Pain characteristic differences between subacute and chronic back pain

Prognostic Factors and Treatment Effect Modifiers for Physical Health, Opioid Prescription, and Health Care Utilization in Patients With Musculoskeletal Disorders in Primary Care: Exploratory Secondary Analysis of the STEMS Randomized Trial of Direct Access to Physical Therapist-Led Care

OBJECTIVE

The aims of the study were to identify prognostic factors associated with health care outcomes in patients with musculoskeletal (MSK) conditions in primary care and to determine whether characteristics associated with choice of care modify treatment effects of a direct-access physical therapist-led pathway in addition to general practitioner (GP)-led care compared to GP-led care alone.

METHODS

A secondary analysis of a 2-parallel-arm, cluster randomized controlled trial involving general practices in the United Kingdom was conducted. Practices were randomized to continue offering GP-led care or to also offer a direct-access physical therapist-led pathway. Data from adults with MSK conditions who completed the 6-month follow-up questionnaire were analyzed. Outcomes included physical health, opioid prescription, and self-reported health care utilization over 6 months. Treatment effect modifiers were selected a priori from associations in observational studies. Multivariable regression models identified potential prognostic factors, and interaction analysis tested for potential treatment effect modifiers.

RESULTS

Analysis of 767 participants indicated that baseline pain self-efficacy, pain severity, and having low back pain statistically predicted outcomes at 6 months. Higher pain self-efficacy scores at baseline were associated with improved physical health scores, reduced opioid prescription, and less health care utilization. Higher bodily pain at baseline and having low back pain were associated with worse physical health scores and increased opioid prescription. Main interaction analyses did not reveal that patients' age, level of education, duration of symptoms, or MSK presentation influenced response to treatment, but visual trends suggested those in the older age group proceeded to fewer opioid prescriptions and utilized less health care when offered direct access to physical therapy.

CONCLUSIONS

Patients with MSK conditions with lower levels of pain self-efficacy, higher pain severity, and presenting with low back pain have less favorable clinical and health care outcomes in primary care. Prespecified characteristics did not modify the treatment effect of the offer of a direct-access physical therapist-led pathway compared to GP-led care.

IMPACT

Patients with MSK conditions receiving primary care in the form of direct-access physical therapist-led or GP-led care who have lower levels of self-efficacy, higher pain severity, and low back pain are likely to have a less favorable prognosis. Age and duration of symptoms should be explored as potential patient characteristics that modify the treatment response to a direct-access physical therapist-led model of care.

Avoidance and Endurance Responses to Pain Before and with Advanced Chronification: Preliminary Results from a Questionnaire Survey in Adult Patients with Non-Cancer Pain Conditions

Purpose

The Avoidance-Endurance Model postulates fear-avoidance responses and endurance responses as important psychological mechanisms in the development and maintenance of chronic pain. The present study aims to investigate potential differences in avoidance and endurance responses to pain before and with advanced chronification.

Patients and Methods

Two samples of adults with non-cancer pain at two different stages of chronicity were compared: One with pain and risk factors for chronicity (n=26, part of the PAIN2020 project) and one with chronic pain (n=33 from a pain day care clinic). The German Pain Questionnaire, the Graded Chronic Pain Scale (GCPS) and medical reports were used to measure duration and severity of pain. Responses to pain were assessed with the Avoidance-Endurance Questionnaire (AEQ) and psychological strain with the Depression, Anxiety and Stress Scales (DASS).

Results

Both groups were primarily affected by musculoskeletal pain. Although not yet chronified, the risk group reported comparable GCPS levels of pain intensity and disability. Depression and stress ratings were also similar, except for anxiety, which was significantly elevated in the chronic pain sample (p<.001). The AEQ scales did not differ between groups, neither on any of the fear-avoidance- nor endurance-related dimensions. A post-hoc regression analysis revealed a significant prediction of fear-avoidance by pain-related disability (p<.001). The regression model for endurance responses was not significant.

Conclusion

Patients with risk factors of chronification experience substantial pain-related burden. Responses to pain in the realm of the Avoidance-Endurance model do not appear to vary as a function of chronification. While fear-avoidance and pain-related disability correlate positively, endurance could not be associated to any of our variables.

Brain-predicted age difference estimated using DeepBrainNet is significantly associated with pain and function-a multi-institutional and multiscanner study

ABSTRACT

Brain age predicted differences (brain-PAD: predicted brain age minus chronological age) have been reported to be significantly larger for individuals with chronic pain compared with those without. However, a debate remains after one article showed no significant differences. Using Gaussian Process Regression, an article provides evidence that these negative results might owe to the use of mixed samples by reporting a differential effect of chronic pain on brain-PAD across pain types. However, some remaining methodological issues regarding training sample size and sex-specific effects should be tackled before settling this controversy. Here, we explored differences in brain-PAD between musculoskeletal pain types and controls using a novel convolutional neural network for predicting brain-PADs, ie, DeepBrainNet. Based on a very large, multi-institutional, and heterogeneous training sample and requiring less magnetic resonance imaging preprocessing than other methods for brain age prediction, DeepBrainNet offers robust and reproducible brain-PADs, possibly highly sensitive to neuropathology. Controlling for scanner-related variability, we used a large sample (n = 660) with different scanners, ages (19-83 years), and musculoskeletal pain types (chronic low back [CBP] and osteoarthritis [OA] pain). Irrespective of sex, brain-PAD of OA pain participants was ∼3 to 4.7 years higher than that of CBP and controls, whereas brain-PAD did not significantly differ among controls and CBP. Moreover, brain-PAD was significantly related to multiple variables underlying the multidimensional pain experience. This comprehensive work adds evidence of pain type-specific effects of chronic pain on brain age. This could help in the clarification of the debate around possible relationships between brain aging mechanisms and pain.

Relationship between the affective dimension of pain and site of the disorder: A cross-sectional study

BACKGROUND

Pain is a complex experience with both sensory and affective dimensions, and the affective dimension can increase the risks of chronic pain development. It is thus critical to identify factors influencing the affective dimension of pain.

OBJECTIVE

This study aimed to identify the relationship between the affective dimension of pain and disorder site (primary pain source).

METHODS

Study participants were recruited from patients referred for physical therapy at an orthopedic outpatient clinic. Pain quality including the affective dimension, disorder site from descriptive medical diagnosis, pain intensity, duration from pain onset, and demographic data, was collected. A multivariable logistic regression model was constructed to analyze the relationship between the affective dimension of pain and the disorder site.

RESULTS

A total of 282 participants were included. Cervical and lumbar spine disorders were significantly associated with an affective dimension of pain compared to limbs disorders when adjusted for age, sex, pain intensity, and duration from the onset in the regression model.

CONCLUSIONS

Regardless of duration from the onset and other confounding factors, disorder site is correlated with the affective dimension of pain. Multidimensional pain assessment is crucial when clinicians evaluate patients with cervical and lumbar spine disorders, even in the acute phase.

The association of spouse interactions and emotional learning in interference related to chronic back pain

Social interactions affect individual behaviours, preferences, and attitudes. This is also critical in the context of experiencing pain and expressing pain behaviours, and may relate to learned emotional responses. In this respect, individual variability in the medial prefrontal cortex (mPFC), which is involved in adjusting an organism's behaviour to its environment by evaluating and interpreting information within the context of past experiences, is important. It is critical for selecting suitable behavioural responses within a social environment and may reinforce maladaptation in chronic pain. In our study, we used brain imaging during appetitive and aversive pavlovian conditioning in persons with chronic back pain (CBP), subacute back pain (SABP), and healthy controls (HC), together with information on spouse responses to pain behaviours. We also examined the relationship of these responses with pain-related interference in the patients. Our findings yielded a significant negative association between mPFC responses to appetitive and aversive learning in CBP. We also observed a significant negative association for mPFC responses during aversive learning and distracting spouse responses, and a significant positive association between mPFC responses during appetitive learning and solicitous spouse responses in CBP. Both significantly predicted pain-related interference in the CBP group (explained variance up to 53%). Significant associations were not found for SABP or HC. Our findings support an association between appetitive and aversive pavlovian learning, related brain circuits and spouse responses to pain in CBP, where appetitive and aversive learning processes seem to be differentially involved. This can inform prevention and early intervention in a mechanistic approach.

Pain Among Latvian Workers: General Prevalence vs. Registered Occupational Diseases

The problem of painful and disabling work-related musculoskeletal disorders (MSDs) is increasing in many employment sectors of Latvia. Official statistics may underestimate the proportion of affected employees, causing delays in preventive interventions, ineffective rehabilitation, and a reduction of the workforce. This study investigated the prevalence of painful health conditions among Latvian workers by analyzing survey data and comparing these to official statistics on registered occupational diseases (ODs). A total of 2,446 workers participated in the state-level “Work conditions and risks in Latvia, 2017–2018” survey that included questions about pain lasting longer than 3 days during the previous year. The frequency of subjective reports on the presence, severity, and location of pain and related behaviors was assessed in relation to sex, age, education, and job position. Descriptive statistics and cross tabulation with the chi-squared test as well as multinomial logistic regression were applied to the data. Overall, 27.7% of respondents (n = 678) reported experiencing pain, predominantly in the lower back (14.3%) and mostly moderate (47.1%) or severe (45.1%). Only one-fifth of respondents (20.5%) took sick leave from work and one-third (29.0%) did not take action to alleviate their pain. Participants aged 55–74 years had a significantly higher odds ratio (OR) for pain in at least one body region—including hands and legs—than those aged 18–24 years. Women had significantly higher odds of headache (OR = 2.55) and neck pain (OR = 1.85) than men. Respondents with a primary or elementary education level had higher odds of pain in at least one body region (OR = 1.60) and in the lower back (OR = 1.86), while those with secondary education had higher odds of pain in hands (OR = 1.51) than employees with higher education. Unskilled workers had significantly higher odds of pain in hands (OR = 2.42) and legs (OR = 2.12) than directors. Official data revealed a dramatic increase in the proportion of MSDs and related disabilities in the last decade, reaching 75.5% of all first registered ODs in 2019. These results demonstrate a high prevalence of painful conditions among Latvian employees; urgent attention to diagnostics, treatment, and prevention is needed to ensure the musculoskeletal health and productivity of this population.

Axial Spondyloarthritis in the Chiropractic Care Setting: A Systematic Literature Review

ABSTRACT

Diagnosis of axial spondyloarthritis (axSpA), an immune-mediated inflammatory disease, is commonly associated with chronic inflammatory back pain (IBP) and often occurs years after initial onset of clinical symptoms. Recognition of IBP is important for timely referral of patients with suspected axSpA to a rheumatologist. Patients with all types of back pain are treated in chiropractic care, but the proportion of patients with undiagnosed axSpA is unknown. This systematic literature review investigated the presence of axSpA in patients treated by chiropractors and identified the chiropractor's role in axSpA diagnosis, referral, and management. A PubMed search was conducted using the following search strings: "chiropract*" AND ("sacroiliac" OR "back pain" OR "spondyloarthritis" OR "ankylosing spondylitis"); English language, since 2009; and (chiropractic OR chiropractor) AND (ankylosing spondylitis OR axial spondyloarthritis), with no date limits. Of 652 articles identified in the searches, 27 met the inclusion criteria. Although back pain was identified as a common reason for patients seeking chiropractic care, there was no mention of axSpA, ankylosing spondylitis, or the distinction between mechanical and IBP. Data from relevant articles suggested that the majority of patients seeking chiropractic care have lower back pain, whereas no articles reported axSpA in this patient population. The near absence of any identified articles on axSpA in chiropractic care may be due to underrecognition of axSpA, resulting in delayed rheumatology referral and appropriate management. Better awareness and increased use of validated screening tools could reduce diagnostic delay of axSpA in chiropractic care.

Pain Catastrophizing Is Related to Static Postural Control Impairment in Patients with Nonspecific Chronic Low Back Pain: A Cross-Sectional Study

Purpose

Pain catastrophizing may contribute to the altered trunk muscle activity in patients with nonspecific chronic low back pain (NSCLBP). It is unclear if pain catastrophizing influences static postural control in patients with NSCLBP. This study aimed to investigate the relationship between pain catastrophizing and static postural control in NSCLBP patients.

Methods

Sixty-eight participants with NSCLBP and 40 healthy participants were recruited. Postural control was assessed by the sway area and the sway length of the center of pressure (COP) during balance tests. Pain catastrophizing in participants with NSCLBP was assessed by the Pain Catastrophizing Scale (PCS). Bilateral transversus abdominis (TrA) activation was evaluated by ultrasound imaging-measured percent change in muscle thickness. Associations between COP parameter and PCS/subscales of PCS were examined by multiple linear regression (MLR).

Results

Our results observed a larger COP sway area in NSCLBP group under eyes-closed condition (p < 0.001) and a lower level of voluntary activation of the bilateral TrA (p < 0.001), compared with the healthy control group. The MLR analyses revealed that the COP area sway under eyes-closed condition was significantly associated with the PCS score/helplessness score of PCS, voluntary activation of the left TrA, and age in participants with NSCLBP (β = 0.222/0.236, 0.341/0.344, and 0.328/0.325; p=0.045/0.033, 0.002, and 0.004, resp.).

Conclusions

Static postural control was associated with pain catastrophizing, voluntary activation of TrA, and age in participants with NSCLBP. This indicated that pain catastrophizing may affect postural control and should be considered when interpreting balance test results and managing NSCLBP.

COMPARATIVE EVALUATION OF THE PSYCHOMETRIC PROPERTIES OF ORTHOPEDIC SCALES FOR LOW BACK PAIN

ABSTRACT Objective: To evaluate the reliability, response capacity and validity of four scales for low back pain and correlate these scales with each other and the Self-Administered Comorbidity Questionnaire (SACQ). Methods: We evaluated the psychometric properties of four previously selected scales for low back pain: the Roland-Morris Disability Questionnaire (RMDQ), the Quebec Back Pain Questionnaire (QBPDS), the Waddell Disability Index (WDI) and the Back Pain Functional Scale (BPFS) and Self-Administered Comorbidity Questionnaire (SACQ) comorbidity scale. Exploratory and confirmatory factor analyses were conducted. Reliability and internal consistency were measured by Cronbach's alpha. Validity was measured through correlation of the scales with the Self-Administered Comorbidity Questionnaire comorbidity scale and an analysis of the structural equations between them. Results: The scales showed adequate indicators based on the factor structure and showed Kaiser-Meyer-Olkin values above 0.90. After the exploratory factor analysis, all scales showed fit indicators suited to a factor model, following the same pattern as the original validations. Similarly, they showed good internal consistency (Cronbach's alpha greater than .78). The only scale that showed factor loadings suggesting the exclusion of any item was the Roland-Morris. In terms of validity, the scales showed positive correlation coefficients similar to the Self-Administered Comorbidity Questionnaire and between them. Conclusion: Regarding the scales evaluated, they showed similar indications of reliability and internal consistency, such that we did not find sufficient evidence to indicate one scale over another. Level of Evidence I; Diagnostic studies – Investigation of a diagnostic test.

Hypothalamic-pituitary-adrenal axis feedback sensitivity in different states of back pain

Pain normally signals a threat to bodily integrity and causes emotional distress. Acute pain serves a protective function, yet, when pain turns chronic, the protective function is lost. A chain of psychophysiological alterations including changes in the stress regulation system, apparent in dysfunctional activity and responsivity of the hypothalamic-pituitary-adrenal (HPA) axis, might be an important factor in this context. Moreover, maladaptive responses may be complicated by affective comorbid symptoms such as anxiety and depression, and alter nociceptive processing. However, the relationship among pain chronicity, stress regulation, and contributing components of comorbid symptomatology as well as somatosensory profiles has rarely been examined. In the present study, we obtained diurnal cortisol profiles at baseline and feedback regulation (following a dexamethasone suppression test (DST)) in subacute (SABP) and chronic (CBP) back pain patients and healthy control individuals (HC). We also assessed anxiety, depression and chronic stress levels and used quantitative sensory testing (QST) to detect sensory abnormalities. We found a hyper-suppression of cortisol following DST and thus enhanced negative stress feedback sensitivity in SABP compared to both CBP and HC. In SABP, DST-related cortisol levels were negatively associated with pain intensity, mediated by cold pain thresholds and anxiety. These data support a stress model of pain chronicity and suggest that stress responses might be indicators of individual vulnerability in the transition period of subacute pain.

The neuropathic pain component among patients with chronic low back-radicular pain

OBJECTIVES

Determining neuropathic pain component (NPC) among patients with chronic low back pain-radicular pain (CLBP-RP) and the adjustment between scales of neuropathic pain.

MATERIAL-METHODS

One hundred and one patients with CLBP-RP were included in the study. The severity of CLBP-RP was evaluated by visual analogue scale (VAS). The Douleur Neuropathique 4 Questions (DN4) and Leeds Assessment of Neuropathic Symptoms and Signs Scales (LANSS) were used to evaluate the NPC.

RESULTS

The mean score of CLBP-RP assessed by VAS was 80 mm. NPC was detected a rate of 65.3% by DN4 and 40.6% by LANSS. NPC was 75.4% in females and 47.2% in males according to DN4, and 52.3% in females and 19.4% in males according to LANSS. The female gender, occupation, and VAS scores were determined to be significant factors contributing to presence of NPC according to logistic regression analyses (p< 0.01, p< 0.05, p< 0.05). A medium degree accordance was established between DN4 and LANSS scales according to kappa coefficient (Kappa = 0.532, p< 0.05).

CONCLUSION

CLBP is among the diseases causing mixed type pain accompanied by nociceptive and neuropathic pain. NPC was detected in a considerable part of patients with radicular pain. Identifying the character of radicular pain is significant to develop proper management strategies.

The evaluation and brain representation of pleasant touch in chronic and subacute back pain

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Chronic back pain (CBP) showed less positive evaluations of touch.

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Highest response to pleasant touch in SI and SII and insula in chronic back pain.

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Highest response to pleasant touch in ventral striatum in subacute back pain (SABP).

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Correlations of brain responses with pain interference in CBP and distress in SABP.

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Brain-behavior changes in pleasant touch processing may be a marker of pain chronicity.

If touch is perceived as pleasant, it can counteract the experience of pain. However, its pain-inhibitory function might be disturbed in chronic pain and this could contribute to pain-related interference. We investigated the perception of pleasant touch and its brain correlates in chronic back pain patients (CBP) compared to subacute back pain patients (SABP) and healthy controls (HC) using soft brush strokes. CBP showed less positive evaluations of touch. We found the highest activation in somatosensory and insular cortices in CBP, ventral striatum (VS) in SABP, and the orbitofrontal cortex in HC. Brain responses were significantly positively correlated with pleasantness ratings in HC and SABP, but not CBP. Further, the insula responses in CBP were positively correlated with pain-related interference and the VS activation in SABP correlated negatively with affective distress. Brain and behavioral changes in the processing of touch and its pleasantness may be a marker of pain chronicity and raise questions about the therapeutic value of pleasant touch in pain prevention and treatment.

Experimental Low Back Pain Decreased Trunk Muscle Activity in Currently Asymptomatic Recurrent Low Back Pain Patients During Step Tasks

Low back pain (LBP) patients show reorganized trunk muscle activity but if similar changes are manifest in recurrent LBP (R-LBP) patients during asymptomatic periods remains unknown. In 26 healthy and 27 currently asymptomatic R-LBP participants electromyographic activity (EMG) was recorded from trunk and gluteal muscles during series of stepping up and down on a step bench before and during experimentally intramuscular induced unilateral and bilateral LBP. Pain intensity was assessed using numeric rating scale (NRS) scores. Root mean square EMG (RMS-EMG) normalized to maximal voluntary contraction EMG and pain-evoked differences from baseline (ΔRMS-EMG) were analyzed. Step task duration was calculated from foot sensors. R-LBP compared with controls showed higher baseline RMS-EMG and NRS scores of experimental pain (P < .05). In both groups, bilateral compared with unilateral experimental NRS scores were higher (P < .001) and patients compared with controls reported higher NRS scores during both pain conditions (P < .04). In patients, unilateral pain decreased ΔRMS-EMG in the Iliocostalis muscle and bilateral pain decreased ΔRMS-EMG in all back and gluteal muscles during step tasks (P < .05) compared with controls. In controls, bilateral versus unilateral experimental pain induced increased step task duration and trunk RMS-EMG whereas both pain conditions decreased step task duration and trunk RMS-EMG in R-LBP patients compared with controls (P < .05).

PERSPECTIVE

Task duration and trunk muscle activity increased in controls and decreased in R-LBP patients during experimental muscle LBP. These results indicate protective strategies in controls during acute pain whereas R-LBP patients showed higher pain intensity and altered strategies that may be caused by the higher pain intensity, but the long-term consequence remains unknown.

Abdominal Pain, the Adolescent and Altered Brain Structure and Function

Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder of unknown etiology. Although relatively common in children, how this condition affects brain structure and function in a pediatric population remains unclear. Here, we investigate brain changes in adolescents with IBS and healthy controls. Imaging was performed with a Siemens 3 Tesla Trio Tim MRI scanner equipped with a 32-channel head coil. A high-resolution T1-weighted anatomical scan was acquired followed by a T2-weighted functional scan. We used a surface-based morphometric approach along with a seed-based resting-state functional connectivity (RS-FC) analysis to determine if groups differed in cortical thickness and whether areas showing structural differences also showed abnormal RS-FC patterns. Patients completed the Abdominal Pain Index and the GI Module of the Pediatric Quality of Life Inventory to assess abdominal pain severity and impact of GI symptoms on health-related quality of life (HRQOL). Disease duration and pain intensity were also assessed. Pediatric IBS patients, relative to controls, showed cortical thickening in the posterior cingulate (PCC), whereas cortical thinning in posterior parietal and prefrontal areas were found, including the dorsolateral prefrontal cortex (DLPFC). In patients, abdominal pain severity was related to cortical thickening in the intra-abdominal area of the primary somatosensory cortex (SI), whereas HRQOL was associated with insular cortical thinning. Disease severity measures correlated with cortical thickness in bilateral DLPFC and orbitofrontal cortex. Patients also showed reduced anti-correlations between PCC and DLPFC compared to controls, a finding that may reflect aberrant connectivity between default mode and cognitive control networks. We are the first to demonstrate concomitant structural and functional brain changes associated with abdominal pain severity, HRQOL related to GI-specific symptoms, and disease-specific measures in adolescents with IBS. It is possible such changes will be responsive to therapeutic intervention and may be useful as potential markers of disease progression or reversal.

Efficacy of a new once daily hydromorphone formulation in comparison with twice daily administration in chronic pain: a randomized, double-blind, cross-over study

Objective Efficacy and safety of a novel multiple-unit hydromorphone once daily (HOD) was compared to an established hydromorphone twice daily (HTD) regimen in patients with moderate-to-severe chronic pain. Design and methods The results from a randomized, double-blind, multicenter, cross-over trial in patients (n = 37) with chronic malignant or non-malignant pain are reported. The primary efficacy parameter was current pain on 0-100 mm VAS assessed four times daily and prior to intake of rescue medication (immediate-release hydromorphone) throughout the last 5 days with each treatment (after an 8 day build-up period to avoid carry-over effects). Total daily dose of hydromorphone (TDD: 8-32 mg/day) was kept stable during the double-blind treatment phase. Results The difference observed in mean current pain (-0.92 mm VAS) over the 5 day assessment period between HOD and HTD (28.44 mm vs. 29.36 mm VAS) was found to lack clinical relevance, as the 95% CI (-4.10 to 2.28 mm VAS) did not exceed the prespecified limit for non-inferiority of 9 mm VAS. Results from the full analysis set were consistent with per protocol data confirming robustness, as did the data for 12 h recalled pain assessed at 08:00 h and 20:00 h, showing no significant differences between once and twice daily medication. Both treatments produced effective and stable pain control with only minor day-to-day and intra-day fluctuations. Switching between treatments was suitable, considering both efficacy and safety, as no relevant or significant differences in adverse events were seen (25.0% HOD, 24.3% HTD). Most frequently typical side-effects of opioid therapy were observed, such as nausea, vomiting and headache. Conclusion Although this study was of short duration and included a limited number of patients, the results confirm that the new HOD is as effective and safe as the established HTD.

Reorganized Trunk Muscle Activity During Multidirectional Floor Perturbations After Experimental Low Back Pain: A Comparison of Bilateral Versus Unilateral Pain

Low back pain changes trunk muscle activity after external perturbations but the relationship between pain intensities and distributions and their effect on trunk muscle activity remains unclear. The effects of unilateral and bilateral experimental low back pain on trunk muscle activity were compared during unpredictable multidirectional surface perturbations in 19 healthy participants. Pain intensity and distribution were assessed using a visual analogue scale (VAS) and pain drawings. Root mean square (RMS) of the electromyographic (EMG) signals from 6 trunk muscles bilaterally after each perturbation was extracted and averaged across perturbations. The difference (ΔRMS-EMG) and absolute difference (absolute ΔRMS-EMG) RMS from baseline conditions were extracted for each muscle during pain conditions and averaged bilaterally for back and abdominal muscle groups. Bilateral compared with unilateral pain induced higher VAS scores (P < .005) and larger pain areas (P < .001). Significant correlation was present between VAS scores and muscle activity during unilateral (P < .001) and bilateral pain (P < .001). Compared with control injections ΔRMS-EMG increased in the back (P < .03) and abdominal (P < .05) muscles during bilateral and decreased in the back (P < .01) and abdominal (P < .01) muscles during unilateral pain. Bilateral pain caused greater absolute ΔRMS-EMG changes in the back (P < .01) and abdominal (P < .01) muscle groups than unilateral pain.

PERSPECTIVE

This study provided novel observations of differential trunk muscle activity in response to perturbations dependent on pain intensity and/or pain distribution. Because of complex and variable changes the relevance of clinical examination of muscle activity during postural tasks is challenged.

Perioperative Pain Correlates and Prolonged Postoperative Pain Predictors: Demographic and Psychometric Questionnaires

Introduction

Perioperatively, patients are near-guaranteed to experience acute pain by virtue of the surgical tissue insult. The transition of acute pain to pathological chronic pain is a complex and poorly understood process. To study this, the prevalence of pain was examined preoperatively, and at 6 weeks and 3 months postoperatively.

Methods

Fifty-four patients undergoing moderate-major gynaecological surgery at Christchurch Women’s Hospital (Christchurch, New Zealand) were recruited over a period of 11 weeks. Follow-up by telephone was conducted at 6 weeks and 3 months following surgery. Demographic information including age, gender, ethnicity, work, and education status were collected, as well as aspects of medical history. Participants were subjected to psychometric questionnaires at each time-point.

Results

Of the participants, 15.7% experienced significant pain at 6 weeks postoperatively; 8.2% of participants experienced significant pain at 3 months postoperatively. The psychometric questionnaires used found differences between those experiencing pain and those not experiencing pain at given observation points. Only the Brief Illness Perception Questionnaire (BIPQ) appeared predictive of developing prolonged postoperative pain. The mean difference (7.4 on a 0–50) scale should assist in clinical decision-making regarding analgesia.

Conclusion

Only the BIPQ was predictive of developing prolonged postoperative pain. While none of the demographic factors observed significantly predicted the development of ‘prolonged pain’, the not significant data followed expected trends. Several relationships were detected in this study that should further efforts in developing preoperative predictors to promote the secondary prevention of postoperative pain states.

Electronic supplementary material

The online version of this article (doi:10.1007/s40122-015-0037-7) contains supplementary material, which is available to authorized users.

Smoking increases risk of pain chronification through shared corticostriatal circuitry

Smoking is associated with increased incidence of chronic pain. However, the evidence is cross-sectional in nature, and underlying mechanisms remain unclear. In a longitudinal observational study, we examined the relationship between smoking, transition to chronic pain, and brain physiology. In 160 subjects with subacute back pain (SBP: back pain lasting 4-12 weeks, and no prior back pain [BP] for at least 1 year) pain characteristics, smoking status, and brain functional properties were measured repeatedly over 1 year. Sixty-eight completed the study, subdivided into recovering (SBPr, n = 31) and persisting (SBPp, n = 37), based on >20% decrease in BP over the year. Thirty-two chronic back pain (CBP: duration > 5 years) and 35 healthy controls were similarly monitored. Smoking prevalence was higher in SBP and CBP but not related to intensity of BP. In SBP, smoking status at baseline was predictive of persistence of BP 1 year from symptom onset (differentiating SBPp and SBPr with 0.62 accuracy). Smoking status combined with affective properties of pain and medication use improved prediction accuracy (0.82). Mediation analysis indicated the prediction of BP persistence by smoking was largely due to synchrony of fMRI activity between two brain areas (nucleus accumbens and medial prefrontal cortex, NAc-mPFC). In SBP or CBP who ceased smoking strength of NAc-mPFC decreased from precessation to postcessation of smoking. We conclude that smoking increases risk of transitioning to CBP, an effect mediated by corticostriatal circuitry involved in addictive behavior and motivated learning.

Exploring the Relationship of Three Medical Entitlement Beliefs and Psychiatric/Psychological Variables for Acute and Chronic Pain Patients

OBJECTIVES

The belief in medical care entitlement has recently resulted in major changes in the medical system in the United States. The objectives of this study were the following: to compare endorsement of three medical entitlement beliefs (I deserve the best medical care no matter what the cost [BMC], I am entitled to all of the medical care I want at no charge [NC], I shouldn't have to wait to see my doctors [W]) in community nonpatients without pain (CNPWP), acute pain patients (APPs), and chronic pain patients (CPPs) and to develop predictor models for these beliefs in APPs and CPPs.

DESIGN

CNPWP, APPs, and CPPs were compared statistically for frequency of endorsement of each belief. All available variables were utilized in logistic regression models to predict each belief in APPs and CPPs. Those affirming/nonaffirming each belief were compared by t-test for affirmation of narcissism, dependency, and antisocial practices on three scales from established inventories.

RESULTS

CPPs were significantly more likely than APPs to endorse BMC. No other comparisons were significant. The logistic regression models identified variables that related to narcissism, anger, doctor dissatisfaction, depression, and anxiety, which entered the models for both APPs and CPPs for some beliefs. Those APPs and CPPs who affirmed the beliefs of NC and W were more likely than their counterparts to affirm antisocial practices, but not narcissism or dependency.

CONCLUSIONS

Patient medical entitlement beliefs may be related to some psychiatric/psychological issues.

Clinical evaluation and surgical decision making for patients with lumbar discogenic pain and facet syndrome

In industrialized countries, more than two thirds of the population suffers from low back pain (LBP) in their lifetime. LBP associated with lumbar disc herniation, stenosis, and instability is a well-known and documented entity. On the other hand, the lumbar discogenic pain and facet syndrome are difficult to be clearly identified, and they are not always detectable by imaging. This article describes the causes of these painful syndromes, which are typically without radicular component, explains the modern diagnostic procedures, and provides guidelines for surgical decision making.

Reorganization of hippocampal functional connectivity with transition to chronic back pain

The hippocampus has been shown to undergo significant changes in rodent models of neuropathic pain; however, the role of the hippocampus in human chronic pain and its contribution to pain chronification have remained unexplored. Here we examine hippocampal processing during a simple visual attention task. We used functional MRI to identify intrinsic and extrinsic hippocampal functional connectivity (synchronous neural activity), comparing subacute back pain (SBP, back pain 1-4 mo) and chronic back pain (CBP, back pain >10 yr) patients to control (CON) subjects. Both groups showed more extensive hippocampal connectivity than CON subjects. We then examined the evolution of hippocampal connectivity longitudinally in SBP patients who recovered (SBPr, back pain decreased >20% in 1 yr) and those with persistent pain (SBPp). We found that SBPp and SBPr subjects have distinct changes in hippocampal-cortical connectivity over 1 yr; specifically, SBPp subjects showed large decreases in hippocampal connectivity with medial prefrontal cortex (HG-mPFC). Furthermore, in SBP patients the strength of HG-mPFC reflected variations in back pain over the year. These relationships were replicated when examined in a different task performed by SBP patients (rating fluctuations of back pain), indicating that functional connectivity of the hippocampus changes robustly in subacute pain and the nature of these changes depends on whether or not patients recover from SBP. The observed reorganization of processing within the hippocampus and between the hippocampus and the cortex seems to contribute to the transition from subacute to chronic pain and may also underlie learning and emotional abnormalities associated with chronic pain.

Intrarater reliability of pain intensity, tissue blood flow, thermal pain threshold, pressure pain threshold and lumbo-pelvic stability tests in subjects with low back pain

Purpose

This preliminary study aimed to determine the intrarater reliability of the quantitative tests for the study of non-specific low back pain.

Methods

Test-retest reliability of the measurements of ratio data was determined by an intraclass correlation coefficient (ICC), standard error of measurements (SEMs), coefficient of variation (CV), and one-way repeated measures ANOVA using the values collected from 13 young individuals (25.8 ± 6.2 years) with chronic non-specific low back pain on two occasions separated by 2 days. Percent agreement of the ordinal data was also determined by Cohen's Kappa statistics (kappa). The measures consisted of tissue blood flow (BF), average pain visual analog scales (VAS), pressure pain threshold (PPT), cold pain threshold (CPT), heat pain threshold (HPT) and lumbo-pelvic stability test (LPST). An acceptable reliability was determined as the ICC values of greater than 0.85, SEMs less than 5%, CV less than 15%, the kappa scores of greater than 80% and no evidence of systematic error (ANOVA, P>0.05).

Results

ICC of all measures in the lumbo-sacral area were greater than 0.87. The kappa was also greater than 83%. Most measures demonstrated a minimal error of measurements and less potential of systemic error in nature. Only the SEMs and the CV of the CPT exceeded the acceptable level.

Conclusions

It is concluded that most of the quantitative measurements are reliable for the study of non-specific low back pain, however the CPT should be applied with care as it has a great variation among individuals and potential of measurement error.

Corticostriatal functional connectivity predicts transition to chronic back pain

The mechanism of brain reorganization in pain chronification is unknown. In a longitudinal brain imaging study, sub–acute back pain (SBP) patients were followed over one year. When pain persisted (SBPp, in contrast to recovering SBP, and healthy controls), brain gray matter density decreased. Importantly, initially greater functional connectivity of nucleus accumbens with prefrontal cortex predicted pain persistence, implying that corticostriatal circuitry is causally involved in the transition from acute to chronic pain.

Correlations between EEG and clinical outcome in chronic neuropathic pain: surgical effects and treatment resistance

Chronic neuropathic pain may require a neurosurgical treatment, but for reasons that have not been fully explored yet, a significant number of patients do not benefit from the intervention. We compared the resting EEG of 15 healthy controls to the EEG of 23 chronic neuropathic pain patients before and 12 months after treatment by the central lateral thalamotomy (CLT). A patient subgroup had a high (n = 14, pain relief (PR)  ≥ 50%) and another subgroup a low (n = 9, PR < 50%) postoperative PR. EEG spectral power and source localization of the high PR patients were normalized postoperatively. In contrast, low PR patients showed postoperative maintenance of insular, cingulate and prefrontal overactivities, and their frustration values were positively correlated with cingulate and prefrontal activity. These findings demonstrate a normalizing effect of CLT on cortical activity and suggest that treatment resistance is associated with a frustration-based dynamics.

Chronic low back pain: a heterogeneous condition with challenges for an evidence-based approach

"Chronic" low back pain (LBP), defined as present for 3 or more months, has become a major socioeconomic problem insufficiently addressed by five major entities largely working in isolation from one another - procedural based specialties, strength based rehabilitation, cognitive behavioral therapy, pain management and manipulative care. As direct and indirect costs continue to rise, many authors have systematically evaluated the body of evidence in an effort to demonstrate the effectiveness (or lack thereof) for various diagnostic and therapeutic interventions. The objective of this Spine Focus issue is not to replicate previous work in this area. Rather, our expert panel has chosen a set of potentially controversial topics for more in-depth study and discussion. A recurring theme is that chronic LBP is a heterogeneous condition, and this affects the way it is diagnosed, classified, treated, and studied. The efficacy of some treatments may be appreciated only through a better understanding of heterogeneity of treatment effects (i.e., identification of clinically relevant subgroups with differing responses to the same treatment). Current clinical guidelines and payer policies for LBP are systematically compared for consistency and quality. Novel approaches for data gathering, such as national spine registries, may offer a preferable approach to gain meaningful data and direct us towards a "results-based medicine." This approach would require more high-quality studies, more consistent recording for various phenotypes and exploration of studies on genetic epidemiologic undertones to guide us in the emerging era of "results based medicine."