Evidence for central sensitization in patients with osteoarthritis pain: A systematic literature review

Hyperexcitability of the Central Nervous System in Children with Chronic Pain: A Systematic Review

Objective

Hyperexcitability of the central nervous system plays an important role in the development and maintenance of chronic pain in adults. This knowledge has led to improved treatment strategies within this population. In children, however, research on the presence of central hyperexcitability is scarce. To further investigate this topic in children with chronic pain, there is a need for a clear literature overview.

Design

Systematic review.

Methods

The literature search was performed using the electronic databases PubMed and Web of Science. An article was considered eligible if it included children (age two to 12 years) diagnosed with chronic pain. Articles had to report original research outcomes related to central hyperexcitability, and a comparison with a healthy control group was necessary. Characteristics of the study sample, the assessment, and conclusions regarding central hyperexcitability were extracted from each included article.

Results

Twelve case-control studies were included with moderate to good methodological quality (510 children with chronic pain and 670 healthy controls). After summarizing the articles' results on indices of central hyperexcitability, we concluded that secondary hyperalgesia might be present in children with recurrent abdominal pain, juvenile fibromyalgia, and juvenile idiopathic arthritis. Preliminary evidence exists for altered cortical nociceptive processing in children with migraine and recurrent abdominal pain.

Conclusion

Based on the results of this review, central hyperexcitability might be present in in several pediatric chronic pain conditions. Further research on other manifestations of central hyperexcitability (e.g., bottom-up and top-down mechanisms and nociceptive brain changes) is necessary to provide firm evidence about its presence in children with chronic pain.

Central Sensitization Is a Risk Factor for Persistent Postoperative Pain and Dissatisfaction in Patients Undergoing Revision Total Knee Arthroplasty

BACKGROUND

The objective of this study is to investigate whether central sensitization (CS) was associated with patient dissatisfaction after revision total knee arthroplasty (TKA).

METHODS

Between 2012 and 2016, 68 cases (68 patients) of revision TKA performed by a single surgeon were included in this study with a minimum follow-up of 2 years. Patients were categorized into 2 groups by 40-point preoperative Central Sensitization Inventory (CSI) scores. The control group consisted of 48 patients (48 knees) with CSI scores of less than 40 points, while the CS group consisted of 20 patients (20 knees) with CSI scores of 40 points or more. Clinical outcomes were evaluated using an 11-point visual analog scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index scores. Patient satisfaction was evaluated using the satisfaction items of the new Knee Society Scores, where scores ≥20 indicated satisfaction.

RESULTS

Higher preoperative pain VAS scores in the CS group were maintained 3, 6, 12, and 24 months postoperatively (all P < .05). The CS group showed significantly worse pain, function subscores, and total scores of the Western Ontario and McMaster Universities Osteoarthritis Index preoperatively and at 2 years postoperatively. Forty-four (91.7%) patients in the control group and 3 (15.0%) patients in the CS group were satisfied with their revision TKAs (P < .001). Multivariate logistic regression analysis demonstrated that the odds of dissatisfaction after revision TKAs were increased 39.081 times (95% confidence interval 6.926-220.504, P < .001) in patients with CSI scores ≥40. Higher VAS intensity 2 years postoperatively also predicted dissatisfaction following revision TKA (odds ratio 1.864, 95% confidence interval 1.086-3.199, P = .024).

CONCLUSION

CS is a risk factor for persistent postoperative pain and dissatisfaction in patients undergoing revision TKAs.

LEVEL OF EVIDENCE

III.

A prospective study of knee pain, low back pain, and risk of dementia: the JAGES project

The aim of this prospective study was to investigate the associations of knee and low back pain with dementia development. Participants were 14,627 older people with no history of stroke, cancer, injuries, depression, Parkinson's disease, or dementia who did not require support for daily living completed self-administered questionnaires with 3-years follow-up. A Cox regression model was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for dementia development. Stratified analyses by age and regular walking were conducted. Dementia risk was higher in participants aged 65-79 years with knee pain and without low back pain than in those without knee and low back pain [HR: 1.73 (95% CI: 1.11-2.68)]. Dementia risk was lower in participants ≥80 years with low back pain but no knee pain than in those without low back or knee pain [HR: 0.50 (95% CI: 0.31-0.80)]. Participants with knee pain who did not walk regularly had the highest dementia risk [HR: 1.71 (95% CI: 1.26-2.33)]. Knee pain may increase dementia risk among individuals aged 65-79 years, and may further increase risk in non-regular walkers. Low back pain may be a marker of maintained cognitive function despite age for individuals ≥80 years.

Multidimensional investigation of chronic pain experience and physical functioning following hip fracture surgery: clinical implications

Introduction

Older adults experience significant chronic pain after hip fracture, resulting in decreased physical functioning. However, pain investigation in this population is mostly limited to self-reported pain intensity. Detailed pain assessment may identify intervention targets other than pain relief. The aim of this study is to investigate multiple dimensions of pain experience (intensity, sensory, affective, evaluative and miscellaneous dimensions) and to correlate them to lower limb functionality and limitations in daily living activities.

Methods

We conducted a cross-sectional study of 50 older adults (77.1 ± 8.1 years old) who underwent hip fracture surgery in the past 4 months. We used the Numeric Rating Scale (NRS), the McGill Pain Questionnaire (MPQ) and an algometer to assess pain intensity, pain quality and pressure pain threshold, respectively. Lower limb functionality and limitation in basic (activities of daily living (ADL)) and instrumental activities of daily living (IADL) were assessed using the Short Physical Performance Battery (SPPB) and the Brazilian OARS Multidimensional Functional Assessment Questionnaire.

Results

Participants described pain as brief, momentary and transient, especially during weight-bearing activities. Although the pain intensity measured by the NRS was reported as moderate to severe (7.5 ± 1.6 points), it was not correlated with physical functioning. However, we observed a moderate negative correlation between pressure pain threshold, ADL and IADL disability (r = -0.41, p < 0.01). Among pain qualities, the sensory category was moderately negatively correlated to SPPB (r = -0.41, p < 0.01), and the evaluative category was moderately correlated to ADL and IADL disability (r = 0.43, p < 0.01).

Conclusion

Pain can be present 4 months after hip fracture surgery, particularly during weight-bearing activities, and it is associated with poor lower limb functionality, as well as ADL and IADL disability. Older adults may benefit from pain assessments that go beyond pain intensity measurements after hip fracture, as this helps clinicians optimise pain management and overall functional recovery.

The Relationship Between β-Endorphin and Experimental Pain Sensitivity in Older Adults With Knee Osteoarthritis

Osteoarthritis (OA) is the most common cause of pain in people aged >45 years, and the knee is the most commonly affected joint. There is a growing interest in understanding the biological factors that influence pain among older adults, but few studies have examined the relationship between β-endorphin and experimental pain sensitivity in older adults with knee OA pain. The purpose of this study was to investigate the relationship between resting plasma levels of β-endorphin and experimental pain sensitivity. This study was a secondary analysis of data for 40 adults with knee OA pain in whom quantitative sensory testing was used to measure experimental sensitivity to heat- and mechanically induced pain. The mean age of the sample was 60 years (SD = 9 years), and approximately half were female (53%). Regression analyses indicated that β-endorphin level was negatively related to pressure pain threshold (β = -17.18, p = .02) and positively related to punctate mechanical pain (β = 17.13, p = .04), after controlling for age, gender, and OA severity. We did not find a significant relationship between β-endorphin and heat pain tolerance. The results suggest that higher circulating levels of β-endorphin at rest are associated with increased sensitivity to mechanical pain in older adults with knee OA. These findings add to the literature regarding biological factors associated with pain sensitivity in older adults with chronic pain. Additional studies are needed to identify mediators of the relationship between β-endorphin and pain sensitivity in OA and other musculoskeletal pain conditions.

Difference in the impact of central sensitization on pain-related symptoms between patients with chronic low back pain and knee osteoarthritis

Purpose: The aims of the present study were to investigate whether the association between the Central Sensitization Inventory (CSI) score, pain-related symptoms, pain-related disability, and health-related quality of life differed by disease (chronic low back pain [CLBP] vs knee osteoarthritis [KOA]), and to determine optimal cutoff scores for the CSI reflecting disease-specific characteristics.

Patients and methods: A total of 104 patients with CLBP and 50 patients with KOA were recruited. Central sensitization-related symptoms (CSI), EuroQol 5-dimension (EQ-5D), Brief Pain Inventory, widespread pain (Widespread Pain Index [WPI]), pressure pain threshold (PPT), and temporal summation (TS) were assessed and compared between the CLBP and KOA groups. Univariate correlation analysis was performed in each group. The receiver operating characteristic (ROC) curve analysis was performed to identify 1) presence/absence of central sensitization (CS), 2) presence/absence of central sensitivity syndromes (CSSs), and 3) pain intensity and pain interference in each group.

Results: The CSI and WPI scores were significantly higher in the CLBP group than in the KOA group. EQ-5D and pain interference scores significantly correlated with the CSI score in both the CLBP and KOA groups. The WPI score, PPT, and TS did not correlate with the CSI score in either the CLBP or KOA group. The suggested cutoff scores were 28 in the CLBP group and 17 in the KOA group to identify presence or absence of CSSs, and 34 in the CLBP group and 18–19 in the KOA group to identify pain severity.

Conclusion: The impact of CS on pain could differ between CLBP and KOA and that cutoff scores differ by each parameter we attempted to identify. Therefore, we should use the appropriate cutoff scores for the purposes and consider the difference in the impact of CS on pain by the patient group.

Pain Mechanisms and Ultrasonic Inflammatory Activity as Prognostic Factors in Patients With Psoriatic Arthritis: A Prospective Cohort Study

OBJECTIVE

To study the prognostic value of widespread pain and of musculoskeletal ultrasound (US) examination for subsequent treatment outcomes in patients with psoriatic arthritis (PsA).

METHODS

An exploratory prospective cohort study enrolled patients with PsA initiating biologic or conventional synthetic disease-modifying antirheumatic drugs in routine care. Clinical, US, and patient-reported measures were collected at baseline and after 4 months. Widespread nonarthritic pain (WP) was defined as a Widespread Pain Index score of ≥4 with pain in ≥4 of 5 regions. PsA activity by US was defined as color Doppler (yes/no) in selected entheses, joints, or tendons. The main response criteria included the American College of Rheumatology 20% improvement, the Disease Activity in Psoriatic Arthritis 50% improvement, and minimal disease activity. The primary analyses were age- and sex-adjusted logistic regression.

RESULTS

WP was present in 24 of 69 included patients (35%) and was associated with worse patient-reported and composite baseline measures, while US and other objective findings were similar to those in patients without WP. The odds of reaching minimal disease activity after 4 months were significantly greater for patients enrolled without WP (odds ratio 18.43 [95% confidence interval 1.51, 224.41]; P = 0.022), while WP did not impair other response measures. Patients with baseline color Doppler activity (n = 42 [61%]) had a worse objective PsA burden, but their chance of treatment response was comparable to those without color Doppler.

CONCLUSION

More than one-third of patients with PsA presented with WP, which was associated with worse patient-reported scores and failure to achieve minimal disease activity following conventional synthetic or biologic disease-modifying antirheumatic drug therapy. PsA activity by color Doppler US had no influence on subsequent treatment response in this PsA cohort.

Osteoarthritis

Osteoarthritis is a leading cause of disability and source of societal cost in older adults. With an ageing and increasingly obese population, this syndrome is becoming even more prevalent than in previous decades. In recent years, we have gained important insights into the cause and pathogenesis of pain in osteoarthritis. The diagnosis of osteoarthritis is clinically based despite the widespread overuse of imaging methods. Management should be tailored to the presenting individual and focus on core treatments, including self-management and education, exercise, and weight loss as relevant. Surgery should be reserved for those that have not responded appropriately to less invasive methods. Prevention and disease modification are areas being targeted by various research endeavours, which have indicated great potential thus far. This narrative Seminar provides an update on the pathogenesis, diagnosis, management, and future research on osteoarthritis for a clinical audience.

Omega-6: Omega-3 PUFA Ratio, Pain, Functioning, and Distress in Adults With Knee Pain

OBJECTIVES

Osteoarthritis (OA) is associated with inflammation, chronic pain, functional limitations, and psychosocial distress. High omega-3 (n-3) polyunsaturated fatty acids (PUFAs) are associated with lower levels of inflammatory mediators, anti-nociception, and adaptive cognitive/emotional functioning. High omega-6 (n-6) PUFAs are associated with inflammation, nociception, and psychological distress. While findings related to n-3 supplementation in knee OA are mixed, consideration of the n-6:n-3 ratio and additional outcome measures may provide improved understanding of the potential relevance of these fatty acids in OA. On the basis of recommended and typical ranges of the n-6:n-3 ratio, we hypothesized that in adults with knee pain, those with a high n-6:n-3 ratio would have greater pain/functional limitations, experimental pain sensitivity, and psychosocial distress compared with those with a low n-6:n-3 ratio.

MATERIALS AND METHODS

A cross-sectional investigation of clinical and experimental pain and physical and psychosocial functioning was completed in 167 adults ages 45 to 85 meeting knee OA screening criteria. Blood samples were collected and the plasma n-6:n-3 PUFA ratio determined. Quartile splits were computed and low (n=42) and high (n=41) ratio groups were compared.

RESULTS

The high ratio group reported greater pain and functional limitations, (all Ps<0.04), mechanical temporal summation (hand and knee, P<0.05), and perceived stress (P=0.008) but not depressive symptoms.

DISCUSSION

In adults with knee pain, a high n-6:n-3 ratio is associated with greater clinical pain/functional limitations, experimental pain sensitivity, and psychosocial distress compared with a low ratio group. Findings support consideration of the n-6:n-3 PUFA ratio and additional clinical endpoints in future research efforts.

The Value of High-Frequency Repetitive Transcranial Magnetic Stimulation of the Motor Cortex to Treat Central Pain Sensitization Associated With Knee Osteoarthritis

Aim

Chronic pain associated with knee osteoarthritis may develop in connection with a maladaptive process of pain sensitization in the central nervous system. Repetitive transcranial magnetic stimulation (rTMS) has been proposed to treat various pain syndromes related to central sensitization phenomenon, but was never applied in the context of knee osteoarthritis.

Methods

A 71-year-old woman presenting clinical evidence of central sensitization of pain associated with left knee osteoarthritis underwent monthly sessions of rTMS delivered at 10 Hz over the right motor cortex.

Results

From the week following the third session, she began to improve on various clinical aspects, including pain. After 10 sessions (i.e., almost one year of follow-up), pain was reduced by 67%, especially regarding neuropathic components, while sleep disorders and fatigue also improved by 57–67%. The central sensitization inventory (CSI) score was reduced by 70%.

Conclusion

This observation suggests that high-frequency motor cortex rTMS could be a therapeutic option to treat neuropathic pain and psychological symptoms associated with central sensitization developing in the context of chronic osteoarthritis of the knee joint.

Central Sensitization in Knee Osteoarthritis: Relating Presurgical Brainstem Neuroimaging and PainDETECT-Based Patient Stratification to Arthroplasty Outcome

OBJECTIVE

The neural mechanisms of pain in knee osteoarthritis (OA) are not fully understood, and some patients have neuropathic-like pain associated with central sensitization. To address this, we undertook the present study in order to identify central sensitization using neuroimaging and PainDETECT and to relate it to postarthroplasty outcome.

METHODS

Patients awaiting arthroplasty underwent quantitative sensory testing, psychological assessment, and functional magnetic resonance imaging (fMRI). Neuroimaging (fMRI) was conducted during punctate stimulation (n = 24) and cold stimulation (n = 20) to the affected knee. The postoperative outcome was measured using the Oxford Knee Score, patient-reported moderate-to-severe long-term pain postarthroplasty, and a range of pain-related questionnaires.

RESULTS

Patients with neuropathic-like pain presurgery (identified using PainDETECT; n = 14) reported significantly higher pain in response to punctate stimuli and cold stimuli near the affected joint (P < 0.05). Neural activity in these patients, compared to those without neuropathic-like pain, was significantly lower in the rostral anterior cingulate cortex (P < 0.05) and higher in the rostral ventromedial medulla (RVM) during punctate stimulation (P < 0.05), with significant functional connectivity between these two areas (r = 0.49, P = 0.018). Preoperative neuropathic-like pain and higher neural activity in the RVM were associated with moderate-to-severe long-term pain after arthroplasty (P = 0.0356).

CONCLUSION

The psychophysical and neuroimaging data suggest that a subset of OA patients have centrally mediated pain sensitization. This was likely due to supraspinally mediated reductions in inhibition and increases in facilitation of nociceptive signaling, and was associated with a worse outcome following arthroplasty. The neurobiologic confirmation of central sensitization in patients with features of neuropathic pain, identified using PainDETECT, provides further support for the investigation of such bedside measures for patient stratification, to better predict postsurgical outcomes.

Widespread Pressure Pain Hypersensitivity, Health History, and Trigger Points in Patients with Chronic Neck Pain: A Preliminary Study

Background

Pain sensitivity in chronic neck pain patients may be influenced by health conditions related to higher levels of widespread pressure pain hypersensitivity (sensitization). Trigger points have also been reported to play a role in the sensitization process.

Objectives

To investigate the association between pressure pain thresholds, trigger points, and health conditions in patients with chronic neck pain.

Design

Original research, preliminary study.

Setting

A private clinic.

Subjects

Thirty-four chronic mechanical neck pain patients and 34 chronic whiplash-associated neck pain patients, giving a final sample of 68 chronic neck pain patients.

Methods

Patients underwent an assessment of pressure pain thresholds over the upper trapezius, extensor carpi radialis longus, and tibialis anterior muscles and were screened for the presence of trigger points in the upper trapezius muscle. Further, information about health history conditions was obtained and collected in a form.

Results

Significantly negative correlations between all pressure pain thresholds and duration of health history conditions were found (all P &lt; 0.02). Significantly lower pressure pain thresholds (all P &lt; 0.01) were found in patients with active trigger points as compared with those with latent trigger points.

Conclusion

Widespread pressure pain hypersensitivity was associated with duration of health history conditions, suggesting that long-lasting health complaints may act as a triggering/perpetuating factor, driving sensitization in individuals with chronic neck pain. Active trigger points may be associated with higher widespread pressure hypersensitivity.

Acupuncture-Analgesia-Mediated Alleviation of Central Sensitization

Pain can trigger central amplification called central sensitization, which ultimately results in hyperalgesia and/or allodynia. Many reports have showed acupuncture has an analgesic effect. We searched the related article on PubMed database and Cochrane database to discover central sensitization pathway in acupuncture analgesia. We summarized that acupuncture enhances the descending inhibitory effect and modulates the feeling of pain, thus modifying central sensitization. The possible mechanisms underlying the analgesic effects of acupuncture include segmental inhibition and the activation of the endogenous opioid, adrenergic, 5-hydroxytryptamine, and N-methyl-D-aspartic acid, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate pathways. Moreover, acupuncture can locally reduce the levels of inflammatory mediators. In clinical settings, acupuncture can be used to treat headache, neuropathic pain, low back pain, osteoarthritis, and irritable bowel syndrome. These mechanisms of acupuncture analgesia may be involved in the alleviation of central sensitization.

Additional femoral nerve block analgesia does not reduce the chronic pain after total knee arthroplasty: A retrospective study in patients with knee osteoarthritis

Femoral nerve block analgesia was deemed to the gold standard for acute pain management after total knee arthroplasty (TKA). But effect on chronic pain management is not investigated fully. We conducted a retrospective study to explore the effect of single-injection femoral nerve block on postsurgical chronic pain.All medical records of patients undertaking TKA between January, 2013 and June, 2014 were reviewed via the Docare anesthesia database. Patients who administrated with the self-controlled intravenous analgesia were assigned to group P. Patients who received a single-injection femoral never block combined with patient self-controlled intravenous analgesia were assigned to group N + P. The visual analog scale (VAS) score before surgery, the first postoperative day (POD 1), POD 2, 3 months, 6 months, and 12 months after surgery were extracted from medical records. Pain score was compared over these 2 groups to investigate treatment outcomes.In all, 470 patients met the selection criteria for group P and 266 patients met the selection criteria for group N + P. Compared with group P, the VAS score decreased significantly in group N + P at POD 1 (P < .001), and the same was observed at POD 2 (P < .001); the moderate to severe pain incidence rate decreased significantly in group N + P at POD 1 (P < .01) and POD 2 (motion, P < .001). The rescued anesthesia rate reduced significantly in group N + P in POD 1 (P = .001), whereas no difference was found in POD 2 (P = .864). No difference was found at 3, 6, and 12 months after surgery (all P > .05).The single-injection femoral nerve block could relieve the acute postsurgical pain in a short period of time. But no evidence was found that it could reduce the chronic pain between 3 and 12 months after TKA.

Rheumatoid Arthritis Patients Achieve Better Satisfaction but Lower Functional Activities as Compared to Osteoarthritis Patients After Total Knee Arthroplasty

BACKGROUND

Recently, poor patient satisfaction after total knee arthroplasty (TKA) has gained attention mainly in osteoarthritis (OA) patients; however, satisfaction after TKA remains to be understood in rheumatoid arthritis (RA) patients. This study aimed to examine satisfaction and function after RA TKA using patient-reported outcome measures and to compare the results with those of OA-TKA.

METHODS

This study enrolled 534 TKAs of 501 patients consisting of 75 TKAs of 70 RA patients and 459 TKAs of 431 OA patients. Data of patient-reported outcome measures such as new Knee Society Score 2011, Pain Catastrophizing Scale, and Pain DETECT Score were collected at 2 years. Multiple regression analysis was performed with Knee Society Score satisfaction score set as a dependent variable in order to clarify factors affecting patient satisfaction. Principle component analysis was performed, and satisfaction and function components were compared between RA and OA.

RESULTS

All activity scores were significantly lower in RA TKA than in OA TKA, whereas the range of motion and patient satisfaction scores were significantly better in RA TKA than in OA TKA. Scores for symptom, expectation, basic activity, and discretional activity positively affected patient satisfaction (P < .001), while Pain Catastrophizing Scale negatively did (P = .021). Importantly, diagnosis of RA itself pushed up the patient satisfaction score by 1.5 points. Principle component analysis revealed that RA TKA achieved significantly higher satisfaction component (P = .001), but lower function component (P < .0001) compared to OA TKA.

CONCLUSION

Patient satisfaction was better but functional activity was lower in RA than in OA. As poor functional activity was evident preoperatively in RA patients, to improve functional outcome should be future challenge for RA TKA.

Subchondral bone osteoclasts induce sensory innervation and osteoarthritis pain

Joint pain is the defining symptom of osteoarthritis (OA) but its origin and mechanisms remain unclear. Here, we investigated an unprecedented role of osteoclast-initiated subchondral bone remodeling in sensory innervation for OA pain. We show that osteoclasts secrete netrin-1 to induce sensory nerve axonal growth in subchondral bone. Reduction of osteoclast formation by knockout of receptor activator of nuclear factor kappa-B ligand (Rankl) in osteocytes inhibited the growth of sensory nerves into subchondral bone, dorsal root ganglion neuron hyperexcitability, and behavioral measures of pain hypersensitivity in OA mice. Moreover, we demonstrated a possible role for netrin-1 secreted by osteoclasts during aberrant subchondral bone remodeling in inducing sensory innervation and OA pain through its receptor DCC (deleted in colorectal cancer). Importantly, knockout of Netrin1 in tartrate-resistant acid phosphatase-positive (TRAP-positive) osteoclasts or knockdown of Dcc reduces OA pain behavior. In particular, inhibition of osteoclast activity by alendronate modifies aberrant subchondral bone remodeling and reduces innervation and pain behavior at the early stage of OA. These results suggest that intervention of the axonal guidance molecules (e.g., netrin-1) derived from aberrant subchondral bone remodeling may have therapeutic potential for OA pain.

Central sensitization in chronic pain and medically unexplained symptom research: A systematic review of definitions, operationalizations and measurement instruments

OBJECTIVE

Central sensitization (CS), a mechanism explaining the persistence of symptoms, has been the focus of many research projects. Explanations given to patients with chronic pain are often based on this mechanism. It is hypothesized that CS also plays an important role in the persistence of medically unexplained symptoms (MUS). However, definitions and operationalizations of CS vary. We conducted a systematic review of definitions, operationalizations and measurement instruments of CS.

METHODS

We searched in PubMed, EMBASE, PsycINFO, Cinahl and The Cochrane Library till September 2017 and included papers that addressed CS in relation to chronic pain and/or MUS. Two reviewers independently selected, analysed and classified information from the selected publications. We performed a thematic analysis of definitions and operationalizations. We listed the measurement instruments.

RESULTS

We included 126 publications, 79 publications concerned chronic pain, 47 publications concerned MUS. Definitions of CS consistently encompass the theme hyperexcitability of the central nervous system (CNS). Additional themes are variably present: CNS locations, nature of sensory input, reduced inhibition and activation and modulation of the NDMA receptor. Hyperalgesia and allodynia are widely mentioned as operationalizations of CS. Quantitative sensory testing (QST) and (f)MRI are the most reported measurement instruments.

CONCLUSIONS

There is consensus that hyperexcitability is the central mechanism of CS. Operationalizations are based on this mechanism and additional components. There are many measurement instruments available, whose clinical value has still to be determined. There were no systematic differences in definitions and operationalizations between the publications addressing MUS and those addressing chronic pain.

Is a Fundamental Change in the Interpretation of Rheumatoid Arthritis Disease Activity Necessary?

Disease Activity Score (DAS) composite models are moderately precise and robust measures of disease severity when they are used in rheumatoid arthritis (RA) cohorts. They are less so when used for individual patients. This is because subjective components, patient global assessment of well-being and tender joint count, modified by factors other than RA biological disease activity, often obfuscate interpretation of disease activity. Comorbidities, especially distress, can disproportionately inflate these components. Fibromyalgia, essentially synonymous with distress, pain augmentation, and depression, is a common comorbidity. Its presence and severity can be determined by the Polysymptomatic Distress Scale (PSD). The differential effects of distress and fibromyalgia syndrome on the DAS can be demonstrated by manipulating information already there: the arithmetic differences or ratios of the tender joint count and swollen joint count and comparison of the modified disease activity score with 28 joints to the disease activity score with 28 joints-patient (DAS28-derived indices that measure the contribution of the relatively objective or relatively subjective components, respectively). The potentially more objective multibiomarker disease activity might also be used to test the severity of biological RA disease activity. These tools may be used to elucidate disproportionate values for subjective DAS model components, which then should facilitate identification of the underlying process factors, including depression, for potential treatment.

Effects of Transcranial Direct Current Stimulation on Knee Osteoarthritis Pain in Elderly Subjects With Defective Endogenous Pain-Inhibitory Systems: Protocol for a Randomized Controlled Trial

BACKGROUND

Knee osteoarthritis (OA) has been the main cause behind chronic pain and disabilities in the elderly population. The traditional treatment for knee OA pain currently concerns a number of combinations of pharmacological and nonpharmacological therapies. However, such combinations have displayed little effects on a significant group of subjects. In addition to this, pharmacological treatments often cause adverse effects, which limits their use on this population. Previous studies showed that chronic knee OA pain may be associated with maladaptive compensatory plasticity in pain-related neural central circuits indexed by a defective descending pain-inhibitory system. Transcranial direct current stimulation (tDCS) can revert some of these maladaptive changes, thus decreasing chronic pain sensation. Numerous studies have demonstrated that the use of anodal tDCS stimulation over the primary motor cortex (M1) has positive effects on chronic neuropathic pain. Yet, data on OA pain in elderly patients, including its effects on the endogenous pain-inhibitory system, remain limited.

OBJECTIVE

The objective of this study is to evaluate the efficacy of tDCS in reducing pain intensity caused by knee OA in elderly subjects with defective endogenous pain-inhibitory systems.

METHODS

We designed a randomized, sham-controlled, single-center, double-blinded clinical trial. Patients with knee OA who have maintained a chronic pain level during the previous 6 months and report a pain score of 4 or more on a 0-10 numeric rating scale (NRS) for pain in that period will undergo a conditioned pain modulation (CPM) task. Participants who present a reduced CPM response, defined as a decrease in NRS during the CPM task of less than 10%, and meet all of the inclusion criteria will be randomly assigned to receive 15 sessions of 2 mA active or sham tDCS for 20 minutes. A sample size of 94 subjects was calculated. The Brief Pain Inventory pain items will be used to assess pain intensity as our primary outcome. Secondary outcomes will include pain impact on functioning, mobility performance, quality of life, CPM, pressure pain threshold, touch-test sensory evaluation, and safety. Follow-up visits will be performed 2, 4, and 8 weeks following intervention. The data will be analyzed using the principle of intention-to-treat.

RESULTS

This study was approved by the institutional review board with the protocol number 1685/2016. The enrollment started in April 2018; at the time of publication of this protocol, 25 subjects have been enrolled. We estimate we will complete the enrollment process within 2 years.

CONCLUSIONS

This clinical trial will provide relevant data to evaluate if anodal tDCS stimulation over M1 can decrease chronic knee OA pain in elderly subjects with defective CPM. In addition, this trial will advance the investigation of the role of central sensitization in knee OA and evaluate how tDCS stimulation may affect it.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03117231; https://clinicaltrials.gov/ct2/show/NCT03117231 (Archived by WebCite at http://webcitation.org/73WM1LCdJ).

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR1-10.2196/11660.

Mechanisms of Osteoarthritis (OA) Pain

PURPOSE OF REVIEW

Osteoarthritis (OA) is a major cause of pain and disability worldwide. There is, however, a relatively poor correlation between the severity of OA based on plain radiograph changes and symptoms. In this review, we consider the mechanisms of pain in OA.

RECENT FINDINGS

It is now widely recognised that OA is a disease of the whole joint. Data from large observational studies which have used magnetic resonance imaging (MRI) suggest that pain in OA is associated with a number of structural factors including the presence of bone marrow lesions (BMLs) and also synovitis. There is evidence also of alterations in nerve processing and that both peripheral and central nerve sensitisation may contribute to pain in OA. Identification of the causes of pain in an individual patient may be of benefit in helping to better target with appropriate therapy to help reduce their symptoms and improve function.

Up to a quarter of patients with certain chronic recalcitrant tendinopathies may have central sensitisation: a prospective cohort of more than 300 patients

Introduction

To identify the possible prevalence of 'central sensitisation', in patients with chronic recalcitrant lower limb tendinopathy conditions, with the Central Sensitisation Inventory (CSI) questionnaire.

Methods

Patients with chronic lower limb tendinopathy conditions treated within a single hospital outpatient clinic specialising in tendinopathy were identified from clinical records. As part of routine care, self-reported numerical markers of pain, global function (using the EuroQol-5D (EQ-5D) questionnaire) and the CSI score to investigate the possibility of central sensitisation were completed.

Results

A total of 312 suitable patients with chronic lower limb tendinopathy and similar conditions were identified, who had completed a CSI questionnaire. Of these, 108 presented with greater trochanteric pain syndrome, 12 with patella tendinopathy, 33 with non-insertional Achilles tendinopathy, 48 with insertional Achilles tendinopathy and 110 with plantar fasciitis. A total of 66% of the patients were female, the median age was 54.9 years and the median duration of symptoms was 24 months. There was a median CSI score of 25%, with statistically significant differences noted between the different conditions studied. Overall, 20% of patients scored above a threshold of 40% on CSI questionnaire, indicating that central sensitisation was possible. Greater trochanteric pain syndrome and plantar fasciitis had the highest proportions in the conditions studied. Weak correlations were found between CSI and other pain scores studied.

Conclusion

The CSI questionnaire may identify up to a quarter of patients with some chronic lower limb tendinopathy and associated conditions as being more likely to have central sensitisation, and these proportions differed between conditions. The clinical significance of this is unclear, but worth further study to see if/how this may relate to treatment outcomes. These are results from a single hospital clinic dealing with patients with chronic tendinopathy, and comparison with a control group is currently lacking. However, on the information presented here, the concept of central sensitisation should be considered in patients being treated for chronic tendinopathy.

Somatosensation in OA: exploring the relationships of pain sensitization, vibratory perception and spontaneous pain

Background

Pain in osteoarthritis (OA) remains poorly understood. Different types of somatosensory alterations exist in OA including hyperesthesia and increased sensitivity to painful stimuli as well as those of decreased sensitivity to cutaneous stimuli including vibratory perception threshold. The relationship between these different somatosensory measures has not been previously evaluated in OA. In this observational study, we evaluated relationships between vibratory perception (VPT), pressure pain detection thresholds (PPT), allodynia and subjective pain in knee OA.

Methods

Forty-two persons with moderate to severe knee OA and 12 controls without OA were evaluated. VPT was measured using a biothesiometer. Allodynia was measured by application of a 60 g Von Frey monofilament repeatedly to predetermined sites. PPTs were measured using a pressure algometer.

Results

Increased vibratory acuity was associated with lower PPTs and presence of allodynia. Allodynia was more common in OA than controls (54.8% vs 16.6%, p = 0.024 in the ipsilateral knee, and 42.9% vs 0%, p = 0.005 in the contralateral knee). OA participants with allodynia had lower PPTs than those without allodynia. In those with OA, spontaneous knee pain was associated with lower PPTs and with allodynia.

Conclusion

This study confirms the presence of somatosensory alterations in OA. Sensory alterations (vibratory perception) were shown to be related to nociceptive alterations (sensitization) in OA, showing a general increased sensitivity to cutaneous mechanical stimulation. Understanding these relationships is an important step in delineating the complicated pathophysiology of pain processing in OA.

Contralateral monoarthritis exacerbated chronic constriction injury-induced pain hypersensitivity through upregulating inducible nitric oxide synthase

Introduction

High comorbidity of osteoarthritis (OA) and neuropathic pain has been reported in aged patients. Evidence shows that central sensitization of pain processing occurs in late-phase OA and may facilitate the development of neuropathic pain. Few studies reveal whether acute monoarthritis (MA) aggravates neuropathic pain on the opposite side of the body from the injury.

Methods

To address whether neuropathic pain is affected by contralateral MA through distinct inflammatory pathway, MA was induced by intra-articular injection of complete Freund’s adjuvant (CFA) into the right tibiotarsal joint, and neuropathic pain was established by chronic constriction injury (CCI) of the left sciatic nerve.

Results

We observed that MA aggravated mechanical allodynia and thermal hyperalgesia in CCI rats. Furthermore, MA affected the other side of the spinal cord in multiple aspects, including the upregulation of iNOS mRNA and the enhancement of forskolin-induced facilitation of excitatory synaptic transmission in the spinal cord dorsal horn substantia gelatinosa neurons.

Discussion

Interestingly, intrathecal injection of 1400W, an antagonist of iNOS, attenuated intensity of pain behaviors in CCI rats with contralateral MA to similar levels in CCI rats without MA, and also normalized the facilitatory effect of forskolin on excitatory synaptic transmission in the spinal cord dorsal horn neurons in contralateral MA rats. Therefore, contralateral MA worsened CCI-induced pain hypersensitivity probably through upregulating iNOS and enhancing the facilitation of synaptic transmission following CCI.

Conclusion

Inhibiting the iNOS might be a potential therapeutic strategy for concurrent OA and neuropathic pain.

The Central Sensitization Inventory and Pain Sensitivity Questionnaire: An exploration of construct validity and associations with widespread pain sensitivity among individuals with shoulder pain

BACKGROUND

The Central Sensitization Inventory (CSI) and Pain Sensitivity Questionnaire (PSQ) are alternatives to quantitative sensory testing (QST) for inferring central sensitization.

OBJECTIVE

Explore 1) comparative validity of the CSI and PSQ with QST (construct validity) and pain-related psychological questionnaires (concurrent validity), and 2) associations with widespread pain sensitivity.

METHODS

Seventy-eight participants with unilateral shoulder pain less than 6 months (mean ± SD age = 39.0 ± 14.5 years, N (%) females = 36 (46.2%)) completed the CSI, PSQ, psychological questionnaires, and underwent QST for local and remote pressure pain thresholds (PPT), heat pain threshold, and suprathreshold heat pain ratings. Data from 25 age and sex-matched healthy participants (mean ± SD age = 35.2 ± 11.1 year, N (%) females = 13 (52.0%)) were used to determine a composite index for widespread pressure pain sensitivity in the shoulder pain group. Analyses included correlations between measures and between-group comparisons.

RESULTS

Only the PSQ was associated with remote PPT (rho range = -0.25 to -0.27). Both the CSI and PSQ were associated with resilience (rho range = -0.29 to -0.39), anxiety (rho range = 0.25 to 0.66), and negative affect (rho range = 0.27 to 0.67). Neither the CSI nor PSQ were associated with widespread pain sensitivity (p > 0.05). Resilience (adjusted OR = 0.41, 95% CI = 0.18; 0.94) was a distinctive feature for widespread pain sensitivity.

CONCLUSIONS

These preliminary findings challenge the exclusive use of the CSI or PSQ for inferring central sensitization among individuals with shoulder pain.

Refinement of the Montreal Instrument for Cat Arthritis Testing, for Use by Veterinarians: detection of naturally occurring osteoarthritis in laboratory cats

Objectives Feline osteoarthritis causes pain and disability. Detection and measurement is challenging, relying heavily on owner report. This study describes refinement of the Montreal Instrument for Cat Arthritis Testing, for Use by Veterinarians. Methods A video analysis of osteoarthritic (n = 6) and non-osteoarthritic (n = 4) cats facilitated expansion of scale items. Three successive therapeutic trials (using gabapentin, tramadol and oral transmucosal meloxicam spray) in laboratory cats with and without natural osteoarthritis (n = 12-20) permitted construct validation (assessments of disease status sensitivity and therapeutic responsiveness) and further scale refinements based on performance. Results Scale osteoarthritic sensitivity improved from phase I to phase III; phase III scale total score ( P = 0.0001) and 4/5 subcategories - body posture ( P = 0.0006), gait ( P = 0.0031), jumping (0.0824) and global distance examination ( P = 0.0001) - detected osteoarthritic cats. Total score inter-rater (intra-class correlation coefficients [ICC] = 0.64-0.75), intra-rater (ICC = 0.90-0.91) and overall internal consistency (Cronbach's alpha = 0.85) reliability were good to excellent. von Frey anesthesiometer-induced paw withdrawal threshold increased with gabapentin in phase I, in osteoarthritic cats ( P <0.001) but not in non-osteoarthritic cats ( P = 0.075). Night-time activity increased during gabapentin treatment. Objective measures also detected tramadol and/or meloxicam treatment effects in osteoarthritic cats in phases II and III. There was some treatment responsiveness: in phase I, 3/10 subcategory scores improved ( P <0.09) in treated osteoarthritic cats; in phase II, 3/8 subcategories improved; and in phase III, 1/5 subcategories improved ( P <0.096). Conclusions and relevance The revised scale detected naturally occurring osteoarthritis, but not treatment effects, in laboratory cats, suggesting future potential for screening of at-risk cats. Further study is needed to confirm reliability, validity (disease sensitivity and treatment responsiveness) and clinical feasibility, as well as cut-off scores for osteoarthritic vs non-osteoarthritic status, in client-owned cats.

Development and psychometric properties of short form of central sensitization inventory in participants with musculoskeletal pain: A cross-sectional study

Background

The central sensitization inventory (CSI) comprises 25 items and is commonly used to measure somatic and emotional symptoms related to central sensitization symptoms. CSI was developed as an easy-to-administer screening instrument for patients at high risk of developing central sensitization in whom it was essential to quickly evaluate the condition. The purpose of the present study was to develop a short form of CSI and evaluate its psychometric properties using a contemporary approach called Rasch analysis.

Methods

A total of 505 patients with musculoskeletal disorders were recruited in this study. The CSI, pain intensity, pain interference, and the health-related quality of life (QOL) were evaluated for each participant. The original CSI items were consecutively analyzed using the Rasch model. Successive Rasch analyses were performed until a final set of items satisfied the model fit requirements. We also analyzed the psychometric properties of the original and short forms of CSI.

Results

Four consecutive Rasch analyses identified the removable items. Finally, the shortest questionnaire obtained that maintained the correct psychometric properties based on the Rasch model contained only 9 items (CSI-9). Rasch analysis showed that the CSI-9 had acceptable internal consistency, exhibited unidimensionality, had no notable differential item functioning, and was functional on the category rating scale.

Conclusions

The nine-item short form of CSI has acceptable psychometric properties and is suitable for use for patients with musculoskeletal pain. Thus, the CSI-9 can be used as a brief instrument to evaluate central sensitization.

A feasibility study of brain-targeted treatment for people with painful knee osteoarthritis in tertiary care

Purpose: To assess the feasibility and clinical impact of brain-targeted treatment (BT; aiming to target sensorimotor processing) in knee osteoarthritis patients attending tertiary care. Methods: Randomized replicated case series. The study involved three phases, each of 2 weeks duration: (1) no-treatment phase; (2) BT phase (left/right judgments and touch discrimination training); and (3) usual care (education, strengthening, and stretching training). Primary outcomes were: timely recruitment; number of participants completing the interventions; treatment compliance and barriers; follow-up rates; and treatment impact on pain and function. Fear-avoidance beliefs and clinical measures of cortical body representation (tactile acuity and left/right judgment performance) were secondary outcomes. Results: A total of 5% (19/355) of all assessed patients were eligible to participate and of these, 58% (11/19) agreed to participate. Ten patients completed the study, and 9 were successfully followed up, with treatment compliance varying between interventions. Compliance was poor for the touch discrimination component of BT. No significant effects were observed for pain relief or knee function after any treatment. A positive impact of treatment was found for fear-avoidance beliefs (usual care vs. washout, p = 0.007; BT vs. washout, p = 0.029) and left/right judgment accuracy (usual care vs. washout; p = 0.006). Conclusions: Clear barriers were identified to implementing BT in tertiary care for knee osteoarthritis. Access to all available services (especially the use of interpreters), and treatment options that do not require additional assistance to perform (e.g., touch discrimination training) represent the main lessons learned.

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.

Differential contributions of peripheral and central mechanisms to pain in a rodent model of osteoarthritis

The mechanisms underlying the transition from acute nociceptive pain to centrally maintained chronic pain are not clear. We have studied the contributions of the peripheral and central nervous systems during the development of osteoarthritis (OA) pain. Male Sprague-Dawley rats received unilateral intra-articular injections of monosodium iodoacetate (MIA 1 mg) or saline, and weight-bearing (WB) asymmetry and distal allodynia measured. Subgroups of rats received intra-articular injections of, QX-314 (membrane impermeable local anaesthetic) + capsaicin, QX-314, capsaicin or vehicle on days 7, 14 or 28 post-MIA and WB and PWT remeasured. On days 7&14 post-MIA, but not day 28, QX-314 + capsaicin signficantly attenuated changes in WB induced by MIA, illustrating a crucial role for TRPV1 expressing nociceptors in early OA pain. The role of top-down control of spinal excitability was investigated. The mu-opioid receptor agonist DAMGO was microinjected into the rostroventral medulla, to activate endogenous pain modulatory systems, in MIA and control rats and reflex excitability measured using electromyography. DAMGO (3 ng) had a significantly larger inhibitory effect in MIA treated rats than in controls. These data show distinct temporal contribtuions of TRPV1 expressing nociceptors and opioidergic pain control systems at later timepoints.

Brain imaging of pain sensitization in patients with knee osteoarthritis

A relevant aspect in osteoarthritic pain is neural sensitization. This phenomenon involves augmented responsiveness to painful stimulation and may entail a clinically worse prognosis. We used functional magnetic resonance imaging (fMRI) to study pain sensitization in patients with knee osteoarthritis. Sixty patients were recruited and pain sensitization was clinically defined on the basis of regional spreading of pain (spreading sensitization) and increased pain response to repeated stimulation (temporal summation). Functional magnetic resonance imaging testing involved assessing brain responses to both pressure and heat stimulation. Thirty-three patients (55%) showed regional pain spreading (simple sensitization) and 19 patients (32%) showed both regional spreading and temporal summation. Sensitized patients were more commonly women. Direct painful pressure stimulation of the joint (articular interline) robustly activated all of the neural elements typically involved in pain perception, but did not differentiate sensitized and nonsensitized patients. Painful pressure stimulation on the anterior tibial surface (sensitized site) evoked greater activation in sensitized patients in regions typically involved in pain and also beyond these regions, extending to the auditory, visual, and ventral sensorimotor cortices. Painful heat stimulation of the volar forearm did not discriminate the sensitization phenomenon. Results confirm the high prevalence of pain sensitization secondary to knee osteoarthritis. Relevantly, the sensitization phenomenon was associated with neural changes extending beyond strict pain-processing regions with enhancement of activity in general sensory, nonnociceptive brain areas. This effect is in contrast to the changes previously identified in primary pain sensitization in fibromyalgia patients presenting with a weakening of the general sensory integration.

Thermal and mechanical pain sensitization in patients with osteoarthritis of the knee

OBJECTIVE

The aim was to assess sensitization using quantitative sensory testing in mechanical and thermal modes in individuals with and without osteoarthritis (OA) of the knee. Pain thresholds were correlated with functionality, symptoms of depression and intensity of pain.

METHODS

Thirty control volunteers and 30 patients with OA of the knee were assessed. Punctate pain thresholds using Von Frey filaments and thermal pain thresholds using a Thermal Sensory Analyzer were evaluated in the periarticular region of the knee and forearm. Using a digital pressure algometer, pressure pain thresholds were assessed in the periarticular region of the knee and on the root exit zone on the lumbar and sacral spine.

RESULTS

Punctate, pressure, and thermal pain thresholds differed significantly between participants with and without OA (p < 0.05). Values in those with OA were consistent with pain sensitization. Pressure pain thresholds also showed moderate and negative correlations with data on functionality, symptoms of depression and intensity of pain (-0.36 < r > -0.56), contributing up to 30% of their variability.

CONCLUSIONS

Allodynia and hyperalgesia were demonstrated in the OA group, suggesting central sensitization in patients with mild to moderate severity of joint damage. Correlation between mechanical hypersensitivity and psychosocial factors seems to be small, despite of its significance.

Peripheral Mechanisms Contributing to Osteoarthritis Pain

PURPOSE OF REVIEW

Osteoarthritis (OA) is the most common form of arthritis and a major source of pain and disability worldwide. OA-associated pain is usually refractory to classically used analgesics, and disease-modifying therapies are still lacking. Therefore, a better understanding of mechanisms and mediators contributing to the generation and maintenance of OA pain is critical for the development of efficient and safe pain-relieving therapies.

RECENT FINDINGS

Both peripheral and central mechanisms contribute to OA pain. Clinical evidence suggests that a strong peripheral nociceptive drive from the affected joint maintains pain and central sensitization associated with OA. Mediators present in the OA joint, including nerve growth factor, chemokines, cytokines, and inflammatory cells can contribute to sensitization. Furthermore, structural alterations in joint innervation and nerve damage occur in the course of OA. Several interrelated pathological processes, including joint damage, structural reorganization of joint afferents, low-grade inflammation, neuroplasticity, and nerve damage all contribute to the pain observed in OA. It can be anticipated that elucidating exactly how these mechanisms are operational in the course of progressive OA may lead to the identification of novel targets for intervention.

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.

Assessment and manifestation of central sensitisation across different chronic pain conditions

Different neuroplastic processes can occur along the nociceptive pathways and may be important in the transition from acute to chronic pain and for diagnosis and development of optimal management strategies. The neuroplastic processes may result in gain (sensitisation) or loss (desensitisation) of function in relation to the incoming nociceptive signals. Such processes play important roles in chronic pain, and although the clinical manifestations differ across condition processes, they share some common mechanistic features. The fundamental understanding and quantitative assessment of particularly some of the central sensitisation mechanisms can be translated from preclinical studies into the clinic. The clinical perspectives are implementation of such novel information into diagnostics, mechanistic phenotyping, prevention, personalised treatment, and drug development. The aims of this paper are to introduce and discuss (1) some common fundamental central pain mechanisms, (2) how they may translate into the clinical signs and symptoms across different chronic pain conditions, (3) how to evaluate gain and loss of function using quantitative pain assessment tools, and (4) the implications for optimising prevention and management of pain. The chronic pain conditions selected for the paper are neuropathic pain in general, musculoskeletal pain (chronic low back pain and osteoarthritic pain in particular), and visceral pain (irritable bowel syndrome in particular). The translational mechanisms addressed are local and widespread sensitisation, central summation, and descending pain modulation.

Significance

Central sensitisation is an important manifestation involved in many different chronic pain conditions. Central sensitisation can be different to assess and evaluate as the manifestations vary from pain condition to pain condition. Understanding central sensitisation may promote better profiling and diagnosis of pain patients and development of new regimes for mechanism based therapy. Some of the mechanisms underlying central sensitisation can be translated from animals to humans providing new options in development of therapies and profiling drugs under development.

Psychosocial factors partially mediate the relationship between mechanical hyperalgesia and self-reported pain

Background and aims:

Amplification of sensory signalling within the nervous system along with psychosocial factors contributes to the variation and severity of knee pain. Quantitative sensory testing (QST) is a non-invasive test battery that assesses sensory perception of thermal, pressure, mechanical and vibration stimuli used in the assessment of pain. Psychosocial factors also have an important role in explaining the occurrence of pain. The aim was to determine whether QST measures were associated with self-reported pain, and whether those associations were mediated by psychosocial factors.

Methods:

Participants with knee pain identified from a population-based cohort completed a tender point count and a reduced QST battery of thermal, mechanical and pressure pain thresholds, temporal summation, mechanical pain sensitivity (MPS), dynamic mechanical allodynia (DMA) and vibration detection threshold performed following the protocol by the German Research Network on Neuropathic Pain. QST assessments were performed at the most painful knee and opposite forearm (if pain-free). Participants were asked to score for their global and knee pain intensities within the past month (range 0–10), and complete questionnaire items investigating anxiety, depression, illness perceptions, pain catastrophising, and physical functioning. QST measures (independent variable) significantly correlated (Spearman’s rho) with self-reported pain intensity (dependent variable) were included in structural equation models with psychosocial factors (latent mediators).

Results:

Seventy-two participants were recruited with 61 participants (36 women; median age 64 years) with complete data included in subsequent analyses. Tender point count was significantly correlated with global pain intensity. DMA at the knee and MPS at the most painful knee and opposite pain-free forearm were significantly correlated with both global pain and knee pain intensities. Psychosocial factors including pain catastrophising sub-scales (rumination and helplessness) and illness perceptions (consequences and concern) were significant partial mediators of the association with global pain intensity when loaded on to a latent mediator for: tender point count [75% total effect; 95% confidence interval (CI) 22%, 100%]; MPS at the knee (49%; 12%, 86%); and DMA at the knee (63%; 5%, 100%). Latent psychosocial factors were also significant partial mediators of the association between pain intensity at the tested knee with MPS at the knee (30%; 2%, 58%), but not for DMA at the knee.

Conclusions:

Measures of mechanical hyperalgesia at the most painful knee and pain-free opposite forearm were associated with increased knee and global pain indicative of altered central processing. Psychosocial factors were significant partial mediators, highlighting the importance of the central integration of emotional processing in pain perception.

Implications:

Associations between mechanical hyperalgesia at the forearm and knee, psychosocial factors and increased levels of clinical global and knee pain intensity provide evidence of altered central processing as a key mechanism in knee pain, with psychological factors playing a key role in the expression of clinical pain.

Molecular Understanding of the Activation of CB1 and Blockade of TRPV1 Receptors: Implications for Novel Treatment Strategies in Osteoarthritis

Osteoarthritis (OA) is a joint disease in which cartilage degenerates as a result of mechanical and biochemical changes. The main OA symptom is chronic pain involving both peripheral and central mechanisms of nociceptive processing. Our previous studies have implicated the benefits of dual- over single-acting compounds interacting with the endocannabinoid system (ECS) in OA treatment. In the present study, we focused on the specific molecular alterations associated with pharmacological treatment. OA was induced in Wistar rats by intra-articular injection of 3 mg of monoiodoacetate (MIA). Single target compounds (URB597, an FAAH inhibitor, and SB366791, a TRPV1 antagonist) and a dual-acting compound OMDM198 (FAAH inhibitor/TRPV1 antagonist) were used in the present study. At day 21 post-MIA injection, rats were sacrificed 1 h after i.p. treatment, and changes in mRNA expression were evaluated in the lumbar spinal cord by RT-qPCR. Following MIA administration, we observed 2-4-fold increase in mRNA expression of targeted receptors (Cnr1, Cnr2, and Trpv1), endocannabinoid degradation enzymes (Faah, Ptgs2, and Alox12), and TRPV1 sensitizing kinases (Mapk3, Mapk14, Prkcg, and Prkaca). OMDM198 treatment reversed some of the MIA effects on the spinal cord towards intact levels (Alox12, Mapk14, and Prkcg). Apparent regulation of ECS and TRPV1 in response to pharmacological intervention is a strong justification for novel ECS-based multi-target drug treatment in OA.

Test Procedures to Assess Somatosensory Abnormalities in Individuals with Peripheral Joint Pain: A Systematic Review of Psychometric Properties

BACKGROUND

Test procedures that were developed to assess somatosensory abnormalities should possess optimal psychometric properties (PMPs) to be used in clinical practice. The aim of this systematic review was to evaluate the literature to assess the level of evidence for PMPs of test procedures investigated in individuals with peripheral joint pain (PJP).

METHODS

A comprehensive electronic literature search was conducted in 7 databases from inception to March 2016. The Quality Appraisal for Reliability Studies (QAREL) checklist and the Consensus-based Standards for the Selection of Health Status Measurement Instruments (COSMIN) tool were used to assess risk for bias of the included studies. Level of evidence was evaluated based on the methodological quality and the quality of the measurement properties.

RESULTS

Forty-one studies related to PJP were included. The majority of included studies were considered to be of insufficient methodological quality, and the level of evidence for PMPs varied across different test procedures. The level of evidence for PMPs varied across different test procedures in different types of PJP. Hand-held pressure algometry is the only test procedure that showed moderate positive evidence of intrarater reliability, agreement, and responsiveness, simultaneously, when it was investigated in patients with chronic knee osteoarthritis.

CONCLUSIONS

This systematic review identified that the level of evidence for PMPs varied across different testing procedures to assess somatosensory abnormalities for different PJP populations. Further research with standardized protocols is recommended to further investigate the predictive ability and responsiveness of reported test procedures in order to warrant their extended utility in clinical practice.