The nerve supply of the lumbar intervertebral disc

Behavioral signs of axial low back pain and motor impairment correlate with the severity of intervertebral disc degeneration in a mouse model

BACKGROUND CONTEXT

Chronic low back pain is debilitating and difficult to treat. Depending on the etiology, responses to treatments vary widely. Although chronic low back pain is frequently related to intervertebral disc degeneration, the relationship between disc degeneration severity and clinical symptoms are still poorly understood. In humans, studies investigating the relationship between disc degeneration severity and low back pain are limited by the difficulty of obtaining disc samples from well-characterized patients and pain-free controls. We have previously described the secreted protein, acidic, rich in cysteine (SPARC)-null mouse model of chronic low back pain. SPARC is a matricellular protein involved in regulating the assembly and composition of extracellular matrix. The SPARC-null mice develop age-dependent disc degeneration of increasing severity accompanied by behavioral signs suggestive of axial low back pain, radiating leg pain, and motor impairment. The existence of this model allows for examination of the relationships between clinical symptoms in vivo and pathological signs of disc degeneration ex vivo.

PURPOSE

The goal of this study was to explore the relationship between behavioral signs of pain and the severity of lumbar disc degeneration using the SPARC-null mouse model of disc degeneration-related low back pain.

STUDY DESIGN

This study used a cross-sectional, multiple-cohort behavioral and histological study of disc degeneration and behavioral symptoms in a mouse model of low back pain associated with disc degeneration.

METHODS

SPARC-null and wild-type control mice ranging from 6 to 78 weeks of age were used in this study. The severity of disc degeneration was determined by ex vivo analysis of the lumbar spine using colorimetric histological staining and a scoring system adapted from the Pfirrmann scale. Behavioral signs of axial low back pain, radiating leg pain, and motor impairment were quantified as tolerance to axial stretching in the grip force assay, hypersensitivity to cold or mechanical stimuli on the hindpaw (acetone and von Frey tests), and latency to fall in the rotarod assay, respectively.

RESULTS

The SPARC-null mice exhibited decreased tolerance to axial stretching, hindpaw cold hypersensitivity, and motor impairment compared with age-matched control mice. The severity of disc degeneration increased with age in both SPARC-null and control mice and by 78 weeks of age, the same proportion of lumbar discs were abnormal in SPARC-null and control mice. However, the degree of degeneration was more severe in the SPARC-null mice. In both SPARC-null and control mice, tolerance to axial stretching but not hindpaw cold sensitivity correlated with disc degeneration severity. Motor impairment correlated with degeneration severity in the SPARC-null mice only.

CONCLUSIONS

These data suggest that internal disc disruption contributes to axial low back pain and motor impairment but not to radiating leg pain. These results have implications for the optimization of mechanism-based treatments strategies.

Total Disc Replacement in Lumbar Degenerative Disc Diseases

More than 10 years have passed since lumbar total disc replacement (LTDR) was introduced for the first time to the world market for the surgical management of lumbar degenerative disc disease (DDD). It seems like the right time to sum up the relevant results in order to understand where LTDR stands on now, and is heading forward to. The pathogenesis of DDD has been currently settled, but diagnosis and managements are still controversial. Fusion is recognized as golden standard of surgical managements but has various kinds of shortcomings. Lately, LTDR has been expected to replace fusion surgery. A great deal of LTDR reports has come out. Among them, more than 5-year follow-up prospective randomized controlled studies including USA IDE trials were expected to elucidate whether for LTDR to have therapeutic benefit compared to fusion. The results of these studies revealed that LTDR was not inferior to fusion. Most of clinical studies dealing with LTDR revealed that there was no strong evidence for preventive effect of LTDR against symptomatic degenerative changes of adjacent segment disease. LTDR does not have shortcomings associated with fusion. However, it has a potentiality of the new complications to occur, which surgeons have never experienced in fusion surgeries. Consequently, longer follow-up should be necessary as yet to confirm the maintenance of improved surgical outcome and to observe any very late complications. LTDR still may get a chance to establish itself as a substitute of fusion both nominally and virtually if it eases the concerns listed above.

Combined transforaminal lumbar interbody fusion with posterolateral instrumented fusion for degenerative disc disease can be a safe and effective treatment for lower back pain

BACKGROUND

Lumbar fusion is a proven treatment for chronic lower back pain (LBP) in the setting of symptomatic spondylolisthesis and degenerative scoliosis; however, fusion is controversial when the primary diagnosis is degenerative disc disease (DDD). Our objective was to evaluate the safety and effectiveness of lumbar fusion in the treatment of LBP due to DDD.

MATERIALS AND METHODS

Two-hundred and five consecutive patients with single or multi-level DDD underwent lumbar decompression and instrumented fusion for the treatment of chronic LBP between the years of 2008 and 2011. The primary outcome measures in this study were back and leg pain visual analogue scale (VAS), patient reported % resolution of preoperative back pain and leg pain, reoperation rate, perioperative complications, blood loss and hospital length of stay (LOS).

RESULTS

The average resolution of preoperative back pain per patient was 84% (n = 205) while the average resolution of preoperative leg pain was 90% (n = 190) while a mean follow-up period of 528 days (1.5 years). Average VAS for combined back and leg pain significantly improved from a preoperative value of 9.0 to a postoperative value of 1.1 (P ≤ 0.0001), a change of 7.9 points for the cohort. The average number of lumbar disc levels fused per patient was 2.3 (range 1-4). Median postoperative LOS in the hospital was 1.2 days. Average blood loss was 108 ml perfused level. Complications occurred in 5% of patients (n = 11) and the rate of reoperation for symptomatic adjacent segment disease was 2% (n = 4). Complications included reoperation at index level for symptomatic pseudoarthrosis with hardware failure (n = 3); surgical site infection (n = 7); repair of cerebrospinal fluid leak (n = 1), and one patient death at home 3 days after discharge.

CONCLUSION

Lumbar fusion for symptomatic DDD can be a safe and effective treatment for medically refractory LBP with or without leg pain.

Electromyography in musculoskeletal pain: A reappraisal and practical considerations

BACKGROUND

Patients with musculoskeletal pain (MSP) and local tenderness in the back and extremities are frequently referred to electromyography (EMG) laboratory to assess the integrity of the spinal nerve roots, peripheral nerves, and skeletal muscles. When focal muscle weakness and anatomical sensory deficits are clinically evident, this procedure is almost always abnormal. In some situations, when the presenting symptoms consist of local pain and tenderness without neuromuscular deficits, its diagnostic utility becomes questionable as illustrated in the present study.

METHODS

EMG findings of 75 patients referred for evaluation of local MSP and tenderness in the neck and lower back and in the upper and lower extremities were reviewed. These patients were selected from a group of 200 patients referred for evaluation of unilateral local pain and tenderness in various parts of the body. All EMG procedures and clinical neurologic examination were performed by the author and all underwent magnetic resonance imaging of the affected parts of the body prior to the procedure. None of the 75 patients studied had concurrent medical disorders or had previous spinal root injuries or surgeries to the spine.

RESULTS

All 75 patients in this study showed normal EMG of the affected extremities and normal peripheral nerve conduction study. Those with herniated disc in the cervical or lumbar spine presenting with local pain and tenderness in the neck and lower back but without neurologic deficits or clear radicular symptoms, had normal study also. The remaining 125 patients excluded from the study, had various EMG and peripheral nerve abnormalities that can be attributed to concurrent medical disorders and previous injuries to the spinal roots.

CONCLUSIONS

Use of EMG in the diagnosis of local MSP, unless associated with clinical neurologic deficits, almost always yields negative results. The utility of this procedure is limited to pathology in the motor unit. It cannot assess the function of the sensory components of the spinal roots, small-diameter sensory nerves, and the sensory innervation of the spine via sinuvertebral nerve. Therefore, if the motor unit is anatomically and physiologically intact, the procedure is of little value in the diagnosis of MSP. Likewise, peripheral nerve conduction study is likely to be normal unless clear neurologic deficits are present. The present study illustrates that a good history and meticulous neurologic examination should be an integral part of an ideal electrodiagnostic procedure.

A Randomized Controlled Trial Comparing Transforaminal Lumbar Interbody Fusion and Uninstrumented Posterolateral Fusion in the Degenerative Lumbar Spine

Study Design Randomized controlled trial. Objective Despite a large number of publications of outcomes after spinal fusion surgery, there is still no consensus on the efficacy of the several different fusion methods. The aim of this study was to determine whether transforaminal lumbar interbody fusion (TLIF) results in an improved clinical outcome compared with uninstrumented posterolateral fusion (PLF) in the surgical treatment for chronic low back pain. Methods This study included 135 patients with degenerative disk disease (n = 96) or postdiskectomy syndrome (n = 39). Inclusion criteria were at least 1 year of back pain with or without leg pain in patients aged 20 to 65 with one- or two-level disease. Exclusion criteria were sequestration of disk hernia, psychosocial instability, isthmic spondylolisthesis, drug abuse, and previous spine surgery other than diskectomy. Pain was assessed by visual analog scale (pain index). Functional disability was quantified by the disability rating index and Oswestry Disability Index. The global outcome was assessed by the patient and classified as much better, better, unchanged, or worse. The patients were randomized to conventional uninstrumented PLF (n = 67) or TLIF (n = 68). PLF was performed in a standardized fashion using autograft. TLIF was performed with pedicle titanium screw fixation and a porous tantalum interbody spacer with interbody and posterolateral autograft. The clinical outcome measurements were obtained preoperatively and at 12 and 24 months postoperatively. The 2-year follow-up rate was 98%. Results The two treatment groups improved significantly from preoperatively to 2 years' follow-up. At final follow-up, the results in the TLIF group were significantly superior to those in the PLF group in pain index (2.0 versus 3.9, p = 0.007) and in disability rating index (22 versus 36, p = 0.003). The Oswestry Disability Index was better in the TLIF group (20 versus 28, p = 0.110, not significant). The global assessment was clearly superior in the TLIF group: 63% of patients scored "much better" in the TLIF group as compared with 48% in the PLF group (p = 0.017). Conclusions The results of the current study support the use of TLIF rather than uninstrumented PLF in the surgical treatment of the degenerative lumbar spine. The less optimal outcome after uninstrumented PLF may be explained by the much higher reoperation rate.

Is lumbar lordosis related to low back pain development during prolonged standing?

BACKGROUND

An induced-pain paradigm has been used in back-healthy people to understand risk factors for developing low back pain during prolonged standing.

OBJECTIVES

The purposes of this study were to (1) compare baseline lumbar lordosis in back-healthy participants who do (Pain Developers) and do not (Non-Pain Developers) develop low back pain during 2 h of standing, and (2) examine the relationship between lumbar lordosis and low back pain intensity.

DESIGN

Cross-sectional.

METHOD

First, participants stood while positions of markers placed superficial to the lumbar vertebrae were recorded using a motion capture system. Following collection of marker positions, participants stood for 2 h while performing light work tasks. At baseline and every 15 min during standing, participants rated their low back pain intensity on a visual analog scale. Lumbar lordosis was calculated using marker positions collected prior to the 2 h standing period. Lumbar lordosis was compared between pain developers and non-pain developers. In pain developers, the relationship between lumbar lordosis and maximum pain was examined.

RESULTS/FINDINGS

There were 24 (42%) pain developers and 33 (58%) non-pain developers. Lumbar lordosis was significantly larger in pain developers compared to non-pain developers (Mean difference = 4.4°; 95% Confidence Interval = 0.9° to 7.8°, Cohen's d = 0.7). The correlation coefficient between lumbar lordosis and maximum pain was 0.46 (P = 0.02).

CONCLUSION

The results suggest that standing in more lumbar lordosis may be a risk factor for low back pain development during prolonged periods of standing. Identifying risk factors for low back pain development can inform preventative and early intervention strategies.

Computer-aided combined movement examination of the lumbar spine and manual therapy implications: Case report

Combined movement examination (CME) of the lumbar spine has been recommended for clinical examination as it confers information about mechanical pain patterns. However, little quantitative study has been undertaken to validate its use in manual therapy practice. This study used computer aided CME to develop a normal reference range, and to guide provisional diagnosis and management. Two cases were assessed, before and after manual therapy using CME, a pain Visual Analogue Scale, the Roland Morris Low Back Pain and Disability Questionnaire and the Short Form (SF-12) Health Survey. Diagnosis and management were guided by comparing each CME pattern with the age and gender matched reference range. Self-reports data and CME total change scores were markedly improved for both cases, particularly for the most painful and restricted CME directions. This report describes how computer-aided CME and a normal reference range may be used objectively to inform a diagnosis and as an outcome measure in cases of mechanical LBP. Future investigations of cases with specific lumbar pathologies are required to validate this concept.

Pathophysiology, diagnosis, and treatment of discogenic low back pain

Discogenic low back pain is a serious medical and social problem, and accounts for 26%-42% of the patients with chronic low back pain. Recent studies found that the pathologic features of discs obtained from the patients with discogenic low back pain were the formation of the zones of vascularized granulation tissue, with extensive innervation in fissures extending from the outer part of the annulus into the nucleus pulposus. Studies suggested that the degeneration of the painful disc might originate from the injury and subsequent repair of annulus fibrosus. Growth factors such as basic fibroblast growth factor, transforming growth factor β1, and connective tissue growth factor, macrophages and mast cells might play a key role in the repair of the injured annulus fibrosus and subsequent disc degeneration. Although there exist controversies about the role of discography as a diagnostic test, provocation discography still is the only available means by which to identify a painful disc. A recent study has classified discogenic low back pain into two types that were annular disruption-induced low back pain and internal endplate disruption-induced low back pain, which have been fully supported by clinical and theoretical bases. Current treatment options for discogenic back pain range from medicinal anti-inflammation strategy to invasive procedures including spine fusion and recently spinal arthroplasty. However, these treatments are limited to relieving symptoms, with no attempt to restore the disc's structure. Recently, there has been a growing interest in developing strategies that aim to repair or regenerate the degenerated disc biologically.

Lumbar spine fusion for chronic low back pain due to degenerative disc disease: a systematic review

STUDY DESIGN

Systematic literature review.

OBJECTIVE

To categorize published evidence systematically for lumbar fusion for chronic low back pain (LBP) in order to provide an updated and comprehensive analysis of the clinical outcomes.

SUMMARY OF BACKGROUND DATA

Despite a large number of publications of outcomes of spinal fusion surgery for chronic LBP, there is little consensus on efficacy.

METHODS

A MEDLINE and Cochrane database search was performed to identify published articles reporting on validated patient-reported clinical outcomes measures (2 or more of visual analogue scale, Oswestry Disability Index, Short Form [36] Health Survey [SF-36] PCS, and patient satisfaction) with minimum 12 months of follow-up after lumbar fusion surgery in adult patients with LBP due to degenerative disc disease. Twenty-six total articles were identified and stratified by level of evidence: 18 level 1 (6 studies of surgery vs. nonoperative treatment, 12 studies of alternative surgical procedures), 2 level 2, 2 level 3, and 4 level 4 (2 prospective, 2 retrospective). Weighted averages of each outcomes measure were computed and compared with established minimal clinically important difference values.

RESULTS

Fusion cohorts included a total of 3060 patients. The weighted average improvement in visual analogue scale back pain was 36.8/100 (standard deviation [SD], 14.8); in Oswestry Disability Index 22.2 (SD, 14.1); in SF-36 Physical Component Scale 12.5 (SD, 4.3). Patient satisfaction averaged 71.1% (SD, 5.2%) across studies. Radiographical fusion rates averaged 89.1% (SD, 13.5%), and reoperation rates 12.5% (SD, 12.4%) overall, 9.2% (SD, 7.5%) at the index level. The results of the collective studies did not differ statistically in any of the outcome measures based on level of evidence (analysis of variance, P > 0.05).

CONCLUSION

The body of literature supports fusion surgery as a viable treatment option for reducing pain and improving function in patients with chronic LBP refractory to nonsurgical care when a diagnosis of disc degeneration can be made.

New hypothesis of chronic back pain: low pH promotes nerve ingrowth into damaged intervertebral disks

The pathogenesis of low back pain is still elusive. Here, we proposed a new hypothesis that low pH is a possible cause of the development and progression of low back pain. We propose that low pH promotes the production of the inflammatory mediators and the depletion of proteoglycan in the damaged intervertebral disk. The inflammation response, evoked by the dorsal root ganglia, changes the delicate nutrient balance in the nucleus, resulting in a vicious cycle and leading to choronic back pain. Our hypothesis may explain many of the available clinical and experimental data on low back pain, thus it may help elucidate the pathogenesis of low back pain and improve clinical management.

Is section of the sympathetic rami communicantes by laparoscopy in patients with refractory low back pain efficient?

OBJECTIVE

The objective of this prospective innovative treatment is to section the pain pathways carried by sympathetic lumbar rami communicantes to achieve lasting pain relief of refractory low back pain.

METHODS

From December 2005 to September 2008, nine patients were operated by bilateral section of rami communicantes for a refractory low back pain. As a diagnostic and predictive test, all patients had, before surgery, a local anaesthetic infiltration of the sympathetic trunk at L2 performed with computed tomography guidance. Surgery is indicated if the tests lead to a reduction in pain of at least 50 %. The procedure, using a retroperitoneal laparoscopic approach, consisted to identify the sympathetic trunk and to section all lumbar rami communicantes from L1 to L2.

RESULTS

No intraoperative complications were observed. The mean postoperative follow-up was 29 ± 15 months. At the last follow-up, only 22 % (2/9) patients had an improvement of their low back pain with this surgery but with a minimal effect (30 and 50 % reduction of pain). An improvement of quality of life was observed in 33 % (3/9) of cases. Due to persistent pain, four patients had a spinal cord stimulation after this surgery.

CONCLUSIONS

Section the pain pathways carried by sympathetic lumbar rami communicantes for refractory low back pain improved 22 % of patients at the last follow-up of 29 months.

Fluoroscopic lumbar interlaminar epidural injections in managing chronic lumbar axial or discogenic pain

Among the multiple causes of chronic low back pain, axial and discogenic pain are common. Various modalities of treatments are utilized in managing discogenic and axial low back pain including epidural injections. However, there is a paucity of evidence regarding the effectiveness, indications, and medical necessity of any treatment modality utilized for managing axial or discogenic pain, including epidural injections. In an interventional pain management practice in the US, a randomized, double-blind, active control trial was conducted. The objective was to assess the effectiveness of lumbar interlaminar epidural injections of local anesthetic with or without steroids for managing chronic low back pain of discogenic origin. However, disc herniation, radiculitis, facet joint pain, or sacroiliac joint pain were excluded. Two groups of patients were studied, with 60 patients in each group receiving either local anesthetic only or local anesthetic mixed with non-particulate betamethasone. Primary outcome measures included the pain relief-assessed by numeric rating scale of pain and functional status assessed by the, Oswestry Disability Index, Secondary outcome measurements included employment status, and opioid intake. Significant improvement or success was defined as at least a 50% decrease in pain and disability. Significant improvement was seen in 77% of the patients in Group I and 67% of the patients in Group II. In the successful groups (those with at least 3 weeks of relief with the first two procedures), the improvement was 84% in Group I and 71% in Group II. For those with chronic function-limiting low back pain refractory to conservative management, it is concluded that lumbar interlaminar epidural injections of local anesthetic with or without steroids may be an effective modality for managing chronic axial or discogenic pain. This treatment appears to be effective for those who have had facet joints as well as sacroiliac joints eliminated as the pain source.

Disk injury in rats produces persistent increases in pain-related neuropeptides in dorsal root ganglia and spinal cord glia but only transient increases in inflammatory mediators: pathomechanism of chronic diskogenic low back pain

STUDY DESIGN

Immunohistological analysis in an injured intervertebral disk (IVD) model.

OBJECTIVE

To elucidate and compare in rats the behavior of the sensory nervous system and inflammatory mediators in experimentally injured IVDs.

SUMMARY OF BACKGROUND DATA

Multiple human and animal studies have verified the presence of sensory nerve fibers in IVDs or investigated the behavior of inflammatory mediators in injured IVDs, but no in vivo study to date has examined the relationship between the 2.

METHODS

Eight-week-old female rats were used. In the disk-injured group, L5/L6 disks were injured with a 24-gauge needle; simultaneously, the neurotracer Fluoro-gold was injected into the L5/L6 IVD. The L5/L6 IVD dorsal root ganglia (DRGs) from the L1 to L6 levels, and the spinal cord was resected at several time points after surgery. Nerve growth factor, tumor necrosis factor (TNF)-α and interleukin (IL)-6 production in the IVDs were quantified using enzyme-linked immunosorbent assay. DRGs were immunostained for calcitonin gene-related peptide, and spinal cord sections were immunostained for ionized calcium-binding adaptor molecule-1 and glial fibrillary acidic protein.

RESULTS

Nerve growth factor, and TNF-α levels (through 1 week) and IL-6 levels (through 4 days) were significantly higher in the disk-injured group than in the noninjured group (P < 0.05). However, starting at 2 weeks (nerve growth factor and TNF-α) or 1 week (IL-6), the differences in inflammatory mediator levels between the 2 groups no longer were significant. In contrast, the percentage of calcitonin gene-related peptide-immunoreactive neurons among Fluoro-gold-labeled DRG neurons, and the numbers of ionized calcium-binding adaptor molecule-1-immunoreactive microglia and glial fibrillary acidic protein-immunoreactive astrocytes in the spinal dorsal horn remained significantly higher in the injured group than in the noninjured group at all-time points (P < 0.05).

CONCLUSION

Disk injury in rats produces persistent increases in neuropeptides in DRGs and glia in the spinal cord, but only transient increases in inflammatory mediators in IVDs.

Nerve fiber staining investigations in traumatic and degenerative disc lesions of the wrist

PURPOSE

Traumatic and degenerative disc lesions cause ulnar-sided wrist pain. To date, anatomical investigations of cadaver triangular fibrocartilage discs examining the innervation of the triangular fibrocartilage complex have found no evidence of nerve fibers in the healthy disc. In this study, we immunohistologically investigated biopsies from patients with either central traumatic or degenerative disc lesions, to determine the existence of nerve fibers. We hypothesized that an ingrowth of nerve fibers causes ulnar-sided wrist pain associated with traumatic and degenerative disc lesions.

METHODS

We included 32 patients with a traumatic Palmer 1A lesion and 17 patients with a degenerative Palmer 2C lesion in the study. We obtained a biopsy of each patient and stained the specimen with protein gene product 9.5 for nerve fiber detection.

RESULTS

There were no nerve fibers in either traumatic or degenerative disc lesions. In addition, the marginal areas of the biopsies showed no evidence of nerve fibers.

CONCLUSIONS

Traumatic and degenerative disc lesions show no ingrowth of nerve fibers.

Free axial vibrations at 0 to 200 Hz positively affect extracellular matrix messenger ribonucleic acid expression in bovine nucleus pulposi

STUDY DESIGN

Bovine caudal intervertebral discs (IVDs) were exposed to free axial vibration for 10 to 60 minutes at 0 to 0.5 g and 0 to 200 Hz. Expression of messenger ribonucleic acid for aggrecan, collagen type I, collagen type II, biglycan, decorin, and versican were assayed, as was apoptosis.

OBJECTIVE

To determine the vibration conditions which are most effective in altering intervertebral disc IVD gene expression.

SUMMARY OF BACKGROUND DATA

Various studies have suggested widely varying effects of vibration in the IVD, ranging from harmful (increased risk of degeneration) to beneficial (increased analgesia) to neutral (no effect).

METHODS

Vibration was applied using a custom designed voice coil system, which generated controlled motion in the axial direction. Gene expression in the nucleus pulposus was assessed using RT-PCR and the SYBR green chemistry; apoptosis was assessed using TUNEL staining.

RESULTS

Expression of messenger ribonucleic acids for biglycan, collagen type I, collagen type II, decorin, and versican were significantly affected by vibration duration, frequency, and amplitude. Aggrecan was unaffected. Of the 3 factors, amplitude had the largest and widest effect.

CONCLUSION

Expression of extracellular matrix genes was significantly upregulated at high amplitudes (>0.4 g) in as little as 10 minutes. This may indicate a potential therapeutic stimulus; periodic application of controlled vibration could positively influence matrix maintenance. Further studies on the protein level and long-term effects are warranted.

Use of Temporary Implantable Biomaterials to Reduce Leg Pain and Back Pain in Patients with Sciatica and Lumbar Disc Herniation

The principle etiology of leg pain (sciatica) from lumbar disc herniation is mechanical compression of the nerve root. Sciatica is reduced by decompression of the herniated disc, i.e., removing mechanical compression of the nerve root. Decompression surgery typically reduces sciatica more than lumbar back pain (LBP). Decompression surgery reduces mechanical compression of the nerve root. However, decompression surgery does not directly reduce sensitization of the sensory nerves in the epidural space and disc. In addition, sensory nerves in the annulus fibrosus and epidural space are not protected from topical interaction with pain mediators induced by decompression surgery. The secondary etiology of sciatica from lumbar disc herniation is sensitization of the nerve root. Sensitization of the nerve root results from a) mechanical compression, b) exposure to cellular pain mediators, and/or c) exposure to biochemical pain mediators. Although decompression surgery reduces nerve root compression, sensory nerve sensitization often persists. These observations are consistent with continued exposure of tissue in the epidural space, including the nerve root, to increased cellular and biochemical pain mediators following surgery. A potential contributor to lumbar back pain (LBP) is stimulation of sensory nerves in the annulus fibrosus by a) cellular pain mediators and/or b) biochemical pain mediators that accompany annular tears or disruption. Sensory fibers located in the outer one-third of the annulus fibrosus increase in number and depth as a result of disc herniation. The nucleus pulposus is comprised of material that can produce an autoimmune stimulation of the sensory nerves located in the annulus and epidural space leading to LBP. The sensory nerves of the annulus fibrosus and epidural space may be sensitized by topical exposure to cellular and biochemical pain mediators induced by lumbar surgery. Annulotomy or annular rupture allows the nucleus pulposus topical access to sensory nerve fibers, thereby leading to LBP. Coverage of the annulus and adjacent structures in the epidural space by absorbable viscoelastic gels appears to reduce LBP following surgery by protecting sensory fibers from cellular and biochemical pain mediators.

Intervertebral disc, sensory nerves and neurotrophins: who is who in discogenic pain?

The normal intervertebral disc (IVD) is a poorly innervated organ supplied only by sensory (mainly nociceptive) and postganglionic sympathetic (vasomotor efferents) nerve fibers. Interestingly, upon degeneration, the IVD becomes densely innervated even in regions that in normal conditions lack innervation. This increased innervation has been associated with pain of IVD origin. The mechanisms responsible for nerve growth and hyperinnervation of pathological IVDs have not been fully elucidated. Among the molecules that are presumably involved in this process are some members of the family of neurotrophins (NTs), which are known to have both neurotrophic and neurotropic properties and regulate the density and distribution of nerve fibers in peripheral tissues. NTs and their receptors are expressed in healthy IVDs but much higher levels have been observed in pathological IVDs, thus suggesting a correlation between levels of expression of NTs and density of innervation in IVDs. In addition, NTs also play a role in inflammatory responses and pain transmission by increasing the expression of pain-related peptides and modulating synapses of nociceptive neurons at the spinal cord. This article reviews current knowledge about the innervation of IVDs, NTs and NT receptors, expression of NTs and their receptors in IVDs as well as in the sensory neurons innervating the IVDs, the proinflammatory role of NTs, NTs as nociception regulators, and the potential network of discogenic pain involving NTs.

New challenges for intervertebral disc treatment using regenerative medicine

The development of tissue engineering therapies for the intervertebral disc is challenging due to ambiguities of disease and pain mechanisms in patients, and lack of consensus on preclinical models for safety and efficacy testing. Although the issues associated with model selection for studying orthopedic diseases or treatments have been discussed often, the multifaceted challenges associated with developing intervertebral disc tissue engineering therapies require special discussion. This review covers topics relevant to the clinical translation of tissue-engineered technologies: (1) the unmet clinical need, (2) appropriate models for safety and efficacy testing, (3) the need for standardized model systems, and (4) the translational pathways leading to a clinical trial. For preclinical evaluation of new therapies, we recommend establishing biologic plausibility of efficacy and safety using models of increasing complexity, starting with cell culture, small animals (rats and rabbits), and then large animals (goat and minipig) that more closely mimic nutritional, biomechanical, and surgical realities of human application. The use of standardized and reproducible experimental procedures and outcome measures is critical for judging relative efficacy. Finally, success will hinge on carefully designed clinical trials with well-defined patient selection criteria, gold-standard controls, and objective outcome metrics to assess performance in the early postoperative period.

Is vibration truly an injurious stimulus in the human spine?

Epidemiological data at one time was taken to suggest that chronic vibrations--for example operating vehicles with low-quality seats--contributed to intervertebral disc degeneration and lower back pain. More recent discussions, based in part upon extended twin studies, have cast doubt upon this interpretation, and question how much of the vibration is actually transmitted to the spine during loading. This review summarizes our recent survey of the current state of knowledge. In particular, we note that current studies are lacking a detailed factorial exploration of frequency, amplitude, and duration; this may be the primary cause for inconclusive and/or contradictory studies. It is our conclusion that vibrations are still an important consideration in discogenic back pain, and further controlled studies are warranted to definitively examine the underlying hypothesis: that chronic vibration can influence IVD cell biology and tissue mechanics.

Anatomy of the human thoracolumbar Rami dorsales nervi spinalis

Medial, lateral, and intermedial ramifications have been described for the dorsal branch of the human spinal nerve (R. dorsalis n. spinalis, (RDNS)). Further branching has not been described. We report a ventral approach for dissecting the nerves around the thoracolumbar vertebral column to visualise the spreading of the nerves within the dorsal muscles and towards the skin. We defined three compartments of the deep back muscles in the thoracolumbar region: (A) the origin from the (1) transverse, (2) accessory, and (3) mammillary processes in the lumbar segments, (B) from the (1) ribs, (2)transverse and, (3) articular processes in the thoracolumbar segments. Each compartment was supplied by a ramification of the RDNS. The medial muscle compartment was reached by the descending medial branch of the RDNS. The lateral iliocostal compartment was innervated by an ascending lateral branch of the RDNS, and also by the descending distal branches of an intermedial branch of RDNS. This is a long nerve of the intermedial branch of the RDNS extended to the dorsal-caudal area, where the lateral and the intermedial nerve connected. This nerve, termed as the dorsal intermedial branch of the RDNS, innervated the skin in a more caudal region. Such nerve divided the lateral and the intermediate compartments. A short intermedial branch entered the intermediate segmental compartment from the ventral side. This is a ventral intermedial branch of the RDNS. The dorsal branches were often connected by a connecting branch of the RDNS. The lateral compartment represented the Iliocostalis. The medial and intermediate compartments comprised the Longissimus, part of the Iliocostalis, and additional dorsal muscles.

The change in the diffusion of water in normal and degenerative lumbar intervertebral discs following joint mobilization compared to prone lying

STUDY DESIGN

Prospective, repeated measures obtained under treatment and control conditions.

OBJECTIVES

The purposes of this study were to provide preliminary evidence regarding the immediate change in the diffusion of water in the nuclear region of normal and degenerative lumbar intervertebral discs (IVDs) following a single session of lumbar joint mobilization, and to compare these findings to the immediate change in the diffusion of water following a 10-minute session of prone lying.

BACKGROUND

There is conflicting evidence regarding the effectiveness and efficacy of lumbar joint mobilization. Increased knowledge of the physiologic effects of lumbar joint mobilization can lead to refinement of its clinical application.

METHODS AND MEASURES

A total of 24 people (15 males and 9 females), ranging in age from 22 to 58 years, participated in this study. All subjects had a history of activity-limiting low back pain. Diffusion-weighted magnetic resonance images (DW-MRIs) were obtained immediately before and after a 10-minute session of lumbar joint mobilization. At least 1 month later, a second session was performed in which DW-MRIs were obtained immediately before and after a 10-minute session of prone lying.

RESULTS

Following lumbar joint mobilization, a significant increase (P = .002) in the mean values for diffusion of water was observed within degenerative IVDs at L5-S1 (22.2% increase; effect size, 0.97). Degenerative IVDs at L1-2 to L4-5 and normal IVDs at L1-2 to L5-S1 did not demonstrate a change in diffusion following joint mobilization. Prone lying was not associated with a change in diffusion for normal or degenerative IVDs.

CONCLUSIONS

The stimulus provided by lumbar joint mobilization may influence the diffusion of water in degenerative IVDs at L5-S1; however, these are preliminary findings and the relationship of these findings to pain and function needs further investigation.

Resolving discogenic pain

Recent basic science studies on discogenic low back pain have provided new knowledge about this condition. This paper reviews some of these results and presents an overview of the following findings. The rat lumbar intervertebral disk may be innervated non-segmentally through the paravertebral sympathetic nerve and segmentally through the sinuvertebral nerves, and also by dichotomizing sensory fibers. The exposure of the nucleus pulposus (NP) to the outer annulus fibrosus (AF) may induce nerve injury and ingrowth into the disk. Nerve growth factor (NGF)-sensitive neurons are predominant in the rat intervertebral disk, which indicates that hyperalgesic responses can be induced by inflammation. NGF in the NP may promote axonal growth. Lumbar fusion may inhibit nerve ingrowth into the degenerated disk and reduce the percentage of calcitonin gene related peptide (CGRP)-positive neurons.

Cervical intradiscal radiofrequency lesioning: a feasiblity study

OBJECTIVE

The objective of this benchtop study was to establish if single site, long duration intradiscal radiofrequency (RF) at two different positions could generate adequate heating throughout the intervertebral disc to potentially ablate intradiscal nociceptors.

DESIGN

The disarticulated cervical spines from four fresh frozen cadavers were studied. Temperature recording was completed from two different positions of the RF needle. The needle was either placed in the middle of the disc in four discs, or it was inserted in the posterior quarter of the disc, in eight discs. Thermocouple measurements were made every 2 minutes from three positions: middle of the disc, posterolateral aspect of the disc, and in the anterior third of the disc.

SETTING

Fluoroscopy suite.

MATERIALS

Disarticulated cervical spine specimens.

INTERVENTIONS

Intradiscal RF lesioning in the middle and posterior portion of the cervical disc at 85 degrees C for 10 minutes.

OUTCOME MEASURES

Local temperature within the disc.

RESULTS

Lesioning in either the middle or posterior portion of the disc failed to provide sufficient temperature increases throughout the cervical disc to achieve adequate denervation.

CONCLUSIONS

As in the lumbar spine, intradiscal cervical RF provides too focal a thermal profile to effectively denervate the disc even in an ex vivo experiment. Thus, single site, long duration cervical intradiscal RF lesioning in vivo cannot be recommended.

Current understanding of lumbar intervertebral disc degeneration: a review with emphasis upon etiology, pathophysiology, and lumbar magnetic resonance imaging findings

Degeneration of the lumbar intervertebral discs (IVDs) is highly prevalent in adults and is nearly universal in the elderly population. Degenerative changes within, and adjacent to, the IVDs are likely to contribute to a variety of pain syndromes; however, the exact association between these findings and symptoms remains speculative. Recent research has provided new information regarding the etiology, pathophysiology, and clinical relevance of degeneration of the IVD. This information will assist clinicians and researchers in understanding the development and clinical course of lumbar disc degeneration, as well as its potential impact upon patients seeking physical therapy care for back pain. The purposes of this clinical commentary are to review the structure and metabolic capacity of the normal and degenerative lumbar IVD, and to discuss factors that influence the onset and progression of disc degeneration. Lumbar magnetic resonance images will be used to illustrate the common findings associated with this condition.