiI) into the DRG of T13, L1 and L2 and showed DiI-labelled sensory nerve fibres in the dorsal portion of the discs from the level of T13/L1 to L5/6. Our results show that the dorsal portion of the lumbar discs is innervated by the DRG from levels T13 to L2

Spinal total disc replacement (TDR) designs rely heavily on total hip replacement (THR) technology and it is therefore prudent to check that typical TDR devices have acceptable friction and torque behaviour. For spherical devices friction factor (f) is used in place of friction coefficient (mju). The range of loading for the lumbar spinal discs is estimated at perhaps 3 times body weight (BW) for normal activity rising to up to 6 times BW for strenuous activity. [1]. For walking this equates to around 2000 N, which is the maximum load required by the ISO standard for TDR wear testing. [2]. . Three Prodisc-L TDR devices (Synthes Spine) were tested in a single station friction simulator. Bovine serum diluted to 25% was used as a lubricating medium. Flexion-extension was ±5 deg for all experiments with constant axial loading of 500, 2000 and 3000 N. The cycle run length was limited to 100 and the f and torque (T) values recorded around the maximum velocity of the cycle point and averaged over multiple cycles. Preliminary results shows that the 500 N loading produced the largest f of 0.05 ± 0.004. The 2000 N load, which approximates daily activity, gave f = 0.036 ± 0.05 and the 3000 N load gave f = 0.013 ± 0.003. The trend was for lower f with increasing loads. A lumbar TDR friction factor of 0.036 for a 2000N load and the reduction in f for increasing loads is comparable to the lower end of the range of values reported for THR in similar simulator studies using metal-on-polyethylene bearing materials. [3]. The 3000 N result showing that increasing the load above that expected in daily activity does not raise the f could be important when considering rotational stability and anchorage in a TDR device because frictional torque at the bearing surfaces is proportional to the product of load, device radius and f

Despite the clinical relevance of back pain and intervertebral disc herniation, the lack of reliable models has strained their molecular understanding. We characterized the lumbar spinal phenotype of C57BL/6 and SM/J mice during aging. Interestingly, old SM/J lumbar discs evidenced accelerated degeneration, associated with high rates of disc herniation. SM/J AF's and degenerative human's AF transcriptomic profiles showed altered immune cell, inflammation, and p53 pathways. Old SM/J mice presented increased neuronal markers in herniated discs, thicker subchondral bone, and higher sensitization to pain. Dorsal root ganglia transcriptomic studies and spinal cord analysis exhibited increased pain and neuroinflammatory markers associated with altered extracellular matrix regulation. Immune system single-cell and tissue level analysis showed distinctive T-cell and B-cell modulation and negative correlation between mechanical allodynia and INF-α, IL-1β, IL2, and IL4, respectively. This study underscores the multisystemic network behind back pain and highlights the role of genetic background and the immune system in disc herniation disease. Acknowledgments: This study is supported by grants from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) R01AR055655, R01AR064733, R01AR074813 to MVR

Using deep learning and image processing technology, a standardized automatic quantitative analysis systerm of lumbar disc degeneration based on T2MRI is proposed to help doctors evaluate the prognosis of intervertebral disc (IVD) degeneration. A semantic segmentation network BianqueNet with self-attention mechanism skip connection module and deep feature extraction module is proposed to achieve high-precision segmentation of intervertebral disc related areas. A quantitative method is proposed to calculate the signal intensity difference (SI) in IVD, average disc height (DH), disc height index (DHI), and disc height-to-diameter ratio (DHR). According to the correlation analysis results of the degeneration characteristic parameters of IVDs, 1051 MRI images from four hospitals were collected to establish the quantitative ranges for these IVD parameters in larger population around China. The average dice coefficients of the proposed segmentation network for vertebral bodies and intervertebral discs are 97.04% and 94.76%, respectively. The designed parameters of intervertebral disc degeneration have a significant negative correlation with the Modified Pfirrmann Grade. This procedure is suitable for different MRI centers and different resolution of lumbar spine T2MRI (ICC=.874~.958). Among them, the standard of intervertebral disc signal intensity degeneration has excellent reliability according to the modified Pfirrmann Grade (macroF1=90.63%~92.02%). we developed a fully automated deep learning-based lumbar spine segmentation network, which demonstrated strong versatility and high reliability to assist residents on IVD degeneration grading by means of IVD degeneration quantitation

The relationship of degeneration to symptoms has been questioned. MRI detects apparently similar disc degeneration and degenerative changes in subjects both with and without back pain. We aimed to overcome these problems by re-annotating MRIs from asymptomatic and symptomatic groups onto the same grading system. We analysed disc degeneration in pre-existing large MRI datasets. Their MRIs were all originally annotated on different scales. We re-annotated all MRIs independent of their initial grading system, using a verified, rapid automated MRI annotation system (SpineNet) which reported degeneration on the Pfirrmann (1-5) scale, and other degenerative features (herniation, endplate defects, marrow signs, spinal stenosis) as binary present/absent. We compared prevalence of degenerative features between symptomatics and asymptomatics. Pfirrmann degeneration grades in relation to age and spinal level were very similar for the two independent groups of symptomatics over all ages and spinal levels. Severe degenerative changes were significantly more prevalent in discs of symptomatics than asymptomatics in the caudal but not the rostral lumbar discs in subjects < 60 years. We found high co-existence of degenerative features in both populations. Degeneration was minimal in around 30% of symptomatics < 50 years. We confirmed age and disc level are significant in determining imaging differences between asymptomatic and symptomatic populations and should not be ignored. Automated analysis, by rapidly combining and comparing data from existing groups with MRIs and information on LBP, provides a way in which epidemiological and ‘big data’ analysis could be advanced without the expense of collecting new groups

Low back pain (LBP) is a worldwide leading cause of disability. Treatment of intervertebral disc (IVD) with stem cells has been used on degenerate discs (IDD), cause of around 40% of LBP cases. Despite pain reduction, clinical studies' follow-up have not shown a structural IVD improvement. A valid alternative may be the use of notocordal cells (NC) or their precursors. Mesendoderm progenitor cells (MEPC) have the ability to replicate and differentiate toward NC. In this preliminary study we evaluated in a preclinical IDD model the viability and NC differentiation of MEPC derived from induced pluripotent stem cells (iPSC). MEPC derived from iPSC were developed during the iPSpine project (# 825925), thawed, plated for 24h on laminin and labeled with PKH26. Two adult sheep were subjected to nucleotomy of five lumbar discs for the induction of IDD. After 5 weeks, 3 degenerated discs were treated with MEPC at 3 different doses (low, medium and high). One sheep was sacrificed after 7 days and one after 30 days. Clinical parameters were collected to evaluate the safety of treatment. Discs were analysed using histological techniques. Survival (PKH26), proliferation (PCNA), notocordal cell differentiation (Brachyury, Cytokeratin 8/18/19, Sox9, Foxa2) and endodermal differentiation (Sox17) were evaluated. At 7 days from treatment, both sheep lost about 20% of body weight. Only in discs treated with the highest dose PKH26 stained cells were alive up to 30 days. These cells turn out to be: proliferating (PCNA); positive for Brachyury, cytokeratin 8/18/19 and Foxa2; positive for SOX17 in a small percentage. This preliminary study shows that MEPC, derived from iPSC and injected into ovine discs degenerated by nucleotomy, are able to survive up to 30 days and differentiate within the disc predominantly towards the notocordal phenotype

Low back pain (LBP) is the leading cause of disability worldwide. Recently, treatment of the intervertebral disc (IVD) with stem cells has been used for the treatment of degenerate discs (IDD) which cause at least the 40% of LBP cases. Despite pain reduction, follow-up in clinical studies have not shown an improvement in the structural integrity of IVD. A valid alternative could be the use of progenitor disc cells (notocordal cells, NC) or of their precursors. Mesendoderm progenitor cells (MEPC) have the ability to replicate and differentiate toward NC. In this preliminary study we evaluated in a preclinical large animal IDD model the viability and NC differentiation of MEPC derived from induced pluripotent stem cells (iPSC). MEPC, derived from iPSC and developed during the iPSpine project (# 825925), were thawed and plated on laminin for 24h and labeled with PKH26. Two adult sheep were subjected to nucleotomy of five lumbar discs for the induction of IDD. After 5 weeks, 3 of the 5 degenerate discs were treated with MEPC at 3 different doses (low, medium and high). One sheep was sacrificed after 7 days and the other after 30 days from the treatment injection procedure. Clinical parameters were collected to evaluate the safety of treatment. Discs were paraffin embedded and analysed using histological techniques. Survival (PKH26), proliferation (PCNA), notocordal cell differentiation (Brachyury, Cytokeratin 8/18/19, Sox9, Foxa2) and endodermal differentiation (Sox17) were evaluated. After the injection of the cells, both sheep lost about 20% of body weight. The analysis showed that only in discs treated with the highest dose the PKH26 stained cells resulted alive after 30 days from the procedure. These cells turn out to be:. -. in proliferation (PCNA). -. positive for Brachyury, cytokeratin 8/18/19 and Foxa2. -. a small percentage positive for SOX17. This preliminary study shows that MEPC, derived from iPSC and injected into ovine discs degenerated by nucleotomy, are able to survive 30 days from treatment and differentiate within the disc predominantly towards the notocordal phenotype

In a study on ten fresh human cadavers we examined the change in the height of the intervertebral disc space, the angle of lordosis and the geometry of the facet joints after insertion of intervertebral total disc replacements. SB III Charité prostheses were inserted at L3-4, L4-5, and L5-S1. The changes studied were measured using computer navigation sofware applied to CT scans before and after instrumentation. After disc replacement the mean lumbar disc height was doubled (p < 0.001). The mean angle of lordosis and the facet joint space increased by a statistically significant extent (p < 0.005 and p = 0.006, respectively). By contrast, the mean facet joint overlap was significantly reduced (p < 0.001). Our study indicates that the increase in the intervertebral disc height after disc replacement changes the geometry at the facet joints. This may have clinical relevance

Study Purpose. To examine the presence of radicular pain and its relationship to the degree of lumbar nerve root compression in patients with a degenerative lumbar spine condition about to undergo surgery for either lumbar disc prolapse or lumbar canal stenosis. Background. The pathophysiology underlying radicular pain is not completely understood but it is thought that nerve root compression is a key factor and from a surgical perspective, decompressing the nerve root is considered to be the key therapeutic step. However, despite often severe root compression in patients with lumbar stenosis, radicular pain is not a typical feature. Methods. Thirty-nine pre-surgical patients with either lumbar disc prolapse or lumbar canal stenosis were studied using the Standardised Evaluation of Pain (StEP), a clinical assessment tool known to predict with a high degree of sensitivity and specificity the presence or absence of lumbar radicular pain. A nerve root compression score was given from lumbar MRI for each patient by a neuroradiologist blinded to the patients history. Results. The StEP assessment tool was able to distinguish the presence or absence of radicular pain with high sensitivity and specificity. This correlated well with the pre-operative diagnosis of disc prolapse or canal stenosis. The relationship between radicular pain and nerve root compression was less clear and will be discussed. Conclusion. This study confirms StEP as a useful bedside tool for identifying the presence of radicular pain in patients with a degenerative lumbar spine condition. Nerve root compression per se does not necessarily produce radicular pain. Conflicts of Interest. None. Source of Funding. None. This study has not been published or presented at a previous meeting

To clarify the pathomechanisms of discogenic low back pain, the sympathetic afferent discharge originating from the L5-L6 disc via the L2 root were investigated neurophysiologically in 31 Lewis rats. Sympathetic afferent units were recorded from the L2 root connected to the lumbar sympathetic trunk by rami communicantes. The L5-L6 discs were mechanically probed, stimulated electrically to evoke action potentials and, finally, treated with chemicals to produce an inflammatory reaction. We could not obtain a response from any units in the L5-L6 discs using mechanical stimulation, but with electrical stimulation we identified 42 units consisting mostly of A-delta fibres. In some experiments a response to mechanical probing of the L5-L6 disc was recognised after producing an inflammatory reaction. This study suggests that mechanical stimulation of the lumbar discs may not always produce pain, whereas inflammatory changes may cause the disc to become sensitive to mechanical stimuli, resulting in nociceptive information being transmitted as discogenic low back pain to the spinal cord through the lumbar sympathetic trunk. This may partly explain the variation in human symptoms of degenerate discs

Extensive annulus fibrosus (AF) radial tears lead to intervertebral disc (IVD) herniation. While unrepaired defects in the AF are associated with postoperative reherniation and high IVD degeneration prevalence, current surgical strategies are limited to symptomatic treatment of pain and disregard the structural integrity of the AF. For all these reasons, this study is focused on i) designing polycaprolactone (PCL) electrospun implants that mimic the multi-lamellar fibrous structure of the native tissue and ii) assessing their ability to properly close and repair an AF defect in a sheep in vivo model. Oriented PCL mats were produced by electrospinning with average fiber diameters of 1.3µm and a tensile modulus (55±1MPa) matching the one of a native human AF lamella (∼47MPa). In vitro experiments demonstrated a spontaneous colonization of PCL mats by human and ovine AF cells. In vivo study was carried out on 6 sheep in which 5 lumbar discs were exposed using a left retroperitoneal approach. Defects (2×5mm, 2mm depth) were created in the outer annulus, with randomized distribution of conditions including 10-layer oriented or non-oriented mats, untreated and healthy groups. X-ray and MRI examinations were performed every month until explantations at 1, 3 and 6 months, followed by immuno-histological analysis. Data showed no dislocation of the implants, cell infiltration between the PCL mats and within the mats, and a continuous type I collagen tissue formation between the implants and the surrounding AF tissue. These results highlight that multi-layer PCL electrospun mat is a promising biomaterial for AF repair

Introduction. Sustained loading on the intervertebral disc leads to loss of disc height. The generally accepted explanation for this is that the disc loses height due to an unbalance between the external load on the disc and the osmotic pressure in the disc. Consequently, water is expelled from the disc until the osmotic attraction reaches an equilibrium with the pressure applied. In this study, we compared the time course of loss of disc height with loss of pressure in the nucleus. We expected to see a similar time course of disc height and intra-discal pressure. Methods. Fifteen caprine lumbar discs were tested in a saline bath. Of each motion segment both vertebral bodies were cut-off close to the endplate. After a preload of 6 hours at 10N, an axial compressive load of 150N was applied to the discs for 18 hours by an Instron testing device. An 1.33mm pressure needle was inserted in the nucleus to measure hydrostatic pressure. Both change of disc height and change of nucleus pressure were measured at 2 samples/s. A double Kelvin–Voigt model was fitted to estimate the time constants of both hydrostatic pressure and disc height loss. The model comprises two time constants: the first modelling a fast change, the second a slow change. A paired t-test was used to compare the time constants of both the pressure and the disc height. Results. The slow time constant of the change of disc height (3.4 hours, sd=0.8) was larger (p=0.0006) than the slow time constant of the change of nucleus pressure (2.4 hours, sd=0.8). The difference between the time constants of the fast regime (0.33 hours resp 0.27 hours) was not significant (p=0.27). Discussion. In contrast to our expectations, we found a difference between the slow time-dependent behavior of the change of disc height and nucleus pressure. The discs reached an equilibrium between internal and external pressure well before the change of disc height came to a stop. This indicates that the change of disc height depends on more variables than mechanical equilibrium alone. Likely, viscoelastic properties of the annulus fibrosis have an important role as well. If confirmed, regenerative therapies should not only focus on restoring nucleus pulposus pressure to regain disc height, but also consider annulus properties

We investigated the distribution of compressive ‘stress’ within cadaver intervertebral discs, using a pressure transducer mounted in a 1.3 mm diameter needle. The needle was pulled along the midsagittal diameter of a lumbar disc with the face of the transducer either vertical or horizontal while the disc was subjected to a constant compressive force. The resulting ‘stress profiles’ were analysed in order to characterise the distribution of vertical and horizontal compressive stress within each disc. A total of 87 discs from subjects aged between 16 and 87 years was examined. Our results showed that age-related degenerative changes reduced the diameter of the central hydrostatic region of each disc (the ‘functional nucleus’) by approximately 50%, and the pressure within this region fell by 30%. The width of the functional annulus increased by 80% and the height of compressive ‘stress peaks’ within it by 160%. The effects of age and degeneration were greater at L4/L5 than at L2/L3, and the posterior annulus was affected more than the anterior. Age and degeneration were themselves closely related, but the stage of degeneration had the greater effect on stress distributions. We suggest that structural changes within the annulus and endplate lead to a transfer of load from the nucleus to the posterior annulus. High ‘stress’ concentrations within the annulus may cause pain, and lead to further disruption

Objectives

Degenerative disc disease (DDD) and osteoarthritis (OA) are relatively frequent causes of disability amongst the elderly; they constitute serious socioeconomic costs and significantly impair quality of life. Previous studies to date have found that aggrecan variable number of tandem repeats (VNTR) contributes both to DDD and OA. However, current data are not consistent across studies. The purpose of this study was to evaluate systematically the relationship between aggrecan VNTR, and DDD and/or OA.

A rat model of lumbar root constriction with an additional sympathectomy in some animals was used to assess whether the sympathetic nerves influenced radicular pain. Behavioural tests were undertaken before and after the operation.

On the 28th post-operative day, both dorsal root ganglia and the spinal roots of L4 and L5 were removed, frozen and sectioned on a cryostat (8 μm to 10 μm). Immunostaining was then performed with antibodies to tyrosine hydroxylase (TH) according to the Avidin Biotin Complex method. In order to quantify the presence of sympathetic nerve fibres, we counted TH-immunoreactive fibres in the dorsal root ganglia using a light microscope equipped with a micrometer graticule (10 x 10 squares, 500 mm x 500 mm). We counted the squares of the graticule which contained TH-immunoreactive fibres for each of five randomly-selected sections of the dorsal root ganglia.

The root constriction group showed mechanical allodynia and thermal hyperalgesia. In this group, TH-immunoreactive fibres were abundant in the ipsilateral dorsal root ganglia at L5 and L4 compared with the opposite side. In the sympathectomy group, mechanical hypersensitivity was attenuated significantly.

We consider that the sympathetic nervous system plays an important role in the generation of radicular pain.

Using a rat model the characteristics of the sensory neurones of the dorsal-root ganglia (DRG) innervating the hip were investigated by retrograde neurotransport and immunohistochemistry.

Fluoro-Gold solution (FG) was injected into the left hip of ten rats. Seven days later the DRG from both sides between T12 and L6 were harvested. The number of FG-labelled calcitonin gene-related peptide-immunoreactive or isolectin B4-binding neurones were counted.

The FG-labelled neurones were distributed throughout the left DRGs between T13 and L5, primarily at L2, L3, and L4. Few FG-labelled isolectin B4-binding neurones were present in the DRGs of either side between T13 and L5, but calcitonin gene-related peptide-immunoreactive neurones made up 30% of all FG-labelled neurones.

Our findings may explain the referral of pain from the hip to the thigh or lower leg corresponding to the L2, L3 and L4 levels. Since most neurones are calcitonin gene-related peptide-immunoreactive peptide-containing neurones, they may have a more significant role in the perception of pain in the hip as peptidergic DRG neurones.