Does pain intensity after total knee arthroplasty depend on somatosensory functioning in knee osteoarthritis patients? A prospective cohort study.

The objective of this study is to determine whether the change in pain intensity over time differs between somatosensory functioning evolution profiles in knee osteoarthritis (KOA) patients undergoing total knee arthroplasty (TKA). This longitudinal prospective cohort study, conducted between March 2018 and July 2023, included KOA patients undergoing TKA in four hospitals in Belgium and the Netherlands. The evolution of the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscale pain over time (baseline, 3 months, and 1 year post-TKA scores) was the outcome variable. The evolution scores of quantitative sensory testing (QST) and Central Sensitization Inventory (CSI) over time (baseline and 1 year post-TKA scores) were used to make subgroups. Participants were divided into separate normal, recovered, and persistent disturbed somatosensory subgroups based on the CSI, local and widespread pressure pain threshold [PPT] and heat allodynia, temporal summation [TS], and conditioned pain modulation [CPM]. Linear mixed model analyses were performed. Two hundred twenty-three participants were included. The persistent disturbed somatosensory functioning group had less pronounced pain improvement (based on CSI and local heat allodynia) and worse pain scores 1 year post-TKA (based on CSI, local PPT and heat allodynia, and TS) compared to the normal somatosensory functioning group. This persistent group also had worse pain scores 1 year post-TKA compared to the recovered group (based on CSI). The study suggests the presence of a "centrally driven central sensitization" subgroup in KOA patients awaiting TKA in four of seven grouping variables, comprising their less pain improvement or worse pain score after TKA. Future research should validate these findings further. The protocol is registered at clinicaltrials.gov (NCT05380648).

Preoperative spinal education for lumbar spinal stenosis: A feasibility study.

INTRODUCTION: Lumbar spinal stenosis (LSS) is a leading cause of chronic musculoskeletal pain among older adults. A common and costly intervention for the treatment of LSS is lumbar decompression with or without fusion (LSS surgery), which has mixed outcomes among patients. Prehabilitation is a strategy designed to optimize the consistency of positive surgical outcomes and promote patient self-efficacy, while attempting to mitigate postoperative complications. No efforts have investigated the prehabilitation strategies specifically for patients undergoing LSS surgery. OBJECTIVE: To determine the feasibility of delivery and acceptability by participants of a novel prehabilitation intervention for patients undergoing LSS surgery. DESIGN: Feasibility study. SETTING: Outpatient orthopedic clinic at an academic medical center. PARTICIPANTS: Patients at least 50 years of age, who were scheduled for LSS surgery between October 2020 and October 2021. INTERVENTION: PreOperative Spinal Education for Lumbar Spinal Stenosis (POSE-LSS), is a novel multimodal, education-focused, time-efficient prehabilitation program for patients undergoing LSS surgery. Participants received the following: (1) Educational booklet and video; (2) In-person physical therapy (PT) session; and (3) Telemedicine visit with a physiatrist. MAIN OUTCOME MEASURE(S): The primary outcomes of interest were feasibility and acceptability of intervention by participants. Key potential surgical outcomes were length of stay and discharge disposition. RESULTS: POSE-LSS was completed by all eligible participants enrolled (n = 15) indicating feasibility and acceptability. Potential effectiveness measures including length of stay and discharge disposition were positively associated with the POSE-LSS intervention. CONCLUSIONS: This study demonstrates that a novel prehabilitation intervention is feasible, acceptable, and appears positively associated with important short-term measures of postoperative recovery that may impact the trajectory of patient care following LSS surgery.

Gray Matter Adaptations to Chronic Pain in People with Whiplash-Associated Disorders are Partially Reversed After Treatment: A Voxel-based Morphometry Study.

Gray matter (GM) changes are often observed in people with chronic spinal pain, including those with chronic whiplash-associated disorders (CWAD). These GM adaptations may be reversed with treatment, at least partially. Pain neuroscience education combined with exercise (PNE+Exercise) is an effective treatment, but its neural underlying mechanisms still remain unexplored in CWAD. Here, we performed both cross-sectional and longitudinal voxel-based morphometry to 1) identify potential GM alterations in people with CWAD (n = 63) compared to age- and sex-matched pain-free controls (n = 32), and 2) determine whether these GM alterations might be reversed following PNE+Exercise (compared to conventional physiotherapy). The cross-sectional whole-brain analysis revealed that individuals with CWAD had less GM volume in the right and left dorsolateral prefrontal cortex and left inferior temporal gyrus which was, in turn, associated with higher pain vigilance. Fifty individuals with CWAD and 29 pain-free controls were retained in the longitudinal analysis. GM in the right dorsolateral prefrontal cortex increased after treatment in people with CWAD. Moreover, the longitudinal whole-brain analysis revealed that individuals with CWAD had decreases in GM volumes of the left and right central operculum and supramarginal after treatment. These changes were not specific to treatment modality and some were not observed in pain-free controls over time. Herewith, we provide the first evidence on how GM adaptations to CWAD respond to treatment. PERSPECTIVE: This article presents which gray matter adaptations are present in people with chronic pain after whiplash injuries. Then, we examine the treatment effect on these alterations as well as whether other neuroplastic effects on GM following treatment occur.

Clinical prediction model for interdisciplinary biopsychosocial rehabilitation in osteoarthritis patients.

BACKGROUND: Osteoarthritis (OA) is a heterogenous condition, in which different subgroups are present. Individualized interdisciplinary multimodal pain treatments (IMPT) based on the biopsychosocial model have resulted in positive improvement of pain, health and disability in OA patients. Moreover, predictive factors for treatment success of IMPT in different musculoskeletal pain populations have been examined, but a clinical prediction model which informs whether an OA patient is expected to benefit or not from IMPT is currently lacking. AIM: The aim was to develop and internally validate a clinical prediction model to inform patient-tailored care based on identified predictors for positive or negative outcomes of IMPT in patients with OA. DESIGN: Longitudinal prospective cohort study. SETTING: Center for Integral Rehabilitation at six locations in the Netherlands. POPULATION: Chronic OA patients. METHODS: Data in this study were collected during January 2019 until January 2022. Participants underwent a 10-week IMPT program based on the biopsychosocial model. Treatment success was defined by a minimal decrease from baseline of 9 points on the Pain Disability Index (PDI). Candidate predictors were selected by experts in IMPT and literature review. Backward logistic regression analysis was performed to develop the clinical predication model and bootstrap validation was performed for internal validation. RESULTS: Overall, 599 OA patients were included, of which 324 experienced treatment success. Thirty-four variables were identified as possible predictors for good IMPT outcome. Age, gender, number of pain locations, PDI baseline score, maximal pain severity, use of pain medication and alcohol, work ability, brief illness perceptions questionnaire subscales timeline, consequences, identity and treatment control, pain catastrophizing scale and self-efficacy questionnaire score were found as predictors for treatment success. The internally validated model has an acceptable discriminative power of 0.71. CONCLUSIONS: This study reports a specific clinical prediction model for good outcome of IMPT in patients with OA. The internally validated model has an acceptable discriminative power of 0.71. CLINICAL REHABILITATION IMPACT: After external validation, this model could be used to develop a clinically useful decision tool.

Corrigendum: Machine learning clinical decision support for interdisciplinary multimodal chronic musculoskeletal pain treatment.

[This corrects the article DOI: 10.3389/fpain.2023.1177070.].

Identification of Metabolic Factors and Inflammatory Markers Predictive of Outcome after Total Knee Arthroplasty in Patients with Knee Osteoarthritis: A Systematic Review.

OBJECTIVE: To identify metabolic factors and inflammatory markers that are predictive of postoperative total knee arthroplasty (TKA) outcome. METHOD: A systematic search of the existing literature was performed using the electronic databases PubMed, Web of Science and Embase until the 1st of August 2022. Studies that evaluated the influence of metabolic or inflammatory markers (I) on postsurgical outcome (O) in end-stage knee osteoarthritis patients awaiting primary TKA (P) were included in this review. RESULTS: In total, 49 studies were included. Risk of bias of the included studies was low for one study, moderate for 10 studies and high for the remaining 38 studies. Conflicting evidence was found for the influence of body mass index, diabetes, cytokine levels and dyslipidaemia on pain, function, satisfaction and quality of life at more than six months after TKA. CONCLUSIONS: Several limitations such as not taking into account known confounding factors, the use of many different outcome measures and a widely varying follow-up period made it challenging to draw firm conclusions and clinical implications. Therefore large-scaled longitudinal studies assessing the predictive value of metabolic and inflammatory factors pre-surgery in addition to the already evidenced risk factors with follow-up of one year after TKA are warranted.

Machine learning clinical decision support for interdisciplinary multimodal chronic musculoskeletal pain treatment.

Introduction: Chronic musculoskeletal pain is a prevalent condition impacting around 20% of people globally; resulting in patients living with pain, fatigue, restricted social and employment capacity, and reduced quality of life. Interdisciplinary multimodal pain treatment programs have been shown to provide positive outcomes by supporting patients modify their behavior and improve pain management through focusing attention on specific patient valued goals rather than fighting pain. Methods: Given the complex nature of chronic pain there is no single clinical measure to assess outcomes from multimodal pain programs. Using Centre for Integral Rehabilitation data from 2019-2021 (n = 2,364), we developed a multidimensional machine learning framework of 13 outcome measures across 5 clinically relevant domains including activity/disability, pain, fatigue, coping and quality of life. Machine learning models for each endpoint were separately trained using the most important 30 of 55 demographic and baseline variables based on minimum redundancy maximum relevance feature selection. Five-fold cross validation identified best performing algorithms which were rerun on deidentified source data to verify prognostic accuracy. Results: Individual algorithm performance ranged from 0.49 to 0.65 AUC reflecting characteristic outcome variation across patients, and unbalanced training data with high positive proportions of up to 86% for some measures. As expected, no single outcome provided a reliable indicator, however the complete set of algorithms established a stratified prognostic patient profile. Patient level validation achieved consistent prognostic assessment of outcomes for 75.3% of the study group (n = 1,953). Clinician review of a sample of predicted negative patients (n = 81) independently confirmed algorithm accuracy and suggests the prognostic profile is potentially valuable for patient selection and goal setting. Discussion: These results indicate that although no single algorithm was individually conclusive, the complete stratified profile consistently identified patient outcomes. Our predictive profile provides promising positive contribution for clinicians and patients to assist with personalized assessment and goal setting, program engagement and improved patient outcomes.

Evolution of somatosensory processing signs after nociceptive targeted surgery in patients with musculoskeletal disorders: a systematic review.

ABSTRACT: Surgery is often advised when conservative treatment fails in musculoskeletal pain conditions, but a substantial proportion still suffers chronic pain after surgery. Somatosensory processing system (SPS) signs were previously studied as potential predictors for chronic postsurgical pain, but results are inconsistent. Therefore, studying the evolution of SPS signs could be of added value. The aim was to summarize all studies that measured how SPS signs evolved after nociceptive targeted surgery in musculoskeletal disorders and to find preoperative, perioperative, and postoperative predictors for the evolution of these SPS signs. Data were summarized, and risk of bias and level of evidence and recommendation were determined. Twenty-one studies were included. Five scored a low, 3 a moderate, and 13 a high risk of bias. In general, no consistent evolution of SPS signs comparing preoperative and postoperative values and predictors for this evolution in musculoskeletal disorders could be found. In most cases, static quantitative sensory testing (QST) did not change or conflicting results were found. On the other hand, dynamic QST mostly improved after surgery. Worthfully mentioning is that worsening of SPS signs was only seen at a follow-up of <3 months after surgery, that conclusions are stronger when evaluating dynamic QST with a follow-up of ≥3 months after surgery, and that pain improvement postsurgery was an important predictor. Future high-quality research should focus on the evolution of SPS signs after nociceptive targeted surgery, accounting for pain improvement groups and focusing on preoperative, perioperative, and postoperative predictors of this evolution.

Prehabilitation for spine surgery: A scoping review.

We aimed to identify and describe the current interventions used in preoperative programs ("prehabilitation") for spine surgery. Knowledge gaps in approaches, feasibility, timing, patient experience, clinical outcomes, and health care costs were explored while describing their potential benefits on physical and psychological outcomes. An electronic search was conducted from January 2004 to February 2022 in Ovid Medline, Embase, EBSCO CINAHL, the Cochrane Database of Systematic Reviews, and PEDro to identify studies in English evaluating adults enrolled in prehabilitation before undergoing elective spine surgeries. Studies were uploaded into DistillerSR for systematic screening after removing duplicates. Four reviewers screened nested references for inclusion based on titles and abstracts, followed by their full-text review. Two reviewers subsequently extracted data and summarized the results. The results were reported using Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews guidelines. Studies were rated for quality using National Health and Medical Research Council criteria. Out of 18,879 potential studies, a total of 23 studies (0.12%) met the eligibility criteria and were included in this scoping review. The prehabilitation programs included general education (n = 6, 26%), exercise (n = 6, 26%), cognitive behavioral therapy (n = 3, 13%), pain neuroscience education (n = 3, 13%), health behavior counseling (n = 3, 13%), and mindfulness (n = 2, 9%). Additional studies are needed to identify optimal patient characteristics, intervention dosage, and whether multimodal approaches using a combination of physical and psychological strategies lead to more favorable outcomes. Although studies on prehabilitation for spine surgery are limited, they seem to demonstrate that prehabilitation programs are feasible, reduce medical expenditures, and improve patients' postoperative pain, disability, self-efficacy, psychological behaviors, and satisfaction with surgical outcomes. The available literature suggests there is an opportunity to improve patient experience, clinical outcomes and reduce medical costs with the use of prehabilitation in spine surgery.

Using Self-Regulation Assessment to Explore Associations between Self-Regulation, Participation and Health-Related Quality of Life in a Rehabilitation Population.

OBJECTIVE: Self-regulation, participation and health-related quality of life are important rehabilitation outcomes. The aim of this study was to explore associations between these outcomes in a multi-diagnostic and heterogenic group of former rehabilitation patients. METHODS: This cross-sectional survey used the Self-Regulation Assessment (SeRA), Utrecht Scale for Evaluation of Rehabilitation-participation (USERParticipation) and the Patient-Reported-Outcome-Measurement-System (PROMIS) ability and PROMIS satisfaction with participation in social roles, and the EuroQol-5L-5D and PROMIS-10 Global Health. Regression analyses, controlling for demographic and condition-related factors, were performed. RESULTS: Respondents (n = 563) had a mean age of 56.5 (standard deviation (SD) 12.7) years. The largest diagnostic groups were chronic pain disorder and brain injury. In addition to demographic and condition-related factors, self-regulation subscales explained 0-15% of the variance in participation outcome scores, and 0-22% of the variance in HRQoL outcome scores. Self-regulation subscales explained up to 22% of the variance in satisfaction subscales of participation (USER-Participation and PROMIS) and the mental health subscale of the PROMIS-10. Self-regulation subscales explained up to 11% of the restriction and frequency subscales of participation (USER-Participation) and the physical health subscale of the PROMIS-10. CONCLUSION: Self-regulation is more strongly associated with outcomes such as satisfaction with participation and mental health compared with outcomes such as restrictions in participation and physical health.

Are contextual factors associated with activities and participation after total hip arthroplasty? A systematic review.

OBJECTIVES: After total hip arthroplasty (THA), over 30% of individuals report activity limitations and participation restrictions. This systematic review aimed to determine the association between contextual factors and outcomes in the activity and participation domain after THA for hip osteoarthritis (OA). METHODS: This systematic review was developed according to the PRISMA guidelines for systematic reviews. PubMed, Web of Science, Embase and Scopus were searched until August 2022. Risk of bias was assessed with the Quality in Prognosis Studies tool (QUIPS). RESULTS: Twenty-nine articles were included. Eighteen had a high risk of bias, 3 had a low risk of bias, and 8 had a moderate risk of bias. Anxiety was only investigated in studies with high risk of bias but showed a consistent negative association with activities and participation after THA across multiple studies. Evidence was inconsistent regarding the associations between depression, trait anxiety, sense of coherence, big 5 personality traits, educational level, marital status, employment status, job position, expectations and social support, and the activity and participation domain. Optimism, general self-efficacy, cognitive appraisal processes, illness perception, ethnicity, and positive life events were associated with activities and participation but were only investigated in 1 study. No associations were identified across multiple studies for living or smoking status. Control beliefs, kinesiophobia, race, discharge location, level of poverty in neighbourhood, negative life events and occupational factors, were not associated with the activity and participation domain but were only investigated in 1 study. CONCLUSION: Methodological quality of the included studies was low. Anxiety was the only factor consistently associated with worse outcomes in the activity and participation domain after THA but was only investigated in studies with high risk of bias. Further research is needed to confirm relationships between other contextual factors and activities and participation after THA. REGISTRATION: PROSPERO CRD42020199070.

Physiotherapists Using the Biopsychosocial Model for Chronic Pain: Barriers and Facilitators-A Scoping Review.

The use of the biopsychosocial model in primary care physiotherapy for chronic pain is far from the recommendations given in research and current guidelines. To understand why physiotherapists have difficulty implementing a biopsychosocial approach, more insight is needed on the barriers and facilitators. This scoping review aimed to investigate and map these barriers and facilitators that physiotherapists working in primary care reportedly face when treating patients with chronic musculoskeletal pain from a biopsychosocial perspective. Four electronic databases (PubMed, Embase, CINAHL and ERIC) and the grey literature were searched. Studies were included if they investigated the experiences of physiotherapists in the treatment of chronic pain from a biopsychosocial perspective in primary care. Extracted data were discussed and sub grouped in themes following a qualitative content analysis approach. To align with current use of theories on behavior change, the resulting themes were compared to the Theoretical Domains Framework. After screening, twenty-four studies were included. Eight groups of barriers and facilitators were identified, thematically clustered in six themes: knowledge, skills, and attitudes; environmental context and resources; role clarity; confidence; therapeutic alliance; and patient expectations. The results of this review can be used to inform the development of implementation programs.

A study protocol for the validation of a prognostic model with an emphasis on modifiable factors to predict chronic pain after a new episode of acute- or subacute nonspecific idiopathic, non-traumatic neck pain presenting in primary care.

BACKGROUND: The primary objective of this study is to identify which modifiable and non-modifiable factors are independent predictors of the development of chronic pain in patients with acute- or subacute nonspecific idiopathic, non-traumatic neck pain, and secondly, to combine these to develop and internally validate a prognostic prediction model. METHODS: A prospective cohort study will be conducted by physiotherapists in 30 primary physiotherapy practices between January 26, 2020, and August 31, 2022, with a 6-month follow-up until March 17, 2023. Patients who consult a physiotherapist with a new episode of acute- (0 to 3 weeks) or subacute neck pain (4 to 12 weeks) will complete a baseline questionnaire. After their first appointment, candidate prognostic variables will be collected from participants regarding their neck pain symptoms, prior conditions, work-related factors, general factors, psychological and behavioral factors. Follow-up assessments will be conducted at six weeks, three months, and six months after the initial assessment. The primary outcome measure is the Numeric Pain Rating Scale (NPRS) to examine the presence of chronic pain. If the pain is present at six weeks, three months, and six months with a score of NPRS ≥3, it is classified as chronic pain. An initial exploratory analysis will use univariate logistic regression to assess the relationship between candidate prognostic factors at baseline and outcome. Multiple logistic regression analyses will be conducted. The discriminative ability of the prognostic model will be determined based on the Area Under the receiver operating characteristic Curve (AUC), calibration will be assessed using a calibration plot and formally tested using the Hosmer and Lemeshow goodness-of-fit test, and model fit will be quantified as Nagelkerke's R2. Internal validation will be performed using bootstrapping-resampling to yield a measure of overfitting and the optimism-corrected AUC. DISCUSSION: The results of this study will improve the understanding of prognostic and potential protective factors, which will help clinicians guide their clinical decision making, develop an individualized treatment approach, and predict chronic neck pain more accurately.

Prehabilitation before total knee arthroplasty: A systematic review on the use and efficacy of stratified care.

BACKGROUND: Preoperative rehabilitation (hereafter called "prehabilitation") has been proposed as a potentially effective treatment to target preoperative risk factors to prevent insufficient outcome after total knee arthroplasty (TKA). PURPOSE: We aimed to assess whether previous clinical trials of non-surgical, non-pharmacological prehabilitation in individuals with knee osteoarthritis (KOA) awaiting TKA focused on specific clinical phenotypes or specific individual characteristics and whether the content of the prehabilitation was stratified accordingly. Second, we aimed to summarize and compare the long-term effects of stratified and non-stratified care on pain, satisfaction, function and quality of life. METHODS: A systematic literature search of PubMed, Web of Science, Scopus and Embase was performed. All relevant articles published up to April 19, 2021 reporting "(randomized controlled) clinical trials or prospective cohort studies" (S) related to the key words "total knee arthroplasty" (P), "preoperative conservative interventions" (I), "pain, function, quality of life and/or satisfaction" (O) were included. RESULTS: After screening 3498 potentially eligible records, 18 studies were assessed for risk of bias. Twelve studies had low, 2 moderate, 3 serious, and one high risk of bias. The latter study was excluded, resulting in 17 included studies. Five studies investigated a"stratified prehabilitation care" and 12 "non-stratified prehabilitation care". Stratified prehabilitation in 4 studies meant that the study sample was chosen considering a predefined intervention, and in the fifth study, the prehabilitation was stratified to individuals' needs. No direct comparison between the 2 approaches was possible. We found weak evidence for a positive effect of biopsychosocial prehabilitation compared to no prehabilitation on function (stratified studies) and pain neuroscience education prehabilitation compared to biomedical education on satisfaction (non-stratified studies) at 6 months post-TKA. We found strong evidence for positive effects of exercise prehabilitation compared to no prehabilitation on pain at 6 months and on function at 12 months post-TKA (non-stratified studies). CONCLUSION: More research is needed of stratified prehabilitation care focusing on individual characteristics in people with KOA awaiting TKA. REGISTRATION NUMBER: This systematic review was prospectively registered at PROSPERO on March 22, 2021 (no. CRD42021221098).

A Person-Centred Prehabilitation Program based on Cognitive Behavioural Physical Therapy for patients scheduled for Lumbar Fusion surgery: A mediation analysis to assess fear of movement (kinesiophobia), self-efficacy and catastrophizing as mediators of health outcomes.

OBJECTIVE: To investigate whether early changes in fear of movement (kinesiophobia), self-efficacy and catastrophizing were mediators of the relationship between allocation to the pre-habilitation intervention and later changes in health outcomes. METHODS: The original pre-habilitation trial (PREPARE, ISRCTN17115599) recruited 118 participants awaiting lumbar fusion surgery, half of whom received a prehabilitation intervention designed based on the modified fear-avoidance model and half of whom received usual care. Mediation analysis was performed to test each mediator separately. Analysis was performed on each outcome of interest separately (Oswestry disability index, patient-specific function, EQ general health and moderate/vigorous physical activity). Mediation analysis was carried out using PROCESS. Beta coefficients and bootstrapped 95% CIs were used to interpret the results. RESULTS: None of the potential mediators was found to mediate the relationship between allocation to the intervention and 3-month scores on any of the health outcomes tested. CONCLUSIONS: Screening patients for higher levels of catastrophizing and fear avoidance and lower levels of self-efficacy could help ensure only the patients who are most likely to benefit from the intervention are included. SIGNIFICANCE: Prehabilitation interventions for spinal fusion surgery have been found to improve health outcomes for patients. Theory-based interventions that target key mechanisms are more effective at improving outcomes than non-theory-based interventions. While no mediating effects were found for this particular intervention, the analysis suggests that the underlying theoretical model and treatment targets are appropriate and could drive improvement if more strongly targeted.

Personal influencing factors for pressure pain threshold in healthy people: A systematic review and meta-analysis.

All studies that investigated personal factors influencing pressure pain threshold (PPT) in healthy people were synthesized. Data was summarized, and risk of bias (RoB) and level of evidence were determined. Results were pooled per influencing factor, grouped by body region and included in meta-analyses. Fifty-four studies were eligible. Five had low, nine moderate, and 40 high RoB. Following meta-analyses, a strong conclusion was found for the influence of scapular position, a moderate for the influence of gender, and a weak for the influence of age (shoulder/arm region) and blood pressure on PPT. In addition, body mass index, gender (leg region), alcohol consumption and pain vigilance may not influence PPT. Based on qualitative summary, depression and menopause may not influence PPT. For other variables there was only preliminary or conflicting evidence. However, caution is advised, since the majority of included studies showed a high RoB and several were not eligible to include in meta-analyses. Heterogeneity was high in the performed meta-analyses, and most conclusions were weak. More standardized research is necessary.

Features and methods to discriminate between mechanism-based categories of pain experienced in the musculoskeletal system: a Delphi expert consensus study.

ABSTRACT: Classification of musculoskeletal pain based on underlying pain mechanisms (nociceptive, neuropathic, and nociplastic pain) is challenging. In the absence of a gold standard, verification of features that could aid in discrimination between these mechanisms in clinical practice and research depends on expert consensus. This Delphi expert consensus study aimed to: (1) identify features and assessment findings that are unique to a pain mechanism category or shared between no more than 2 categories and (2) develop a ranked list of candidate features that could potentially discriminate between pain mechanisms. A group of international experts were recruited based on their expertise in the field of pain. The Delphi process involved 2 rounds: round 1 assessed expert opinion on features that are unique to a pain mechanism category or shared between 2 (based on a 40% agreement threshold); and round 2 reviewed features that failed to reach consensus, evaluated additional features, and considered wording changes. Forty-nine international experts representing a wide range of disciplines participated. Consensus was reached for 196 of 292 features presented to the panel (clinical examination-134 features, quantitative sensory testing-34, imaging and diagnostic testing-14, and pain-type questionnaires-14). From the 196 features, consensus was reached for 76 features as unique to nociceptive (17), neuropathic (37), or nociplastic (22) pain mechanisms and 120 features as shared between pairs of pain mechanism categories (78 for neuropathic and nociplastic pain). This consensus study generated a list of potential candidate features that are likely to aid in discrimination between types of musculoskeletal pain.

Exposure in Vivo as a Treatment Approach to Target Pain-Related Fear: Theory and New Insights From Research and Clinical Practice.

Pain-related fear (PRF) can be a significant factor contributing to the development and maintenance of pain-related disability in individuals with persistent pain. One treatment approach to target PRF and related avoidance behavior is exposure in vivo (EXP). EXP has a long history in the field of anxiety, a field that is constantly evolving. This Perspective outlines recent theoretical advancements and how they apply to EXP for PRF, including suggestions for how to optimize inhibitory learning during EXP; reviews mechanistic work from neuroimaging supporting the targeting of PRF in people with chronic pain; and focuses on clinical applications of EXP for PRF, as EXP is moving into new directions regarding who is receiving EXP (eg, EXP in chronic secondary pain) and how treatment is provided (EXP in primary care with a crucial role for physical therapists). Considerations are provided regarding challenges, remaining questions, and promising future perspectives. IMPACT: For patients with chronic pain who have elevated pain-related fear (PRF), exposure is the treatment of choice. This Perspective highlights the inhibitory learning approach, summarizes mechanistic work from experimental psychology and neuroimaging regarding PRF in chronic pain, and describes possible clinical applications of EXP in chronic secondary pain as well as in primary care.