Evidence for Shared Pain Mechanisms in Osteoarthritis, Low Back Pain, and Fibromyalgia

A Self-Reported Association between Temporomandibular Joint Disorders, Headaches, and Stress

AIMS AND OBJECTIVES

Temporomandibular joint disorder (TMD) is an umbrella term for a number of conditions in the area of the joint, temple, and masticatory system. Many of those with TMD also suffer from headaches and anxiety. The aims and objectives of this study were to determine if there exists an association between the Diagnostic Criteria of TMD (DC/TMD) symptom questionnaire and report of headaches as well as stress.

MATERIALS AND METHODS

A cross-sectional study was implemented via the use of the DC/TMD symptom questionnaire and the perceived stress scale (PSS). This was distributed conveniently among dental students in a multi-dental school setting in Riyadh, Saudi Arabia, and was completed by 152 dental students. Odds ratios, Chi-square, and their corresponding 95% confidence intervals are reported. Statistical significance was set at P ≤ 0.05.

RESULTS

Those who ticked yes for pain on the TMD pain screener for pain with chewing hard or tough food, pain on mouth opening and lateral excursion, and pain with jaw habits as parafunction were at an odds risk from twice to thrice as likely to experience headaches. Similarly, those with poor coping skills on the PSS were more likely to have headaches (P = 0.002). Likewise, positive answers on the screener and symptom questionnaire were relevant with higher stress scores on the PSS.

CONCLUSION

This study clarifies and reiterates the intertwined power of both stress and headaches; the former being a role player in TMD progression and the latter its product. TMD is unfortunately on the rise; it should not be brushed off as a nuisance. A multidisciplinary approach in diagnosis and treatment of both TMD and headaches by a team of orofacial pain specialist, neurologist, psychiatrist and/or psychologist, and physical therapists to untangle the deceiving presentation of both conditions would not only provide a more favorable prognosis but also improve cost and time expenditures.

Factors affecting the results of analgesic therapy. Results of the Russian multicentre study of NOTE (NSAID: Open-label Trial of Efficacy)

AIM

To identify factors affecting the effectiveness of NSAIDs in patients with OA and LBP.

MATERIALS AND METHODS

An observational study was conducted to evaluate the effectiveness of a 2-week course of NSAIDs in OA and LBP in real clinical practice. The study group consisted of 3604 patients with OA and LBP (60.6% women and 39.4% men, mean age 55.0±13.4 years). According to the study design, aceclofenac (Airtal) and other NSAIDs used in the ratio 1:1. The main criterion of effectiveness was the frequency of complete pain relief after 2 weeks of therapy. In addition, the decrease of pain and general health were determined on a 10-point numerical rating scale (NRS). We compared the frequency of complete pain relief in patients who had and did not have the studied factors. The value of the studied factors was determined using OR (95% CI).

RESULTS

Most patients received aceclofenac (54.9%), as well as diclofenac (2.0%), ketoprofen (1.9%), lornoxicam (2.2%), meloxicam (13.7%), naproxen (2.1%), nimesulide (5.8%), celecoxib (5.9%), ethicoxib (7.1%) and other NSAIDs (4.4%); 56.2% of patients received muscle relaxants, mainly tolperisone (74.7%), vitamin B (10.4%), and proton pump inhibitors (42.8%). Complete pain relief was achieved in 54.8% of patients. The pain decrease and general health improvement were (for NRS) 63.9±13.4% and 61.7±14.8%, respectively. The efficacy of aceclofenac was slightly higher than in the whole group: complete pain relief was in 59.9% of patients. Adverse events in aceclofenac use were observed in 2.3% of patients, other NSAIDs-from 2.4 to 14.1%. The frequency of complete pain relief was higher in men: OR 1,239 (95% CI 1.08-1.418; p=0.002), who had the first episode of pain - OR 3.341 (95% CI 2.873-3.875; p=0.000), a good" response " to NSAIDs in history - OR 1.656 (95% CI 1.385-1.980; p=0.000) and received NSAIDs in combination with muscle relaxants - OR 1.218 (95% CI 1.067-1.390; p=0.004). The effect of therapy is lower in patients 65 years and older-OR 0,378 (95% CI 0.324-0.442; p=0,000), with body mass index >30 kg/m² - OR 0.619 (95% CI 0.529-0.723; p=0.000), with severe pain (≥7 points NRS) - OR 0.662 (95% CI 0.580-0.756; p=0.002), with pain at rest, - OR 0.515 (95% CI 0.450-0,589; p=0.000), pain at night - OR 0.581 (95% CI 0.501-0.672; p=0.000) and the presence of stiffness - OR 0.501 (95% CI 0.438-0,573; p=0.000). Treatment results are significantly worse in the cases of combination of LBP and joint pain, as well as pain in the trochanter major and pes anserinus area (p<0.001).

CONCLUSION

NSAIDs are the first-line medications for the pain treatment in LBP and OA. Aceclofenac is effective and safe in this conditions. When carrying out analgesic therapy should take into account factors that affect the effectiveness of treatment: old age, overweight, insufficient effect of NSAIDs in history, severe pain, signs of "inflammatory" pain, multiple sources of pain.

Cluster subgroups based on overall pressure pain sensitivity and psychosocial factors in chronic musculoskeletal pain: Differences in clinical outcomes

Objective: We aimed to empirically derive psychosocial and pain sensitivity subgroups using cluster analysis within a sample of individuals with chronic musculoskeletal pain (CMP) and to investigate derived subgroups for differences in pain and disability outcomes. Methods: Eighty female participants with CMP answered psychosocial and disability scales and were assessed for pressure pain sensitivity. A cluster analysis was used to derive subgroups, and analysis of variance (ANOVA) was used to investigate differences between subgroups. Results: Psychosocial factors (kinesiophobia, pain catastrophizing, anxiety, and depression) and overall pressure pain threshold (PPT) were entered into the cluster analysis. Three subgroups were empirically derived: cluster 1 (high pain sensitivity and high psychosocial distress; n = 12) characterized by low overall PPT and high psychosocial scores; cluster 2 (high pain sensitivity and intermediate psychosocial distress; n = 39) characterized by low overall PPT and intermediate psychosocial scores; and cluster 3 (low pain sensitivity and low psychosocial distress; n = 29) characterized by high overall PPT and low psychosocial scores compared to the other subgroups. Cluster 1 showed higher values for mean pain intensity (F_(2,77) = 10.58, p < 0.001) compared with cluster 3, and cluster 1 showed higher values for disability (F_(2,77) = 3.81, p = 0.03) compared with both clusters 2 and 3. Conclusions: Only cluster 1 was distinct from cluster 3 according to both pain and disability outcomes. Pain catastrophizing, depression, and anxiety were the psychosocial variables that best differentiated the subgroups. Overall, these results call attention to the importance of considering pain sensitivity and psychosocial variables to obtain a more comprehensive characterization of CMP patients' subtypes.

Pain Adaptability in Individuals With Chronic Musculoskeletal Pain Is Not Associated With Conditioned Pain Modulation

Healthy humans can be divided into the pain adaptive (PA) and the pain nonadaptive (PNA) groups; PA showed a greater decrease in pain rating to a cold pressor test (CPT) than PNA. This study examined if the dichotomy of pain adaptability existed in individuals with chronic musculoskeletal pain. CPTs at 2°C and 7°C were used to assess the status of pain adaptability in participants with either chronic nonspecific low back pain or knee osteoarthritis. The participants' potency of conditioned pain modulation (CPM) and local inhibition were measured. The strengths of pain adaptability at both CPTs were highly correlated. PA and PNA did not differ in their demographic characteristics, pain thresholds from thermal and pressure stimuli, or potency of local inhibition or CPM. PA reached their maximum pain faster than PNA (t₄₁ = -2.76, P < .01), and had a gradual reduction of pain unpleasantness over 7 days whereas PNA did not (F_6,246 = 3.01, P = .01). The dichotomy of pain adaptability exists in musculoskeletal pain patients. Consistent with the healthy human study, the strength of pain adaptability and potency of CPM are not related. Pain adaptability could be another form of endogenous pain inhibition of which clinical implication is yet to be understood.

PERSPECTIVE

The dichotomy of pain adaptability was identified in healthy humans. The current study confirms that this dichotomy also exists in individuals with chronic musculoskeletal pain, and could be reliably assessed with CPTs at 2°C and 7°C. Similar to the healthy human study, pain adaptability is not associated with CPM, and may reflect the temporal aspect of pain inhibition.

Pressure Pain Threshold and Anxiety in Adolescent Females With and Without Juvenile Fibromyalgia: A Pilot Study

OBJECTIVES

Reduced pain thresholds have been documented in adult fibromyalgia, but there are no quantitative studies of altered pain sensitivity in adolescents with juvenile fibromyalgia (JFM). The current study examined differences in pressure pain sensitivity between adolescent females with JFM and healthy controls. The relationship between levels of anxiety and pain were also examined.

METHODS

A total of 34 JFM (15.4±1.4 y old) and 31 controls (14.5±1.3 y old) completed self-report measures of pain and anxiety. Pressure pain threshold was assessed (palm and forehead sites) with a hand-held algometer. Participants indicated the first sensation of pain and then rated the intensity of pain on a Numerical Rating Scale.

RESULTS

Adolescents with JFM exhibited greater sensitivity to pressure pain compared with controls. While the difference between JFM and controls was only observed at the forehead, the intensity of pain produced by the pressure algometry at both sites was significantly higher in the JFM participants compared with controls. Correlations between clinical pain and anxiety were significant for the JFM group only. No relationships were observed between anxiety and pressure pain for either group.

DISCUSSION

This study is a first step toward investigating mechanisms of altered pain processing in adolescents with JFM. Adolescents with JFM were found be more sensitive to pressure pain than their healthy peers, which suggests a propensity for sensitization of peripheral and/or central nociceptive information often reported in adult fibromyalgia, and which does not appear to be affected by anxiety.

Convergent Validity of the Dutch Central Sensitization Inventory: Associations with Psychophysical Pain Measures, Quality of Life, Disability, and Pain Cognitions in Patients with Chronic Spinal Pain

OBJECTIVE

Symptoms of central sensitization (CS) have been described in patients with chronic spinal pain (CSP). Although a gold standard to diagnose CS is lacking, psychophysical pain measures are often used. The Central Sensitization Inventory (CSI) is proposed as an alternative method and indirect tool for the evaluation of CS symptomatology. The aim of the current study was to evaluate the convergent validity of the CSI by investigating the association with psychophysical pain measures and self-reported measures of current pain intensity, quality of life, disability, and catastrophizing in CSP patients.

METHODS

One hundred sixteen patients with nonspecific CSP were included in the present study. Patients completed the CSI, were subjected to pressure pain thresholds (PPTs) and a conditioned pain modulation (CPM) paradigm, and completed questionnaires for current pain intensity, quality of life, pain disability, and pain catastrophizing.

RESULTS

Higher CSI scores were weakly correlated with lower PPTs (-0.276 ≤ r ≤ -0.237; all P ≤ 0.01) and not with CPM efficacy (r = 0.017; P = 0.858). Higher CSI scores were moderately correlated with higher current pain intensity (r = 0.320; P < 0.001), strongly correlated with lower physical (r = -0.617; P < 0.001) and emotional (r = -0.635; P < 0.001) quality of life, and moderately correlated with higher pain disability (r = 0.472; P < 0.001) and higher pain catastrophizing (r = 0.464; P < 0.001).

CONCLUSION

The CSI was weakly associated with PPTs and not with CPM efficacy in CSP patients. Moderate to strong associations were found with current pain intensity, quality of life, disability, and catastrophizing. The current results illustrate that the CSI does not reflect a direct measure of CS, yet is a representation of general distress, possible originating from CS symptoms.

An update on emerging drugs for fibromyalgia treatment

INTRODUCTION

Fibromyalgia (FM) is a chronic disorder whose symptoms of pain, fatigue, sleep disturbances and depression have a devastating effect on patients' lives as it limits their ability to engage in everyday working and social activities, and make it difficult to maintain normal relationships with family, friends and employers. None of the currently available drugs are fully effective against the whole spectrum of symptoms. The aim of this narrative review is to summarise the data relating to the new therapeutic options that have become available over the last few years. Areas covered: Increasing efforts by the pharmaceutical industry have led to the introduction of new investigational drugs and new formulations of older drugs, and studies have been carried out in order to investigate the possibility of using drugs that are currently used for other diseases. Expert opinion: Slight improvements in the health of FM patients treated with drugs targeting a range of molecular mechanisms have been observed, but there is still no single drug that is capable of offering substantial efficacy against all of the characteristic symptoms of FM. The identification of new and improved therapies for FM requires consideration of the heterogeneity of the condition, which suggests the existence of different patient subgroups, a relationship between central and peripheral aspects of the pathophysiology, and the need for combined treatment with drugs targeting multiple molecular mechanisms.

Validation of the Japanese version of the Central Sensitization Inventory in patients with musculoskeletal disorders

Background

Many musculoskeletal pain conditions are characterized by hypersensitivity, which is induced by central sensitization (CS). A questionnaire, the Central Sensitization Inventory (CSI), was recently developed to help clinicians identify patients whose presenting symptoms may be related to central sensitivity syndrome (CSS). The aims of the present study were to examine criterion validity and construct validity of the Japanese version of the CSI (CSI-J), and to investigate prevalence rates of CS severity levels in patients with musculoskeletal disorders.

Methods

Translation of the CSI into Japanese was conducted using a forward-backward method. Two hundred and ninety patients with musculoskeletal pain disorders completed the resultant CSI-J. A subset of the patients (n = 158) completed the CSI-J again one week later. The relationships between CSI and clinical symptoms, EuroQol 5-dimension (EQ-5D) and Brief Pain Inventory (BPI), were examined for criterion validity. EQ-5D assesses Health-related QOL and BPI measures pain intensity and pain interference. The psychometric properties were evaluated with analyses of construct validity, factor structure and internal consistency, and subsequently investigate the prevalence rates of CS severity levels.

Results

The CSI-J demonstrated high internal consistency (Cronbach’s α = 0.89) and test-retest reliability was excellent value (ICC = 0.85). The CSI-J was significantly correlated with EQ-5D (r = −0.44), pain intensity (r = 0.42), and pain interference (r = 0.48) (p < 0.01 for all). Ten percent of the participants were above the cutoff “40”. The exploratory factor analysis resulted in 5-factor model.

Conclusions

This study reported that the CSI-J was a useful and psychometrically sound tool to assess CSS in Japanese patients with musculoskeletal disorders. The finding of the prevalence rates of CS severity levels in patients with musculoskeletal disorders may help clinicians to decide strategy of treatment.

Age Differences in the Time Course and Magnitude of Changes in Circulating Neuropeptides After Pain Evocation in Humans

This study tested the hypothesis that older adults would have a stronger response for substance P (facilitatory) but weaker response to β-endorphin (inhibitory), in magnitude as well as time course. Eight younger and 9 older adults underwent 3 experimental sessions using well validated laboratory pain models: cold pressor task, contact heat pain, and a nonpainful control. Blood was collected through an indwelling catheter at baseline and 3, 15, 30, 45, and 60 minutes after stimuli administration. Older adults had higher baseline levels of both neuropeptides suggesting increased peripheral activity compared with younger adults. After the cold pressor task, older adults demonstrated a quick and strong release of substance P with dramatic recovery, whereas young adults maintained a constant low-grade response. Unlike substance P, β-endorphin increased between 3 and 15 minutes for both groups with the upsurge substantially higher for older adults. After heat pain, younger adults had an immediate surge in circulating substance P and β-endorphin that was more pronounced than among older adults. However, levels of substance P for younger adults slowly tapered whereas they continued to climb for the older adults through 30 minutes. β-endorphin peaked at 30 minutes for both groups and returned to baseline. No changes were observed during the nonpainful control session.

PERSPECTIVE

Older adults had higher baseline levels of substance P and β-endorphin suggesting increased peripheral activity compared with younger adults. After pain evocation, older adults demonstrated a more intense early response for both neuropeptides suggesting peripheral mechanisms involved in the response to pain may change with age.

TMJ Arthrocentesis Alone and in Combination with Duloxetine in Temporomandibular Joint Pain

Purpose

The purpose of the study was to compare the efficacy of arthrocentesis alone and arthrocentesis with duloxetine in patients with TMJ pain.

Materials and methods

This study comprised of 20 patients. Patients with TMJ pain as confirmed by RDC/TMD and with pain duration of at least 3 months were included in the study. Patients were randomly divided into two groups, group A in which patients were treated with arthrocentesis alone and group B in which patients were treated with arthrocentesis followed by duloxetine 30 mg twice daily for 12-week therapy. Patients were followed up at regular interval at day 1, day 5, day 7, week 4, week 6 and week 12. Outcome assessment of pain, swelling, maximal mouth opening, painful/pain-free lateral or protrusive jaw movement was done. Hospital anxiety and depression (HAD) scale was used to assess pre- and post-treatment anxiety and depression. Radiologic assessment was done based on OPG and CBCT. Biochemical assessment of IL-6 in lavage fluid between groups A and B was done pre-operatively and postoperatively.

Results

There was significant reduction of pain in both groups, but reduction of pain was more in group B than in group A at week 4, week 6 and week 12. Mouth opening was significantly higher in group B than in group A patients. Reduced painful lateral and protrusive movements were seen in group B than in group A patients. There was no significant difference in hospital anxiety and depression scale among the groups at pre-operative and at 4th week post-operative. Though a significant reduction of IL-6 levels was seen post-operatively, there was no significant difference between the two groups.

Conclusion

Arthrocentesis is an effective procedure for relieving symptoms in patients with temporomandibular disorders. In this study, combination of duloxetine with arthrocentesis gave much better outcome than arthrocentesis alone. Further studies with large sample size required to evaluate the effect of arthrocentesis plain or in combination with duloxetine in providing permanent relief to the patient.

The Reliability and Validity of Using Ice to Measure Cold Pain Threshold

Cold pain threshold (CPT) measures an individual's pain threshold in response to a cold stimulus. CPT is most accurately determined with specialised equipment; however this technology is not readily accessible to clinicians. Instead, ice has been employed to measure CPT. An optimal ice protocol has not yet been identified. The aim of this study was to evaluate the reliability and validity of two CPT protocols using ice in a young, healthy population. Twenty-two participants aged 22.6 (SD 1.81) years underwent CPT measurements over 6 anatomical sites across 3 protocols, which were repeated in 2 sessions. One protocol measured pain (PVAS) following ice applied for a standardised period of 30 seconds; a second protocol measured time to onset of pain, and the reference standard measured CPT using laboratory equipment (TSA-II). The PVAS protocol demonstrated the best reliability (mean ICC 0.783, 95% CI 0.706 to 0.841), but the Timed protocol demonstrated superior validity compared to the reference standard (mean ICC −0.504, 95% CI −0.621 to −0.365).

Nonvitamin, Nonmineral Dietary Supplement Use among Adults with Fibromyalgia: United States, 2007-2012

BACKGROUND

Fibromyalgia (FMS) is a pain condition affecting 2-6% of US adults; effective treatment remains limited. Determinants of nonvitamin, nonmineral dietary supplement (NVNM) use among adults with FMS are not well-studied. We investigated the relation of NVNM use to FMS, and trends, in two nationally representative samples of US adults ≥18 years.

METHODS

Data were drawn from 2007 and 2012 National Health Interview Surveys (N's = 20127 and 30672, resp.). Logistic regression was used to examine associations of FMS to NVNM use (past 12 months) and evaluate potential modifying influences of gender and comorbidities. Multivariate models adjusted for sampling design, demographic, lifestyle, and health-related factors.

RESULTS

FMS was significantly higher in 2012 than in 2007 (1.7% versus 1.3%), whereas NVNM use decreased (57% versus 41%; p < 0.0001). Adults reporting diagnosis were more likely to use NVNMs within 12 months, 30 days, or ever relative to adults without; positive associations remained significant after controlling for demographics, lifestyle characteristics, medical history, and other confounders (ranges: 2007 and 2012 AORs = 2.3-2.7; 1.5-1.6, resp.; p's < 0.0001).

CONCLUSION

In this cross-sectional study of two national samples, NVNM use was strongly and positively associated with FMS, highlighting the need for further study.

Duloxetine 60 mg for chronic low back pain: post hoc responder analysis of double-blind, placebo-controlled trials

Introduction

Duloxetine has demonstrated efficacy in chronic low back pain (CLBP). We examined the predictors of response to duloxetine for CLBP.

Patients and methods

This was a post hoc analysis of pooled data from 4 double-blind, ran-domized, placebo-controlled trials of duloxetine (60 mg/day for 12–14 weeks) in adult patients with CLBP. Primary outcome was proportion of patients with ≥30% reduction in Brief Pain Inventory (BPI) average pain (“pain reduction”) at 12–14 weeks. The proportion of patients with ≥30% and ≥50% (secondary outcome) pain reduction in duloxetine and placebo groups was compared. Variables for responder analyses were early improvement (≥15% pain reduction at Week 2), sex, age, baseline BPI average pain score, duration of CLBP, and number of painful body sites according to the Michigan Body Map (≥2 vs 1 [isolated CLBP]; 1 trial); relative risk (RR) and 95% confidence interval (CI) were calculated.

Results

Compared with placebo (n = 653), a greater proportion of duloxetine-treated patients (n = 642) achieved ≥30% (59.7% vs 47.8%; P < 0.001) and ≥50% pain reduction (48.6% vs 35.1%; P < 0.001). Among duloxetine-treated patients, early improvement was associated with greater likelihood of ≥30% (RR [95% CI], 2.91 [2.30–3.67]) or ≥50% (3.24 [2.44–4.31]) pain reduction. Women were slightly more likely than men to achieve ≥30% (RR [95% CI], 1.14 [1.00–1.30]) or ≥50% (1.17 [0.99–1.38]) pain reduction. Response rates were similar between age, CLBP duration, and baseline BPI average pain score subgroups. Patients with ≥2 painful sites were more likely to respond to duloxetine 60 mg relative to placebo than patients with isolated CLBP (RR, duloxetine vs placebo [95% CI]: ≥30% reduction, ≥2 painful sites 1.40 [1.18–1.66], isolated CLBP 1.07 [0.78–1.48]; ≥50% reduction, ≥2 painful sites 1.51 [1.20–1.89], isolated CLBP 1.23 [0.81–1.88]).

Conclusion

Early pain reduction was indicative of overall response. Patients with multiple painful sites had more benefit from duloxetine than patients with isolated CLBP.

Potential Mediators between Fibromyalgia and C-Reactive protein: Results from a Large U.S. Community Survey

BACKGROUND

Fibromyalgia, a potentially debilitating chronic pain syndrome of unknown etiology, may be characterized by inflammation. In this study, we investigated the relation of FMS to serum C-reactive protein (CRP) in a large population of adults (18+) and investigated the influence of other factors on this relationship, including BMI, comorbidities, as well as mood and sleep disturbance.

METHODS

Participants were 52,535 Ohio Valley residents (Fibromyalgia n = 1125). All participants completed a comprehensive health survey (2005-2006) part of the C8 Health Project; serum levels of CRP were obtained, as was history of Fibromyalgia physician diagnosis. Logistic and linear regressions were used for this cross-sectional analysis.

RESULTS

Mean CRP was higher among participants reporting Fibromyalgia than those without (5.54 ± 9.8 vs.3.75 ± 7.2 mg/L, p < .0001)). CRP level showed a strong, positive association with FMS (unadjusted odds ratio (OR) for highest vs. lowest quartile = 2.5 (CI 2.1,3.0;p for trend < .0001)); adjustment for demographic and lifestyle factors attenuated but did not eliminate this association (AOR for highest vs. lowest quartile = 1.4 (CI 1.1,1.6;p for trend < .0001)). Further addition of body mass index (BMI) and comorbidities to the model markedly weakened this relationship (AORs, respectively, for highest vs lowest CRP quartile = 1.2 (CI 1.0,1.4) and 1.1 (CI 0.9,1.3). In contrast, inclusion of mood and sleep impairment only modestly reduced the adjusted risk estimate (AORs for highest vs. lowest quartile = 1.3 (CI 1.1,1.5) for each)).

CONCLUSIONS

Findings from this large cross-sectional study indicate a significant positive cross-sectional association of Fibromyalgia to serum C-reactive protein may be explained, in part, by BMI and comorbidity. Prospective research is needed to confirm this, and clarify the potential mediating influence of obesity and comorbid conditions on this relationship.

Association Between Pain at Sites Outside the Knee and Knee Cartilage Volume Loss in Elderly People Without Knee Osteoarthritis: A Prospective Study

OBJECTIVE

Pain is common in the elderly. Knee pain may predict knee cartilage loss, but whether generalized pain is associated with knee cartilage loss is unclear. This study, therefore, aimed to determine whether pain at multiple sites predicts knee cartilage volume loss among community-dwelling older adults, and, if so, to explore potential mechanisms.

METHODS

Data from the prospective Tasmanian Older Adult Cohort study was utilized (n = 394, mean age 63 years, range 52-79 years). Experience of pain at multiple sites was assessed using a questionnaire at baseline. T1-weighted fat-saturated magnetic resonance imaging of the right knee was performed to assess the cartilage volume at baseline and after 2.6 years. Linear regression modeling was used with adjustment for potential confounders.

RESULTS

The median number of painful sites was 3 (range 0-7). There was a dose-response relationship between the number of painful sites and knee cartilage volume loss in the lateral and total tibiofemoral compartments (lateral β = -0.28% per annum; total β = -0.25% per annum, both P for trend < 0.05), but not in the medial compartment. These associations were stronger in participants without radiographic knee osteoarthritis (OA) (P < 0.05) and independent of age, sex, body mass index, physical activity, pain medication, and knee structural abnormalities.

CONCLUSION

The number of painful sites independently predicts knee cartilage volume loss, especially in people without knee OA, suggesting that widespread pain may be an early marker of more rapid knee cartilage loss in those without radiographic knee OA. The underlying mechanism is unclear, but it is independent of anthropometrics, physical activity, and knee structural abnormalities.

Psychological predictors of change in the number of musculoskeletal pain sites among Norwegian employees: a prospective study

Background

The pathogenesis of syndromes of widespread musculoskeletal pain remains an enigma. The present study sought to determine if psychological states, job satisfaction, pain intensity, and sleep problems contributed to the spread and decline of the number of musculoskeletal pains.

Methods

A sample of 2989 Norwegian employees completed a questionnaire at baseline and follow-up 2 years later. Data were analyzed with multinomial and ordinal logistic regression analyses to determine effects on direction and degree of change of number of pain sites (NPS).

Results

After adjustment for sex, age, skill level, and number of pain sites at baseline, increases in the number of pain sites from baseline to follow-up were predicted by emotional exhaustion, mental distress, having little surplus, feeling down and sad, sleep disturbances, and intensity of headache. Decreases were predicted by low levels of emotional exhaustion, mental distress, sleep disturbances, restlessness, and lower intensity of headache, neck pain, shoulder pain, and back pain. Higher numbers of pain sites at baseline were associated with reduction of number of pain sites and lower likelihood of spread. Some factors that did not predict whether decrease or increase occurred were nevertheless associated with the degree of decrease (depression, anxiety, having surplus, self-efficacy) or increase (anxiety).

Conclusions

Several psychological and physiological factors predicted change in the number of pain sites. There is a need for further investigations to identify possible mechanisms by which psychological and behavioral factors propagate the spread of pain.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-017-1503-7) contains supplementary material, which is available to authorized users.

Juvenile Fibromyalgia: Different from the Adult Chronic Pain Syndrome?

While a majority of research has focused on adult fibromyalgia (FM), recent evidence has provided insights into the presence and impact of FM in children and adolescents. Commonly referred as juvenile fibromyalgia (JFM), youths, particularly adolescent girls, present with persistent widespread pain and cardinal symptoms observed in adult FM. A majority of youth with JFM continue to experience symptoms into adulthood, which highlights the importance of early recognition and intervention. Some differences are observed between adult and juvenile-onset FM syndrome with regard to comorbidities (e.g., joint hypermobility is common in JFM). Psychological comorbidities are common but less severe in JFM. Compared to adult FM, approved pharmacological treatments for JFM are lacking, but non-pharmacologic approaches (e.g., cognitive-behavioral therapy and exercise) show promise. A number of conceptual issues still remain including (1) directly comparing similarities and differences in symptoms and (2) identifying shared and unique mechanisms underlying FM in adults and youths.

Chronic Temporomandibular Disorders: disability, pain intensity and fear of movement

Background

The objective was to compare and correlate disability, pain intensity, the impact of headache on daily life and the fear of movement between subgroups of patients with chronic temporomandibular disorder (TMD).

Methods

A cross-sectional study was conducted in patients diagnosed with chronic painful TMD. Patients were divided into: 1) joint pain (JP); 2) muscle pain (MP); and 3) mixed pain. The following measures were included: Craniomandibular pain and disability (Craniofacial pain and disability inventory), neck disability (Neck Dsiability Index), pain intensity (Visual Analogue Scale), impact of headache (Headache Impact Test 6) and kinesiophobia (Tampa Scale of Kinesiophobia-11).

Results

A total of 154 patients were recruited. The mixed pain group showed significant differences compared with the JP group or MP group in neck disability (p < 0.001, d = 1.99; and p < 0.001, d = 1.17), craniomandibular pain and disability (p < 0.001, d = 1.34; and p < 0.001, d = 0.9, respectively), and impact of headache (p < 0.001, d = 1.91; and p < 0.001, d = 0.91, respectively). In addition, significant differences were observed between JP group and MP group for impact of headache (p < 0.001, d = 1.08). Neck disability was a significant covariate (37 % of variance) of craniomandibular pain and disability for the MP group (β = 0.62; p < 0.001). In the mixed chronic pain group, neck disability (β = 0.40; p < 0.001) and kinesiophobia (β = 0.30; p = 0.03) were significant covariate (33 % of variance) of craniomandibular pain and disability.

Conclusion

Mixed chronic pain patients show greater craniomandibular and neck disability than patients diagnosed with chronic JP or MP. Neck disability predicted the variance of craniofacial pain and disability for patients with MP. Neck disability and kinesiophobia predicted the variance of craniofacial pain and disability for those with chronic mixed pain.

Influence of the actions observed on cervical motion in patients with chronic neck pain: a pilot study

The aim of the present pilot study was to prove if the action-observation (AOb) improved the cervical range of motion (CROM) in patients with nonspecific chronic neck pain (CNP). Double blind pilot study. A total of 28 subjects were randomly assigned to an effective-movement group (n=14) and an ineffective-movement group (n=14). The follow-up consisted of: pretreatment, posttreatment and 10 min after second measurement (motor imagery). Outcome measures were CROM, and pres-sure pain detection thresholds (PPDTs). No statistical differences were found in baseline on CROM and on the PPDT. Test for independent groups revealed significant changes in cervical rotation movement. Both groups in posttreatment (P=0.042; Cohen d=0.81) and after 10 min (P=0.019; Cohen d=0.9). For intragroup PPDT, the Wilcoxon test revealed significant effects in the effective movement at C2 of the pre to 10-min post (P=0.040). However, the ineffective movement revealed a significant reduction in PPDT in zygapophyseal joint of C5-C6 as the pre to post (P=0.010) as the pre to 10-min post (P=0.041) periods. In conclusions this pilot study demonstrated that the effective AOb produced significant changes versus ineffective AOb in the CROM and it could influences in PPT in subject with CNP immediately.

Toward a Mechanism-Based Approach to Pain Diagnosis

The past few decades have witnessed a huge leap forward in our understanding of the mechanistic underpinnings of pain, in normal states where it helps protect from injury, and also in pathological states where pain evolves from a symptom reflecting tissue injury to become the disease itself. However, despite these scientific advances, chronic pain remains extremely challenging to manage clinically. Although the number of potential treatment targets has grown substantially and a strong case has been made for a mechanism-based and individualized approach to pain therapy, arguably clinicians are not much more advanced now than 20 years ago, in their capacity to either diagnose or effectively treat their patients. The gulf between pain research and pain management is as wide as ever. We are still currently unable to apply an evidence-based approach to chronic pain management that reflects mechanistic understanding, and instead, clinical practice remains an empirical and often unsatisfactory journey for patients, whose individual response to treatment cannot be predicted. In this article we take a common and difficult to treat pain condition, chronic low back pain, and use its presentation in clinical practice as a framework to highlight what is known about pathophysiological pain mechanisms and how we could potentially detect these to drive rational treatment choice. We discuss how present methods of assessment and management still fall well short, however, of any mechanism-based or precision medicine approach. Nevertheless, substantial improvements in chronic pain management could be possible if a more strategic and coordinated approach were to evolve, one designed to identify the specific mechanisms driving the presenting pain phenotype. We present an analysis of such an approach, highlighting the major problems in identifying mechanisms in patients, and develop a framework for a pain diagnostic ladder that may prove useful in the future, consisting of successive identification of 3 steps: pain state, pain mechanism, and molecular target. Such an approach could serve as the foundation for a new era of individualized/precision pain medicine. The Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION)-American Pain Society (APS) Pain Taxonomy (AAPT) includes pain mechanisms as 1 of the 5 dimensions that need to be considered when making a diagnostic classification. The diagnostic ladder proposed in this article is consistent with and an extension of the AAPT.

PERSPECTIVE

We discuss how identifying the specific mechanisms that operate in the nervous system to produce chronic pain in individual patients could provide the basis for a targeted and rational precision medicine approach to controlling pain, using chronic low back pain as our example.

Effectiveness of repetitive trancranial or peripheral magnetic stimulation in neuropathic pain

PURPOSE

Maladaptive plasticity in the sensorimotor system, following neurological lesions or diseases, plays a central role in the generation and maintenance of neuropathic pain. Repetitive magnetic stimulation of the central and peripheral nervous system has gained relevance as noninvasive approach for neuromodulation and pain relief. Systematic reviews that evaluate the effectiveness and specificity of different protocols of repetitive magnetic stimulation to control neuropathic pain in clinical populations have the potential to improve the therapeutic applicability of this technique.

METHODS

Studies whose primary goal was to evaluate the effectiveness of repetitive magnetic stimulation for the treatment of various types of neuropathic pain published in PubMed until August 2015 have been included in this systematic review.

RESULTS

A total of 39 articles fulfilling the inclusion criteria were analyzed of which 37 studies investigated pain modulation using repetitive magnetic stimulation over the motor or non-motor cortices and two studies evaluated pain modulation using repetitive peripheral magnetic stimulation protocols.

CONCLUSIONS

Repetitive transcranial magnetic stimulation of the primary motor cortex using high frequency stimulation protocols can effectively reduce neuropathic pain, particularly in individuals with pain related to non-cerebral lesions. The application of multiple sessions can lead to long-lasting pain modulation and cumulative effects. Implications for Rehabilitation Maladaptive plasticity plays a central role in sensitization of nociceptive pathways, generation and maintainance of neuropathic pain; Most neuropathic pain conditions are refractory to pharmacological therapies; Repetitive magnetic stimulation of the central and peripheral nervous system has gained relevance as noninvasive approach for neuromodulation and pain relief.

Augmented Pain Processing in Primary and Secondary Somatosensory Cortex in Fibromyalgia: A Magnetoencephalography Study Using Intra-Epidermal Electrical Stimulation

The aim of this study was to investigate augmented pain processing in the cortical somatosensory system in patients with fibromyalgia (FM). Cortical evoked responses were recorded in FM (n = 19) and healthy subjects (n = 21) using magnetoencephalography after noxious intra-epidermal electrical stimulation (IES) of the hand dorsum (pain rating 6 on a numeric rating scale, perceptually-equivalent). In addition, healthy subjects were stimulated using the amplitude corresponding to the average stimulus intensity rated 6 in patients with FM (intensity-equivalent). Quantitative sensory testing was performed on the hand dorsum or thenar muscle (neutral site) and over the trapezius muscle (tender point), using IES (thresholds, ratings, temporal summation of pain, stimulus-response curve) and mechanical stimuli (threshold, ratings). Increased amplitude of cortical responses was found in patients with FM as compared to healthy subjects. These included the contralateral primary (S1) and bilateral secondary somatosensory cortices (S2) in response to intensity-equivalent stimuli and the contralateral S1 and S2 in response to perceptually-equivalent stimuli. The amplitude of the contralateral S2 response in patients with FM was positively correlated with average pain intensity over the last week. Quantitative sensory testing results showed that patients with FM were more sensitive to painful IES as well as to mechanical stimulation, regardless of whether the stimulation site was the hand or the trapezius muscle. Interestingly, the slope of the stimulus-response relationship as well as temporal summation of pain in response to IES was not different between groups. Together, these results suggest that the observed pain augmentation in response to IES in patients with FM could be due to sensitization or disinhibition of the cortical somatosensory system. Since the S2 has been shown to play a role in higher-order functions, further studies are needed to clarify the role of augmented S2 response in clinical characteristics of FM.

A Comparison of the Sensitivity of Brush Allodynia and Semmes-Weinstein Monofilament Testing in the Detection of Allodynia Within Regions of Secondary Hyperalgesia in Humans

BACKGROUND

Two of the most common Quantitative Sensory Techniques (QST) employed to detect allodynia include mechanical brush allodynia and Semmes-Weinstein monofilaments. However, their relative sensitivity at detecting allodynia is poorly understood. The purpose of this study was to compare the sensitivity of brush allodynia against Semmes-Weinstein monofilament technique for detecting allodynia within regions of secondary hyperalgesia in humans.

METHODS

Twenty subjects (10 males, 10 females; 21.1 ± 0.9 years) were recruited and randomly allocated to allodynia or monofilament groups. Topical capsaicin (Zostrix 0.075%) was applied to a target region defined by C4-C7 dermatomes. Allodynia testing was performed at 0- (baseline) and 10 minutes postcapsaicin. The Semmes-Weinstein group assessed changes in skin sensitivity 8 cm inferior to target region and 2 cm lateral to the spinous process, while brush allodynia was employed to detect the point inferior to the target region where subjects reported changes in skin sensitivity. The distance (cm) from this point to the inferior border of the target region was termed the Allodynia Score.

RESULTS

Statistically significant increases in the Allodynia Score were observed at 10 minutes postcapsaicin compared to baseline (P < 0.001). No differences in monofilament scores were observed between 10 minutes postcapsaicin and baseline (P = 0.125). Brush allodynia also demonstrated superior sensitivity, detecting allodynia in 100% of cases compared to 60% in the Semmes-Weinstein group.

CONCLUSION

Brush allodynia is more sensitive than Semmes-Weinstein monofilaments for detecting mechanical allodynia in regions of secondary hyperalgesia. Brush allodynia may be preferred over Semmes-Weinstein monofilaments for clinical applications requiring reliable detection of allodynia.

Paraspinous Lidocaine Injection for Chronic Nonspecific Low Back Pain: A Randomized Controlled Clinical Trial

In this large, sham-controlled, randomized trial, we examined the efficacy of the combination of standard treatment and paraspinous lidocaine injection compared with standard therapy alone in subjects with chronic low back pain. There is little research-based evidence for the routine clinical use of paraspinous lidocaine injection for low back pain. A total of 378 subjects with nonspecific chronic low back pain were randomized to 3 groups: paraspinous lidocaine injection, analgesics, and exercises (group 1, LID-INJ); sham paraspinous lidocaine injection, analgesics, and exercises (group 2, SH-INJ); and analgesics and exercises (group 3, STD-TTR). A blinded rater assessed the study outcomes at 3 time points: baseline, after treatment, and after 3 months of follow-up. There were increased frequency of pain responses and better low back functional scores in the LID-INJ group compared with the SH-INJ and STD-TTR groups. These effects remained at the 3-month follow-up but differed between all 3 groups. There were significant changes in pain threshold immediately after treatment, supporting the effects of this intervention in reducing central sensitization. Paraspinous lidocaine injection therapy is not associated with a higher risk of adverse effects compared with conventional treatment and sham injection. Its effects on hyperalgesia might correlate with changes in central sensitization.

CLINICAL TRIAL REGISTRATION

NCT02387567.

PERSPECTIVE

There are few data to support paraspinous lidocaine injection use in patients with nonspecific chronic low back pain. Our results show that this therapy when combined with standard therapy significantly increases the number of responders versus standard treatment alone. Its effects on hyperalgesia might correlate with a change in central sensitization.

The Modified painDETECT Questionnaire for Patients with Hip or Knee Osteoarthritis: Translation into Dutch, Cross-Cultural Adaptation and Reliability Assessment

There is a growing amount of evidence that alteration in pain processing by the peripheral and central nervous system play a role in osteoarthritis pain, leading to neuropathic-like symptoms. It is essential to identify knee and hip osteoarthritis patients with a neuropathic pain profile in order to offer such patients education and additional treatment options besides conventional pain treatment. The painDETECT Questionnaire is a self-report questionnaire developed to discriminate between nociceptive and neuropathic pain. This questionnaire was modified to fit patients suffering from knee osteoarthritis. The aim of this study was to translate and cross-culturally adapt the modified painDETECT Questionnaire to the Dutch language and to provide a modified version to fit patients with hip osteoarthritis. Reliability for internal consistency, repeatability and floor and ceiling effects were subsequently assessed. A total of 278 patients were included in the reliability study and 123 patients in the repeatability analysis. The Dutch modified painDETECT Questionnaire shows good internal consistency and small relative measurement errors, represented by a good intraclass correlation coefficient. Absolute measurement error, represented by the Standard Error of Measurement, was acceptable. However, a measurement bias might be present when it comes to repeatability. To our knowledge, this study is the first to provide a Dutch modified painDETECT Questionnaire to fit hip and knee osteoarthritis patients and to assess internal consistency, reliability and agreement. International guidelines were followed in the translation process and this study has ample sample size with an adequate time interval for repeatability. Based on this study, the Dutch modified painDETECT Questionnaire seems to be fit as a discriminative tool to identify knee and hip osteoarthritis patients with a neuropathic pain profile. Whether it is also suitable as an evaluative tool to record changes over time or after an intervention remains open to further investigation.

An Examination of Pain Catastrophizing and Endogenous Pain Modulatory Processes in Adults with Chronic Low Back Pain

OBJECTIVE

Research on chronic low back pain (cLBP) has focused heavily on structural abnormalities with emphasis on diagnostic imaging. However, for many cLBP patients, clinical pain and disability are not clearly associated with identifiable pathology of the spine or associated tissues. Therefore, alternative determinants such as psychological factors and dysfunctional pain modulatory processes have been suggested to be important.

METHODS

This observational study examined differences in pain catastrophizing and endogenous pain modulation between 25 cLBP patients and 25 pain-free controls. Associations among pain catastrophizing, endogenous pain modulatory processes, clinical pain reports, and disability were also examined in cLBP patients. Endogenous pain modulation was examined using temporal summation (TS) of mechanical and heat pain stimuli as well as conditioned pain modulation (CPM) with algometry (test stimulus) and the cold pressor task (conditioning stimulus).

RESULTS

Findings demonstrated significantly greater pain catastrophizing as well as greater TS of mechanical and heat pain for cLBP patients compared with controls. CPM was not present in cLBP patients or controls. Among cLBP patients, pain catastrophizing was significantly associated with disability, while TS of mechanical pain was significantly associated with clinical pain severity and disability.

CONCLUSIONS

This study suggests that endogenous pain modulatory processes are altered for cLBP patients, particularly TS of mechanical and heat stimuli. Pain catastrophizing and TS of mechanical pain may have important clinical relevance for cLBP, given associations with clinical pain and disability; however, future research is needed to replicate these findings.

Neuropathic-like pain features and cross-sectional associations in rheumatoid arthritis

INTRODUCTION

Increasing evidence indicates that features suggestive of neuropathic pain may also be present in patients with common rheumatic conditions. The objective of this study was to examine neuropathic-like pain symptoms and associated factors in patients with rheumatoid arthritis.

METHODS

We used the painDETECT screening tool to identify possible or likely neuropathic pain in 159 outpatients with rheumatoid arthritis. Patients additionally completed other self-reported measures, while clinical measures were assessed to calculate the 28-joint Disease Activity Score. Univariate analyses and multivariable logistic regression were used to identify factors associated with neuropathic pain features.

RESULTS

According to the painDETECT, 27 patients (17.0 %) were classified as having likely neuropathic pain and 34 patients (21.4 %) as having possible neuropathic pain. Besides reporting more severe pain, patients with likely or possible neuropathic pain were more likely to meet the diagnostic criteria for fibromyalgia, to use analgesics, and to have more tender joints and a worse physical and mental health status as measured by the 36-item Short-Form health survey. In multivariable analysis, physical (P < 0.001) and mental health status (P = 0.006) remained significantly associated with neuropathic pain features, even after controlling for pain severity.

CONCLUSIONS

These findings suggest that a sizeable proportion of patients with relatively well-controlled rheumatoid arthritis report symptoms suggestive of neuropathic pain. Neuropathic-like pain symptoms are independently associated with worse self-reported physical and mental health.

The role of sensitization in musculoskeletal shoulder pain

INTRODUCTION

Peripheral and central sensitization are neurophysiological processes that can prolong painful conditions. Painful shoulder conditions are often persistent, perhaps due to the presence of sensitization.

METHOD

This manuscript summarizes six studies that have evaluated those with musculoskeletal shoulder pain for the presence of sensitization.

RESULTS

All six manuscripts report evidence of peripheral sensitization, while central sensitization was described in five of the studies. The chronicity of symptoms in subjects who were included in the studies is probably influencing this finding. The primary somatosensory test used to assess sensitization in these studies was Pressure Pain Threshold, a test for lowered nociceptive thresholds.

DISCUSSION

It appears that peripheral sensitization manifests consistently in those with musculoskeletal shoulder pathology, probably due to the inflammatory processes related to tissue injury. Central sensitization, while not universally present, was reported in a majority of the manuscripts. Because central sensitization is thought to be a key step on the pathway to chronic pain, evidence for its presence in those with shoulder pain is significant. Clinicians should expect the presence of sensitization with shoulder pathology and make appropriate choices about interventions so as not to exacerbate pain.

Variations in patient-reported physical health between cardiac and musculoskeletal diseases: systematic review and meta-analysis of population-based studies

Population-based assessments of physical health are important to evaluate healthcare resource allocation. Normative data on the level of physical impairments attributable to specific diseases and severity levels within these diseases is critical to interpreting such data. Our objective, by means of a systematic review and meta-analysis, was to test the hypothesis that specific diseases which form cardiovascular and musculoskeletal disease spectra are associated with gradients of physical impairments. We examined a cardiovascular disease spectrum which consisted of hypertension, ischaemic heart disease and heart failure, and a musculoskeletal disease spectrum of lower back pain, osteoarthritis and rheumatoid arthritis. Using Medline, EMBASE and CINAHL databases, articles which had examined these morbidities and used either the SF-12 or SF-36 in general or primary care populations were selected; data was extracted independently by three reviewers. Study characteristics were described and the mean physical component summary scores of the SF-12 or SF-36 was analysed by disease, using random-effects meta-analysis. The association between disease and physical health (mean physical component summary scores) was assessed using multilevel meta-regression analysis, adjusting for age, health setting, country, disease definition and SF-12 or 36 format. From this search, 26 articles were identified, yielding 70 separate estimates of mean physical component summary scores across the morbidities from 14 different countries. For the selected conditions, pooled unadjusted mean physical component summary scores were: 44.4 for hypertension, 38.9 for ischaemic heart disease, 35.9 for heart failure, 39.5 for lower back pain, 36.0 for osteoarthritis and 36.5 for rheumatoid arthritis. The adjusted meta-regression showed mean physical component summary score difference for ischaemic heart disease of −4.6 (95 % confidence interval −6.0 to −3.2) and heart failure −7.5 (−9.1 to −5.9) compared to the hypertension category. For osteoarthritis −4.2 (−5.3 to −3.0) and rheumatoid arthritis −3.9 (−9.5 to 1.6) compared to the lower back pain category. Our findings provide the benchmark norms for the differences in physical health within and between disease spectra. Improved characterisation of the relative impact of individual conditions on physical health will facilitate public health assessments of chronic diseases as well as assessments of interventions using functional patient-reported outcomes.

Central sensitization and changes in conditioned pain modulation in people with chronic nonspecific low back pain: a case-control study

Quantitative sensory testing is widely used in human research to investigate the state of the peripheral and central nervous system contributions in pain processing. It is a valuable tool to help identify central sensitization and may be important in the treatment of low back pain. The aim of this study was to evaluate changes in local and segmental hypersensitivity and endogenous pain inhibition in people with chronic nonspecific low back pain. Thirty patients with chronic low back pain and thirty healthy subjects were studied. Pressure pain thresholds (PPTs) were measured from the lumbar region and over the tibialis anterior muscle (TA). A cold pressor test was used to assess the activation of conditioned pain modulation (CPM), and PPTs in the lumbar region were recorded 30 s after immersion of participant's foot in a bucket with cold water. People with chronic low back pain have significantly lower PPT than controls at both the lumbar region [89.5 kPa (mean difference) 95 % CI 40.9-131.1 kPa] and TA [59.45 kPa (mean difference) 95 % CI 13.49-105.42 kPa]. During CPM, people with chronic low back pain have significantly lower PPT than controls in lumbar region [118.6 kPa (mean difference) 95 % CI 77.9-159.2 kPa]. Women had significantly lower PPTs than men in both lumbar region [101.7 kPa (mean difference) 95 % CI 37.9-165.7 kPa] and over the TA [189.7 kPa (mean difference) 95 % CI 14.2-145.2 kPa]. There was no significant difference in PPTs in men between healthy controls and those with low back pain, suggesting the significant differences are mediated primarily by difference between women.

Pain sensitivity subgroups in individuals with spine pain: potential relevance to short-term clinical outcome

BACKGROUND

Cluster analysis can be used to identify individuals similar in profile based on response to multiple pain sensitivity measures. There are limited investigations into how empirically derived pain sensitivity subgroups influence clinical outcomes for individuals with spine pain.

OBJECTIVE

The purposes of this study were: (1) to investigate empirically derived subgroups based on pressure and thermal pain sensitivity in individuals with spine pain and (2) to examine subgroup influence on 2-week clinical pain intensity and disability outcomes.

DESIGN

A secondary analysis of data from 2 randomized trials was conducted.

METHODS

Baseline and 2-week outcome data from 157 participants with low back pain (n=110) and neck pain (n=47) were examined. Participants completed demographic, psychological, and clinical information and were assessed using pain sensitivity protocols, including pressure (suprathreshold pressure pain) and thermal pain sensitivity (thermal heat threshold and tolerance, suprathreshold heat pain, temporal summation). A hierarchical agglomerative cluster analysis was used to create subgroups based on pain sensitivity responses. Differences in data for baseline variables, clinical pain intensity, and disability were examined.

RESULTS

Three pain sensitivity cluster groups were derived: low pain sensitivity, high thermal static sensitivity, and high pressure and thermal dynamic sensitivity. There were differences in the proportion of individuals meeting a 30% change in pain intensity, where fewer individuals within the high pressure and thermal dynamic sensitivity group (adjusted odds ratio=0.3; 95% confidence interval=0.1, 0.8) achieved successful outcomes.

LIMITATIONS

Only 2-week outcomes are reported.

CONCLUSIONS

Distinct pain sensitivity cluster groups for individuals with spine pain were identified, with the high pressure and thermal dynamic sensitivity group showing worse clinical outcome for pain intensity. Future studies should aim to confirm these findings.

Examining sex differences in knee pain: the multicenter osteoarthritis study

OBJECTIVE

To determine whether women experience greater knee pain severity than men at equivalent levels of radiographic knee osteoarthritis (OA).

DESIGN AND METHODS

A cross-sectional analysis of 2712 individuals (60% women) without knee replacement or a recent steroid injection. Sex differences in pain severity at each Kellgren-Lawrence (KL) grade were assessed by knee using visual analog scale (VAS) scale and Western Ontario and McMaster Universities Arthritis Index (WOMAC) with and without adjustment for age, analgesic use, Body mass index (BMI), clinic site, comorbid conditions, depression score, education, race, and widespread pain (WSP) using generalized estimating equations. Effect sizes (Cohen's d) were also calculated. Analyses were repeated in those with and without patellofemoral OA (PFOA).

RESULTS

Women reported higher VAS pain at all KL grades in unadjusted analyses (d = 0.21-0.31, P < 0.0001-0.0038) and in analyses adjusted for all covariates except WSP (d = 0.16-0.22, P < 0.0001-0.0472). Pain severity differences further decreased with adjustment for WSP (d = 0.10-0.18) and were significant for KL grade ≤2 (P = 0.0015) and 2 (P = 0.0200). Presence compared with absence of WSP was associated with significantly greater knee pain at all KL grades (d = 0.32-0.52, P < 0.0001-0.0008). In knees with PFOA, VAS pain severity sex differences were greater at each KL grade (d = 0.45-0.62, P = 0.0006-0.0030) and remained significant for all KL grades in adjusted analyses (d = 0.31-0.57, P = 0.0013-0.0361). Results using WOMAC were similar.

CONCLUSIONS

Women reported greater knee pain than men regardless of KL grade, though effect sizes were generally small. These differences increased in the presence of PFOA. The strong contribution of WSP to sex differences in knee pain suggests that central sensitivity plays a role in these differences.

Management of a patient with chronic low back pain and multiple health conditions using a pain mechanisms-based classification approach

STUDY DESIGN

Case report.

BACKGROUND

Pain can lead to a significant reduction in quality of life. A pain mechanisms-based classification scheme has been outlined to improve management of patients with pain, but studies describing its use are limited. Evidence for physical therapy interventions in those with chronic pain and multiple health conditions is also lacking. This case report describes management of a patient with chronic pain and multiple health conditions.

CASE DESCRIPTION

A 29-year-old man presented with a 3-year history of low back pain and 11-month history of lower extremity paresthesia. Current health conditions included left-sided hemiparesis secondary to a stroke, pancreatic kidney transplant, left-sided blindness, and osteoporosis secondary to hyperparathyroidism. Inability to walk to school and sit through class, and pain-related sleep disruption were the primary activity and participation restrictions. Outcome measures included the numeric pain rating scale, global rating of change, Oswestry Disability Index, and pain medication usage. A score of 12 on the Leeds assessment of neuropathic symptoms and signs (LANSS) pain scale indicated the presence of neuropathic pain, but other pain mechanisms were also hypothesized to be present. Treatment was designed to improve patient goals considering these pain mechanisms.

OUTCOMES

The patient was seen for 20 visits over 6 months. Ten months after the initial evaluation, the patient's Oswestry Disability Index scores improved by more than 50% and the patient achieved all initially stated goals without pain medication.

DISCUSSION

A pain mechanisms-based approach assisted in the management of a patient with chronic pain and multiple health conditions. Using this approach may enhance clinical decision making when managing individuals with chronic pain.

LEVEL OF EVIDENCE

Therapy, level 4.

Evoked temporal summation in cats to highlight central sensitization related to osteoarthritis-associated chronic pain: a preliminary study

In cats, osteoarthritis causes significant chronic pain. Chronicity of pain is associated with changes in the central nervous system related to central sensitization, which have to be quantified. Our objectives were 1) to develop a quantitative sensory testing device in cats for applying repetitive mechanical stimuli that would evoke temporal summation; 2) to determine the sensitivity of this test to osteoarthritis-associated pain, and 3) to examine the possible correlation between the quantitative sensory testing and assessment using other pain evaluation methods. We hypothesized that mechanical sub-threshold repetitive stimuli would evoke temporal summation, and that cats with osteoarthritis would show a faster response. A blinded longitudinal study was performed in 4 non-osteoarthritis cats and 10 cats with naturally occurring osteoarthritis. Quantification of chronic osteoarthritis pain-related disability was performed over a two week period using peak vertical force kinetic measurement, motor activity intensity assessment and von Frey anesthesiometer-induced paw withdrawal threshold testing. The cats afflicted with osteoarthritis demonstrated characteristic findings consistent with osteoarthritis-associated chronic pain. After a 14-day acclimation period, repetitive mechanical sub-threshold stimuli were applied using a purpose-developed device. Four stimulation profiles of predetermined intensity, duration and time interval were applied randomly four times during a four-day period. The stimulation profiles were different (P<0.001): the higher the intensity of the stimulus, the sooner it produced a consistent painful response. The cats afflicted with osteoarthritis responded more rapidly than cats osteoarthritis free (P = 0.019). There was a positive correlation between the von Frey anesthesiometer-induced paw withdrawal threshold and the response to stimulation profiles #2 (2N/0.4 Hz) and #4 (2N/0.4 Hz): Rhos = 0.64 (P = 0.01) and 0.63 (P = 0.02) respectively. This study is the first report of mechanical temporal summation in awake cats. Our results suggest that central sensitization develops in cats with naturally occurring osteoarthritis, providing an opportunity to improve translational research in osteoarthritis-associated chronic pain.

A modern neuroscience approach to chronic spinal pain: combining pain neuroscience education with cognition-targeted motor control training

Chronic spinal pain (CSP) is a severely disabling disorder, including nontraumatic chronic low back and neck pain, failed back surgery, and chronic whiplash-associated disorders. Much of the current therapy is focused on input mechanisms (treating peripheral elements such as muscles and joints) and output mechanisms (addressing motor control), while there is less attention to processing (central) mechanisms. In addition to the compelling evidence for impaired motor control of spinal muscles in patients with CSP, there is increasing evidence that central mechanisms (ie, hyperexcitability of the central nervous system and brain abnormalities) play a role in CSP. Hence, treatments for CSP should address not only peripheral dysfunctions but also the brain. Therefore, a modern neuroscience approach, comprising therapeutic pain neuroscience education followed by cognition-targeted motor control training, is proposed. This perspective article explains why and how such an approach to CSP can be applied in physical therapist practice.

Knee pain during daily tasks, knee osteoarthritis severity, and widespread pain

BACKGROUND

The presence of widespread pain is easily determined and is known to increase the risk for persistent symptoms.

OBJECTIVE

The study hypothesis was that people with no or minimal knee osteoarthritis (OA) and high Western Ontario and McMaster Universities (WOMAC) Pain Scale scores would be more likely than other subgroups to report widespread pain.

DESIGN

A cross-sectional design was used.

METHODS

Data were obtained from the Multicenter Osteoarthritis Study, which includes people with or at high risk for knee OA. The inclusion criteria were met by 755 people with unilateral knee pain and 851 people with bilateral knee pain. Widespread pain was assessed with body diagrams, and radiographic Kellgren-Lawrence grades were recorded for each knee. Knee pain during daily tasks was quantified with WOMAC Pain Scale scores.

RESULTS

Compared with people who had high levels of pain and knee OA, people with a low level of pain and a high level of knee OA, and people with low levels of pain and knee OA, a higher proportion of people with a high level of knee pain and a low level of knee OA had widespread pain. This result was particularly true for people with bilateral knee pain, for whom relative risk estimates ranged from 1.7 (95% confidence interval=1.2-2.4) to 2.3 (95% confidence interval=1.6-3.3).

LIMITATIONS

The cross-sectional design was a limitation.

CONCLUSIONS

People with either no or minimal knee OA and a high level of knee pain during daily tasks are particularly likely to report widespread pain. This subgroup is likely to be at risk for not responding to knee OA treatment that focuses only on physical impairments. Assessment of widespread pain along with knee pain intensity and OA status may assist physical therapists in identifying people who may require additional treatment.

Conditioned pain modulation: a predictor for development and treatment of neuropathic pain

Psychophysical evaluation of endogenous pain inhibition via conditioned pain modulation (CPM) represents a new generation of laboratory tests for pain assessment. In this review we discuss recent findings on CPM in neuropathic pain and refer to psychophysical, neurophysiological, and methodological aspects of its clinical implications. Typically, chronic neuropathic pain patients express less efficient CPM, to the extent that incidence of acquiring neuropathic pain (e.g. post-surgery) and its intensity can be predicted by a pre-surgery CPM assessment. Moreover, pre-treatment CPM evaluation may assist in the correct choice of serotonin-noradrenalin reuptake inhibitor analgesic agents for individual patients. Evaluation of pain modulation capabilities can serve as a step forward in individualizing pain medicine.

Exploring the central modulation hypothesis: do ancient memory mechanisms underlie the pathophysiology of trigger points?

A myofascial trigger point (TrP) is a point of focal tenderness, associated with a taut band of muscle fibers, that can develop in any skeletal muscle. TrPs are a common source of pain and motor dysfunction in humans and other vertebrates. There is no universally accepted pathophysiology to explain the etiology, symptomatology and treatment of TrPs. This article reviews and extends the author's previously published hypothesis for the pathophysiology of TrPs, "Trigger Points and Central Modulation-A New Hypothesis." The author proposes that central nervous system-maintained global changes in α-motoneuron function, resulting from sustained plateau depolarization, rather than a local dysfunction of the motor endplate, underlie the pathogenesis of TrPs.

Clinical experience with duloxetine in the management of chronic musculoskeletal pain. A focus on osteoarthritis of the knee

Duloxetine is a serotonin and norepinephrine reuptake inhibitor (SNRI) with central nervous system activity. Its analgesic efficacy in central pain is putatively related to its influence on descending inhibitory pain pathways. The analgesic efficacy of duloxetine has been demonstrated in four distinct chronic pain conditions. These include neuropathic pain associated with diabetic peripheral neuropathy, fibromyalgia, chronic low back pain, and osteoarthritis knee pain (OAKP). The purpose of this review is to examine the clinical efficacy and safety of duloxetine in the management of chronic OAKP. Three separate randomized, double-blind placebo-controlled trials have demonstrated that (1) a clinically meaningful decrease in pain severity occurs at about 4 weeks relative to placebo, (2) patients receiving duloxetine report better improvements in physical functioning relative to placebo, (3) duloxetine is safe and effective when used adjunctively with nonsteroidal anti-inflammatory drugs, and (4) that there are no new safety signals beyond what has been observed in other indications.

The role of descending inhibitory pathways on chronic pain modulation and clinical implications

The treatment and management of chronic pain is a major challenge for clinicians. Chronic pain is often underdiagnosed and undertreated, and there is a lack of awareness of the pathophysiologic mechanisms that contribute to chronic pain. Chronic pain involves peripheral and central sensitization, as well as the alteration of the pain modulatory pathways. Imbalance between the descending facilitatory systems and the descending inhibitory systems is believed to be involved in chronic pain in pathological conditions. A pharmacological treatment that could restore the balance between these 2 pathways by diminishing the descending facilitatory pain pathways and enhancing the descending inhibitory pain pathways would be a valuable therapeutic option for patients with chronic pain. Due to the lack of evidence for pharmacological options that act on descending facilitation pathways, in this review we summarize the role of the descending inhibitory pain pathways in pain perception. This review will focus primarily on monoaminergic descending inhibitory pain pathways and their contribution to the mechanism of chronic pain and several pharmacological treatment options that enhance these pathways to reduce chronic pain. We describe anatomical structures and neurotransmitters of the descending inhibitory pain pathways that are activated in response to nociceptive pain and altered in response to sustained and persistent pain which leads to chronic pain in various pathological conditions.

Reproducibility of the heat/capsaicin skin sensitization model in healthy volunteers

Introduction

Heat/capsaicin skin sensitization is a well-characterized human experimental model to induce hyperalgesia and allodynia. Using this model, gabapentin, among other drugs, was shown to significantly reduce cutaneous hyperalgesia compared to placebo. Since the larger thermal probes used in the original studies to produce heat sensitization are now commercially unavailable, we decided to assess whether previous findings could be replicated with a currently available smaller probe (heated area 9 cm² versus 12.5–15.7 cm²).

Study design and methods

After Institutional Review Board approval, 15 adult healthy volunteers participated in two study sessions, scheduled 1 week apart (Part A). In both sessions, subjects were exposed to the heat/capsaicin cutaneous sensitization model. Areas of hypersensitivity to brush stroke and von Frey (VF) filament stimulation were measured at baseline and after rekindling of skin sensitization. Another group of 15 volunteers was exposed to an identical schedule and set of sensitization procedures, but, in each session, received either gabapentin or placebo (Part B).

Results

Unlike previous reports, a similar reduction of areas of hyperalgesia was observed in all groups/sessions. Fading of areas of hyperalgesia over time was observed in Part A. In Part B, there was no difference in area reduction after gabapentin compared to placebo.

Conclusion

When using smaller thermal probes than originally proposed, modifications of other parameters of sensitization and/or rekindling process may be needed to allow the heat/capsaicin sensitization protocol to be used as initially intended. Standardization and validation of experimental pain models is critical to the advancement of translational pain research.