Because depression and painful symptoms commonly occur together, we conducted a literature review to determine the prevalence of both conditions and the effects of comorbidity on diagnosis, clinical outcomes, and treatment. The prevalences of pain in depressed cohorts and depression in pain cohorts are higher than when these conditions are individually examined. The presence of pain negatively affects the recognition and treatment of depression. When pain is moderate to severe, impairs function, and/or is refractory to treatment, it is associated with more depressive symptoms and worse depression outcomes (eg, lower quality of life, decreased work function, and increased health care utilization). Similarly, depression in patients with pain is associated with more pain complaints and greater impairment. Depression and pain share biological pathways and neurotransmitters, which has implications for the treatment of both concurrently. A model that incorporates assessment and treatment of depression and pain simultaneously is necessary for improved outcomes.

https://jamanetwork.com/journals/jamainternalmedicine/articlepdf/216320/ira30040_2433_2445.pdf

Depression and pain comorbidity: a literature review.

/pdf/chapter-4-european-guidelines-for-the-management-of-chronic-4lrtve55lo.pdf

Chapter 4. European guidelines for the management of chronic nonspecific low back pain.

and Introduction Abstract Study Design: Review and reinterpretation of existing literature. Objective: To suggest how intervertebral disc degeneration might be distinguished from the physiologic processes of growth, aging, healing, and adaptive remodeling. Summary of Background Data: The research literature concerning disc degeneration is particularly diverse, and there are no accepted definitions to guide biomedical research, or medicolegal practice. Definitions: The process of disc degeneration is an aberrant, cell-mediated response to progressive structural failure. A degenerate disc is one with structural failure combined with accelerated or advanced signs of aging. Early degenerative changes should refer to accelerated age-related changes in a structurally intact disc. Degenerative disc disease should be applied to a degenerate disc that is also painful. Justification: Structural defects such as endplate fracture, radial fissures, and herniation are easily detected, unambiguous markers of impaired disc function. They are not inevitable with age and are more closely related to pain than any other feature of aging discs. Structural failure is irreversible because adult discs have limited healing potential. It also progresses by physical and biologic mechanisms, and, therefore, is a suitable marker for a degenerative process. Biologic progression occurs because structural failure uncouples the local mechanical environment of disc cells from the overall loading of the disc, so that disc cell responses can be inappropriate or aberrant. Animal models confirm that cell-mediated changes always follow structural failure caused by trauma. This definition of disc degeneration simplifies the issue of causality: excessive mechanical loading disrupts a disc's structure and precipitates a cascade of cell-mediated responses, leading to further disruption. Underlying causes of disc degeneration include genetic inheritance, age, inadequate metabolite transport, and loading history, all of which can weaken discs to such an extent that structural failure occurs during the activities of daily living. The other closely related definitions help to distinguish between degenerate and injured discs, and between discs that are and are not painful.

What is intervertebral disc degeneration, and what causes it?

Study Design. A systematic review of prospective cohort studies in low back pain.

Objectives. To evaluate the evidence implicating psychological factors in the development of chronicity in low back pain.

Summary of Background Data. The biopsychosocial model is gaining acceptance in low back pain, and has provided a basis for screening measurements, guidelines and interventions; however, to date, the unique contribution of psychological factors in the transition from an acute presentation to chronicity has not been rigorously assessed.

Methods. A systematic literature search was followed by the application of three sets of criteria to each study: methodologic quality, quality of measurement of psychological factors, and quality of statistical analysis. Two reviewers blindly coded each study, followed by independent assessment by a statistician. Studies were divided into three environments: primary care settings, pain clinics, and workplace.

Results. Twenty-five publications (18 cohorts) included psychological factors at baseline. Six of these met acceptability criteria for methodology, psychological measurement, and statistical analysis. Increased risk of chronicity (persisting symptoms and/or disability) from psychological distress/depressive mood and, to a lesser extent, somatization emerged as the main findings. Acceptable evidence generally was not found for other psychological factors, although weak support emerged for the role of catastrophizing as a coping strategy.

Conclusion. Psychological factors (notably distress, depressive mood, and somatization) are implicated in the transition to chronic low back pain. The development and testing of clinical interventions specifically targeting these factors is indicated. In view of the importance attributed to other psychological factors (particularly coping strategies and fear avoidance) there is a need to clarify their role in back-related disability through rigorous prospective studies

https://pure.royalholloway.ac.uk/portal/files/25553610/syst_rev_spine_psych_factors.pdf

A systematic review of psychological factors as predictors of chronicity/disability in prospective cohorts of low back pain.

The intervertebral disc is a cartilaginous structure that resembles articular cartilage in its biochemistry, but morphologically it is clearly different. It shows degenerative and ageing changes earlier than does any other connective tissue in the body. It is believed to be important clinically because there is an association of disc degeneration with back pain. Current treatments are predominantly conservative or, less commonly, surgical; in many cases there is no clear diagnosis and therapy is considered inadequate. New developments, such as genetic and biological approaches, may allow better diagnosis and treatments in the future.

/pdf/degeneration-of-the-intervertebral-disc-297lygwdik.pdf

Degeneration of the intervertebral disc

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(97)02135-1.pdf

Nerve ingrowth into diseased intervertebral disc in chronic back pain

This study outlines the design and validation of a new self-administered instrument for assessing foot pain and disability. The 19-item questionnaire was tested on 45 rheumatology patients, 33 patients who had attended their general practitioner with a foot-related problem and 1000 responders to a population survey of foot disorders. Levels of reported disability were found to be greatest for rheumatology patients and least for community subjects. In addition, the instrument was able to detect differences in disability levels reported by community subjects who did and did not consult with a health care professional and those who did and did not have a history of past and current foot pain. A good level of agreement was found when items on the questionnaire were compared with similar items on the ambulation sub-scale of the Functional Limitation Profile questionnaire. A Cronbach's alpha value of 0.99 and item-total correlation values between 0.25 and 0.62 confirmed the internal consistency of the instrument. Finally the results of a principal components analysis identified three constructs that reflected disabilities that are associated with foot pain: functional limitation, pain intensity and personal appearance. The design of the foot disability questionnaire makes it a suitable instrument for assessing the impact of painful foot conditions in both community and clinical populations.

Development and validation of a questionnaire to assess disabling foot pain

Low back pain symptoms are extremely common. affecting as many as 80% of the population at some time in their lives. However, the majority of the medical costs arise from the minority of patients whose symptoms become chronic. The authors propose a model in which chronicity is determined not only by factors related to the episode of low back pain, but also factors prior to the onset of symptoms (pre-morbid factors). No previous study has collected information on predictors of low back pain chronicity prior to the onset of symptoms. Participants in the South Manchester Low Back Pain Study, recruited by means of a cross-sectional population survey were followed prospectively over 18 months to identify those who consulted their general practitioner with a new episode of low back pain. At interview, 1-2 weeks post-consultation, it was determined whether or not subjects' symptoms had improved. In males, low levels of psychological distress, a higher than average reported level of physical activity, being in employment, and being satisfied with current work status were associated with a quick improvement in symptoms. In addition factors related to the episode, namely a short duration before consultation and symptoms with a sudden onset and confined to the lower back area, also strongly predicted a good early outcome. Using information on both pre-morbid and episode related factors, groups of male patients were identified whose probability of an early resolution of symptoms ranged between 0.25 and 1. Few factors, either pre-morbid or episode-related, were strongly associated with outcome amongst females. This large population-based study has shown, despite the known heterogeneity in the origin of low back pain and the pathologies associated with symptoms, an early improvement in symptoms amongst male attenders at general practice can be predicted on the basis of a small number of variables.

Predictors of early improvement in low back pain amongst consulters to general practice: the influence of pre-morbid and episode-related factors.

This study investigated whether paraspinal muscle wasting occurs in association with chronic low back pain (LBP). Cross-sectional areas (CSA) of spinal and paraspinal structures were measured radiographically, at the level of L4, in 43 patients with recent and 44 with chronic LBP. Crude anthropometry demonstrated no differences between the groups with regard to L4 and paraspinal and psoas muscle CSAs, but inter-individual differences were large. Since body weight correlated significantly with L4 CSA this dimension was used as an 'internal standard' and further inter-individual comparisons were made using paraspinal: L4 and psoas: L4 (i.e. muscle to bone) CSA ratios. Muscle assessments made in this 'relative' fashion revealed significant reductions in paraspinal and psoas dimensions in patients with chronic compared to recent onset LBP. These changes could cause paraspinal and psoas muscle weakness and thereby predispose to spinal instability and progressive dysfunction.

Radiographic demonstration of paraspinal muscle wasting in patients with chronic low back pain

STUDY DESIGN. Prospective histologic comparison of perineural tissues from patients requiring decompression surgery for herniated intervertebral disc with those from cadaveric controls. OBJECTIVES. To examine the significance of herniated intervertebral-disc-associated perineural vascular and fibrotic abnormalities with respect to back pain symptom generation. SUMMARY OF BACKGROUND DATA. Previous cadaveric studies have demonstrated perineural vascular congestion, dilatation, and thrombosis and perineural and intraneural fibrosis occurring in association with herniated intervertebral disc. It was suggested that these neural abnormalities were the result of ischemia, due to venous outflow obstruction, and also represented a possible cause of ongoing back pain symptoms. Criticisms of such a conclusion arose, however, because the possibility could not be excluded that these abnormalities were the result of postmortem artifact. METHODS. Histologic and immunohistochemical comparison of discal and peridiscal tissues removed from 11 patients with radiographically proven herniated intervertebral disc requiring decompressive surgery and from 6 fresh cadavers without history of back pain in life. RESULTS. Histology and immunohistochemistry of perineural and extraneural tissues from patients revealed vascular congestion, neovascularization, and endothelial abnormalities including luminal platelet adhesion, in association with reductions in von Willebrand factor levels, together with perivascular and perineural fibrosis. Elevated fibrogenic cytokine concentrations were also detected in patients' tissues. These changes occurred without evidence of inflammation and were absent in cadaveric control tissues. CONCLUSIONS. The vascular abnormalities detected in patients may represent an important etiopathologic factor predisposing to intraneural and perineural fibrosis, and hence to chronic pain symptoms, after disc herniation. It seems important to preserve the perineural microcirculation following disc herniation.

Malcolm I. V. Jayson

Papers

Nerve ingrowth into diseased intervertebral disc in chronic back pain

Development and validation of a questionnaire to assess disabling foot pain

Predictors of early improvement in low back pain amongst consulters to general practice: the influence of pre-morbid and episode-related factors.

Radiographic demonstration of paraspinal muscle wasting in patients with chronic low back pain

Herniated intervertebral disc-associated periradicular fibrosis and vascular abnormalities occur without inflammatory cell infiltration.