Possible pathogenesis of painful intervertebral disc degeneration

STUDY DESIGN

We collected the specimens of lumbar intervertebral disc (i.e., the symptomatic degenerative disc) from patients with discogenic low back pain to study the histopathologic features and growth factor expressions.

OBJECTIVES

To study the pathogenesis of disc degeneration, meanwhile discriminating between common disc degeneration (aging disc) (i.e., black asymptomatic disc, not clinically relevant) and painful disc degeneration (i.e., symptomatic disc, clinically relevant).

SUMMARY OF BACKGROUND DATA

The pathogenesis of intervertebral disc degeneration is poorly understood, mainly because of the difficulty to establish the experimental model with good reproducibility. Recently, the popularity of spinal fusion leads to more opportunities to obtain disc specimens, which could be applied to explore the pathogenesis of disc degeneration with modern biologic techniques.

METHODS

There were 21 specimens of lumbar intervertebral discs from 15 patients with discogenic low back pain during posterior lumbar interbody fusion, 16 aging discs from patients without low back pain, and 10 normal discs as control collected for the study of their histopathologic features, as well as the expressions of basic fibroblast growth factor (bFGF) and its receptor (Flg), transforming growth factor-beta1 (TGF-beta1) and its receptor (TGF-betaRI) by immunohistochemistry. The distribution of macrophages and mast cells was also noted. Proliferating cell nuclear antigen was assessed to evaluate proliferating activities of disc cells.

RESULTS

The distinct histologic characteristic of the disc from the patient with discogenic low back pain was the ingrowth of vascularized granulation tissue along torn fissures, extending from the external layer of the anulus fibrosus into the nucleus pulposus. The immunohistochemical staining showed that there were strong expressions of bFGF and TGF-beta1 and their receptors, as well as a strong expression of proliferating cell nuclear antigen in the zones of granulation tissue in the painful discs. However, there were only weak expressions in the nongranulation tissue zones in the painful discs and aging discs, and no expression in the control discs. In addition, abundant macrophages and mast cells were found in the granulation tissue zones of painful discs but absent in the nongranulation tissue zones of painful discs or aging discs and the normal control discs.

CONCLUSIONS

The findings indicated that degeneration of the painful disc might originate from the injury and subsequent repair of anulus fibrosus. Growth factors, such as bFGF and TGF-beta1, macrophages and mast cells might play a key role in the repair of the injured anulus fibrosus and subsequent disc degeneration.

The pathogenesis of discogenic low back pain

Discogenic low back pain is a common cause of disability, but its pathogenesis is poorly understood. We collected 19 specimens of lumbar intervertebral discs from 17 patients with discogenic low back pain during posterior lumbar interbody fusion, 12 from physiologically ageing discs and ten from normal control discs. We investigated the histological features and assessed the immunoreactive activity of neurofilament (NF200) and neuropeptides such as substance P (SP) and vasoactive-intestinal peptide (VIP) in the nerve fibres. The distinct histological characteristic of the painful disc was the formation of a zone of vascularised granulation tissue from the nucleus pulposus to the outer part of the annulus fibrosus along the edges of the fissures. SP-, NF- and VIP-immunoreactive nerve fibres in the painful discs were more extensive than in the control discs. Growth of nerves deep into the annulus fibrosus and nucleus pulposus was observed mainly along the zone of granulation tissue in the painful discs. This suggests that the zone of granulation tissue with extensive innervation along the tears in the posterior part of the painful disc may be responsible for causing the pain of discography and of discogenic low back pain.

The pathogenesis and clinical significance of a high-intensity zone (HIZ) of lumbar intervertebral disc on MR imaging in the patient with discogenic low back pain

Recently, the presence of a high-intensity zone (HIZ) within the posterior annulus seen on T2-weighted MRI has aroused great interest and even controversy among many investigators, particularly on whether the HIZ was closely associated with a concordant pain response on awake discography. The study attempted to interpret the correlation between the presence of the HIZ on MRI and awake discography, as well as its characteristic pathology. Fifty two patients with low back pain without disc herniation underwent MRI and discography successively. Each disc with HIZ was correlated for an association between the presence of a HIZ and the grading of annular disruption and a concordant pain response. Eleven specimens of lumbar intervertebral discs which contain HIZ in the posterior annulus from 11 patients with discogenic low back pain were harvested for histologic examination to interpret the histologic basis of a nociceptive response during posterior lumbar interbody fusion (PLIF). The study found that in all of 142 discograms in 52 patients, 17 presented HIZ. All 17 discs with HIZ showed painful reproduction and abnormal morphology with annular tears extending either well into or through the outer third of the annulus fibrosus. The consecutive sagittal slices through the HIZ lesion showed that a notable histologic feature of the formation of vascularized granulation tissue in the outer region of the annulus fibrosus. The current study suggests that the HIZ of the lumbar disc on MRI in the patient with low back pain could be considered as a reliable marker of painful outer anular disruption.

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.

A randomized placebo-controlled trial of intradiscal methylene blue injection for the treatment of chronic discogenic low back pain

A preliminary report of clinical study revealed that chronic discogenic low back pain could be treated by intradiscal methylene blue (MB) injection. We investigated the effect of intradiscal MB injection for the treatment of chronic discogenic low back pain in a randomized placebo-controlled trial. We recruited 136 patients who were found potentially eligible after clinical examination and 72 became eligible after discography. All the patients had discogenic low back pain lasting longer than 6 months, with no comorbidity. Thirty-six were allocated to intradiscal MB injection and 36 to placebo treatment. The principal criteria to judge the effectiveness included alleviation of pain, assessed by a 101-point numerical rating scale (NRS-101), and improvement in disability, as assessed with the Oswestry Disability Index (ODI) for functional recovery. At the 24-month follow-up, both the groups differed substantially with respect to the primary outcomes. The patients in MB injection group showed a mean reduction in pain measured by NRS of 52.50, a mean reduction in Oswestry disability scores of 35.58, and satisfaction rates of 91.6%, compared with 0.70%, 1.68%, and 14.3%, respectively, in placebo treatment group (p<0.001, p<0.001, and p<0.001, respectively). No adverse effects or complications were found in the group of patients treated with intradiscal MB injection. The current clinical trial indicates that the injection of methylene blue into the painful disc is a safe, effective and minimally invasive method for the treatment of intractable and incapacitating discogenic low back pain.

Cervical Proprioception Impairment in Neck Pain-Pathophysiology, Clinical Evaluation, and Management: A Narrative Review

Neck pain is very common, but most of the causes are unknown, making diagnosis and treatment extremely challenging. Current studies have found that one of the main problems in patients with neck pain is the impairment of cervical proprioception, which subsequently leads to cervical sensorimotor control disturbances. Cervical spine has a very delicate proprioceptive system that plays a crucial role in controlling posture and balance. Cervical proprioceptive impairment in neck pain occurs through a variety of mechanisms. Experimental neck muscle pain induced by injection of hypertonic saline results in inhibition of the activation of painful muscle; chronic neck pain causes structural and functional impairment of cervical muscles; excessive activation of mechanoreceptors in degenerative cervical discs and facet joints produces a large number of erroneous sensory signals. Clinical examinations to assess the link between structural pathology and neck pain have been unsuccessful, opening the way for the development of function-based tests. To date, eight neck sensorimotor control tests have been reported to evaluate patients with chronic neck pain. Although some tests may involve different subsystems (such as oculomotor system and vestibular system), all tests measure sensorimotor control in the neck, and the most commonly used is cervical joint position error (JPE) test. Current studies support the effectiveness of exercises targeting different aspects of sensorimotor function, in particular retraining aimed at improving cervical proprioception and muscle coordination. Based on the available evidence, it is recommended that patients with neck pain should be assessed and managed for cervical proprioceptive impairment and sensorimotor control disturbances.

The pathogenesis of Schmorl's nodes

We examined the pathogenesis of Schmorl's nodes, correlating the histological findings from 12 lumbar vertebrae with the corresponding conventional radiographs, tomographs, MR images and CT scans. The last revealed round, often multiple cystic lesions with indistinct sclerotic margins beneath the cartilaginous endplate. The appearances are similar to the typical CT changes of osteonecrosis. Histological examination of en-bloc slices through Schmorl's nodes gave clear evidence of subchondral osteonecrosis. Beneath the cartilage endplate, we found fibrosis within the marrow cavities with the disappearance of fat cells. Osteocytes within bone trabeculae were either dead or had disappeared. We suggest that Schmorl's nodes are the end result of ischaemic necrosis beneath the cartilaginous endplate and that herniation into the body of the vertebra is secondary.

Cervical disc degeneration and neck pain

Cervical intervertebral disc has long been considered a common source of neck pain. However, the pain caused by the disc itself has not been clearly defined so far, and its diagnosis and treatment has always been controversial. Degenerative cervical disc has a rich supply of nerve fibers, is prone to inflammatory reactions, and is susceptible to pain that can be provoked by disc stimulation or distention, and can be eliminated by block. Overwhelming clinical evidence demonstrates that neck pain in patients with degenerative cervical radiculopathy or myelopathy can be subsided rapidly by anterior cervical surgery, further indicating that this neck pain stems from the pathology of cervical disc itself. Cervical discography is advocated as the only test that connects disease to symptoms, but the procedure remains controversial. If strict criteria and technique are maintained, discography can discriminate painful, symptomatic discs from nonpainful, asymptomatic discs. Discogenic neck pain alone without cervical disc herniation or cervical spondylosis accounts for a large proportion of chronic neck pain. For these patients who continue to have refractory neck pain and fail to respond to conservative treatment, anterior cervical fusion surgery or artificial cervical disc replacement may be a better choice, and preoperative cervical discography can guarantee the excellent surgical results. Existing basic and clinical studies have scientifically shown that cervical intervertebral disc degeneration can lead to neck pain.

Diagnosis and surgical treatment of back pain originating from endplate

Twenty-one patients with back pain originating from the endplate injuries were selected to explore the methods of diagnosis and surgical treatment. All patients underwent examinations using radiography, CT, and MR imaging. Pain level of disc was determined through discography in each patient. The principal outcome judgments were pain and disability, and the efficacy of surgical treatment was assessed through the use of the visual analog scale (VAS) for pain and the Oswestry disability index (ODI) for functional recovery. All 21 patients with a diagnosis of back pain originating from endplate injuries according to discography were treated with anterior or posterior fusion surgery. The mean follow-up period was 3 years and 5 months (range, 2-6 years). Of the 21 patients, 20 (20/21) reported a disappearance or marked alleviation of low back pain and experienced a definite improvement in physical function. Statistically significant and clinically meaningful improvements in the VAS and ODI scores were obtained after treatment in the patients with chronic low back pain originating from the endplate injuries (P = 0.0001). The study suggests that discography and fusion surgery may be very effective methods for the diagnosis and treatment, respectively, of chronic back pain originating from the endplate injuries.

Expression and role of connective tissue growth factor in painful disc fibrosis and degeneration

STUDY DESIGN

We collected the specimens of lumbar intervertebral discs from patients with discogenic low back pain, to study the histopathological features and connective tissue growth factor (CTGF) expressions.

OBJECTIVE

To study the expression and role of CTGF in fibrosis and degeneration of painful disc tissue.

SUMMARY OF BACKGROUND DATA

Previous studies have demonstrated that degenerative disc commonly showed fibrosis in histology. CTGF, a downstream effector mediated by transforming growth factor-beta1 (TGF-beta1), is commonly related to tissue fibrosis. We do not know whether CTGF is expressed in painful disc, and related to painful disc degeneration and fibrosis.

METHODS

This study included 43 lumbar intervertebral disc specimens from 28 patients with discogenic low back pain obtained during posterior lumbar interbody fusion and 16 asymptomatic degenerative discs from patients without low back pain. Further, 8 normal discs were included as controls. Their histopathological features were studied, and the expression of CTGF was assessed using immunohistochemistry.

RESULTS

Histologic examination revealed that the painful discs showed chronic inflammatory reaction with blood vessel infiltration in varying degrees. The anulus fibrosus had lost its normal lamellar architecture, and instead, disorganization, disruption, and crossed fusion were observed. Normal fibroblasts were replaced by chondrocytes in the anulus fibrosus. The nucleus pulposus showed marked fibrosis, blood vessel infiltration, and inflammatory granulation tissue formation. Immunohistochemical staining demonstrated strong CTGF expression in the painful discs, weak expression in the asymptomatic degenerative disc, and no expression in the control discs.

CONCLUSION

The painful degenerative disc is significantly different from the asymptomatic degenerative disc with regard to histopathological findings. The strong CTGF expression in the painful disc may be related to disc fibrosis and degeneration.

Intradiscal methylene blue injection for the treatment of chronic discogenic low back pain

This article was a preliminary report of prospective clinical trial of a group of patients with chronic discogenic low back pain who met the criteria for lumbar interbody fusion surgery but were treated instead with an intradiscal injection of methylene blue (MB) for the pain relief. Twenty-four patients with chronic discogenic low back pain underwent diagnostic discography with intradiscal injection of MB. The principal criteria to judge the effectiveness included alleviation of pain, assessed by visual analog scale (VAS), and improvement in disability, as assessed with the Oswestry Disability Index (ODI) for functional recovery. The mean follow-up period was 18.2 months (range 12-23 months). Of the 24 patients, 21 (87%) reported a disappearance or marked alleviation of low back pain, and experienced a definite improvement in physical function. A statistically significant and clinically meaningful improvement in the changes in the ODI and the VAS scores were obtained in the patients with chronic discogenic low back pain (P=0.0001) after the treatment. The study suggests that the injection of MB into the painful disc may be a very effective alternative for the surgical treatment of chronic discogenic low back pain.

Chemical radiculitis

The theory of chemical radiculitis had been put forward about 30 years ago, but as yet it has not been proved by clinical studies. The aim of the current studies was to determine whether the annular tear of a painful disc proved by discography is the cause of radiating leg pain (radiculopathy) in patients with discogenic low back pain. Forty-two patients with discogenic low back pain at single disc level with concomitant radiating leg pain were studied in order to analyse the relationship between site of annular tear and side of radiating leg pain. Electromyogram and motor nerve conduction velocity were monitored to examine nerve root injury. The current studies found that there was a significant positive correlation between the site of annular tear and the side of radiation pain. Abnormalities of electromyogram and reduction of motor nerve conduction velocity were found on the side of radiating leg pain. The studies indicated that leakage of chemical mediators or inflammatory cytokines, which are produced in the painful disc, into epidural space through annular tear could lead to injury to adjacent nerve roots, and it might constitute the primary pathophysiologic mechanism of radiating leg pain in patients with discogenic low back pain but with no disc herniation.

Cervical Vertigo: Historical Reviews and Advances

Vertigo is one of the most common presentations in adult patients. Among the various causes of vertigo, so-called cervical vertigo is still a controversial entity. Cervical vertigo was first thought to be due to abnormal input from cervical sympathetic nerves based on the work of Barré and Liéou in 1928. Later studies found that cerebral blood flow is not influenced by sympathetic stimulation. Ryan and Cope in 1955 proposed that abnormal sensory information from the damaged joint receptors of upper cervical regions may be related to pathologies of vertigo of cervical origin. Further studies found that cervical vertigo seems to originate from diseased cervical intervertebral discs. Recent research found that the ingrowth of a large number of Ruffini corpuscles into diseased cervical discs may be related to vertigo of cervical origin. Abnormal neck proprioceptive input integrated from the signals of Ruffini corpuscles in diseased cervical discs and muscle spindles in tense neck muscles secondary to neck pain is transmitted to the central nervous system and leads to a sensory mismatch with vestibular and other sensory information, resulting in a subjective feeling of vertigo and unsteadiness. Further studies are needed to illustrate the complex pathophysiologic mechanisms of cervical vertigo and to better understand and manage this perplexing entity.

Cervical spondylosis and hypertension: a clinical study of 2 cases

Cervical spondylosis and hypertension are all common diseases, but the relationship between them has never been studied. Patients with cervical spondylosis are often accompanied with vertigo. Anterior cervical discectomy and fusion is an effective method of treatment for cervical spondylosis with cervical vertigo that is unresponsive to conservative therapy. We report 2 patients of cervical spondylosis with concomitant cervical vertigo and hypertension who were treated successfully with anterior cervical discectomy and fusion. Stimulation of sympathetic nerve fibers in pathologically degenerative disc could produce sympathetic excitation, and induce a sympathetic reflex to cause cervical vertigo and hypertension. In addition, chronic neck pain could contribute to hypertension development through sympathetic arousal and failure of normal homeostatic pain regulatory mechanisms. Cervical spondylosis may be one of the causes of secondary hypertension. Early treatment for resolution of symptoms of cervical spondylosis may have a beneficial impact on cardiovascular disease risk in patients with cervical spondylosis.

The effectiveness of anterior cervical decompression and fusion for the relief of dizziness in patients with cervical spondylosis: a multicentre prospective cohort study

AIMS

Cervical spondylosis is often accompanied by dizziness. It has recently been shown that the ingrowth of Ruffini corpuscles into diseased cervical discs may be related to cervicogenic dizziness. In order to evaluate whether cervicogenic dizziness stems from the diseased cervical disc, we performed a prospective cohort study to assess the effectiveness of anterior cervical discectomy and fusion on the relief of dizziness.

PATIENTS AND METHODS

Of 145 patients with cervical spondylosis and dizziness, 116 underwent anterior cervical decompression and fusion and 29 underwent conservative treatment. All were followed up for one year. The primary outcomes were measures of the intensity and frequency of dizziness. Secondary outcomes were changes in the modified Japanese Orthopaedic Association (mJOA) score and a visual analogue scale score for neck pain.

RESULTS

There were significantly lower scores for the intensity and frequency of dizziness in the surgical group compared with the conservative group at different time points during the one-year follow-up period (p = 0.001). There was a significant improvement in mJOA scores in the surgical group.

CONCLUSION

This study indicates that anterior cervical surgery can relieve dizziness in patients with cervical spondylosis and that dizziness is an accompanying manifestation of cervical spondylosis. Cite this article: Bone Joint J 2018;100-B:81-7.

Cervical Discs as a Source of Neck Pain. An Analysis of the Evidence

OBJECTIVESBACKGROUND

Objectives To determine the extent and strength of evidence that supports the belief that cervical intervertebral discs are a source of neck pain.

DESIGN

Design The evidence from anatomical, laboratory, experimental, diagnostic, and treatment studies was summarized and analyzed for concept validity, face validity, content validity, and construct validity.

RESULTS

Results Evidence from basic sciences shows that cervical discs have a nociceptive innervation, and experimental studies show that they are capable of producing neck pain. Disc stimulation has been developed as a diagnostic test but has rarely been used in a disciplined fashion. The prevalence of cervical disc pain has not been properly established but appears to be low. No treatment has been established that reliably achieves complete relief of neck pain in substantial proportions of patients.

CONCLUSIONS

Conclusions Basic science evidence supports the concept of cervical disc pain, but epidemiologic and clinical evidence to vindicate the clinical application of the concept is poor or lacking.

Surgical Management of 3-Level Lumbar Spondylolyses

Three-level lumbar spondylolyses are extremely rare. So far, only 11 cases were reported in the literature. Treatment of multilevel spondylolyses has not been consistent. Conservative treatment is commonly considered first in most patients, but those who remain symptomatic may benefit from operative treatment. We report here 3 cases of 3-level lumbar spondylolyses that were treated successfully with direct isthmic repair in 2 cases and a combined surgery of isthmic repair and interbody fusion in 1 case. Our clinical results indicated that direct defect repair using the screw-hook technique is a simple and safe procedure for the motion segment with normal disc. If the involved disc shows degenerative change, fusion surgery should be consideredSurgical treatment of multilevel spondylolyses varies between fusion, direct isthmic repair, and combined management associating 2 procedures at different levels. The success of management of the 3 patients with 3-level spondylolyses depends on the choice of appropriate treatment for every patient.

A kind of specific osteolytic destruction of the vertebral bodies

This report describes two young patients with osteolytic destruction in two adjacent vertebral bodies along with the intervertebral disc, and reveals its possible mechanism. A lateral radiograph and CT scan displayed a giant osteolytic cavity in the L4 vertebral body. An MRI or CT scan with a two-dimensional reconstruction displayed the same changes in the L4 vertebral body and lower endplate erosion in the L3 vertebral body. A comprehensive preoperative evaluation did not identify a specific cause of vertebral destruction. Both patients underwent anterior lumbar fusion surgery. The lesions were removed for histological and immunohistochemical examination. Histopathological study of the destructed vertebral bodies in the two patients revealed the disruption or atrophy of bone trabeculae with infiltration of a large amount of B-lymphocytes and macrophages into the marrow cavities. Studies of its pathogenesis reveal that it is likely to be a B-lymphocyte-mediated local immune inflammatory reaction in the lumbar spine.