Trajectories of acute low back pain: a latent class growth analysis

Can physical and psychological factors predict pain recurrence or an exacerbation of persistent non-specific low back pain? A protocol for a systematic review and meta-analysis

INTRODUCTION

Low back pain (LBP) is a global health concern. Approximately two-thirds of those who recover from LBP experience a relapse within a year, with many chronic cases encountering acute flare-ups (exacerbation). This systematic review will synthesise and analyse whether physical and/or psychological features can predict recurrent episodes of LBP or exacerbation of pain.

METHODS AND ANALYSIS

This systematic review protocol follows the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols guidelines. Comprehensive literature searches will be conducted in MEDLINE, EMBASE, APA PsycInfo, PubMed, CINAHL Plus, Web of Science, Scopus and ZETOC, spanning from each database's inception through to January 2025. Google Scholar and grey literature sources, including OpenGrey, will also be searched to ensure comprehensive coverage. Two independent reviewers will screen titles, abstracts and full texts, assessing the risk of bias with a modified Quality in Prognosis Studies tool. The overall certainty of evidence will be evaluated using an adapted Grading of Recommendations Assessment, Development and Evaluation approach. If sufficient data homogeneity is present, a meta-analysis will be performed; otherwise, findings will be synthesised narratively. The results will identify the ability of physical and/or psychological factors to predict pain recurrence or acute exacerbation in case of persistent non-specific LBP.

ETHICS AND DISSEMINATION

This study protocol does not present any ethical concerns. The findings from the systematic review will be submitted for publication in a peer-reviewed journal and will also be presented at relevant conferences.

PROSPERO REGISTRATION NUMBER

CRD42024599514.

Classifying Low Back Pain Through Pain Mechanisms: A Scoping Review for Physiotherapy Practice

Background: Low back pain (LBP) is a leading cause of disability worldwide, often driven by distinct pain mechanisms: nociceptive, neuropathic, and central sensitization. Accurate classification of these mechanisms is critical for guiding effective, targeted treatments. Methods: A scoping review was conducted following the Joanna Briggs Institute methodology and reported according to PRISMA-ScR guidelines. A comprehensive literature search was performed in MEDLINE, Cochrane CENTRAL, Scopus, PEDro, and Web of Science. Eligible studies included adults with LBP and focused on clinical criteria for classifying pain mechanisms. Data on study methods, population characteristics, and outcomes were extracted and synthesized. Results: Nine studies met the inclusion criteria. Nociceptive pain was characterized by localized symptoms proportional to mechanical triggers, with no neurological signs. Neuropathic pain was associated with burning sensations, dysaesthesia, and a positive neurodynamic straight leg raise (SLR) test. Central sensitization featured widespread pain, hyperalgesia, and disproportionate symptoms. Tools such as painDETECT, DN4, and the Central Sensitisation Inventory (CSI) were validated for neuropathic and central sensitization pain. Central sensitization and neuropathic pain were linked to greater disability and psychological distress compared to nociceptive pain. Conclusions: This review aims to provide a historical perspective on pain mechanism classifications and to explore how previous frameworks have influenced current diagnostic concepts in physiotherapy practice. By synthesizing key clinical criteria used to differentiate between nociceptive, neuropathic, and central sensitization pain, this review proposes a practical framework to improve the accuracy of pain classification in clinical settings.

Prospective Back Pain Trajectories or Retrospective Recall-Which Tells Us Most About the Patient?

In patients with low back pain (LBP), a visually identified retrospective pain trajectory often mismatches with a trajectory derived from prospective repeated measures. To gain insight into the clinical relevance of the 2 trajectory types, we investigated which showed a higher association with clinical outcomes. Participants were 724 adults seeking care for LBP in Danish chiropractic primary care. They answered weekly short-message-services on pain intensity and frequency over 52 weeks, which we translated into 8 trajectory classes. After 52 weeks, participants selected a retrospective visual pain trajectory from the same 8 trajectory classes. Clinical outcomes included disability, back/leg pain intensity, back beliefs, and work ability. The patient-selected pain trajectory classes were more strongly associated with clinical outcomes than the short-message-service trajectory classes at baseline, at follow-up, and with outcome changes between baseline and follow-up. This held across all 5 clinical outcomes, with the strongest associations observed at week 52 and the weakest at baseline. Patients' retrospective assessment of their LBP is more strongly associated with their clinical status than their prospective assessments translated into trajectory classes. This suggests that retrospective assessments of pain trajectories may provide valuable information not captured by prospective assessments. Researchers collecting prospective pain data should know that the captured pain trajectories are not strongly reflected in patients' perceptions of clinical status. Patients' retrospective assessments seem to offer an interpretation of their pain course that is likely more clinically relevant in understanding the perceived impact of their condition than trajectories based on repeated measures. PERSPECTIVE: Prospective pain data inadequately reflect patients' clinical status. Retrospective assessments provide a more clinically valuable understanding of the impact of their condition.

Mindful Breathing as an Adjunctive Approach to Chronic Low Back Pain Management: A Scoping Review

BACKGROUND

Chronic low back pain (CLBP) is a common and challenging condition. This scoping review explores the literature on mindful breathing's role in managing CLBP, either alone or alongside physiotherapy.

METHODS

A thorough database search identified studies on mindful breathing and CLBP. Various study designs, from descriptive to randomized controlled trials, were included.

RESULTS

Reviewed studies suggest that mindful breathing can improve body awareness and patients with CLBP. In a randomized controlled trial both mindful breathing and physiotherapy groups reported significant pain reduction (VAS: -2.7 mindful breathing, VAS: -2.4 physiotherapy) and improved quality of life (SF-36*: +14.9 mindful breathing, SF-36: +21.0 physiotherapy). Yu et al. found that combining mindful breathing with core stability exercises yielded superior outcomes (ORR* = 96.67%) compared to core exercises alone (ORR = 73.33%).

CONCLUSIONS

Mindful breathing holds promise for chronic low back pain management, with studies revealing pain reduction and improved quality of life. Combining it with core stability exercises enhances outcomes. However, standardized protocols are lacking, limiting clinical use. Future research should focus on precise guidelines for integration into practice. Mindful breathing offers a holistic approach to pain management.

Characterizing Acute Low Back Pain in a Community-Based Cohort: Results from a Feasibility Cohort Study

Introduction

Acute low back pain (LBP) is a common experience; however, the associated pain severity, pain frequency, and characteristics of individuals with acute LBP in community settings have yet to be well understood. In this manuscript, two acute-LBP severity categorization definitions were developed: 1) pain impact frequency (impact-based) and 2) pain intensity (intensity-based) severity categories. The purpose of this manuscript is to describe and then compare these acute-LBP severity groups in the following characteristics: 1) sociodemographic, 2) general and physical health, and 3) psychological using a feasibility cohort study.

Methods

This cross-sectional study used baseline data from 131 community-based participants with acute LBP (<4 weeks duration before screening and ≥30 pain-free days before acute LBP onset). Descriptive associations were calculated as prevalence ratios of categorical variables and Hedges' g for continuous variables.

Results

Our analyses identified several large associations for impact-based and intensity-based categories with global mental health, global physical health, STarT Back Screening Tool risk category, and general health. Larger associations were found with social constructs (racially and ethnically minoritized, performance of social roles, and isolation) when using the intensity-based versus impact-based categorization.

Discussion

This study adds to the literature by providing standard ways to characterize community-based individuals experiencing acute-LBP. The robust differences observed between these categorization approaches suggest that how we define acute-LBP severity is consequential; these different approaches may be used to improve the early identification of factors potentially contributing to the development of chronic-LBP.

Identifying Weekly Trajectories of Pain Severity Using Daily Data From an mHealth Study: Cluster Analysis

BACKGROUND

People with chronic pain experience variability in their trajectories of pain severity. Previous studies have explored pain trajectories by clustering sparse data; however, to understand daily pain variability, there is a need to identify clusters of weekly trajectories using daily pain data. Between-week variability can be explored by quantifying the week-to-week movement between these clusters. We propose that future work can use clusters of pain severity in a forecasting model for short-term (eg, daily fluctuations) and longer-term (eg, weekly patterns) variability. Specifically, future work can use clusters of weekly trajectories to predict between-cluster movement and within-cluster variability in pain severity.

OBJECTIVE

This study aims to understand clusters of common weekly patterns as a first stage in developing a pain-forecasting model.

METHODS

Data from a population-based mobile health study were used to compile weekly pain trajectories (n=21,919) that were then clustered using a k-medoids algorithm. Sensitivity analyses tested the impact of assumptions related to the ordinal and longitudinal structure of the data. The characteristics of people within clusters were examined, and a transition analysis was conducted to understand the movement of people between consecutive weekly clusters.

RESULTS

Four clusters were identified representing trajectories of no or low pain (1714/21,919, 7.82%), mild pain (8246/21,919, 37.62%), moderate pain (8376/21,919, 38.21%), and severe pain (3583/21,919, 16.35%). Sensitivity analyses confirmed the 4-cluster solution, and the resulting clusters were similar to those in the main analysis, with at least 85% of the trajectories belonging to the same cluster as in the main analysis. Male participants spent longer (participant mean 7.9, 95% bootstrap CI 6%-9.9%) in the no or low pain cluster than female participants (participant mean 6.5, 95% bootstrap CI 5.7%-7.3%). Younger people (aged 17-24 y) spent longer (participant mean 28.3, 95% bootstrap CI 19.3%-38.5%) in the severe pain cluster than older people (aged 65-86 y; participant mean 9.8, 95% bootstrap CI 7.7%-12.3%). People with fibromyalgia (participant mean 31.5, 95% bootstrap CI 28.5%-34.4%) and neuropathic pain (participant mean 31.1, 95% bootstrap CI 27.3%-34.9%) spent longer in the severe pain cluster than those with other conditions, and people with rheumatoid arthritis spent longer (participant mean 7.8, 95% bootstrap CI 6.1%-9.6%) in the no or low pain cluster than those with other conditions. There were 12,267 pairs of consecutive weeks that contributed to the transition analysis. The empirical percentage remaining in the same cluster across consecutive weeks was 65.96% (8091/12,267). When movement between clusters occurred, the highest percentage of movement was to an adjacent cluster.

CONCLUSIONS

The clusters of pain severity identified in this study provide a parsimonious description of the weekly experiences of people with chronic pain. These clusters could be used for future study of between-cluster movement and within-cluster variability to develop accurate and stakeholder-informed pain-forecasting tools.

Recovery Trajectories Following Complex Elbow Injuries and Radial Head Arthroplasty: A Longitudinal Study Over 8 Years

PURPOSE

Radial head arthroplasty (RHA) is commonly performed to manage comminuted unreconstructible radial head fractures. Although the outcomes of RHA are often satisfactory, revisions are usually considered when pain intensity is higher than expected. Therefore, it is important to investigate the recovery trajectories of patients following RHA over an extended period and the characteristics that may lead to unfavorable outcomes.

METHODS

The Patient-Rated Elbow Evaluation (PREE) was used to assess recovery in 94 patients at baseline (within 2-7 days after surgery); 3 and 6 months; and 1, 2, 3, 4, 5, and 8 years after RHA. Lower PREE values indicate lower pain and disability. Latent growth curve analysis was used to determine classes of recovery. The characteristics of the participants in the identified recovery trajectory classes were then compared.

RESULTS

Two distinct recovery trajectories were identified: optimal and suboptimal recoveries. Most patients (84%) belonged to the optimal recovery class, which exhibited significantly lower baseline PREE scores, a consistent pattern of recovery, and a relatively high rate of change. Patients in the suboptimal recovery class (16%) had significantly higher baseline PREE scores and continued to experience relatively higher levels of pain and disability for the duration of the study; their rate of recovery was much slower. Patients belonging to the 2 recovery trajectories did not differ based on age or sex. Although we had low power in other variables, a qualitative exploration showed that the number of current or previous smokers was higher in the suboptimal recovery trajectory class.

CONCLUSIONS

In this longitudinal cohort study, we show that high postsurgical pain and disability, and potentially smoking, may adversely affect the recovery trajectory following RHA. Clinicians are recommended to assess these potential factors while considering revision surgeries.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic IV.

Characterizing Acute Low Back Pain in a Community-Based Cohort

Acute low back pain (LBP) is a common experience, however, the associated pain severity, pain frequency, and characteristics of individuals with acute LBP in community settings have yet to be well understood. In this manuscript, three acute LBP severity categorization definitions were used based on LBP frequency combined with either 1) pain impact frequency (impact-based) or 2) pain intensity (intensity-based), as well as LBP pain interference frequency (interference only-based) severity categories. The purpose of this manuscript is to describe and then compare these acute LBP severity groups in the following characteristics: 1) sociodemographic, 2) general and physical health, and 3) psychological. This cross-sectional study used baseline data from 131 community-based participants with acute LBP (<4 weeks duration before screening and ≥30 pain-free days before acute LBP onset). Descriptive associations were calculated as prevalence ratios for categorical variables and Hedges' g for continuous variables. Our analyses identified several large associations for impact-based and intensity-based categories with global mental health, global physical health, STarT Back Screening Tool risk category, and general health. Larger associations were found with social constructs (racially and ethnically minoritized, performance of social roles, and isolation) when using the intensity-based versus impact-based categorization. The interference-based category did not capture as much variability between acute LBP severity categories. This study adds to the literature by providing standard ways to characterize community-based individuals experiencing acute LBP. The robust differences observed between these categorization approaches suggest that how we define acute LBP severity is consequential; these different approaches may be used to improve the early identification of factors potentially contributing to the development of chronic LBP.

Trajectories of arm recovery early after stroke: an exploratory study using latent class growth analysis

AIM

To investigate trajectories of recovery of motor arm function after stroke during inpatient rehabilitation.

MATERIALS AND METHODS

Data were available from 74 consecutively-admitted stroke survivors receiving inpatient rehabilitation from an inception cohort study. Heterogeneity of arm recovery in the first 4-weeks was investigated using latent class analysis and weekly Box and Block Test (BBT) scores. Optimal number of clusters were determined; characterised and cluster associated factors explored.

RESULTS

A 4-cluster model was identified, including 19 participants with low baseline arm function and minimal recovery ('LOWstart/LOWprogress', 26%), 15 with moderate function and low recovery ('MODstart/LOWprogress', 20%), 15 with low function and high recovery ('LOWstart/HIGHprogress', 20%), and 25 with moderate function and recovery ('MODstart/MODprogress', 34%). Compared to LOWstart/LOWprogress: LOWstart/HIGHprogress presented earlier post-stroke (β, 95%CI) (-4.81 days, -8.94 to -0.69); MODstart/MODprogress had lower modified Rankin Scale scores (-0.74, -1.15 to -0.32); and MODstart/LOWprogress, LOWstart/HIGHprogress and MODstart/MODprogress had higher admission BBT (23.58, 18.82 to 28.34; 4.85, 0.85 to 9.61; 28.02, 23.82 to 32.21), Upper Limb-Motor Assessment Scale (9.60, 7.24 to 11.97; 3.34, 0.97 to 5.70; 10.86, 8.77 to 12.94), Action Research Arm Test (31.09, 22.86 to 39.33; 12.69, 4.46 to 20.93; 38.01, 30.76 to 45.27), and Manual Muscle Test scores (10.64, 7.07 to 14.21; 6.24, 2.67 to 9.81; 11.87, 8.72 to 15.01).

CONCLUSIONS

We found unique patterns of arm recovery with distinct characteristics for each cluster. Better understanding of patterns of arm recovery can guide future models and intervention development.KEY MESSAGESArm recovery early after stroke follows four distinct trajectories that relate to time post stroke, initial stroke severity and baseline level of motor arm function.Identification of recovery patterns gives insight into the uniqueness of individual's recovery.This study offers a novel approach on which to build and develop future models of arm recovery.

Composite Biomarkers, Behavioral Symptoms, and Comorbidities in Axial Low Back Pain: A Systematic Review

PURPOSE

Proinflammatory cytokines play a critical role in chronic inflammation and pain and contribute to behavioral symptoms (depressive symptoms, anxiety, fatigue, sleep disturbance) and comorbidities (diabetes, cardiac diseases, cancer). Evidence is lacking on the specific proinflammatory cytokines associated with these behavioral symptoms/comorbidities co-occurring with axial low back pain (aLBP). This review aimed to systematically analyze the following: (1) specific proinflammatory cytokines associated with aLBP in adults, (2) associations among proinflammatory cytokines and behavioral symptoms in aLBP, and (3) relationships among proinflammatory cytokines and comorbidities in aLBP, to develop a new clinical framework for future diagnostic and intervention targets for patients with aLBP.

METHODS

Electronic databases, including PubMed/MEDLINE, ProQuest Nursing & Allied Health Source, and CINAHL Complete (EBSCO) were searched for the period January 2012 to February 2023. Eligible studies included cross-sectional, case-control, longitudinal, and cohort studies in which proinflammatory cytokines were reported in adults above 18 years with aLBP. Intervention studies and randomized controlled trails were excluded. The Joanna Briggs Institute (JBI) criteria were used for quality evaluation.

RESULTS

Findings from 11 studies showed 3 proinflammatory cytokines associated with pain intensity in adult patients with aLBP: C-Reactive Protein (CRP), Tumor Necrosis Factor (TNF-α), and Interleukin (IL-6). Some studies assessed associations between proinflammatory cytokines and depressive symptoms; none explored the association of proinflammatory cytokines with fatigue, anxiety, sleep disturbance, or comorbidities (diabetes, cardiac diseases, and cancer) in aLBP.

CONCLUSIONS

Proinflammatory cytokines in aLBP can serve as composite biomarkers for pain, associated symptoms, and comorbidities and may serve as a target for future interventions. There is need for well-designed studies assessing associations among chronic inflammation, behavioral symptoms, and comorbidities.

First Provider Seen for an Acute Episode of Low Back Pain Influences Subsequent Health Care Utilization

OBJECTIVE

Costs associated with low back pain (LBP) continue to rise. Despite numerous clinical practice guidelines, the evaluation and treatments for LBP are variable and largely depend on the individual provider. As yet, little attention has been given to the first choice of provider. Early research indicates that the choice of first provider and the timing of interventions for LBP appear to influence utilization. We sought to examine the association between the first provider seen and health care utilization.

METHODS

Using 2015-2018 data from a large insurer, this retrospective analysis focused on patients (29,806) seeking care for a new episode of LBP. The study identified the first provider chosen and examined the following year of medical utilization. Cox proportional hazards models were calculated using inverse probability weighting on propensity scores to evaluate the time to event and the relationship to the first choice of provider.

RESULTS

The primary outcome was the timing and use of health care resources. Total health care use was lowest in those who first sought care with chiropractic care or physical therapy. Highest health care use was seen in those patients who chose the emergency department.

CONCLUSION

Overall, there appears to be an association between the first choice of provider and future health care use. Chiropractic care and physical therapy provide nonpharmacologic and nonsurgical, guideline-based interventions. The use of physical therapists and chiropractors as entry points into the health system appears related to a decrease in immediate and long-term use of health resources. This study expands the existing body of literature and provides a compelling case for the influence of the first provider on an acute episode of LBP.

IMPACT

The first provider seen for an acute episode of LBP influences immediate treatment decisions, the trajectory of a specific patient episode, and future health care choices in the management of LBP.

The Role of Back Muscle Dysfunctions in Chronic Low Back Pain: State-of-the-Art and Clinical Implications

Changes in back muscle function and structure are highly prevalent in patients with chronic low back pain (CLBP). Since large heterogeneity in clinical presentation and back muscle dysfunctions exists within this population, the potential role of back muscle dysfunctions in the persistence of low back pain differs between individuals. Consequently, interventions should be tailored to the individual patient and be based on a thorough clinical examination taking into account the multidimensional nature of CLBP. Considering the complexity of this process, we will provide a state-of-the-art update on back muscle dysfunctions in patients with CLBP and their implications for treatment. To this end, we will first give an overview of (1) dysfunctions in back muscle structure and function, (2) the potential of exercise therapy to address these dysfunctions, and (3) the relationship between changes in back muscle dysfunctions and clinical parameters. In a second part, we will describe a framework for an individualised approach for back muscle training in patients with CLBP.

Do Visual Pain Trajectories Reflect the Actual Course of Low Back Pain? A Longitudinal Cohort Study

Different trajectories of low back pain (LBP) have been identified prospectively using repeated measures. For these trajectories to inform clinical practice, they must be available in the clinical consultation. Therefore, identified LBP trajectories have been translated into visual pain trajectories (VPTs) that allow people with LBP, at the time of consult, to reflect upon their pain experience and identify the VPT that best categorizes their pain course. We have limited knowledge regarding the extent to which a chosen VPT reflects the prospectively experienced trajectory. Thus, we explored the distribution of pain intensity and pain pattern characteristics (from prospective pain trajectory data) within the retrospectively chosen VPT classes. We enrolled patients with LBP from Danish chiropractic practice. Using SMS, participants (n = 719) scored their pain weekly on an 11-point numerical rating scale for 52 weeks. At week 52, participants identified 1 of 8 VPTs that reflected their perceived back pain trajectory during the preceding year. We found that the chosen VPTs reflected pain intensity, but that pain patterns (episodic, fluctuating, and persistent) were not systematically recognized, and the experienced course varied substantially amongst participants within the same VPT. The VPTs are related to some aspects of the experienced LBP course but are not a proxy for the SMS-measured trajectories. Reasons for apparent mismatches between the experienced course of LBP and VPT recall warrant further investigation. PERSPECTIVE: Self-reported back pain trajectories reflected pain intensities obtained through weekly SMS tracking over a year, but participants' recall did not reflect the pain patterns (episodes and fluctuations) discovered prospectively. Clinicians can use self-reported pain trajectories to facilitate a dialog about pain experience, but not as a proxy for prospective measures.

Association between physical activity, sedentary behaviour and the trajectory of low back pain

BACKGROUND

Low back pain (LBP) is one of the world's most prevalent health issues. Patients with LBP experience various intensities and durations of symptoms, which can lead to distinctive course patterns commonly described as symptom trajectories.

PURPOSE

This study aimed to investigate the association between different amounts of physical activity and sedentary behavior and the trajectory of LBP, in people with a lifetime history of LBP.

STUDY DESIGN

The study involved a secondary analysis of observational longitudinal data collected from the AUstralian Twin low BACK pain (AUTBACK) study.

METHODS

A total of 329 individual twins met the inclusion criteria for analysis. Latent Class Growth Analysis was used to identify distinct patterns of LBP and select the primary outcome (probability of having a severe LBP trajectory, 0%-100%). Linear regression models were used to investigate the association between different amounts of physical activity or sedentary behavior at baseline, and the probability of having a severe LBP trajectory. Results were expressed as β coefficients and 95% confidence intervals (CI).

RESULTS

Moderate-to-vigorous intensity physical activity was significantly associated with the probability of having a severe LBP trajectory (unadjusted β -0.0276; 95%CI -0.0456 to -0.0097, p=.003). For every 1-minute increase in moderate-to-vigorous intensity physical activity per week, there was a 2.8%-point reduction in a participant's probability of having a severe LBP trajectory. No significant associations were identified between sedentary behavior or light intensity physical activity, and the probability of having a severe LBP trajectory.

CONCLUSIONS

In people with a lifetime history of LBP, engagement in higher volumes of moderate to vigorous intensity physical activity at baseline was associated with a lower probability of developing a severe trajectory of LBP over 1 year.

Biopsychosocial sequelae and recovery trajectories from whiplash injury following a motor vehicle collision

BACKGROUND CONTEXT

Five out of 10 injured in a motor vehicle collision (MVC) will develop persistent pain and disability. It is unclear if prolonged symptoms are related to peritraumatic pain/disability, psychological distress, muscle fat, lower extremity weakness.

PURPOSE

To test if widespread muscle fat infiltration (MFI) was (1) unique to those with poor recovery, (2) present in the peritraumatic stage, (3) related to known risk factors.

STUDY DESIGN/SETTING

A cohort study, single-center academic hospital.

PATIENT SAMPLES

A total of 97 men and women (age 18-65) presenting to an urban academic emergency medicine department following MVC, but not requiring inpatient hospitalization.

PRIMARY OUTCOME MEASURE

Neck disability at 12-months.

METHODS

Participants underwent magnetic resonance imaging (MRI) to quantify neck and lower extremity MFI, completed questionnaires on pain/disability and psychological distress (< 1-week, 2-weeks, 3-, and 12-months) and underwent maximum volitional torque testing of their lower extremities (2-weeks, 3-, and 12-months). Percentage score on the Neck Disability Index at 12-months was used for a model of (1) Recovered (0%-8%), (2) Mild (10%-28%), and (3) Moderate/Severe (≥ 30%). This model was adjusted for BMI and age.

RESULTS

Significant differences for neck MFI were revealed, with the Recovered group having significantly lower neck MFI than the Mild and Moderate/Severe groups at all time points. The Mild group had significantly more leg MFI at 12-months (p=.02) than the Recovered group. There were no other significant differences at any other time point. Lower extremity torques revealed no group differences. The Traumatic Injury Distress Scale (TIDS) and MFI of the neck at 1-week postinjury significantly predicted NDI score at 12-months.

CONCLUSIONS

Higher neck MFI and distress may represent a risk factor though it is unclear whether this is a pre-existing phenotype or result of the trauma.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02157038.

The Foundations for Chronic Low Back Pain Management may Start in Early Life. Exploring the Role of Caregiver Parental Leave on Future Low Back Pain in the Offspring

Chronic low back pain is difficult to treat and despite increased spending on health services, clinical outcomes for people with low back pain have not improved. Innovative, large scale initiatives seem necessary to stem the cost of low back pain. Psychological health contributes to the development and persistence of chronic low back pain and psychological interventions are important in the management of low back pain. Given the contribution of psychological health to low back pain development and management, it raises the question; can we support psychological health in later life by bolstering emotional development in early life, and reduce the burden of this common condition? Positive early life experiences, including those induced by extended paid parental leave, could bolster emotional development and support the psychological health necessary to manage low back pain in later life. We present the current state of evidence demonstrating the potential value of increasing support for parent-child relationships in early life to reduce the burden of low back pain in future generations. The current evidence is limited to cross-sectional associations, but strong preclinical data clearly shows the potential negative impacts of maternal separation on rodent pup health that compels consideration in human populations. PERSPECTIVE: The benefits stemming from enhanced child development include stable emotional foundations, possibly improving psychological health and low back pain management in the future. This perspective raises questions for future studies - within the context of low back pain, what ingredients bolster stable psychological health? And are these ingredients influenced by parental leave?

Identification and Characterisation of Trajectories of Sickness Absence Due to Musculoskeletal Pain: A 1-Year Population-based Study

Purpose This study aimed to identify trajectories of sickness absence in workers on sick leave due to musculoskeletal disorders and explore the association between these trajectories and established prognostic factors for sickness absence. Methods We conducted a prospective cohort study of 549 workers (56% women, aged 18-67 years) on sick leave due to musculoskeletal disorders in Norway in 2018-2019. Sickness absence data were collected from the Norwegian sick leave registry and prognostic factors via self-reported baseline questionnaires. We used group-based trajectory modelling to define the different trajectories of sickness absence spanning a 1-year period. Multivariable multinomial logistic regression was used to estimate odds ratios and 95% confidence intervals for prognostic factors associated with the identified trajectory groups. Results We identified six distinct trajectories of sickness absence over 1 year: 'fast decrease' (27% of the cohort): 'moderate decrease' (22%); 'slow decrease' (12%); 'u-shape' (7%); 'persistent moderate' (13%); and 'persistent high' (18%). Prognostic factors, such as previous sickness absence days, return-to-work expectancy, workability, multisite pain, and health scores, differentiated between the sickness absence trajectories (all P < 0.05). Negative return-to-work expectancy was associated with the three trajectory groups with the highest number of sickness absence days ('slow decrease', 'persistent moderate', and 'persistent high'). Conclusions This is the first study to explore the association of return-to-work expectancy with trajectories of sickness absence. Our findings highlight different patterns of sickness absence and the complex range of prognostic factors. These findings have implications for secondary and tertiary prevention strategies for work absence in workers with musculoskeletal disorders.

Tracking clusters of patients over time enables extracting information from medico-administrative databases

CONTEXT

Identifying clusters (i.e., subgroups) of patients from the analysis of medico-administrative databases is particularly important to better understand disease heterogeneity. However, these databases contain different types of longitudinal variables which are measured over different follow-up periods, generating truncated data. It is therefore fundamental to develop clustering approaches that can handle this type of data.

OBJECTIVE

We propose here cluster-tracking approaches to identify clusters of patients from truncated longitudinal data contained in medico-administrative databases.

MATERIAL AND METHODS

We first cluster patients at each age. We then track the identified clusters over ages to construct cluster-trajectories. We compared our novel approaches with three classical longitudinal clustering approaches by calculating the silhouette score. As a use-case, we analyzed antithrombotic drugs used from 2008 to 2018 contained in the Échantillon Généraliste des Bénéficiaires (EGB), a French national cohort.

RESULTS

Our cluster-tracking approaches allow us to identify several cluster-trajectories with clinical significance without any imputation of data. The comparison of the silhouette scores obtained with the different approaches highlights the better performances of the cluster-tracking approaches.

CONCLUSION

The cluster-tracking approaches are a novel and efficient alternative to identify patient clusters from medico-administrative databases by taking into account their specificities.

Effects of non-pharmacological interventions on sleep in chronic low back pain: A systematic review and meta-analysis of randomised controlled trials

Low back pain is a leading cause of disability worldwide and adults with chronic low back pain (≥12weeks) commonly experience sleep impairments (e.g., insomnia, sleep disturbance). This study examined the effects of non-pharmacological interventions on sleep in adults with chronic low back pain. Six databases (PubMed, CINAHL, SPORTDiscus, PsycINFO, EMBASE, CENTRAL) were searched from inception to 2 June 2021 for randomised controlled trials. Pairwise random-effect meta-analysis estimated standardised mean difference (Hedges' g) at end-of-intervention follow-up. Nineteen studies (participants: 1348) were included. When compared to control, non-pharmacological interventions improved sleep (g [95%CI]: -0.33 [-0.56, -0.11], p = 0.004, small effect, I² = 59.3%; n = 879; studies: n = 13; GRADE: low). This small improvement in sleep was associated with a moderate reduction in pain intensity (-0.69 [-1.00, -0.38], p < 0.001, I² = 75.3%; n = 812; studies: n = 12; GRADE: very low) and no changes in back-related disability (-0.50 [-1.13, 0.14], p = 0.129, I² = 91.4%; n = 517; studies: n = 6; GRADE: low). Notably, all eligible studies reported interventions primarily aimed to reduce pain, although our search criteria were not limited to pain interventions. Key limitations were data paucity and high risk of bias. Future research should investigate sleep-based interventions (i.e., those purposely designed to improve sleep) using subjective and objective measures across a range of sleep domains (CRD42021275227).

Association between recent overdose and chronic pain among individuals in treatment for opioid use disorder

Chronic pain increases risk for opioid overdose among individuals with opioid use disorder. The purpose of this study is to evaluate the relationship between recent overdose and whether or not chronic pain is active. 3,577 individuals in treatment for opioid use disorder in 2017 or 2018 were surveyed regarding recent overdoses and chronic pain. Demographics from the 2017 Treatment Episode Data Set, which includes all U.S. facilities licensed or certified to provide substance use care, were used to evaluate the generalizability of the sample. χ2 tests and logistic regression models were used to compare associations between recent overdoses and chronic pain. Specifically, active chronic pain was associated with opioid overdose among people in treatment for opioid use disorder. Individuals with active chronic pain were more likely to have had a past month opioid overdose than those with no history chronic pain (adjusted OR = 1.55, 95% CI 1.16-2.08, p = 0.0003). In contrast, individuals with prior chronic pain, but no symptoms in the past 30 days, had a risk of past month opioid overdose similar to those with no history of chronic pain (adjusted OR = 0.88, 95% CI 0.66-1.17, p = 0.38). This suggests that the incorporation of treatment for chronic pain into treatment for opioid use disorder may reduce opioid overdoses.

Creating a Self-management Mobile Application for People With Chronic Low Back Pain: A Focus Group Study of Unmet Needs and Strategies

Mobile health can fulfill the unmet needs of patients with chronic low back pain by recommending individualized management plans. Limited mobile applications have been developed based on the needs, preferences, and values relative to self-management of patients with chronic low back pain. This study aimed to explore the experience of patients with chronic low back pain and the desired content, designs, and features of a self-management application. We conducted five focus groups (N = 24). Participants provided feedback on draft contents and they also discussed the desired designs and features of an application while reviewing a low-fidelity prototype. Data were audio-recorded, transcribed verbatim, and analyzed using qualitative content analysis. Three categories and eight subcategories emerged. Participants: (1) confronted difficulties of their pain experience along with vicious cycles of pain and unmet needs; (2) acknowledged the importance of self-management as they lived with chronic low back pain and realized how to self-manage their pain; and (3) suggested ways to fulfill needs and preferences among patients with chronic low back pain. The nature of chronic low back pain causes disruptions well-being and requires constant management. Developing user-centered strategies to enhance knowledge and promote self-management among chronic low back pain patients is required.

Temporal stability of self-reported visual back pain trajectories

ABSTRACT

Low back pain (LBP) follows different pain trajectories, and patients seem to recognize their trajectory. This allows self-reported visual pain trajectories (SRVTs) to support patient-provider communication. Pain trajectories appear stable over time for many patients, but the evidence is sparse. Our objectives were to investigate the (1) temporal stability of SRVTs over 1 year concerning pain intensity and course patterns and (2) association of transitions between SRVTs and changes in pain and disability. This study used data from 2 prospective primary care cohorts: the Danish Chiropractic LBP Cohort (n = 1323) and the GLA:D Back cohort (n = 1135). Participants identified one of the 8 SRVTs at baseline and 12-month follow-up, each asking about LBP trajectories the preceding year. Trajectories were described using 2 subscales (intensity and pattern). Temporal stability was quantified by "stability odds ratios" (ORs), depicting the likelihood of staying in the same SRVT after 12 months compared with baseline, and by "preference ORs," depicting the likelihood of choosing a specific alternative SRVT at follow-up. Both ORs compare the observed proportion with the chance level. Finally, we examined associations between transitioning to a different trajectory and changes in clinical outcomes. Approximately 30% stayed in the same SRVT. The stability ORs were all >1. The preference ORs indicated that transitions occurred mainly to similar SRVTs differing in only 1 subscale. Transitions to less or more intense SRVTs were associated with changes in clinical outcomes in the expected direction. Despite distinctly different SRVTs identified, individuals reported relatively stable LBP phenotypes but with potential for change.

Reliability of trunk strength measurements with an isokinetic dynamometer in non-specific low back pain patients: A systematic review

BACKGROUND

Imbalance or decreased trunk strength has been associated with non-specific low back pain (NSLBP).

OBJECTIVE

This systematic review aimed (I) to evaluate the quality of evidence of studies evaluating the reliability of trunk strength assessment with an isokinetic dynamometer in NSLBP patients, (II) to examine the reliability of trunk strength assessment using an isokinetic dynamometer in NSLBP patients and (III) to determine the most reliable protocol for trunk strength assessment in NSLBP patients.

METHOD

PRISMA guidelines were followed. Three databases were used: PubMed, Scopus, and Web of Science with the following keywords: Isokinetic, Dynamometer, Trunk strength testing, Muscle testing, Isokinetic measurement, CORE, Abdominal muscles, Abdominal wall, Torso, Trunk, Spine, Reliability and, Reproducibility. We included only test-retest studies, focused on the reliability of isometric and isokinetic strength assessed with an isokinetic dynamometer in NSLBP adults' patients, published in English and from inception to March 30, 2021. The methodological quality was evaluated with the CAT scale and QAREL checklist.

RESULTS

Five hundred and seventy-seven articles were retrieved, of which five are included in this review. Three articles provide good quality of evidence, the reliability of trunk strength assessment in NSLBP patients is excellent, and the most reliable protocol for isometric assessment is in a seated position (ICC = 0.94-0.98) and for isokinetic strength in standing position, at 60∘/s and 120∘/s (ICC = 0.98).

CONCLUSION

There is good quality evidence regarding the trunk strength assessment's reliability. Reliability is excellent in NSLBP patients; however, a familiarization process should be considered to obtain clinically reliable data. The most reliable protocol is in a seated position for isometric strength and a standing position for isokinetic strength.

Exploring Social Determinants of Posttraumatic Pain, Distress, Depression, and Recovery Through Cross-Sectional, Longitudinal, and Nonlinear Trends

OBJECTIVES

Pain, distress, and depression are predictors of posttrauma pain and recovery. We hypothesized that pretrauma characteristics of the person could predict posttrauma severity and recovery.

METHODS

Sex, age, body mass index, income, education level, employment status, pre-existing chronic pain or psychopathology, and recent life stressors were collected from adults with acute musculoskeletal trauma through self-report. In study 1 (cross-sectional, n=128), pain severity was captured using the Brief Pain Inventory (BPI), distress through the Traumatic Injuries Distress Scale (TIDS) and depression through the Patient Health Questionnaire-9 (PHQ-9). In study 2 (longitudinal, n=112) recovery was predicted using scores on the Satisfaction and Recovery Index (SRI) and differences within and between classes were compared with identify pre-existing predictors of posttrauma recovery.

RESULTS

Through bivariate, linear and nonlinear, and regression analyses, 8.4% (BPI) to 42.9% (PHQ-9) of variance in acute-stage predictors of chronicity was explainable through variables knowable before injury. In study 2 (longitudinal), latent growth curve analysis identified 3 meaningful SRI trajectories over 12 months. Trajectory 1 (start satisfied, stay satisfied [51%]) was identifiable by lower TIDS, BPI, and PHQ-9 scores, higher household income and less likely psychiatric comorbidity. The other 2 trajectories (start dissatisfied, stay dissatisfied [29%] versus start dissatisfied, become satisfied [20%]) were similar across most variables at baseline save for the "become satisfied" group being mean 10 years older and entering the study with a worse (lower) SRI score.

DISCUSSION

The results indicate that 3 commonly reported predictors of chronic musculoskeletal pain (BPI, TIDS, PHQ-9) could be predicted by variables not related to the injurious event itself. The 3-trajectory recovery model mirrors other prior research in the field, though 2 trajectories look very similar at baseline despite very different 12-month outcomes. Researchers are encouraged to design studies that integrate, rather than exclude, the pre-existing variables described here.

Profiles of Pain Acceptance and Values-Based Action in the Assessment and Treatment of Chronic Pain

Pain acceptance and values-based action are relevant to treatment outcomes in those with chronic pain. It is unclear if patterns of responding in these two behavioral processes can be used to classify patients into distinct classes at treatment onset and used to predict treatment response. This observational cohort study had two distinct goals. First, it sought to classify patients at assessment based on pain acceptance and values-based action (N = 1746). Second, it sought to examine treatment outcomes based on class membership in a sub-set of patients completing an interdisciplinary pain rehabilitation program of Acceptance and Commitment Therapy for chronic pain (N = 343). Latent profile analysis was used in the larger sample to identify three distinct patient classes: low acceptance and values-based (AV) action (Low AV; n = 424), moderate acceptance and values-based action (Moderate AV; n = 983) and high acceptance and values-based action (High AV; n = 339). In the smaller treated sample, participants in the Low AV and Moderate AV class demonstrated improvements across all outcome variables, whereas those in the High AV class did not. These findings support the role of pain acceptance and values-based action in those with chronic pain.

Trajectories of disability in low back pain

Four recovery trajectories from low back pain were identified: high-stable (20.9%), high-decreasing (20.7%), medium-stable (29.9%), and low-decreasing (28.5%). Pain and depression predicted the high-stable trajectory.

Introduction:

Low back pain (LBP) is the leading course of years lived with disability. Unfortunately, not much knowledge exists about distinct trajectories of recovery from disability after LBP and their potential psychological predictors.

Objectives:

Hence, the aim of the present study was to identify trajectories of functional disability in LBP and their potential baseline psychological predictors.

Methods:

A 1-year consecutive cohort (N = 1048) of patients with LBP referred to the Spine Centre if they have not improved satisfactorily from a course of treatment in primary care after 1 to 2 months were assessed by self-report questionnaires at their first visit and at 6- and 12-month follow-up. Data from patients who responded to the Roland Morris Disability Questionnaire at least twice (N = 747) were used to assess trajectories of functional disability by Latent Growth Mixture Modeling. The following measures were used as baseline predictors of the trajectories: Pain Intensity Numerical Rating Scales, Pain Catastrophizing Scale, Tampa Scale for Kinesiophobia, and Hospital Anxiety and Depression Scale.

Results:

Four distinct trajectories were identified: high-stable (22.0%), high-decreasing (20.4%), medium-stable (29.7%), and low-decreasing (27.9%). Using the low-decreasing trajectory as reference, baseline pain intensity, depressive symptoms, and pain-catastrophizing predicted membership of all 3 symptomatic trajectories. However, using the high-decreasing trajectory as reference, age, baseline pain intensity, and depression were predictors of the high-stable trajectory.

Conclusion:

In particular, the finding of a high-stable trajectory characterized by high levels of baseline psychological distress is of potential clinical importance because psychological distress may be targeted by cognitive behavioral therapeutic approaches.

Evidence-Based Practice for Non-Specific Low Back Pain: Canadian Physiotherapists' Adherence, Beliefs, and Perspectives

Purpose: Physiotherapists are key providers of care for patients with low back pain (LBP); however, information on Canadian physiotherapists' use of evidence-based clinical practice guidelines (EBCPGs) for LBP is lacking. We aimed to (1) describe Canadian physiotherapists' adherence to EBCPGs for LBP; (2) compare beliefs and attitudes of physiotherapists with higher and lower adherence; (3) identify predictors of adherence; and (4) gather physiotherapists' perceptions about the care provided to patients with LBP. Method: This mixed methods study involved two phases: (1) a survey containing a LBP clinical scenario and (2) qualitative semi-structured interviews with physiotherapists. Results: A total of 406 (77%) of the 525 survey respondents demonstrated higher adherence (score of 3 or 4) to EBCPGs; however, only 29.5% chose interventions to address psychosocial issues. Postgraduate training was the strongest predictor of higher adherence. Interviewed physiotherapists reported being highly satisfied with the care provided to patients with LBP even when psychosocial issues are present, despite low confidence in addressing those issues. Conclusions: Although overall adherence was high, Canadian physiotherapists do not frequently address psychosocial issues with LBP patients, and often do not feel confident or competent in that aspect of practice. This suggests an opportunity for developing additional training for addressing psychosocial issues in LBP patients.

Pain trajectories and possible predictors of a favourable course of low back pain in patients consulting musculoskeletal physicians in The Netherlands

BACKGROUND

In The Netherlands, low back pain patients can consult physicians specialized in musculoskeletal (MSK) medicine. Previous studies have reported on the characteristics of patients consulting MSK physicians, and the treatment options used. There are no studies yet reporting on the course of Low Back Pain (LBP) after treatment by musculoskeletal (MSK) physicians in The Netherlands.

METHODS

In an observational cohort study MSK physicians recorded data about all low back pain patients presenting for a first consultation. At baseline they recorded age, gender, type and duration of the main complaint, and concomitant complaints. At the end of treatment they recorded the type of treatment and the number of treatment sessions. Patients were recruited to answer questionnaires at baseline, and at 6-weekly intervals during a follow-up period of six months. Patient questionnaires included information about previous medical consumption, together with PROMs measuring the level of pain and functional status. Latent Class Growth Analysis (LCGA) was used to classify patients into different groups according to their pain trajectories. Baseline variables were evaluated as predictors of a favourable trajectory using logistic regression analyses, and treatment variables were evaluated as possible confounders.

RESULTS

A total of 1377 patients were recruited, of whom 1117 patients (81%) answered at least one follow-up measurement. LCGA identified three groups of patients with distinct pain trajectories. A first group (N = 226) with high pain levels showed no improvement, a second group (N = 578) with high pain levels showed strong improvement, and a third group (N = 313) with mild pain levels showed moderate improvement. The two groups of patients presenting with high baseline pain scores were compared, and a multivariable model was constructed with possible predictors of a favourable course. Male gender, previous specialist visit, previous pain clinic visit, having work, a shorter duration of the current episode, and a longer time since the complaints first started were predictors of a favourable course. The multivariable model showed a moderate area under the curve (0.68) and a low explained variance (0.09).

CONCLUSIONS

In low back pain patients treated by musculoskeletal physicians in The Netherlands three different pain trajectories were identified. Baseline variables were of limited value in predicting a favourable course.

Knowledge and management of low back pain as running-related injuries among Italian physical therapists: findings from a national survey

OBJECTIVES

To investigate the beliefs, knowledge, attitudes, behavior, and the clinical management procedures of the Italian physical therapists specialized in orthopedic manipulative physical therapy (OMPT) toward running and its correlation with low back pain (LBP).Design: A cross-sectional online survey was conducted in 2019, according to the Checklist for Reporting Results of Internet E-Surveys (CHERRIES) and Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.Setting: Italy.Participants: One thousand two hundred and eighteen Italian OMPTs.

METHODS

Survey Monkey software was used to administer the survey. The questionnaire was self-reported and included 26 questions. Descriptive statistics were used and related to the effective respondents for each question.

RESULTS

One thousand two hundred and eighteen questionnaires (60.9%) were included in the analysis. A considerable cohort of OMPTs working in private practice clinical settings (n = 845; 69.4%; 95% CI 66.7-71.9) has indicated running not to be a relevant risk factor for the onset of LBP (n = 806; 66.2%; 95% CI 63.4-68.8). Moreover, most of the participants (n = 679; 55.7%; 95% CI 52.9-58.5) adopted a combination of manual therapy techniques and therapeutic exercise for the management of runners with LBP.

CONCLUSIONS

Widespread knowledge of clinical and theoretical management of LBP in runners-patients has emerged among Italian OMPTs. The OMPTs' academic background agrees with the recent literature and therefore highlights the paucity of studies related to LBP as running-related injuries.

Expected impact of lockdown measures due to COVID-19 on disabling conditions: a modelling study of chronic low back pain

Purpose

The COVID-19 pandemic and the containment measures such as social distancing, mobility restrictions and quarantine have significantly impacted the delivery of healthcare services, with possible negative effects on low back pain patients. In this study, we used an innovative agent-based model to quantify the effects of COVID-19 on the prevalence and severity of low back pain in the general population.

Methods

Epidemiological data were used to simulate the low back pain evolution in a population of 300,000 agents. Reduced access to treatment due to the containment measures was simulated with a probabilistic approach, in which 500 random scenarios (differing in: length of the lockdown, probability of having access to treatment, time before the resumption of treatment, duration of the effects of the treatment after its interruption) were simulated.

Results

The lockdown may increase the mean pain score higher than 1/10 points for patients suffering from acute low back pain, up to 4–5/10 points for specific individuals. The lockdown also affected the length of pain episodes, possibly impacting chronicity and disability. All the variables describing the random scenarios had a relevant impact in determining both the increase of pain intensity in the population and the length of the effects of the lockdown.

Conclusions

“Optimal lockdown parameters” which minimize the impact on low back pain while preserving the effects on infection spread and mortality could not be identified. Policies favouring a prompt resumption of treatments after the lockdown may be effective in shortening the duration of its negative effects.

AAAPT: Assessment of the Acute Pain Trajectory

OBJECTIVE

Define and contrast acute pain trajectories vs. the aggregate pain measurements, summarize appropriate linear and nonlinear statistical analyses for pain trajectories at the patient level, and present methods to classify individual pain trajectories. Clinical applications of acute pain trajectories are also discussed.

SETTING

In 2016, an expert panel involving the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION), American Pain Society (APS), and American Academy of Pain Medicine (AAPM) established an initiative to create a pain taxonomy, named the ACTTION-APS-AAPM Pain Taxonomy (AAAPT), for the multidimensional classification of acute pain. The AAAPT panel commissioned the present report to provide further details on analysis of the individual acute pain trajectory as an important component of comprehensive pain assessment.

METHODS

Linear mixed models and nonlinear models (e.g., regression splines and polynomial models) can be applied to analyze the acute pain trajectory. Alternatively, methods for classifying individual pain trajectories (e.g., using the 50% confidence interval of the random slope approach or using latent class analyses) can be applied in the clinical context to identify different trajectories of resolving pain (e.g., rapid reduction or slow reduction) or persisting pain. Each approach has advantages and disadvantages that may guide selection. Assessment of the acute pain trajectory may guide treatment and tailoring to anticipated symptom recovery. The acute pain trajectory can also serve as a treatment outcome measure, informing further management.

CONCLUSIONS

Application of trajectory approaches to acute pain assessments enables more comprehensive measurement of acute pain, which forms the cornerstone of accurate classification and treatment of pain.

Prolonged opioid use among opioid-naive individuals after prescription for nonspecific low back pain in the emergency department

ABSTRACT

Low back pain is a leading cause of disability globally. It is a common reason for presentation to the emergency department where opioids are commonly prescribed. This is a retrospective cohort study of opioid-naive adults with low back pain presenting to 1 of 4 emergency departments in Nova Scotia. We use routinely collected administrative clinical and drug-use data (July 2010-November 2017) to investigate the prevalence of prolonged opioid use and associated individual and prescription characteristics. In total, 23,559 eligible individuals presented with nonspecific low back pain, with 84.4% being opioid-naive. Our study population included 4023 opioid-naive individuals who filled a new opioid prescription within 7 days after their index emergency department visit (24.4%). The prevalence of prolonged opioid use after a new opioid prescription for low back pain (filling an opioid prescription 8-90 days after the emergency department visit and filling a subsequent prescription ±30 days of 6 months) was 4.6% (185 individuals). Older age and female sex were associated with clinically important increased odds of prolonged opioid use. First prescription average >90 morphine milligram equivalents/day (odds ratio 1.6, 95% confidence interval 1.0-2.6) and greater than 7-day supply (1.9, 1.1-3.1) were associated with prolonged opioid use in adjusted models. We found evidence of declining opioid prescriptions over the study period, but that 24.3% of first opioid prescriptions in 2016 would not have aligned with current guideline recommendations. Our study provides evidence to support a cautious approach to prescribing in opioid-naive populations.

Cold pain hypersensitivity predicts trajectories of pain and disability after low back surgery: a prospective cohort study

Improving the ability to predict persistent pain after spine surgery would allow identification of patients at risk and guide treatment decisions. Quantitative sensory tests (QST) are measures of altered pain processes, but in our previous study, preoperative QST did not predict pain and disability at single time-points. Trajectory analysis accounts for time-dependent patterns. We hypothesized that QST predict trajectories of pain and disability during 1 year after low back surgery. We performed a trajectory analysis on the cohort of our previous study (n = 141). Baseline QST included electrical, pressure, heat, and cold stimulation of the low back and lower extremity, temporal summation, and conditioned pain modulation. Pain intensity and Oswestry Disability Index were measured before, and 2, 6, and 12 months after surgery. Bivariate trajectories for pain and disability were computed using group-based trajectory models. Multivariable regressions were used to identify QST as predictors of trajectory groups, with sociodemographic, psychological, and clinical characteristics as covariates. Cold pain hypersensitivity at the leg, not being married, and long pain duration independently predicted worse recovery (complete-to-incomplete, incomplete-to-no recovery). Cold pain hypersensitivity increased the odds for worse recovery by 3.8 (95% confidence intervals 1.8-8.0, P < 0.001) and 3.0 (1.3-7.0, P = 0.012) in the univariable and multivariable analyses, respectively. Trajectory analysis, but not analysis at single time-points, identified cold pain hypersensitivity as strong predictor of worse recovery, supporting altered pain processes as predisposing factor for persisting pain and disability, and a broader use of trajectory analysis. Assessment of cold pain sensitivity may be a clinically applicable, prognostic test.

Identification of clinically-useful cut scores of the Traumatic Injuries Distress Scale (TIDS) for predicting rate of recovery following musculoskeletal trauma

Objective

The Traumatic Injuries Distress Scale (TIDS) is a 12-item self-report tool intended for prognostic risk phenotyping in people with acute musculoskeletal (MSK) trauma. The initial validation study showed good associations with outcomes 12 weeks later in a cohort of 72 acutely injured patients from one region in Canada. This study aims to provide further clinical utility through identification of meaningful cut scores in a larger, mixed geography sample, and expands the prediction window from 12 to 52 weeks.

Methods

Data were drawn from databanks in London, Canada and Chicago, United States. Participants were recruited within 3 weeks of non-catastrophic MSK trauma and followed for 12 months. Using outcomes trajectories, the TIDS underwent linear regression-based analysis to predict 52-week outcomes, and area under the receiver operating characteristic curves to identify discriminative accuracy and meaningful cut scores.

Results

N = 224 participants with acute trauma were followed and both %Interference and Pain Severity were captured at intake and 3 follow-ups to establish curvilinear recovery trajectories. The TIDS explained significant variance in both the interference and severity outcomes after controlling for sex, region of injury, and baseline scores. ROC analysis revealed significant discriminative accuracy for predicting both the trajectories and the distal outcomes over 52 weeks. The TIDS was more accurate for identifying the low-risk than high-risk patients.

Conclusion

The TIDS is a useful tool for ‘ruling out’ high risk of poor outcome in a mixed sample of participants from two different countries.

Impact statement

The TIDS will be a useful tool for clinicians to predict the rate of recovery by displaying meaningful cut-scores for their patients after an acute musculoskeletal injury. This could lead to reduced burden of care for low risk patients and more informed treatment options for higher risk patients.

Low back pain among Italian runners: A cross-sectional survey

BACKGROUND

Low Back Pain (LBP) is commonly reported as a very frequent disorder in sports, but its prevalence in runners remains unclear.

OBJECTIVES

To determine the prevalence of LBP in a wide sample of Italian runners.

DESIGN

A cross-sectional online survey.

SETTING

A national survey, according to the CHERRIES and STROBE guidelines, was performed in 2019.

PARTICIPANTS

2539 Italian runners.

METHODS

A sample of Italian runners registered with national running associations was recruited. The survey was conducted using an online survey development platform. The questionnaire was self-reported and included 38 questions.

MAIN OUTCOME MEASURES

Descriptive statistics and frequencies were used to analyze results. Relationships between demographics, daily habits and running characteristics and the responses given was calculated with Cramer's V. Only correlation values higher >0.60 were deemed of interest.

RESULTS

2539 questionnaires (63.5%) were valid for analysis. In total, 22.6% of runners reported having experienced LBP in the past year. Most participants (77.0%) reporting episodes of LBP believed it was not caused by running. No significant correlations (Cramer's V < 0.60) were found between LBP and demographics, training characteristics or lifestyle habits.

CONCLUSION

The prevalence of LBP among Italian runners was 22,57%. LBP was not associated with training, equipment or lifestyle.

Relationship between acute pain trajectories after an emergency department visit and chronic pain: a Canadian prospective cohort study

OBJECTIVES

Inadequate acute pain management can reduce the quality of life, cause unnecessary suffering and can often lead to the development of chronic pain. Using group-based trajectory modelling, we previously identified six distinct pain intensity trajectories for the first 14-day postemergency department (ED) discharge; two linear ones with moderate or severe pain during follow-up (~40% of the patients) and four cubic polynomial order trajectories with mild or no pain at the end of the 14 days (low final pain trajectories). We assessed if previously described acute pain intensity trajectories over 14 days after ED discharge are predictive of chronic pain 3 months later.

DESIGN

Prospective cohort study.

SETTING

Tertiary care trauma centre academic hospital.

PARTICIPANTS

This study included 18 years and older ED patients who consulted for acute (≤2 weeks) pain conditions that were discharged with an opioid prescription. Patients completed a 14-day diary in which they listed their daily pain intensity (0-10 numeric rating scale).

OUTCOMES

Three months after ED visit, participants were questioned by phone about their current pain intensity (0-10 numeric rating scale). Chronic pain was defined as patients with current pain intensity ≥4 at 3 months.

RESULTS

A total of 305 participants remained in the study at 3 months, 49% were women and a mean age of 55±15 years. Twelve per cent (11.9; 95% CI 8.2 to 15.4) of patients had chronic pain at the 3-month follow-up. Controlling for age, sex and pain condition, patients with moderate or severe pain trajectories and those with only a severe pain trajectory were respectively 5.1 (95% CI 2.2 to 11.8) and 8.2 (95% CI 3.4 to 20.0) times more likely to develop chronic pain 3 months later compared with patients in the low final pain trajectories.

CONCLUSION

Specific acute pain trajectories following an ED visit are closely related to the development of chronic pain 3 months later.

TRIAL REGISTRATION NUMBER

NCT02799004; Results.

The transition from acute to persistent pain: the identification of distinct trajectories among women presenting to an emergency department

Posttraumatic stress disorder (PTSD) symptoms and other negative psychosocial factors have been implicated in the transition from acute to persistent pain. Women (N = 375) who presented to an inner-city emergency department (ED) with complaints of acute pain were followed up for 3 months. They completed a comprehensive battery of questionnaires at an initial visit and provided ratings of pain intensity at the site of pain presented in the ED during 3 monthly phone calls. Latent class growth analyses were used to detect possible trajectories of change in pain intensity from the initial visit to 3 months later. A 3-trajectory solution was found, which identified 3 groups of participants. One group (early recovery; n = 93) had recovered to virtually no pain by the initial visit, whereas a second group (delayed recovery; n = 120) recovered to no pain only after 1 month. A third group (no recovery; n = 162) still reported elevated pain at 3 months after the ED visit. The no recovery group reported significantly greater PTSD symptoms, anger, sleep disturbance, and lower social support at the initial visit than both the early recovery and delayed recovery groups. Results suggest that women with high levels of PTSD symptoms, anger, sleep disturbance, and low social support who experience an acute pain episode serious enough to prompt an ED visit may maintain elevated pain at this pain site for at least 3 months. Such an array of factors may place women at an increased risk of developing persistent pain following acute pain.

AAAPT Diagnostic Criteria for Acute Low Back Pain with and Without Lower Extremity Pain

OBJECTIVE

Low back pain is one of the most common reasons for which people visit their doctor. Between 12% and 15% of the US population seek care for spine pain each year, with associated costs exceeding $200 billion. Up to 80% of adults will experience acute low back pain at some point in their lives. This staggering prevalence supports the need for increased research to support tailored clinical care of low back pain. This work proposes a multidimensional conceptual taxonomy.

METHODS

A multidisciplinary task force of the ACTTION-APS-AAPM Pain Taxonomy (AAAPT) with clinical and research expertise performed a focused review and analysis, applying the AAAPT five-dimensional framework to acute low back pain.

RESULTS

Application of the AAAPT framework yielded the following: 1) Core Criteria: location, timing, and severity of acute low back pain were defined; 2) Common Features: character and expected trajectories were established in relevant subgroups, and common pain assessment tools were identified; 3) Modulating Factors: biological, psychological, and social factors that modulate interindividual variability were delineated; 4) Impact/Functional Consequences: domains of impact were outlined and defined; 5) Neurobiological Mechanisms: putative mechanisms were specified including nerve injury, inflammation, peripheral and central sensitization, and affective and social processing of acute low back pain.

CONCLUSIONS

The goal of applying the AAAPT taxonomy to acute low back pain is to improve its assessment through a defined evidence and consensus-driven structure. The criteria proposed will enable more rigorous meta-analyses and promote more generalizable studies of interindividual variation in acute low back pain and its potential underlying mechanisms.

Predicting pain recovery in patients with acute low back pain: a study protocol for a broad validation of a prognosis prediction model

BACKGROUND

The clinical course of acute low back pain (LBP) is generally favourable; however, there is significant variability in the prognosis of these patients. A clinical prediction model to predict the likelihood of pain recovery at three time points for patients with acute LBP has recently been developed. The aim of this study is to conduct a broad validation test of this clinical prediction model, by testing its performance in a new sample of patients and a different setting.

METHODS

The validation study with a prospective cohort design will recruit 420 patients with recent onset non-specific acute LBP, with moderate pain intensity, seeking care in the emergency departments of hospitals in São Paulo, Brazil. The primary outcome measure will be days to recovery from pain. The predicted probability of pain recovery for each individual will be computed based on predictions of the development model and this will be used to test the performance (calibration and discrimination) in the validation dataset.

DISCUSSION

The findings of this study will better inform about the performance of the clinical prediction model, helping both clinicians and patients. If the model's performance is acceptable, then future research should evaluate the impact of the prediction model, assessing whether it produces a change in clinicians' behaviour and/or an improvement in patient outcomes.

ETHICS AND DISSEMINATION

Ethics were granted by the Research Ethics Committee of the Universidade Cidade de São Paulo, #20310419.4.0000.0064. Study findings will be disseminated widely through peer-reviewed publications and conference presentations.

Trajectories of Pain Intensity Over 1 Year in Adults With Disabling Subacute or Chronic Neck Pain

Supplemental Digital Content is available in the text.

Objectives:

The objectives of this study were to describe the 1-year trajectories of disabling subacute or persistent neck pain and to investigate whether baseline age, sex, pain characteristics, and depressive symptoms are associated with such trajectories.

Study Design and Setting:

Participants (n=617) included in a randomized controlled trial provided weekly pain intensity ratings by responding to text messages over 1 year. We used latent class mixed model analyses to identify clusters of individual trajectories. Thereafter, we used logistic regression to determine the association between baseline age, sex, pain characteristics, depressive symptoms and treatment, and trajectories of neck pain.

Results:

Six different clusters of trajectories were identified. Most participants (73%) followed a trajectory of decreasing pain throughout follow-up. The remaining experienced unfavorable trajectories: persistent pain of high intensity (22%) and slightly (3%) or highly (2%) fluctuating levels of pain reaching high levels of pain intensity. Pain intensity at baseline: odds ratio (OR): 3.76 (95% confidence interval [CI]: 2.49-5.68), depressive symptoms: OR: 3.46 (95% CI: 2.01-5.95), younger age: OR: 2.29 (95% CI: 1.48-3.54), female sex: OR: 1.51 (95% CI: 1.01-2.26), and sudden onset of pain: OR: 1.74 (95% CI: 1.13-2.69) were associated with unfavorable trajectories.

Conclusions:

Most individuals with disabling subacute or chronic neck pain show improvement in pain intensity over a year. However, a quarter present unfavorable trajectories. High pain intensity at baseline, depressive symptoms, younger age, female sex, and sudden onset of pain are factors associated with unfavorable trajectories.

Defining pain and interference recovery trajectories after acute non-catastrophic musculoskeletal trauma through growth mixture modeling

BACKGROUND

Recovery trajectories support early identification of delayed recovery and can inform personalized management or phenotyping of risk profiles in patients. The objective of this study was to investigate the trajectories in pain severity and functional interference following non-catastrophic musculoskeletal (MSK) trauma in an international, mixed injury sample.

METHODS

A prospective longitudinal cohort (n = 241) was formed from patients identified within four weeks of trauma, from attendance at emergency or urgent care centres located in London, ON, Canada, or Chicago, IL, USA. Pain interference was measured via the Brief Pain Inventory (London cohort) or the Neck Disability Index (Chicago cohort). Pain severity was captured in both cohorts using the numeric pain rating scale. Growth mixture modeling and RM repeated measures ANOVA approaches identified distinct trajectories of recovery within pain interference and pain severity data.

RESULTS

For pain interference, the three trajectories were labeled accordingly: Class 1 = Rapid recovery (lowest intercept, full or near full recovery by 3 months, 32.0% of the sample); Class 2 = Delayed recovery (higher intercept, recovery by 12 months, 26.7% of the sample); Class 3 = Minimal or no recovery (higher intercept, persistently high interference scores at 12 months, 41.3% of the sample). For pain severity, the two trajectories were labeled: Class 1 = Rapid recovery (lower intercept, recovery by 3 months, 81.3% of the sample); and Class 2 = Minimal or no recovery (higher intercept, flat curve, 18.7% of the sample). The "Minimal or No Recovery" trajectory could be predicted by female sex and axial (vs. peripheral) region of trauma with 74.3% accuracy across the 3 classes for the % Interference outcome. For the Pain Severity outcome, only region (axial trauma, 81.3% accuracy) predicted the "Minimal or No Recovery" trajectory.

CONCLUSIONS

These results suggest that three meaningful recovery trajectories can be identified in an international, mixed-injury sample when pain interference is the outcome, and two recovery trajectories emerge when pain severity is the outcome. Females in the sample or people who suffered axial injuries (head, neck, or low back) were more likely to be classed in poor outcome trajectories.

TRIAL REGISTRATION

National Institutes of Health - clinicaltrials.gov ( NCT02711085 ; Retrospectively registered Mar 17, 2016).

A prospective observational study on trajectories and prognostic factors of mid back pain

Background

Although mid back pain (MBP) is a common condition that causes significant disability, it has received little attention in research and knowledge about trajectories and prognosis of MBP is limited. The purpose of this study was to identify trajectories of MBP and baseline risk factors for an unfavorable outcome in MBP patients undergoing chiropractic treatment.

Methods

This prospective-observational study analyzes outcome data of 90 adult MBP patients (mean age = 37.0 ± 14.6 years; 49 females) during one year (at baseline, after 1 week, 1 month, 3, 6 and 12 months) after start of chiropractic treatment. Patients completed an 11-point (0 to 10) numeric pain rating scale (NRS) at baseline and one week, one month, three, six and twelve months after treatment start and the Patient’s Global Impression of Change (PGIC) questionnaire at all time points except baseline. To determine trajectories, clustering with the package kml (software R), a variant of k-means clustering adapted for longitudinal data, was performed using the NRS-data. The identified NRS-clusters and PGIC data after three months were tested for association with baseline variables using univariable logistic regression analyses, conditional inference trees and random forest plots.

Results

Two distinct NRS-clusters indicating a favourable (rapid improvement within one month from moderate pain to persistent minor pain or recovery after one year, 80% of patients) and an unfavourable trajectory (persistent moderate to severe pain, 20% of patients) were identified. Chronic (> 3 months) pain duration at baseline significantly predicted that a patient was less likely to follow a favourable trajectory [OR = 0.16, 95% CI = 0.05–0.50, p = 0.002] and to report subjective improvement after twelve months [OR = 0.19, 95% CI = 0.07–0.51, p = 0.001], which was confirmed by the conditional inference tree and the random forest analyses.

Conclusions

This prospective exploratory study identified two distinct MBP trajectories, representing a favourable and an unfavourable outcome over the course of one year after chiropractic treatment. Pain chronicity was the factor that influenced outcome measures using NRS or PGIC.

Effects of exercise therapy in patients with acute low back pain: a systematic review of systematic reviews

BACKGROUND

Acute low back pain is associated with pain and disability, but symptoms are often self-healing. The effectiveness of exercise therapy for acute low back pain remains uncertain with conflicting evidence from systematic reviews. The aim of this systematic review of systematic reviews was to assess the overall certainty of evidence for the effects of exercise therapy, compared with other interventions, on pain, disability, recurrence, and adverse effects in adult patients with acute low back pain.

METHODS

PubMed, the Cochrane library, CINAHL, PEDro, Open Grey, Web of Science, and PROSPERO were searched for systematic reviews of randomized controlled trials. Methodological quality was assessed independently by two authors using AMSTAR. Meta-analyses were performed if possible, using data from the original studies. Data for pain, disability, recurrence, and adverse effects were analyzed. Certainty of evidence was assessed using GRADE.

RESULTS

The searches retrieved 2602 records, of which 134 publications were selected for full-text screening. Twenty-four reviews were included, in which 21 randomized controlled trials (n = 2685) presented data for an acute population, related to 69 comparisons. Overlap was high, 76%, with a corrected covered area of 0.14. Methodological quality varied from low to high. Exercise therapy was categorized into general exercise therapy, stabilization exercise, and McKenzie therapy. No important difference in pain or disability was evident when exercise therapy was compared with sham ultrasound, nor for the comparators usual care, spinal manipulative therapy, advice to stay active, and educational booklet. Neither McKenzie therapy nor stabilization exercise yielded any important difference in effects compared with other types of exercise therapy. Certainty of evidence varied from very low to moderate.

CONCLUSIONS

The findings suggest very low to moderate certainty of evidence that exercise therapy may result in little or no important difference in pain or disability, compared with other interventions, in adult patients with acute low back pain. A limitation of this systematic review is that some included reviews were of low quality. When implementing findings of this systematic review in clinical practice, patients' preferences and the clinician's expertise also should be considered, to determine if and when exercise therapy should be the intervention of choice.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO: CRD46146, available at: https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=46146 .

An individualised self-management exercise and education program did not prevent recurrence of low back pain but may reduce care seeking: a randomised trial

QUESTION

What is the effect of a McKenzie-based self-management exercise and education program on the risk of recurrence of low back pain (LBP) and on the impact of LBP?

DESIGN

Randomised controlled trial with concealed allocation, blinded assessors and intention-to-treat analysis.

PARTICIPANTS

262 adults recently recovered from an episode of LBP.

INTERVENTION

The experimental group received a McKenzie-based self-management exercise and education program delivered over two individual sessions of 30 to 45 minutes with a physiotherapist, approximately 2 weeks apart. The control group received a single advice session over the phone.

OUTCOME MEASURES

The primary outcome was time to first recurrence of an episode of activity-limiting LBP. Secondary outcomes included time to recurrence of any LBP, time to a recurrence causing care seeking and a composite measure of pain and function ('impact of LBP'). Participants were followed-up monthly for ≥ 12 months.

RESULTS

The estimated effect of the experimental intervention on the risk of recurrence of an episode of: activity-limiting LBP was HR 1.11 (95% CI 0.80 to 1.54), any LBP was HR 0.95 (95% CI 0.72 to 1.26), and LBP for which care was sought was HR 0.69 (95% CI 0.46 to 1.04). The quarterly estimates of the experimental intervention's effect on impact of LBP and their 95% CIs were all within 4 points above or below 0 (no effect) on this scale from 8 to 50.

CONCLUSION

This study's best estimate is that a McKenzie-based self-management exercise and education program does not produce a worthwhile reduction in the risk of an activity-limiting episode of LBP; however, modestly reduced or moderately increased risk cannot be ruled out. It may markedly reduce the risk of an episode of LBP resulting in care seeking, but does not have any worthwhile effect on the impact of LBP over 12 months.

TRIAL REGISTRATION

ACTRN12616000926437.

Development of More Precise Measurement to Predict Pain 1 Month Postoperatively Based on Use of Acute Postoperative Pain Score in Patients With Distal Radial Fracture

BACKGROUND

A method for modeling the acute pain trajectory using the simple linear fit of an individual's pain intensity scores after surgery was developed and affords more precise measurement than conventional pain assessment. However, the method has the disadvantage of using only the slope without considering the intercept. The purpose of this study was to verify our modification of the pain trajectory model including slope and intercept and to identify clusters.

METHODS

The pain intensity was measured in 60 patients after surgery, and we calculated their pain trajectories. The pain trajectory normally resolves in intensity over a period of days, and the linear fit of an individual patient's pain intensity score defines the trajectory. In this simple linear model (x axis, days; y axis, pain intensity), each patient's trajectory has the slope and the intercept. A multiple regression analysis model known as structural equation modeling was used to predict postoperative pain at 30 days after surgery. Finally, we performed hierarchical cluster analysis using the pain trajectory.

RESULTS

The slope and intercept model was the best fit among the models. Based on cluster analysis results, we created 4 pain trajectory groups (slope and intercept).

CONCLUSION

Our results suggest that the pain trajectory using the slope and intercept is quite useful for predicting postoperative pain at 30 days after surgery. Additionally, patients were classified into 4 groups using the slope and intercept. By considering both the slope and intercept, clinicians may be able to detect the risk for prolonged pain earlier than other methods.

Course of Back Pain in the Canadian Population: Trajectories, Predictors, and Outcomes

OBJECTIVE

To identify and describe back pain trajectory groups and to compare indicators of health status, medication, and health care use in these groups.

METHODS

A representative sample (n = 12,782) of the Canadian population was followed-up from 1994/1995 to 2010/2011. Participants were interviewed biannually and provided data on sociodemographic (e.g., education) and behavior-related (e.g., physical activity) factors, depression, comorbidities, pain, disability, medication use (e.g., opioids), and health care use (e.g., primary care visits). We used group-based trajectory analysis to categorize participants according to patterns in the course of their back pain during the 16-year follow-up period and compared indicators of pain, disability, medication, and health care use in the trajectory groups.

RESULTS

A total of 45.6% of the participants reported back pain at least once during follow-up. Of those, we identified 4 trajectories: persistent (18.0%), developing (28.1%), recovery (20.5%), and occasional (33.4%). The persistent and developing groups were characterized as having pain that prevented activities, disability, depression, and comorbidities. There were significant differences in the patterns of medication and health care use across the groups, with a general trend of most to least health care and medication use in the persistent, developing, recovering, and occasional groups. Those in the recovery group had an increasing trajectory reflecting opioid and antidepressant use.

CONCLUSION

Approximately 1 in 5 people with back pain experience a persistent pain trajectory with an associated increase in pain, disability, and health care use. Further research is needed to determine whether the groups identified represent different diagnoses, which may provide insight into the selection of stratified treatment and aid in designing early prevention and management strategies in the population.

Modeling Learning Patterns to Predict Placebo Analgesic Effects in Healthy and Chronic Orofacial Pain Participants

Successfully predicting the susceptibility of individuals to placebo analgesics will aid in developing more effective pain medication and therapies, as well as aiding potential future clinical use of placebos. In pursuit of this goal, we analyzed healthy and chronic pain patients' patterns of responsiveness during conditioning rounds and their links to conditioned placebo analgesia and the mediating effect of expectation on those responses. We recruited 579 participants (380 healthy, 199 with temporomandibular disorder [TMD]) to participate in a laboratory placebo experiment. Individual pain sensitivity dictated the temperatures used for high- and low-pain stimuli, paired with red or green screens, respectively, and participants were told there would be an analgesic intervention paired with the green screens. Over two conditioning sessions and one testing session, participants rated the painfulness of each stimulus on a visual analogue scale from 0 to 100. During the testing phase, the same temperature was used for both red and green screens to assess responses to the placebo effect, which was defined as the difference between the average of the high-pain-cue stimuli and low-pain-cue stimuli. Delta scores, defined as each low-pain rating subtracted from its corresponding high-pain rating, served as a means of modeling patterns of conditioning strength and placebo responsiveness. Latent class analysis (LCA) was then conducted to classify the participants based on the trajectories of the delta values during the conditioning rounds. Classes characterized by persistently greater or increasing delta scores during conditioning displayed greater placebo analgesia during testing than those with persistently lower or decreasing delta scores. Furthermore, the identified groups' expectation of pain relief acted as a mediator for individual placebo analgesic effects. This study is the first to use LCA to discern the relationship between patterns of learning and the resultant placebo analgesia in chronic pain patients. In clinical settings, this knowledge can be used to enhance clinical pain outcomes, as chronic pain patients with greater prior experiences of pain reduction may benefit more from placebo analgesia.