OBJECTIVES: Improvements in pain management might be achieved by matching treatment to underlying mechanisms for pain persistence Many authors argue for a mechanism-based classification of pain, but the field is challenged by the wide variation in the proposed terminology, definitions, and typical characteristics This study aimed to (1) systematically review mechanism-based classifications of pain experienced in the musculoskeletal system; (2) synthesize and thematically analyze classifications, using the International Association for the Study of Pain categories of nociceptive, neuropathic, and nociplastic as an initial foundation; and (3) identify convergence and divergence between categories, terminology, and descriptions of each mechanism-based pain classification MATERIALS AND METHODS: Databases were searched for papers that discussed a mechanism-based classification of pain experienced in the musculoskeletal system Terminology, definitions, underlying neurobiology/pathophysiology, aggravating/easing factors/response to treatment, and pain characteristics were extracted and synthesized on the basis of thematic analysis RESULTS: From 224 papers, 174 terms referred to pain mechanisms categories Data synthesis agreed with the broad classification on the basis of ongoing nociceptive input, neuropathic mechanisms, and nociplastic mechanisms (eg, central sensitization) "Mixed," "other," and the disputed categories of "sympathetic" and "psychogenic" pain were also identified Thematic analysis revealed convergence and divergence of opinion on the definitions, underlying neurobiology, and characteristics DISCUSSION: Some pain categories were defined consistently, and despite the extensive efforts to develop global consensus on pain definitions, disagreement still exists on how each could be defined, subdivided, and their characteristic features that could aid differentiation These data form a foundation for reaching consensus on classification

Systematic Review and Synthesis of Mechanism-based Classification Systems for Pain Experienced in the Musculoskeletal System.

Mechanism-based classification of pain has been advocated widely to aid tailoring of interventions for individuals experiencing persistent musculoskeletal pain. Three pain mechanism categories (PMCs) are defined by the International Association for the Study of Pain: nociceptive, neuropathic, and nociplastic pain. Discrimination between them remains challenging. This study aimed to build on a framework developed to converge the diverse literature of PMCs to systematically review methods purported to discriminate between them; synthesise and thematically analyse these methods to identify the convergence and divergence of opinion; and report validation, psychometric properties, and strengths/weaknesses of these methods. The search strategy identified articles discussing methods to discriminate between mechanism-based categories of pain experienced in the musculoskeletal system. Studies that assessed the validity of methods to discriminate between categories were assessed for quality. Extraction and thematic analysis were undertaken on 184 articles. Data synthesis identified 200 methods in 5 themes: clinical examination, quantitative sensory testing, imaging, diagnostic and laboratory testing, and pain-type questionnaires. Few methods have been validated for discrimination between PMCs. There was general convergence but some disagreement regarding findings that discriminate between PMCs. A combination of features and methods, rather than a single method, was generally recommended to discriminate between PMCs. Two major limitations were identified: an overlap of findings of methods between categories due to mixed presentations and many methods considered discrimination between 2 PMCs but not others. The results of this review provide a foundation to refine methods to differentiate mechanisms for musculoskeletal pain.

Methods to discriminate between mechanism-based categories of pain experienced in the musculoskeletal system: a systematic review.

Fundamentals of Intervertebral Disc Degeneration.

Purpose Numerous studies have applied a variety of methods to assess paraspinal muscle degeneration. However, the methodological differences in imaging evaluation may lead to imprecise or inconsistent results. This article aimed to provide a pragmatic summary review of the current imaging modalities, measurement protocols, and imaging parameters in the evaluation of paraspinal muscle fat infiltration (FI) in MRI studies. Methods Web of Science, EMBASE, and PubMed were searched from January 2005 to March 2020 to identify studies that examined the FI of paraspinal muscles on MRI among patients with lumbar degenerative diseases. Results Intramyocellular lipids measured by magnetic resonance spectroscopy and FI measured by chemical-shift MRI were both correlated to low back pain and several degenerative lumbar diseases, whereas results on the relationship between FI and degenerative lumbar pathologies using conventional MRI were conflicting. Multi-segment measurement of FI at the lesion segment and adjacent segments could be a prognostic indicator for lumbar surgery. Most studies adopted the center of the intervertebral disc or endplate as the level of slice to evaluate the FI. Compared with visual semiquantitative assessment, quantitative parameters appeared to be precise for eliminating individual or modality differences. It has been demonstrated that fat CSA/total CSA (based on area) and muscle-fat index (based on signal intensity) as quantitative FI parameters are associated with multiple lumbar diseases and clinical outcomes after surgery. Conclusion Having a good command of the methodology of paraspinal muscle FI on MRI was effective for diagnosis and prognosis in clinical practice.

Imaging Evaluation of Fat Infiltration in Paraspinal Muscles on MRI: A Systematic Review with a Focus on Methodology.

Epidural neuroplasty, often called percutaneous epidural adhesiolysis, is often performed in refractory patients with chronic lumbar radiculopathy or neurogenic claudication. Recent studies have showed that decompressive adhesiolysis with an inflatable balloon catheter (balloon neuroplasty) is efficient in patients who experience refractory pain from epidural steroid injection or even epidural neuroplasty with a balloon-less catheter. However, exact indications or predictive factors for epidural balloon neuroplasty have not been fully evaluated. Therefore, to assess associated factors that could affect a favorable outcome, we analyzed a prospectively collected multicenter cohort of patients with chronic refractory lumbar foraminal stenosis after balloon neuroplasty. At the 6-month point in follow-up, 92 (44.4%) patients among 207 subjects were classified as successful responders according to a robust combination of outcome measures. Multivariate logistic regression analysis also showed that mild grade lumbar foraminal stenosis may be an independent factor associated with a successful response 6 months after balloon neuroplasty (odds ratio = 2.829; 95% confidence interval = 1.351-5.923; p = 0.006). However, we found that there were 29.4% and 24.6% successful responders with moderate and severe foraminal stenosis, respectively. Attempting balloon neuroplasty in refractory lumbar foraminal stenosis, especially mild grade, may be worthwhile.&nbsp.

Eva Vagaská

Papers

Do lumbar magnetic resonance imaging changes predict neuropathic pain in patients with chronic non-specific low back pain?

Changes of paraspinal muscle morphology in patients with chronic non-specific low back pain