Objectives - Acute postsurgical pain (APSP) may persist over time and become chronic. Research on predictors for APSP and chronic postsurgical pain (CPSP) has produced inconsistent results. This observational study aimed to analyze psychological and psychophysical variables associated with APSP and CPSP after total knee or hip arthroplasty, and to explore the role of sex. Methods - Assessments were conducted before surgery, 48 h, and 3 months postsurgery, including questionnaires (sociodemographic, pain related, and psychological) and quantitative sensory testing (QST). Hierarchical linear regression models analyzed potential predictors of APSP and CPSP, and moderation analyses evaluated the role of sex. Results - The study included 63 participants undergoing total knee (34, 54%) or hip (29, 46%) arthroplasty. Thirty-one (49.2%) were female and 32 (50.8%) were male. APSP (48 h) was associated with impaired conditioned pain modulation (CPM) (beta = 0.301, p = 0.019). CPSP (3 months) was associated with being female (beta = 0.282, p = 0.029), longer presurgical pain duration (beta = 0.353, p = 0.006), knee arthroplasty (beta = -0.312, p = 0.015), higher APSP intensity (beta = 373, p = 0.004), and impaired CPM (beta = 0.126, p = 0.004). In multivariate analysis, these clinical variables were significant predictors of CPSP, unlike sex, and CPM (adj. R-2 = 0.349). Moderation analyses showed that wind-up ratio (WUR) was a significant predictor of APSP in men (WUR x sex: b = -1.373, p = 0.046) and CPM was a significant predictor of CPSP in women (CPM x sex: b = 1.625, p = 0.016). Conclusions - Specific QST parameters could identify patients at risk for high-intensity APSP and CPSP, with sex as a moderator. This has important clinical implications for patient care, paving the way for developing tailored preventive pain management strategies.

BACKGROUND:Opioid analgesics are essential for managing acute and chronic pain in diseases such as cancer. Inadequate opioid access remains a major public health concern in low-income regions including Africa. This study aimed to provide updated and comprehensive data on changes in opioid consumption, specifically in Africa. METHODS:This longitudinal study has updated and expanded upon the International Narcotics Control Board data obtained from 1999 to 2021, assessing opioid consumption trends across all African countries. The defined daily doses for statistical purposes (SDDD) was used to determine the changes in opioid consumption in Africa. In addition, we used sub-analyses of the data to delve into individual substances, income levels, cancer incidence, cancer mortality, and sub-regional cluster analysis (based on the language spoken) to identify possible disparities and inform further research and tailored solutions. FINDINGS:Our results indicate a persistently low and stagnant trend in opioid consumption between 2001-03 and 2019-21, from 73 SDDD (95% CI 69-77) to 55 SDDD (32-79). In-depth analysis revealed a morphine consumption increase from 735 SDDD in 1999 to 1115 SDDD in 2021. Moreover, opioid consumption was closely related to country-level income levels, with most of the low-income and lower-middle-income African countries reporting low opioid consumption. Notably, the escalating incidence and mortality rates associated with cancer in Africa indicated a misalignment with the trajectory of opioid use. Additionally, French-speaking African countries exhibited lower opioid usage than the rest of the continent, suggesting avenues for research into cultural, political, and social aspects. INTERPRETATION:In the context of global doubling in opioid consumption, Africa has shown insufficient and stagnant opioid consumption during the last 20 years. These findings underscore the need for policy reform to facilitate safe and responsible opioid access in Africa, particularly for legitimate indications such as cancer pain and palliative care. FUNDING:None. TRANSLATION:For the French translation of the abstract see Supplementary Materials section.

OBJECTIVE:The World Endometriosis Research Foundation established the Endometriosis Phenome and Biobanking Harmonisation Project (EPHect) to create standardized documentation tools (with common data elements) to facilitate the comparison and combination of data across different research sites and studies. In 2014, 4 data research standards were published: clinician-reported surgical data, patient-reported clinical data, and fluid and tissue biospecimen collection. Our current objective is to create an EPHect standard for the clinician-reported physical examination (EPHect-PE) for research studies. DESIGN:An international consortium involving 26 clinical and academic experts and patient partners from 11 countries representing 25 institutions and organizations. Two virtual workshops, followed by the development of the physical examination standards underwent multiple rounds of iterations and revisions. SUBJECTS:N/A MAIN OUTCOME MEASURE(S): N/A RESULT(S): The EPHect-PE tool provides standardized assessment of physical examination characteristics and pain phenotyping. Data elements involve examination of back and pelvic girdle; abdomen including allodynia and trigger points; vulva including provoked vestibulodynia; pelvic floor muscle tone and tenderness; tenderness on unidigital pelvic examination; presence of pelvic nodularity; uterine size and mobility; presence of adnexal masses; presence of incisional masses; speculum examination; tenderness and allodynia at an extra-pelvic site (e.g., forearm); and recording of anthropometrics. CONCLUSION(S):The EPHect-PE standards will facilitate the standardized documentation of the physical examination, including the assessment and documentation of examination phenotyping of endometriosis-associated pelvic pain.

Intervertebral disc degeneration is characterized by deterioration in structural support that is potentially followed by stimulated neuronal ingrowth, and dysfunction of cellular physiology in the disc. Discogenic low back pain originates from nociceptors within the intervertebral disc or the cartilage endplate. This narrative review examines the mechanisms of disc degeneration, the association between degeneration and pain, and the current diagnosis and treatment of discogenic low back pain. Mechanisms of disc degeneration include dysregulated homeostasis of the extracellular matrix of the disc, altered spine mechanics, DNA damage, oxidative stress, perturbed cell signaling pathways, and cellular senescence. Although disc degeneration is more common in individuals with low back pain than in asymptomatic ones, degeneration occurs in a large proportion of asymptomatic individuals. Therefore, degeneration itself is not sufficient to trigger low back pain. Imaging and discography are common diagnostic tools of discogenic low back pain but have limited validity to diagnose discogenic pain. Most of current treatments options are not specific to discogenic pain but are unspecific treatments of low back pain of any origin. There is an urgent need to clarify and distinguish the molecular mechanisms of discogenic pain from mechanisms of disc degeneration that are not involved in nociception. Future research should make use of current methods to study molecular mechanisms of human pain in comprehensively and quantitatively phenotyped patients with low back pain, with the objective to identify molecular triggers of discogenic pain and determine the relationship between molecular mechanisms, pain, and patient-relevant outcomes.

Total knee replacement (TKR) is the gold-standard treatment for end-stage chronic osteoarthritis pain, yet many patients report chronic postoperative pain after TKR. The search for preoperative predictors for chronic postoperative pain following TKR has been studied with inconsistent findings. This study investigates the predictive value of quantitative sensory testing (QST) and PainDETECT for postoperative pain 3, 6, and 12 months post-TKR. We assessed baseline and postoperative (3- and 6-months) QST measures in 77 patients with knee OA (KOA) and 41 healthy controls, along with neuropathic pain scores in patients (PainDETECT). QST parameters included pressure pain pressure threshold (PPT), pain tolerance threshold (PTT), conditioned pain modulation (CPM), and temporal summation (TS) using cuff algometry, alongside mechanical hyperalgesia, and mechanical temporal summation to repeated pinprick stimulation. Compared to healthy controls, KOA patients at baseline demonstrated hyperalgesia to pinprick stimulation at the medial OA-affected knee and cuff pressure on the ipsilateral calf. Lower cuff algometry PTT and mechanical pinprick hyperalgesia were associated with baseline KOA pain intensity. Moreover, baseline pinprick pain hyperalgesia explained 25% of variance in pain intensity 12 months post-TKR and preoperative neuropathic pain scores also captured 30% and 20% of the variance in postoperative pain at 6- and 12-months, respectively. A decrease in mechanical pinprick hyperalgesia from before surgery to 3 months after TKR was associated with lower postoperative pain at the 12 months post-TKR follow-up, and vice-versa. Our findings suggest that preoperative pinprick hyperalgesia and PainDETECT neuropathic-like pain symptoms show predictive value for the development of chronic post-TKR pain.

ImportanceUp to 20% of patients develop chronic pain after total knee arthroplasty (TKA), yet there is a scarcity of effective interventions for this population.ObjectiveTo evaluate whether neuromuscular exercise and pain neuroscience education were superior to pain neuroscience education alone for patients with chronic pain after TKA.Design, Setting, and ParticipantsA superiority randomized clinical trial was conducted at 3 outpatient clinics at Aalborg University Hospital in Denmark. Participants with moderate-to-severe average daily pain intensity and no signs of prosthesis failure at least 1 year after primary TKA were included. Participant recruitment was initiated on April 12, 2019, and completed on October 31, 2022. The 12-month follow-up was completed on March 21, 2023.InterventionsThe study included 24 sessions of supervised neuromuscular exercise (2 sessions per week for 12 weeks) and 2 total sessions of pain neuroscience education (6 weeks between each session) or the same pain neuroscience education sessions alone. The interventions were delivered in groups of 2 to 4 participants.Main Outcomes and MeasuresThe primary outcome was change from baseline to 12 months using the mean score of the Knee Injury and Osteoarthritis Outcome Score, covering the 4 subscales pain, symptoms, activity of daily living, and knee-related quality of life (KOOS4; scores range from 0 to 100, with higher scores indicating better outcomes). The outcome assessors and statistician were blinded. All randomized participants were included in the intention-to-treat analysis.ResultsAmong the 69 participants (median age, 67.2 years [IQR, 61.2-71.9 years]; 40 female [58%]) included in the study, 36 were randomly assigned to the neuromuscular exercise and pain neuroscience education group, and 33 to the pain neuroscience education–alone group. The intention-to-treat analysis showed no between-group difference in change from baseline to 12 months for the KOOS4 (7.46 [95% CI, 3.04-11.89] vs 8.65 [95% CI, 4.67-12.63] points; mean difference, −1.33 [95% CI, −7.59 to 4.92]; P = .68). Among the 46 participants who participated in the 12-month assessment in the 2 groups, 16 (34.8%) experienced a clinically important improvement (a difference of ≥10 points on the KOOS4) with no between-group difference. No serious adverse events were observed.Conclusions and RelevanceIn this randomized clinical trial, the results demonstrated that neuromuscular exercises and pain neuroscience education were not superior to pain neuroscience education alone in participants with chronic pain after TKA. Approximately one-third of the participants, regardless of intervention, experienced clinically important improvements. Future studies should investigate which patient characteristics indicate a favorable response to exercises and/or pain neuroscience education.Trial RegistrationClinicalTrials.gov Identifier: NCT03886259

The limited understanding of the mechanisms underlying human discogenic low back pain (DLBP) has hampered the development of effective treatments. While there is much research on disc degeneration, the association between degeneration and pain is weak. Therefore, there is an urgent need to identify pain-inducing molecular mechanism to facilitate the development of mechanism-specific therapeutics. This scoping review aims to determine the current knowledge of molecular mechanisms associated with human DLBP. A systematic search on CENTRAL, CINAHL, Citation searching, ClinicalTrials.gov, Embase, Google Scholar, MEDLINE, PsycINFO, PubMed, Scopus, Web of Science, and World Health Organization was performed. Studies with human DLBP as diagnosed by discography or imaging that analyzed human disc tissues and reported pain-related outcomes were included, and those on predominant radicular pain were excluded. The search returned 6012 studies. Most studies did not collect pain-related outcomes. Those that included pain assessment relied on self-report of pain intensity and disability. Six studies qualified for data extraction and synthesis. The main molecular mechanisms associated with DLBP were the expressions of nociceptive neuropeptides and cytokines, particularly TNF-αdue to its strong association with pain outcomes. Activation of NF-κB signaling pathway, alterations in adrenoceptor expressions, and increase in reactive oxygen species (ROS) were also associated with DLBP through regulation of pro-inflammatory factors and pain-related neuropeptides. Current evidence converges to TNF-α, NF-κB signaling, and ROS-induced pro-inflammation. Major weaknesses in the current literature are the focus on degeneration without pain phenotyping, and lack of association of molecular findings with pain outcomes. Perspective This scoping review identified TNF-α, NF-κB signaling, and ROS-induced pro-inflammation as relevant mechanisms of human discogenic low back pain. Major weaknesses in the current literature are the focus on degeneration without pain phenotyping, and lack of association of molecular findings with pain outcomes.

Background: Diabetic peripheral neuropathy (DPN) is a prevalent and debilitating complication of diabetes, often leading to severe neuropathic pain. Although other diabetes-related complications have witnessed a surge of emerging treatments in recent years, DPN has seen minimal progression. This stagnation stems from various factors, including insensitive diagnostic methods and inadequate treatment options for neuropathic pain. Methods: In this comprehensive review, we highlight promising novel diagnostic techniques for assessing DPN, elucidating their development, strengths, and limitations, and assessing their potential as future reliable clinical biomarkers and endpoints. In addition, we delve into the most promising emerging pharmacological and mechanistic treatments for managing neuropathic pain, an area currently characterized by inadequate pain relief and a notable burden of side effects. Results: Skin biopsies, corneal confocal microscopy, transcutaneous electrical stimulation, blood-derived biomarkers, and multi-omics emerge as some of the most promising new techniques, while low-dose naltrexone, selective sodium-channel blockers, calcitonin gene-related peptide antibodies, and angiotensin type 2 receptor antagonists emerge as some of the most promising new drug candidates. Conclusion: Our review concludes that although several promising diagnostic modalities and emerging treatments exist, an ongoing need persists for the further development of sensitive diagnostic tools and mechanism-based, personalized treatment approaches.

This chapter provides an overview of the research regarding exercise and muscle pain in humans, focusing on both the potential for exercise to reduce pain sensitivity and for pain to interfere with muscle function. It describes the acute effects of exercise on pain in both healthy individuals and those with chronic pain conditions. The chapter discusses the effects of pain on motor control systems with an emphasis on understanding how acute pain may translate into chronic pain conditions. Exercise is frequently used in pain management settings. Systematic reviews have concluded that exercise is beneficial for a variety of pain conditions, including neck pain, low back pain, pelvic girdle pain, osteoarthritis, knee osteoarthritis, fibromyalgia and rheumatoid arthritis. Individual combinations of increased, decreased and co-contraction activity of trunk flexors and extensors may be another strategy adopted to maintain spine stability in conditions of experimental low back pain.

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Chronic itch is an annoying and disabling symptom that severely affects patients' quality of life in several dermatological as well as non-dermatological disorders. Chronic itch may be maintained and even aggravated by sensitization of peripheral and central neuronal structures. The possibilities to effectively relieve chronic itch are often limited and the need of more specific, effective and quick-acting treatment options is huge. This review summarizes the fundamental aspects of itch, the neuronal transmission and modulation of itch, and discusses new treatment opportunities.