Origin and pathway of sensory nerve fibers to the ventral and dorsal sides of the sacroiliac joint in rats

The Effect of Lumbopelvic Manipulation for Pain Reduction in Patellofemoral Pain Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Patellofemoral pain syndrome (PFPS) is one of the most common etiologies of knee pain and might be relieved with lumbopelvic manipulation (LPM). This meta-analysis aimed to investigate the effects of LPM on pain reduction in patients with PFPS. Electronic databases were searched from inception to December 2023 for randomized controlled trials (RCTs) investigating the effects of LPM on PFPS. The primary outcome was the change in visual analog or numeric rating scale scores assessing pain. Ten studies comprising 346 participants were included. Significant pain reduction was noted in the LPM group (Hedges' g = -0.706, 95% confidence interval [CI] = -1.197 to -0.214, p = 0.005, I2 = 79.624%) compared with the control group. Moreover, pain relief was more pronounced when LPM was combined with other physical therapies (Hedges' g = -0.701, 95% CI = -1.386 to -0.017, p = 0.045, I2 = 73.537%). No adverse events were reported during the LPM. The LPM appears to be a safe and effective adjuvant therapy for pain reduction in patients with PFPS. Clinicians should consider adding LPM to other physical therapies (e.g., quadriceps muscle strengthening) during the management of these patients.

Comparative Efficacy of Clinical Interventions for Sacroiliac Joint Pain: Systematic Review and Network Meta-analysis With Preliminary Design of Treatment Algorithm

OBJECTIVE

We aimed to identify the most effective clinical treatment method for sacroiliac joint (SIJ)-related pain based on the systematic review and network meta-analysis (NMA) to evaluate the comparative efficacy of clinical interventions for sacroiliac joint pain by pooling the randomized controlled trials (RCTs).

METHODS

Our team conducted a systematic review and NMA of RCTs to determine the most effective clinical treatment for SIJ-related pain. We searched the PubMed (MEDLINE), Web of Science, Cochrane Library, and Scopus databases for RCTs until February 2023. The PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines were followed. Pairwise and network meta-analyses were conducted using a random effects model.

RESULTS

Based on the search strategy and inclusion criteria, our systematic review and NMA included 9 randomized studies with 652 participants. Research has mainly focused on various radiofrequency sources, but their number is still low. In the network analysis, according to the NMA and mean ranking probabilities for the improvement of pain intensity (PI) and quality of life (QoL), sacroiliac joint fusion and cooled radiofrequency were associated with high treatment rank for improving PI and QoL in patients with sacroiliac joint pain.

CONCLUSION

This NMA suggest that SIJ fusion and cooled radiofrequency could be potential options for improving the QoL and relieving pain in patients with SIJ-related pain. Comparison studies of outcomes between these 2 procedures with solid methodology and a low risk of bias would be very beneficial to identify the optimal treatment option for this challenging disease.

Sensory innervation of the lumbar 5/6 intervertebral disk in mice

Introduction

Over the years, most back pain-related biological studies focused on the pathogenesis of disk degeneration. It is known that nerve distributions at the outer layer of the annulus fibrosus (AF) may be an important contributor to back pain symptoms. However, the types and origins of sensory nerve terminals in the mouse lumbar disks have not been widely studied. Using disk microinjection and nerve retrograde tracing methods, the current study aimed to characterize the nerve types and neuropathway of the lumbar 5/6 (L5/6) disk in mice.

Methods

Using an anterior peritoneal approach, the L5/6 disk of adult C57BL/6 mice (males, 8–12 weeks) disk microinjection was performed. Fluorogold (FG) was injected into the L5/6 disk using the Hamilton syringe with a homemade glass needle driven by a pressure microinjector. The lumbar spine and bilateral thoracic 13 (Th13) to L6 DRGs were harvested at 10 days after injection. The number of FG+ neurons among different levels was counted and analyzed. Different nerve markers, including anti-neurofilament 160/200 (NF160/200), anti-calcitonin gene-related peptide (CGRP), anti-parvalbumin (PV), and anti-tyrosine hydroxylase (TH), were used to identify different types of nerve terminals in AF and their origins in DRG neurons.

Results

There were at least three types of nerve terminals at the outer layer of L5/6 AF in mice, including NF160/200+ (indicating Aβ fibers), CGRP+ (Aδ and C fibers), and PV+ (proprioceptive fibers). No TH+ fibers (sympathetic nerve fibers and some C-low threshold mechanoreceptors) were noticed in either. Using retrograde tracing methods, we found that nerve terminals in the L5/6 disk were multi-segmentally from Th13-L6 DRGs, with L1 and L5 predominately. An immunofluorescence analysis revealed that FG+ neurons in DRGs were co-localized with NF160/200, CGRP, and PV, but not TH.

Conclusion

Intervertebral disks were innervated by multiple types of nerve fibers in mice, including Aβ, Aδ, C, and proprioceptive fibers. No sympathetic nerve fibers were found in AF. The nerve network of the L5/6 disk in mice was multi-segmentally innervated by the Th13-L6 DRGs (mainly L1 and L5 DRGs). Our results may serve as a reference for preclinical studies of discogenic pain in mice.

The Sacroiliac Joint as a Cause of Pain - Review of the Sacroiliac Joint Morphology and Models for Pain Genesis

INTRODUCTION

In recent years, the sacroiliac joint has become increasingly important as a generator of low back pain with and without pseudo-radicular pain in the legs. Up to 27% of reported back pain is generated by disorders in the sacroiliac joint.

METHOD

This review is based on a selective literature search of the sacroiliac joint (SIJ) as a possible pain generator. It also considers the anatomical structures and innervation of the sacroiliac joint.

RESULTS

The SIJ is a complex joint in the region of the posterior pelvis and is formed by the sacrum and the ilium bones. The SIJ is very limited in movement in all three planes. Joint stability is ensured by the shape and especially by strong interosseous and extraosseous ligaments. Different anatomical variants of the sacroiliac joint, such as additional extra-articular secondary joints or ossification centres, can be regularly observed in CT scans. There is still controversy in the literature regarding innervation. However, there is agreement on dorsal innervation of the sacroiliac joint from lateral branches of the dorsal rami of the spinal nerves S I-S III with proportions of L III and L IV as well S IV. Nerve fibres and mechanoreceptors can also be detected in the surrounding ligaments.

CONCLUSION

A closer look at the anatomy and innervation of the SIJ shows that the SIJ is more than a simple joint. The complex interaction of the SIJ with its surrounding structures opens the possibility that pain arises from this area. The SIJ and its surrounding structures should be included in the diagnosis and treatment of back and leg pain. Published literature include a number of plausible models for the sacroiliac joint as pain generator. The knowledge of the special anatomy, the complex innervation as well as the special and sometimes very individual functionality of this joint, enhance our understanding of associated pathologies and complaints.

Effectiveness of local exercise therapy versus spinal manual therapy in patients with patellofemoral pain syndrome: medium term follow-up results of a randomized controlled trial

Background

Increasing evidence has shown benefits of spinal manipulations in patients with patellofemoral pain syndrome (PFPS). There is scarcity regarding medium term effects of spinal manual therapy on outcome measures in PFPS patients. Therefore, the aim of the present study was to compare the effectiveness of local exercise therapy and spinal manual therapy for knee pain, function and maximum voluntary peak force (MVPF) velocity of the quadriceps in PFPS patients.

Methods

Forty-three patients with PFPS were randomly assigned to a local exercise or spinal manual therapy group. The local exercise group received six sessions (one session per week) of supervised training of the knee-and hip muscles with mobilization of the patellofemoral joint. The spinal manual therapy group received six interventions (one intervention per week) of high velocity low thrust manipulations at the thoracolumbar region, sacroiliac joint, and/or hip. All patients were also asked to do home exercises. Maximum, minimum and current pain were measured using the visual analogue scale. Function was assessed with the anterior knee pain scale (AKPS) and MPFV was recorded using a Biodex System 3 dynamometer. Patients were assessed before intervention, after 6 weeks of intervention and after 6 weeks of follow-up. Between-group differences at assessments were analysed by way of analysis of covariance with Bonferroni correction.

Results

Pain and functionality improved more following spinal manipulative therapy than local exercise therapy. After 6 weeks of intervention the between-group difference (local versus spinal) for maximal pain was 23.4 mm [95% CI: 9.3, 37.6; effect size (ES): 1.04] and − 12.4 [95% CI: − 20.2, − 4.7; ES: 1.00] for the AKPS. At 6 weeks of follow-up the between-group difference for maximal pain was 18.7 mm [95% CI: 1.4, 36.0; ES: 0.68] and − 11.5 [95% CI: − 19.9, − 3.3; ES: − 0.87] for the AKPS.

Conclusions

This study suggests that spinal manual therapy is more effective than local exercise therapy in improving pain and function in patients with PFPS in the medium term. We suggest for future research to investigate whether combining local exercise therapy and spinal manual therapy is more effective than either single intervention on its own.

This clinical trial study was approved by the Medical Ethics Committee METC Z under registration number NL57207.096. and registered retrospectively in ClinicalTrials.gov PRS with registration ID number NCT04748692 on the 10th of February 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04310-9.

Accuracy of the Diagnostic Tests of Sacroiliac Joint Dysfunction

Objective

The purpose of this study was to assess the reliability and validity of motion palpation and pain provocation compared with sacroiliac joint (SIJ) block as the gold-standard assessment method of patients with sacroiliac joint dysfunction (SIJD).

Methods

A cross-sectional study was conducted in the Department of Sports and Exercise Medicine at Rasool Akram Hospital. Forty-eight patients suspected of having SIJD were selected from a total of 150 patients on the basis of a combination of symptoms, physical tests, and magnetic resonance imaging findings. The patients suspected of having SIJD received the SIJ block, to which the accuracy of all the physical tests was compared. Sensitivity, specificity, and positive and negative predictive values were calculated for each test. The receiver operating characteristic curve and the area under the receiver operating characteristic curve were measured.

Results

The Flexion, Abduction and External Rotation (FABER) test had the highest specificity and positive predictive values of the physical tests. Furthermore, the combination of the FABER test and the thigh thrust test improved overall diagnostic ability more so than any of the other test combinations.

Conclusion

A combination of the motion and provocation tests increased specificity and positive predictive values, and the FABER test had the highest of these single values. The palpation tests did not change after the SIJ block, suggesting that their accuracy cannot be determined using this method.

The value of SPECT/CT in localizing pain site and prediction of treatment response in patients with chronic low back pain

In many circumstances, causing sites of low back pain (LBP) cannot be determined only by anatomical imaging. Combined functional and morphological imaging such as bone scan with single-photon emission computed tomography/computed tomography (SPECT/CT) may be helpful in identifying active lesions. The purpose of this study was to evaluate the usefulness of bone SPECT/CT in localizing the pain site and the treatment of chronic LBP. One hundred seventy-five patients suffering from chronic LBP who underwent SPECT/CT were included, retrospectively. All of the patients received multiple general treatments according to the symptoms, and some of them underwent additional target-specific treatment based on SPECT/CT. Numerical rating scale (NRS) pain score was used to assess the pain intensity. Of 175 patients, 127 showed good response to the given therapies, while the rest did not. Overall, 79.4% of patients with definite active lesions showed good response. Patients with mild active or no lesions on SPECT/CT had relatively lower response rate of 63.0%. Good response was observed by the treatment with the guidance of active lesions identified on SPECT/CT. SPECT/CT could be useful in identifying active lesions in patients with chronic LBP and guiding the clinicians to use adequate treatment.

Sensory and autonomic innervation of the cervical intervertebral disc in rats: the pathomechanics of chronic discogenic neck pain

STUDY DESIGN

An immunohistological analysis of the cervical intervertebral disc (IVD).

OBJECTIVE

To investigate sensory and autonomic innervation of the rat cervical IVD.

SUMMARY OF BACKGROUND DATA

Many clinicians are challenged with treating wide-ranging chronic neck pain. Several authors have reported that sympathetic nerves participate in chronic pain, and various sympathectomy procedures can effectively treat chronic pain.

METHODS

The neuro-tracer Fluoro-gold (FG) was applied to the anterior surfaces of C5-C6 IVDs from 10 Sprague-Dawley rats to label the neurons of the innervating dorsal root ganglion (DRG), stellate ganglion (SG; sympathetic ganglion), and nodose ganglion (NG; parasympathetic ganglion). Seven days postsurgery, DRGs from level C1-C8, SG, and NG neurons were harvested, sectioned, and immunostained for calcitonin gene-related peptide (CGRP; a marker for peptide-containing neurons) and isolectin B4 (IB4; a marker for nonpeptide-containing neurons). The proportion of FG-labeled DRG neurons that were CGRP-immunoreactive (CGRP-IR), IB4-binding, and non-CGRP-IR and IB4-binding, and the proportion of FG-labeled SG neurons and NG neurons were calculated.

RESULTS

FG-labeled neurons innervating the C5-C6 IVD were distributed throughout the C2-C8 DRGs. The proportions of FG-labeled DRG neurons that were CGRP-IR, IB4-binding, non-CGRP-IR and IB4-binding, as well as SG neurons, and NG neurons were 20.6%, 3.3%, 55.7%, 8.9%, and 11.5%, respectively. The proportion of CGRP-IR FG-labeled DRG neurons was significantly higher than the proportion of IB4-binding FG-labeled DRG neurons at each level (P < 0.05).

CONCLUSION

The C5-C6 IVD was innervated multisegmentally from neurons of the C2-C8 DRG, SG, and NG. Overall, 79.6% of the nerve fibers innervating the IVD were sensory nerves and 20.4% were autonomic nerves. Furthermore, 23.9% of the nerve fibers innervating the IVD were afferent sensory pain-related nerves, 8.9% were efferent sympathetic nerves, and 11.5% were efferent parasympathetic nerves. These findings may explain the wide-ranging and chronic discogenic pain that occurs via the somatosensory and autonomic nervous system.

Investigation of dichotomizing sensory nerve fibers projecting to the lumbar multifidus muscles and intervertebral disc or facet joint or sacroiliac joint in rats

STUDY DESIGN

Immunohistological analysis of dichotomizing sensory nerve fibers projecting to the lumbar multifidus muscles and intervertebral disc (IVD), facet joint (FJ), or sacroiliac joint (SIJ) in rats.

OBJECTIVE

To elucidate dichotomizing sensory nerve fibers projecting to the lumbar multifidus muscles and to IVDs, FJs, or SIJs.

SUMMARY OF BACKGROUND DATA

Clinically, the origin of low back pain remains unknown. Multiple studies have identified lumbar muscles, IVDs, FJs, and SIJs as sources of low back pain. Pain may originate directly from lumbar muscles or be referred from the spine, or both. Dorsal root ganglion (DRG) neurons with dichotomizing axons have been reported in several species and are thought to be related to referred pain.

METHODS

We used 2 neurotracers, 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI) and fluorogold (FG), in this double-labeling study involving 30 Sprague Dawley rats. DiI was applied to lumbar multifidus muscles in all rats. Simultaneously, FG was applied to the anterior left portion of L5-L6 IVDs in the IVD group (n = 10), to the left L5-L6 FJs in the FJ group (n = 10), and to the left SIJs in the SIJ group (n = 10). Fourteen days after surgery, left DRGs from L1 to L6 were harvested, sectioned, and observed under a fluorescence microscope.

RESULTS

We verified the existence of double-labeled DRG neurons (i.e., dichotomizing sensory nerve fibers) projecting to lumbar multifidus muscles and to IVDs, FJs, or SIJs, depending on the group. The proportion of double-labeled cells in all DiI-labeled DRG neurons was higher in the FJ group (6.8%) and SIJ group (7.1%) than in the IVD group (3.1%) (P < 0.05).

CONCLUSION

Our results document the presence of dichotomizing sensory nerve fibers projecting to lumbar multifidus muscles and to IVDs, FJs, and SIJs. Referred low back muscle pain may reflect disorders of lumbar posterior structures, such as FJs and SIJs, rather than disorders of lumbar anterior structures, such as IVDs.

Possible nociceptive structures in the sacroiliac joint cartilage: An immunohistochemical study

The sacroiliac joint (SI joint) is a known source of low back pain. In the absence of validated physical signs and imaging studies, the diagnosis of SI joint pain can be secured by positive response to SI joint intra-articular infiltration with local anesthetics. The current anatomical and histological knowledge concerning intra-articular structures of the sacroiliac joint is insufficient to explain the efficacy of this infiltration. Consequently, this study was undertaken to detect the intra-articular presence of substance P and calcitonin gene-related peptide (CGRP) positive nerve fibers, providing indirect evidence of nociceptive innervation of the SI joint. Free-floating sections, obtained from iliac and sacral cartilage and subchondral bone of the SI joint and adjacent ligamentous tissue, of 10 human cadavers were studied immunohistochemically. Tissue of nine human cadavers showed the presence of substance P and CGRP immunoreactivity in the superficial layer of sacral and iliac cartilage, and the surrounding ligamentous structures. Subchondral bone reacted weakly to the antisera used. These findings support the view that the SI joint may be capable of intra-articular nociception and may explain the positive response to the intra-articular deposition of local anesthetic.

Clinical study of low back pain and radicular pain pathways by using l2 spinal nerve root infiltration: a randomized, controlled, clinical trial

STUDY DESIGN

Randomized control trial (RCT) for L2 spinal nerve infiltration (L2 block) in clinical cases.

OBJECTIVES

To confirm or refute the effect of L2 block using RCT, and to study the pathway of low back pain (LBP) and radicular pain in clinical cases.

SUMMARY OF BACKGROUND DATA

It has been reported in animal experiments that one of the main pathways of pain originating from the lumbar spine is the sympathetic trunk through the L2 spinal nerve rootvia sympathetic afferents.

METHODS

To evaluate the effectiveness of L2 block, patients who had LBP and were treated with nonsteroidal anti-inflammatory drugs for at least 2 weeks were then randomized to the L2 block or control block groups. The intensities of LBP and radicular pain were measured using visual analog scale and face scale before and at 5 minutes and 7 days after the injection. These values were compared, and the effects of the injections on the pain pathway were studied.

RESULTS

The average visual analog scale scores for LBP before and at 5 minutes and 7 days after the injection were 69, 14, and 44 mm in the L2 block group and 68, 62, and 59 mm in the control block group, respectively. After L2 block, 28 patients reported adequate therapeutic effect at 10 weeks, and the effect lasted for more than 24 weeks in 10 of these patients. After control block, 9 patients reported adequate therapeutic effect at 10 and 24 weeks.

CONCLUSION

The LBP and radicular pain pathways were likely interrupted by L2 block. An L2 block is useful in reducing LBP due to the disorders of L2 spinal nerve-innervated structures, such as the disc, facet joint, and sacroiliac joint. However, the therapeutic value of an L2 block may be occasionally insufficient to alleviate pain completely because of the short duration of its' effect.

Sacroiliac joint dysfunction: evaluation and treatment

Sacroiliac joint (SIJ) dysfunction is once again garnering attention as a treatable diagnosis for the millions of individuals suffering from acute and chronic low back pain. Theoretically, excessive or restricted motion at the SIJ can alter the mechanics of the spine and pelvis causing pain. Oft en the clinician's history and physical examination are nonspecific in the evaluation of low back pain and a high index of suspicion is required to consider SIJ dysfunction as the cause for the patient's symptoms. Multiple physical examination maneuvers exist to detect SIJ dysfunction, but none are individually sensitive or specific enough to diagnose SIJ dysfunction alone. The clinician should learn 3 to 5 tests that can easily be performed and replicated for the evaluation of SIJ dysfunction and use them consistently in patients presenting with low back pain. Sacroiliac joint anesthetic blocks using computed tomography (CT) or fluoroscopic-guided injection are considered the gold standards for diagnosing SIJ dysfunction as the cause for nonspecific low back pain. Imaging studies and laboratory evaluations are generally unnecessary for the diagnosis of SIJ dysfunction unless specific elements of the history and physical suggest alternate etiologies. Interventions to treat the pain of SIJ dysfunction include nonsteroidal anti-inflammatory drugs (NSAIDs), physical therapy, corti costeroid injections, osteopathic manipulation, radiofrequency denervation, SIJ belts, and surgery. While there are few high-level evidence studies evaluating and comparing these treatments in individuals with SIJ pain, patients may respond to one, or a combination of these treatments.

KEYWORDS

sarcoiliac joint; sarcoiliac joint dysfunction; spine; low back pain.

Structural and biomechanical aspects of equine sacroiliac joint function and their relationship to clinical disease

Pain originating from the sacroiliac joint (SIJ) in horses has long been associated with poor performance, yet specific diagnosis of sacroiliac dysfunction (SID) has been difficult to achieve. Clinical presentation of SID appears to fall into two categories. The first, presenting as pain and poor performance, is responsive to local analgesia of periarticular structures with poorly defined pathology. The second presents primarily as poor performance with bony pathological changes as a result of chronic instability. Diagnostic tests based on biomechanics as well as manual provocation for SIJ pain have formed the basis of tests currently used to diagnose SIJ dysfunction in humans. This review summarises the anatomy and biomechanics of the equine SIJ and current biomechanical, innervation and motor control concepts in human SID. The relationship between abnormal SIJ motion and altered neuromotor control with clinical disease of the equine SIJ are discussed. Future utilisation of these principles to develop new diagnostic and management tools for the equine SID is promising.

Cauda equina syndrome presentation of sacral insufficiency fractures

INTRODUCTION

Sacral insufficiency fractures are a well recognised cause for low back, buttock and groin pain in the elderly. However, over a 4 year period, four patients have presented with symptoms of cauda equina syndrome, who were found on investigation to have acute sacral insufficiency fracture without any other aetiological spinal abnormality.

PATIENTS AND METHOD

Four patients who presented to the spinal surgeons of our institution with symptoms of cauda equina syndrome were referred for spinal MR. Sagittal and axial T1 and T2 weighted turbo spin echo sequences of the lower thoracic and lumbar spine were performed on all patients. Subsequent studies included MR of the sacrum supplemented where appropriate by CT and technetium MDP bone scintigraphy.

RESULTS

No evidence of a compressive lesion of the lower thoracic or lumbar spine was present in any of the four patients. Dedicated MR examination of the sacrum in these patients revealed unilateral acute insufficiency fractures involving zone 1 from S1 to S3 extending from the sacro-iliac joint to the lateral margin of the sacral foramen. There was no evidence of compression of the sacral nerve roots. The possible mechanism for the symptomatic presentation is discussed.

CONCLUSION

Sacral insufficiency fractures should be excluded in elderly or osteoporotic patients presenting with cauda equina syndrome who have no evidence of compression in the thoraco-lumbar MR studies.

Provocative sacroiliac joint maneuvers and sacroiliac joint block are unreliable for diagnosing sacroiliac joint pain

Mapping studies of pain elicited by injections into the sacroiliac joints (SIJs) suggest that sacroiliac joint syndrome (SIJS) may manifest as low back pain, sciatica, or trochanteric pain. Neither patient-reported symptoms nor provocative SIJ maneuvers are sensitive or specific for SIJS when SIJ block is used as the diagnostic gold standard. This has led to increasing diagnostic use of SIJ block, a procedure in which an anesthetic is injected into the joint under arthrographic guidance. However, several arguments cast doubt on the validity of SIJ block as a diagnostic gold standard. Thus, the effects of two consecutive blocks are identical in only 60% of cases, and the anesthetic diffuses out of the joint in 61% of cases, often coming into contact with the sheaths of the adjacent nerve trunks or roots, including the lumbosacral trunk (which may contribute to pain in the groin or thigh) and the L5 and S1 nerve roots. These data partly explain the limited specificity of SIJ block for the diagnosis of SIJS and the discordance between the pain elicited by the arthrography injection and the response to the block. The limitations of provocative maneuvers and SIJ blocks may stem in part from a contribution of extraarticular ligaments to the genesis of pain believed to originate within the SIJs. These ligaments include the expansion of the iliolumbar ligaments, the dorsal and ventral sacroiliac ligaments, the sacrospinous ligaments, and the sacrotuberous ligaments (sacroiliac joint lato-sensu). They play a role in locking or in allowing motion of the SIJs. Glucocorticoids may diffuse better than anesthetics within these ligaments. Furthermore, joint fusion may result in ligament unloading.

Distribution and immunocytochemical characterization of dorsal root ganglion neurons innervating the lumbar intervertebral disc in rats: a review

Previously, it was believed that the lumbar intervertebral disc was innervated segmentally by dorsal root ganglion (DRG) neurons via the sinuvertebral nerves. Recently, it was demonstrated using retrograde tracing methods that the lower disc (L5-L6) is innervated predominantly by upper (L1 and L2) DRG neurons via the sympathetic trunks. Furthermore, we investigated the expression of various pain-related molecules such as calcitonin gene-related peptide (CGRP), isolectin B4 (IB4), P2X(3) receptor and vanniloid receptor 1 (VR1) in DRG neurons innervating the disc using a combination of immunostaining with the retrograde tracing method. This review outlines the distribution and immunocytochemical characterization of DRG neurons innervating the disc. Small nociceptive DRG neurons are classified into nerve growth factor (NGF)-dependent neurons and glial cell line-derived neurotrophic factor (GDNF)-dependent neurons and they can be distinguished by their reactivity for CGRP and IB4, respectively. We found that about half of the neurons innervating the disc were CGRP-immunoreactive (-ir), whilst, only 0.6% of the DRG neurons were IB4-positive, thereby indicating that NGF-dependent neurons are the main subpopulation which transmits and modulates nociceptive information from the disc. In addition, we also demonstrated P2X(3)- and VR1-immunoreactivity in DRG neurons innervating the disc and noted that they were mainly localized in NGF-dependent neurons. It is well known that NGF has sensitizing effects on DRG neurons, with a recent study demonstratng the presence of NGF in the painful intervertebral disc. Therefore, it is suggested that NGF is involved in the generation of discogenic low back pain.

Stereoscopic structure of sensory nerve fibers in the lumbar spine and related tissues

STUDY DESIGN

Neurotracer was applied to various sites in the rat lumbar spine and related tissues. The segmental distribution of labeled neurons in dorsal root ganglia (DRG) was investigated.

OBJECTIVES

To clarify the stereoscopic structure of afferent fibers innervating the lumbar spine and related tissues.

SUMMARY OF BACKGROUND DATA

Afferent fibers in the rat L5-L6 lumbar intervertebral disc are reported to originate from neurons in L1 and L2 DRG. However, anatomic studies determined that each dorsal ramus of the spinal nerve sends nerves to dorsal elements of the corresponding lumbar vertebra.

METHODS

Fluorescent neurotracer DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) was applied to various sites of the lumbar spine and related tissues in the L2, L5, and L6 levels in rats. DRG were sectioned 3 weeks after DiI application. Rostrocaudal distribution of DiI-labeled neurons was investigated.

RESULTS

At L5, DiI-labeled neurons were prominent in DRG L3 for the lamina, L2 for the spinous process, L2 for the back muscle fascia, and L1 for the skin. Dorsal elements are therefore innervated by neurons in more rostral DRG. In the transverse plane, the more distant from the DRG a site was, the more rostral the DRG innervating the site. This structure suggested a concentric innervation pattern in the transverse plane.

CONCLUSION

Stereoscopically, the peripheral innervation territory of a lumbar DRG is conical, with the apex at the ganglion and the base circumference located on the dermatome. The lumbar spine itself is involved in the conical innervation territories of DRG.

Facet blocks and sacroiliac joint injections

Facet and sacroiliac joint pathology are not an uncommon cause of back or neck pain. Imaging-guided techniques provide ready access to these synovial joints. Percutaneous injection of the facet or sacroiliac joints yields important diagnostic information as to whether or not the interrogated joint is involved in the patient's pain syndrome. The injection of a steroid-anesthetic mixture into these joints is capable of providing significant, albeit temporary, pain relief.