'Progressive-onset' versus injury-associated discogenic low back pain: features of disc internal derangement in patients studied with provocation lumbar discography

Pathomechanics of Early-Stage Lumbar Intervertebral Disc Degradation Leading to Discogenic Pain-A Narrative Review

Although the existence of highly prevalent pain, disability, and work time lost associated with discogenic low back pain is well known, the recognition of the culpability of universally present disc degradation and mechanical insufficiency in the first three decades of life is often overlooked. There is a corresponding "treatment gap" and no current interventions with demonstrated capabilities to address the pain and resist the usual progression of increasing structural failure of spinal tissues with increasing levels of pain and disability. This narrative review summarizes more than forty years of the literature describing the pathomechanics of progressive degradation of lumbar discs, with a focus on studies that implicate an increasing mechanical insufficiency in the etiology of early-stage chronic and recurrent discogenic low back pain. Topics highlighted in this review include the deleterious biological changes that begin soon after birth, stress intensification due to the loss of fluid phase load support, fatigue weakening and damage accumulation in non-regenerative tissue, disc tears, segmental instability, and the timeline for first incidence of chronic low back pain. The review concludes with preferred treatment characteristics and a brief summary of emerging treatment approaches.

Temporal Trends in the Epidemiology of Lower Back Pain in the United States

STUDY DESIGN

This was an observational study.

OBJECTIVE

This study aims to explore sociodemographic and regional geographic variations in lower back pain (LBP) incidence, prevalence, and burden in the United States (US from 2000 to 2019).

SUMMARY OF BACKGROUND DATA

LBP is a major contributor to lost wages and disability in the United States. As LBP is associated with increasing age and sedentary lifestyle, the incidence of LBP is expected to rise. Due to LBP's multifactorial causes, US epidemiological trends lack sufficient data.

MATERIALS AND METHODS

Descriptive epidemiological data including disability-adjusted life years (DALYs), incidence, and prevalence per 100,000 population from 2000 to 2019 were collected from the Global Burden of Disease database. State-level data regarding poverty, insurance and employment status were obtained from the US Government Census Bureau and US Department of Labor. Statistical significance was indicated by P <0.05.

RESULTS

From 2000 to 2019, the US demonstrated reductions in LBP incidence, prevalence, and DALYs. Regional analysis demonstrated the Midwest to have the greatest mean incidence, prevalence, and DALYs; with Midwestern females significantly more affected than females in other regions. Those aged 25 to 49 in the Midwest were impacted significantly more across all measures compared with age-matched populations in other regions. Nationally, there were no significant associations between unemployment and LBP. Poverty was inversely correlated with LBP incidence. Uninsured status was positively correlated with prevalence and DALYs.

CONCLUSION

Although there has been progress in reducing the impact of LBP in the United States, the Midwest region has greater rates for all measures compared with other US regions. Further, females and those aged 25 to 49 in the Midwest were more likely to be affected by LBP compared with counterparts in other regions. Future studies should identify specific factors contributing to elevated LBP rates in the Midwest in order to guide targeted interventions to reduce the incidence and burden of LBP there.

A Self-Polymerizing Mesh of Nano-Tethers for the Mechanical Constraint of Degraded Intervertebral Discs-A Review of 25 Years of Pre-Clinical and Early Clinical Research

Genipin polymers are self-forming tensile-load-carrying oligomers, derived from the gardenia fruit, that covalently bond to amines on collagen. The potential therapeutic mechanical benefits of a non-discrete in situ forming mesh of genipin oligomers for degraded spinal discs were first conceived in 1998. Over more than two decades, numerous studies have demonstrated the immediate mechanical effects of this injectable, intra-annular polymeric mesh including an early demonstration of an effect on clinical outcomes for chronic or recurrent discogenic low back pain. This literature review focused on articles investigating mechanical effects in cadaveric animal and human spinal discs, biochemical mechanism of action studies, articles describing the role of mechanical degradation in the pathogenesis of degenerative disc disease, initial clinical outcomes and articles describing current discogenic low back pain treatment algorithms. On the basis of these results, clinical indications that align with the capabilities of this novel injectable polymer-based treatment strategy are discussed. It is intended that this review of a novel nano-scale material-based solution for mechanical deficiencies in biologically limited tissues may provide a helpful example for other innovations in spinal diseases and similarly challenging musculoskeletal disorders.

Frequency of use of discography findings for the diagnosis of low back pain of discogenic origin. Systematic review of the literature

INTRODUCTION

There are different techniques and interpretations of discography findings to determine it positive for the diagnosis of discogenic pain. This study aims to evaluate the frequency of use of discography findings for the diagnosis of low back pain of discogenic origin.

MATERIAL AND METHODS

A systematic review of the literature of the last 17 years was performed in MEDLINE and BIREME. A total of 625 articles were identified, 555 were excluded for duplicates, title and abstract. We obtained 70 full texts of which 36 were included in the analysis after excluding 34 for not meeting the inclusion criteria.

RESULTS

Among the criteria in discography to determine it as positive, 8 studies used only the pain response to the procedure, 28 studies used more than one criterion during discography to consider it as positive, the evaluation of at least one adjacent intervertebral disc with a negative result was necessary in 26 studies to consider a discography as positive. Five studies formally expressed the use of the technique described by SIS/IASP to determine a discography as positive.

CONCLUSIONS

Pain in response to contrast medium injection, assessed with the visual analog pain scale≥6, was the most used criterion in the studies included in this review. Although there are already criteria to determine a discography as positive, the use of different techniques and interpretations of discography findings to determine a positive discography for low back pain of discogenic origin persists.

[Translated article] Frequency of use of discography findings for the diagnosis of low back pain of discogenic origin. Systematic review of the literature

INTRODUCTION

There are different techniques and interpretations of discography findings to determine it positive for the diagnosis of discogenic pain. This study aims to evaluate the frequency of use of discography findings for the diagnosis of low back pain of discogenic origin.

MATERIAL AND METHODS

A systematic review of the literature of the last 17 years was performed in MEDLINE and BIREME. A total of 625 articles were identified, 555 were excluded for duplicates, title and abstract. We obtained 70 full texts of which 36 were included in the analysis after excluding 34 for not meeting the inclusion criteria.

RESULTS

Among the criteria in discography to determine it as positive, 8 studies used only the pain response to the procedure, 28 studies used more than one criterion during discography to consider it as positive, the evaluation of at least one adjacent intervertebral disc with a negative result was necessary in 26 studies to consider a discography as positive. Five studies formally expressed the use of the technique described by SIS/IASP to determine a discography as positive.

CONCLUSIONS

Pain in response to contrast medium injection, assessed with the visual analogue pain scale ≥6, was the most used criterion in the studies included in this review. Although there are already criteria to determine a discography as positive, the use of different techniques and interpretations of discography findings to determine a positive discography for low back pain of discogenic origin persists.

Mast Cell/Proteinase Activated Receptor 2 (PAR2) Mediated Interactions in the Pathogenesis of Discogenic Back Pain

Mast cells (MCs) are present in the painful degenerate human intervertebral disc (IVD) and are associated with disease pathogenesis. MCs release granules containing enzymatic and inflammatory factors in response to stimulants or allergens. The serine protease, tryptase, is unique to MCs and its activation of the G-protein coupled receptor, Protease Activated Receptor 2 (PAR2), induces inflammation and degradation in osteoarthritic cartilage. Our previously published work has demonstrated increased levels of MC marker tryptase in IVD samples from discogenic back pain patients compared to healthy control IVD samples including expression of chemotactic agents that may facilitate MC migration into the IVD. To further elucidate MCs’ role in the IVD and mechanisms underlying its effects, we investigated whether (1) human IVD cells can promote MC migration, (2) MC tryptase can mediate up-regulation of inflammatory/catabolic process in human IVD cells and tissue, and (3) the potential of PAR2 antagonist to function as a therapeutic drug in in vitro human and ex vivo bovine pilot models of disease. MC migration was quantitatively assessed using conditioned media from primary human IVD cells and MC migration examined through Matrigel. Exposure to soluble IVD factors significantly enhanced MC migration, suggesting IVD cells can recruit MCs. We also demonstrated significant upregulation of MC chemokine SCF and angiogenic factor VEGFA gene expression in human IVD cells in vitro in response to recombinant human tryptase, suggesting tryptase can enhance recruitment of MCs and promotion of angiogenesis into the usually avascular IVD. Furthermore, tryptase can degrade proteoglycans in IVD tissue as demonstrated by significant increases in glycosaminoglycans released into surrounding media. This can create a catabolic microenvironment compromising structural integrity and facilitating vascular migration usually inhibited by the anti-angiogenic IVD matrix. Finally, as a “proof of concept” study, we examined the therapeutic potential of PAR2 antagonist (PAR2A) on human IVD cells and bovine organ culture IVD model. While preliminary data shows promise and points toward structural restoration of the bovine IVD including down-regulation of VEGFA, effects of PAR2 antagonist on human IVD cells differ between gender and donors suggesting that further validation is required with larger cohorts of human specimens.