Enhanced Pain Sensitivity Among Individuals With Symptomatic Knee Osteoarthritis: Potential Sex Differences in Central Sensitization

Altered pain processing and sensitisation is evident in adults with patellofemoral pain: a systematic review including meta-analysis and meta-regression

Background and aims

Previous systematic reviews have reported manifestations of pain sensitisation as a feature of painful knee disorders, in particular osteoarthritis, with moderate evidence for pain sensitisation in patellofemoral pain (PFP). However, despite past studies recruiting female mostly adolescent PFP patients, it is unclear if sex or age plays a role. Investigation is required to determine if altered pain processing is a key feature of PFP and if a subgroup of patients is at an increased risk to help provide targeted management. The primary aim of this systematic review was to examine evidence investigating pain processing in PFP. Secondary aims were to evaluate the relationship between pain processing and (1) sex, (2) age and (3) symptom duration.

Methods

The protocol was prospectively registered with PROSPERO (CRD42019129851). PubMed, CINAHL, Web of Science and EMBASE were systematically searched from inception to April 2019 for studies investigating pain processing in PFP patients compared to controls using quantitative sensory testing. Each included paper was assessed for methodological quality using a modified version of Downs and Black. Means and standard deviations were extracted to calculate standardised mean differences (SMD) and 95% confidence intervals (95% CI). Where possible meta-analysis and meta-regression were performed using a random effects model.

Results

Eleven studies were identified, two medium and nine high quality. Meta-analysis indicates moderate evidence for decreased pressure pain thresholds (SMD −0.68, 95% CI −0.93 to −0.43), increased tactile detection thresholds (SMD 1.35, 95% CI 0.49–2.22) and increased warmth detection thresholds (SMD 0.61, 95% CI 0.30–0.92) in PFP patients compared to controls. Secondary analysis indicates moderate evidence for decreased pressure pain thresholds in female compared to male patients (SMD −0.75, 95% CI −1.34 to −0.16). Meta-regression indicates a moderate correlation between decreasing local and distal pressure pain thresholds and decreasing patient age (local R2 = 0.556, p = 0.0211; distal R2 = 0.491, p = 0.0354) but no correlation with symptom duration (p > 0.05).

Conclusions

Evidence from this systematic review with meta-analysis and meta-regression appears to suggest the presence of altered pain processing and sensitisation in patients with PFP with increased sensitivity indicated in female patients and younger patients.

Implications

With evidence of altered pain processing and sensitisation in PFP, it may be beneficial for clinicians to consider management approaches that aim specifically at adressing neuropathic pain, for example neuroscience education, to improve patients outcomes. With female patients and younger patients indicated as experiencing greater degree of sensitivity, this may be a good demographic to start screening for sensitisation, in order to better identify and treat those most affected.

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.

The short-term effects of hydrotherapy on pain and self-perceived functional status in individuals living with osteoarthritis of the knee joint

BACKGROUND

People living with knee osteoarthritis (OA) commonly present with difficulty in walking long distances, ascending and descending stairs or rising from sitting. These functional limitations have been shown to have a negative effect on their overall activities of daily living.

OBJECTIVES

The aim of this study was to determine the effects of a 4-week hydrotherapy programme on measures of pain and self-perceived functional status in individuals living with knee OA.

METHOD

A total of 18 participants with chronic knee OA participated in this study. Participants completed 4 weeks of hydrotherapeutic intervention provided by an independent physiotherapist. Outcome measures for the study included pain assessed using the visual analogue scale (VAS) and self-perceived functional status using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Outcome measures were assessed at baseline and after the 4 weeks of intervention.

RESULTS

The 4-week hydrotherapy programme resulted in a significant decrease in pain and a significant improvement in self-perceived functional status in all participants. There was a statistically significant mean decrease in VAS scores of 3.72 (± 2.45), p ≤ 0.05, with a 95% confidence interval ranging from 2.506 to 4.938. There was also a statistically significant mean decrease in WOMAC scores of 29.5 (± 15.51), p ≤ 0.05. with a 95% confidence interval ranging from 21.788 to 37.212.

CONCLUSION

This study demonstrated that a 4-week hydrotherapeutic exercise programme results in significantly reduced pain and improved self-perceived functional status in individuals living with knee OA.

CLINICAL IMPLICATIONS

Four weeks of hydrotherapy exercises twice a week in a heated pool can significantly decrease pain and improve functional status in individuals with knee OA.

Pressure pain thresholds in adults with patellofemoral pain and patellofemoral joint osteoarthritis: a case-control study

Background and aims

Patellofemoral pain (PFP) and patellofemoral joint osteoarthritis (PFJOA) are common non-self-limiting conditions causing significant pain and disability. The underlying pain pathologies lack consensus with evidence suggesting reduced pressure pain thresholds (PPTs) in adolescent females with PFP and individuals with knee osteoarthritis. A paucity of evidence exists for mixed-sex adults with PFP and PFJOA in isolation. Exploring if pain sensitisation is a dominant feature of PFP and PFJOA may have important implications for the delivery of a patient centred management approach. The primary aim was to measure local and remote PPTs in PFP and PFJOA patients compared to matched controls. Secondary aims were to evaluate the relationship between PPTs and (1) condition severity and (2) knee function.

Methods

13 PFP patients plus 20 matched controls and 15 PFJOA patients plus 34 matched controls were recruited from a UK mixed-sex adult population. Controls were matched on age, sex and activity level. Demographic details, Tegner activity level score, symptom duration, condition severity (Kujala and KOOS-PF scores for PFP and PFJOA, respectively) and knee function (Modified Whatman score rating of five single leg squats) were recorded. PPTs were measured at six sites: five local around the knee, one remote on the contralateral leg. Between-group differences were tested using a two-way mixed model analysis of variance with repeated measures. Strength of association between PPTs and condition severity and knee function were tested using Spearman’s rank order correlation.

Results

No statistically significant difference in PPTs were observed between the PFP patients [F(1,31) = 0.687, p = 0.413, η2 = 0.022] or PFJOA patients [F(1,47) = 0.237, p = 0.629, η2 = 0.005] and controls. Furthermore, no correlation was found between PPTs and condition severity or knee function in PFP or PFJOA (p > 0.05).

Conclusions

Results suggest mechanical pain sensitisation is not a dominant feature of UK mixed-sex adults with PFP or PFJOA.

Implications

PFP and PFJOA remain persistent pain complaints which may not be well explained by objective measures of sensitivity such as PPTs. The findings suggest that peripheral pain processing changes leading to pain sensitisation is not a key feature in PFP or PFJOA. Instead the underlying pain pathway is likely to remain primary nociceptive, possibly with a subgroup of patients who experience pain sensitisation and might benefit from a more targeted management approach.

Chronic pain intervention using pulsed shortwave therapy: the relationship between pain demographics and central sensitization inventory

Aim: The central sensitization inventory (CSI) is a validated, patient-reported questionnaire that quantifies symptoms of hypersensitivity disorders such as chronic pain, for which central sensitization (CS) may be the etiology. Objective: To investigate the analgesic effectiveness of ActiPatch and analyze the relationship between baseline CSI scores and demographics of chronic pain sufferers. Methods: Upon completing a 7-day ActiPatch trial, baseline CSI scores along with other assessment measures were obtained via e-mail from 174 chronic pain sufferers. Conclusion: CSI scores were positively correlated with gender (higher for women), baseline visual analog scale scores and pain duration. ActiPatch was found to be effective in reducing baseline pain for all subjects by an average of 4.3 visual analog scale points.

Clinical characteristics and disability in patients with knee osteoarthritis: real world experience from Bulgaria

Objectives

Although knee osteoarthritis (KOA) is a leading cause of impaired functioning among older adults globally, little is still known about the complex mechanisms of disability accumulation in these patients. The aim of the study was to analyze the clinical parameters of patients with KOA in a Bulgarian population and to determine which of these clinical characteristics define disability to the greatest extent.

Material and methods

Patients aged 40–80 years with symptomatic KOA were included. The assessment tools for pain, clinical disease severity, and disability were the pain visual analogue scale (VAS) and disease-specific questionnaires: Algofunctional Index of Lequesne, Western Ontario and McMaster Universities OA Index (WOMAC), and the Health Assessment Questionnaire-Disability Index (HAQ-DI), respectively. Radiographs of the knees were obtained and graded according to the Kellgren-Lawrence (KL) system.

Results

One hundred and thirty-two patients (81% women) participated in the study. The median values of VAS (mm), WOMAC, Lequesne, and HAQ-DI scores were 52, 37.5, 11, 0.88, respectively. Men had milder disease, resulting in lower VAS, WOMAC, Lequesne, and HAQ-DI scores and less structural damage compared to women (p < 0.05). WOMAC index correlated positively with age of the patients but not with duration of the complaints. Patients with severe and very severe pain did not differ in their HAQ-DI, disease severity and KL grading. WOMAC physical function score and Lequesne index were independent predictors for the HAQ-DI in patients with KOA.

Conclusions

Bulgarian patients with KOA had moderate disability which showed a strong relationship with physical function of WOMAC and disease severity. Multiple layers of causality coexist to determine the knee pain in Bulgarian patients with KOA.

Peripheral and Central Sensitization of Pain in Individuals With Hand Osteoarthritis and Associations With Self-Reported Pain Severity

OBJECTIVE

Pain sensitization, an important osteoarthritis (OA) pain mechanism, has not been substantially investigated in patients with hand OA. It is unknown how peripheral and central sensitization are related to self-reported hand pain.

METHODS

Individuals with verified hand OA in the Nor-Hand study underwent quantitative sensory testing of pressure pain thresholds (PPTs) locally (painful and nonpainful finger joints) and remotely (wrist, trapezius, and tibialis anterior muscles), and testing of temporal summation (TS), a manifestation of central sensitization. We examined cross-sectional associations of PPT tertiles and TS with hand pain using the Numerical Rating Scale (NRS) (range 0-10) and the Australian/Canadian Osteoarthritis Hand Index (AUSCAN) pain subscale (range 0-20). Linear regression models were adjusted for demographics, psychosocial factors, and radiographic severity.

RESULTS

This study included 282 participants (88% female) with a median age of 61 years (interquartile range [IQR] 57-66). Participants with the lowest PPTs in their finger joints and in most remote locations reported higher NRS pain values, compared to patients with the highest PPTs, with adjusted β values ranging from 0.6 (95% confidence interval [95% CI] 0.0, 1.2) to 0.9 (95% CI 0.3, 1.5). The 118 participants (42%) with TS reported higher mean ± SD NRS pain values compared to those without TS (4.1 ± 2.4 versus 3.1 ± 1.7; adjusted β = 0.6 [95% CI 0.2, 1.1]). Neither PPTs nor the presence of TS were associated with AUSCAN pain.

CONCLUSION

Central sensitization was common in patients with hand OA. Lower local and widespread PPTs and the presence of TS were associated with higher hand pain intensity, even after adjustment for demographics, psychosocial factors, and radiographic severity. Sensitization may therefore represent a possible treatment target.

The Effect of Medical Exercise Therapy on Pressure Sensitivity in Patients with Knee Osteoarthritis: A Cohort Pilot Study

Introduction

While continued research into pain and exercise may address the underlying mechanisms, the mechanisms through which exercise may act are still poorly understood. The purpose of this study was to examine the effects of medical exercise therapy on pressure sensitivity in knee osteoarthritis patients, and to assess whether the decreased pain perception after medical exercise therapy can be explained by changes in pressure sensitivity.

Methods

We adopted acohort design in which 16 patients with long term pain were tested before and after 3 months of medical exercise therapy intervention. Pain was detected by visual analogue scale (VAS) and a digital pressure algometer, which also assessed pressure sensitivity. Function (Knee Osteoarthritis Outcome Score, KOOS), anxiety and depression (HAD) and kinesiophobia (Tampa Scale of Kinesiophobia, TSK) were also measured.

Results

The VAS showed a statistically significant reduction of perceived pain, from 5.19 (SD 2.04) to 4.12 (SD 2.09) from pre- to post-test (p < 0.05). There was no significant change in pressure algometry on either the painful side or the non-painful side.

Conclusion

As there were no significant correlations between the reduced pain perception and pressure sensitivity in knee osteoarthritis patients, we suggest that local knee pain does not necessarily alter generalized sensitivity. These findings should be further investigated in a randomized trial in the future.

Trial Registration

Clinicaltrials.gov, identifier NCT02905747.

Designing and conducting proof-of-concept chronic pain analgesic clinical trials

Introduction:

The evolution of pain treatment is dependent on successful development and testing of interventions. Proof-of-concept (POC) studies bridge the gap between identification of a novel target and evaluation of the candidate intervention's efficacy within a pain model or the intended clinical pain population.

Methods:

This narrative review describes and evaluates clinical trial phases, specific POC pain trials, and approaches to patient profiling.

Results:

We describe common POC trial designs and their value and challenges, a mechanism-based approach, and statistical issues for consideration.

Conclusion:

Proof-of-concept trials provide initial evidence for target use in a specific population, the most appropriate dosing strategy, and duration of treatment. A significant goal in designing an informative and efficient POC study is to ensure that the study is safe and sufficiently sensitive to detect a preliminary efficacy signal (ie, a potentially valuable therapy). Proof-of-concept studies help avoid resources wasted on targets/molecules that are not likely to succeed. As such, the design of a successful POC trial requires careful consideration of the research objective, patient population, the particular intervention, and outcome(s) of interest. These trials provide the basis for future, larger-scale studies confirming efficacy, tolerability, side effects, and other associated risks.

Duration of symptoms is associated with conditioned pain modulation and somatosensory measures in knee osteoarthritis

Impaired descending pain inhibition has been linked to chronic pain and poorer patient outcomes. Vibration perception threshold (VPT) has also been observed and linked to radiographic stage of OA. However, it is not known how duration of symptoms may influence these neurophysiological measures. Our purpose was to evaluate the relationship between duration of symptoms and conditioned pain modulation (CPM), a measure of descending pain inhibition, and VPT, and to determine whether these relationships differed in men and women seeking orthopedic care. We evaluated 18 men and 27 women with moderate to severe knee OA. We assessed CPM using a submaximal-effort tourniquet test: Pressure pain threshold (PPT) at the symptomatic knee was evaluated before and after a noxious stimulus. CPM impairment was indicated by a ratio of pre-to-post stimulus PPT ≥1. VPT was assessed using a biothesiometer at the medial femoral condyle. We used chi-square, t-tests and Pearson correlations to address study questions. 72% of men, but only 44% of women had CPM impairment. Duration of symptoms was associated with CPM impairment in women (R = 0.566, p = 0.003) but not men (R = 0.366, p = 0.135). Duration of symptoms was also associated with VPT in both men (R = 0.580, p = 0.012) and women (R = 0.406, p = 0.039). These results suggest that longer duration of knee OA may predict more severe pain sensitization and that important sex differences exist in descending pain inhibition in people with chronic knee OA that may affect disease and course of treatment in male and female patients. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Assessment of pain-related fear in individuals with chronic painful conditions

Background

Heightened fear and anxiety related to pain may result in emotional and behavioral avoidance responses causing disability, distress, and depression. Fear and anxiety associated with pain can potentially change the course of the pain experience. It is plausible that fear and anxiety related to pain affect the duration and frequency of pain experienced by the patient.

Aim

The study aimed to examine the applicability of the Fear of Pain Questionnaire-III (FPQ-III) in identifying who are likely to report longer duration and greater frequency of pain experience.

Methods

To test this hypothesis, a cross-sectional study was conducted with 579 individuals from a community-based sample living with chronic pain. The factor structure and validity of FPQ-III in the community-based sample were also tested.

Results

The findings suggest higher fear of severe pain but lower fear of medical pain, associated with longer duration and more frequent pain experience. The analysis also confirmed the three-factor structure of FPQ-III, demonstrating good internal consistency for fear of severe pain (0.71) and fear of medical pain (0.73) and acceptable range for fear of minor pain (0.65).

Conclusion

These findings suggest that the FPQ-III can be potentially applied to identify individuals at risk for prolonged continuous pain and as a screening tool to measure fear and anxiety related to pain.

Tourniquetless Total Knee Arthroplasty With Modern Perioperative Protocols Decreases Pain and Opioid Consumption in Women

BACKGROUND

This study examined whether a modern total knee arthroplasty (TKA) protocol without a tourniquet results in less patient-reported pain and in-hospital opioid consumption compared to TKA with a tourniquet.

METHODS

A retrospective study of 203 primary unilateral cemented TKAs consecutively performed with or without tourniquet was performed. Identical perioperative pain and blood loss protocols were used in all cases. In tourniquetless TKAs, the tourniquet was not inflated at any time, and sterile CO₂ gas compression maximized cement interdigitation.

RESULTS

After exclusions for scientific confounds, 184 TKAs (93 with tourniquet; 91 tourniquetless) were analyzed. Controlling for multiple covariates, females with a tourniquet reported significantly more pain (P = .002) and opioid consumption (P < .001) the first 24 hours after surgery compared to females without a tourniquet. There were no differences in pain (P = .192) or amount of opioids consumed (P = .203) among males with and without a tourniquet. Tourniquet use resulted in a significant reduction in blood loss for both females (P ≤ .040) and males (P ≤ .020), although the total blood savings of approximately 200 mL is of unknown clinical significance.

CONCLUSION

Avoiding tourniquet use during TKA for females may be a relatively risk-free adjunct to minimize opioid consumption during hospitalization. Further study is warranted to elucidate the factors accounting for different outcomes in females and males.

Lean mass mediates the relation between temporal summation of pain and sex in young healthy adults

Background

Previous studies have shown that women experience greater temporal summation (TS) of pain than men using a repetitive thermal stimulus. These studies, however, did not individualize the thermal stimulus to each subject’s thermal pain sensitivity. The aim of this study was to investigate sex differences in TS using an individualized protocol and potential mediators that have been shown to influence TS including physical activity and body composition.

Methods

Fifty young healthy men and women (21 men) participated in the study. Subjects completed TS testing on the right forearm using a repetitive thermal stimulus at a temperature that the subject reported 6/10 pain. Other testing included body composition (lunar iDXA), activity monitoring (Actigraph), and Pain Catastrophizing Scale (PCS).

Results

Women reported greater TS than men (p = 0.019), and TS was correlated with right arm lean mass (r = − 0.36, p = 0.01) and magnification subscale of PCS (r = − 0.32, p = 0.03). Mediation analysis showed a complete mediation for the relation between sex and TS by right arm lean mass (indirect effect = 2.33, 95% BCa CI [0.42, 4.58]) after controlling for the temperature, the magnification subscale of PCS, and the average time spent in moderate to vigorous physical activity.

Conclusion

The results of this study suggest that lean mass is a contributing factor to the sex differences in TS. Future studies should investigate whether interventions that increase lean mass have a positive effect on TS.

Sex Differences in Brain Regions Modulating Pain Among Older Adults: A Cross-Sectional Resting State Functional Connectivity Study

Objective

A long-standing hypothesis is that when compared with males, females may be at increased risk of experiencing greater pain sensitivity and unpleasantness. The purpose of this study was to examine sex differences in pain psychophysics and resting state functional connectivity (RSFC) in core pain regions in an age- and sex-matched sample of healthy older adults.

Design

Between groups, cross-sectional.

Setting

Vanderbilt University and Medical Center.

Subjects

The sample in the analyses reported here consisted of 19 cognitively intact males matched with 19 cognitively intact females of similar ages (median ages: females = 70 years, males = 68 years).

Methods

Psychophysical assessment of experimental thermal pain and RSFC.

Results

There were no significant differences in perceptual thresholds or unpleasantness ratings in response to thermal stimuli. Older males showed greater RSFC between the affective and sensory networks and between affective and descending modulatory networks. Conversely, older females showed greater RSFC between the descending modulatory network and both sensory and affective networks. The strongest evidence for sex differences emerged in the associations of thermal pain with RSFC between the anterior cingulate cortex (ACC) and amygdala and between the ACC and periaqueductal gray matter in older females relative to older males.

Conclusions

We found no differences in pain sensitivity or pain affect between older males and older females. Additionally, we found that older females exhibited a greater association between thermal pain sensitivity and RSFC signal between regions typically associated with pain affect and the descending modulatory system. One interpretation of these findings is that older females may better engage the descending pain modulatory system. This better engagement possibly translates into older females having similar perceptual thresholds for temperature sensitivity and unpleasantness associated with mild and moderate pain. These findings contrast with studies demonstrating that younger females find thermal pain more sensitive and more unpleasant.

Sex Differences in the Psychophysical Response to Contact Heat in Moderate Cognitive Impairment Alzheimer's Disease: A Cross-Sectional Brief Report

Background:

People with Alzheimer’s disease (AD) report pain less frequently and receive less pain medication than people without AD. Recent studies have begun to elucidate how pain may be altered in those with AD. However, potential sex differences in pain responsiveness have never been explored in these patients. It is unclear whether sex differences found in prior studies of healthy young and older individuals extend to people with AD.

Objective:

The purpose of this study was to examine sex differences in the psychophysical response to experimental thermal pain in people with AD.

Methods:

Cross-sectional analysis of 14 male and 14 female age-matched (≥65 years of age, median = 74) and AD severity-matched (Mini-Mental State Exam score <24, median = 16) communicative people who completed thermal psychophysics.

Results:

There was a statistically significant main effect of sex for both temperature and unpleasantness ratings that persisted after controlling for average and current pain (mixed-effects general liner model: temperature: p = 0.004, unpleasantness: p < 0.001). Females reported sensing mild pain and moderate pain percepts at markedly lower temperatures than did males (mild: Cohen’s d = 0.72, p = 0.051, moderate: Cohen’s d = 0.80, p = 0.036). By contrast, males rated mild and moderate thermal pain stimuli as more unpleasant than did females (mild: Cohen’s d = 0.80, p = 0.072, moderate: Cohen’s d = 1.32, p = 0.006). There were no statistically significant correlations of temperature with perceived unpleasantness for mild or moderate pain (r_s = 0.29 and r_s = 0.20 respectively, p > 0.05).

Conclusions:

Results suggest experimental pain-related sex differences persist in older adults with AD in a different manner than those previously demonstrated in cognitively intact older adults. These findings could potentially aid in developing targeted pain management approaches in this vulnerable population. Further studies are warranted to replicate the findings from this pilot work.

Sex and Race Differences in Pain Sensitization among Patients with Chronic Low Back Pain

Growing evidence suggests that chronic low back pain (CLBP) is associated with pain sensitization, and that there are sex and race disparities in CLBP. Given the sex and race differences in pain sensitization, this has been hypothesized as a mechanism contributing to the sex and race disparities in CLBP. This study examined sex and race differences in pain sensitization among patients with CLBP, as well as the role of catastrophizing as a potential mediator of those differences. The study found that compared with men, women required less pressure to produce deep muscle pain and rated mechanical punctate pain as more painful. Compared with non-Hispanic white patients, black patients demonstrated greater pain sensitivity for measures of deep muscle hyperalgesia and mechanical punctate pain. Furthermore, catastrophizing partially mediated the race differences in deep muscle pain such that black participants endorsed greater pain catastrophizing, which partially accounted for their increased sensitivity to, and temporal summation of, deep muscle pain. Taken together, these results support the need to further examine the role of catastrophizing and pain sensitization in the context of sex and race disparities in the experience of CLBP. PERSPECTIVE: This study identifies sex and race differences in pain sensitization among patients with CLBP. Further, it recognizes the role of catastrophizing as a contributor to such race differences. More research is needed to further dissect these complex relationships.

Predictors of Osteoarthritis Pain: the Importance of Resilience

PURPOSE OF REVIEW

Osteoarthritis (OA) is one of the most common and disabling forms of arthritis worldwide, with joint pain being a primary symptom. Given that clinical symptoms often show poor concordance with tissue damage in OA, processes other than joint remodeling likely play a role in the condition. Using the biopsychosocial model of pain as a guiding framework, the purpose of this review is to highlight the extra-articular mechanisms that contribute to pain and dysfunction in OA, with a specific focus on resilience.

RECENT FINDINGS

Whereas previous research has mostly focused on risk factors for worsening of OA pain, recently emerging evidence places greater emphasis on the identification of protective mechanisms that enhance pain adaptation and palliate the negative effects of joint pain. In view of this new and important research, more emphasis should be placed on endogenous pain modulation and, in particular, pain attenuation. The result of such work could serve as a basis for optimizing treatment in the OA population.

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.

Pain Sensitivity and its Relation to Spreading on the Body, Intensity, Frequency, and Duration of Pain: A Cross-Sectional Population-based Study (SwePain)

OBJECTIVES

Individuals with chronic pain often report increased pain sensitivity compared with pain-free individuals; hence, it is crucial to determine whether and how different pain characteristics influence or interact with pain sensitivity. An alternative to experimental pain sensitivity testing is the self-reported pain sensitivity questionnaire (PSQ), which captures pain sensitivity in various body areas.This study compares PSQ in individuals with and without pain and clarifies how pain sensitivity relates to spreading of pain on the body, and to intensity, frequency, duration of pain and to age and sex.

MATERIALS AND METHODS

A total of 5905 individuals with pain and 572 individuals without pain from the general population in southeastern Sweden completed and returned a postal questionnaire.

RESULTS

The mean PSQ score was 3.9 (95% confidence interval [CI], 3.88-3.98) in individuals with pain and 3.5 (95% CI, 3.38-3.64) in pain-free individuals. Hence, PSQ was the highest among individuals with pain, with a difference of 0.4 (95% CI, 0.30-0.56). There was a considerable variation in the PSQ values (mean=3.5; SD=1.54) among pain-free individuals. Pain sensitivity was positively related to spreading, intensity, and frequency of pain, with a correlation coefficient of 0.3. PSQ was higher in widespread pain, 4.5 (95% CI, 4.27-4.69) in women and 4.3 (95% CI, 3.94-4.71) in men, than in local pain, 3.7 (95% CI, 3.61-3.91) in women and 3.8 (95% CI, 3.66-3.95) in men. The score for women with regional pain was between local and widespread pain at 4.0 (95% CI, 3.95-4.11) and that for men with regional pain was 3.8 (95% CI, 3.69-3.87), which is equal to that of local pain.

DISCUSSION

The positive association between pain sensitivity and spreading of pain on the body provides some evidence that the extent of spreading may be related to the degree of pain sensitivity. Before clinical use of PSQ, psychometric development and further research are needed.

Factors associated with knee pain in 5148 women aged 50 years and older: A population-based study

Objective

This study was performed to investigate the factors associated with the level of knee pain in a nationally representative sample of noninstitutionalized women aged 50 years or older.

Methods

Women aged 50 years or older were selected and included in the data analyses from the Korean National Health and Nutrition Examination Surveys (2010–2013). Those having malignant diseases or using osteoarthritis medication were excluded. Significant factors associated with the level of knee pain were analyzed using multivariate regression analysis.

Results

A total of 5148 women (average age, 62.9 years; standard deviation, 9.3 years) were included. For women without knee osteoarthritis, level of hip pain (p<0.001), presence of back pain (p<0.001), age (p<0.001), and body mass index (BMI) (p<0.001) were found to be significant factors associated with the level of knee pain. For women with knee osteoarthritis, the radiographic grade of knee osteoarthritis (p<0.001), presence of back pain (p<0.001), level of hip pain (p<0.001), presence of depressive symptoms (p<0.001), and BMI (p = 0.026) were the factors significantly associated with the level of knee pain.

Conclusions

Women without knee osteoarthritis tended to report increasing knee pain with increasing age. BMI is considered a significant controllable factor in knee pain in women regardless of the presence of radiographic knee osteoarthritis. The presence of depressive symptoms may aggravate knee pain in women with knee osteoarthritis. Attention needs to be focused on concomitant musculoskeletal problems such as lumbar spinal and hip diseases in women with knee pain.

Neuropathic pain in end-stage hip and knee osteoarthritis: differential associations with patient-reported pain at rest and pain on activity

OBJECTIVE

We investigated whether pain at rest and pain on activity were differentially associated with neuropathic pain scores in individuals with end-stage hip and knee OA.

DESIGN

Study participants were 843 patients with hip or knee OA scheduled for total joint arthroplasty. In pre-surgery questionnaires, measures of socio-demographics, health status, medication use, neuropathic pain (painDETECT), pain at rest and pain on activity (WOMAC pain items), depression (HADS) and pain catastrophizing (PCS) were collected. Multivariable linear regression models were estimated for men and women separately to examine the association between neuropathic pain scores (outcome) and study measures, entered in blocks.

RESULTS

Sample mean age was 65.1 years (SD: 9.6); 57.1% were women. Mean painDETECT scores were significantly higher (P ≤ֹ 0.001) for women (11.2 ± 6.6 out of 38) than men (9.3 ± 7.0), with 35.6% of women and 27.7% of men meeting cut-offs for possible or likely neuropathic pain. In the final regression model for women, the coefficients for both types of pain were statistically significant, although the coefficient for pain at rest was 1.6 times greater than that for pain on activity. For men, only pain at rest was significantly associated with neuropathic pain scores.

CONCLUSIONS

Findings support that possible neuropathic pain is experienced by a notable proportion of patients with end-stage hip and knee OA and is more strongly associated with pain at rest than pain on activity, particularly in men. Clinical presentation of pain at rest may warrant more thorough evaluation for potential neuropathic pain and have implications for appropriate pain management.

Men and Women Differ in the Biochemical Composition of Platelet-Rich Plasma

BACKGROUND

Autologous platelet-rich plasma (PRP) is widely used for a variety of clinical applications. However, clinical outcome studies have not consistently shown positive effects. The composition of PRP differs based on many factors. An improved understanding of factors influencing the composition of PRP is important for the optimization of PRP use.

HYPOTHESIS

Age and sex influence the PRP composition in healthy patients.

STUDY DESIGN

Controlled laboratory study.

METHODS

Blood from 39 healthy patients was collected at a standardized time and processed into leukocyte-poor PRP within 1 hour of collection using the same laboratory centrifuge protocol and frozen for later analysis. Eleven female and 10 male patients were "young" (aged 18-30 years), while 8 male and 10 female patients were "older" (aged 45-60 years). Thawed PRP samples were assessed for cytokine and growth factor levels using a multiplex assay and enzyme-linked immunosorbent assay. The platelet count and high-sensitivity C-reactive protein levels were measured. Two-way analysis of variance determined age- and sex-based differences.

RESULTS

Platelet and high-sensitivity C-reactive protein concentrations were similar in PRP between the groups ( P = .234). Male patients had higher cytokine and growth factor levels in PRP compared with female patients for inflammatory cytokines such as interleukin-1 beta (IL-1β) (9.83 vs 7.71 pg/mL, respectively; P = .008) and tumor necrosis factor-alpha (TNF-α) (131.6 vs 110.5 pg/mL, respectively; P = .048); the anti-inflammatory IL-1 receptor antagonist protein (IRAP) (298.0 vs 218.0 pg/mL, respectively; P < .001); and growth factors such as fibroblast growth factor-basic (FGF-basic) (237.9 vs 194.0 pg/mL, respectively; P = .01), platelet-derived growth factor (PDGF-BB) (3296.2 vs 2579.3 pg/mL, respectively; P = .087), and transforming growth factor-beta 1 (TGF-β1) (118.8 vs 92.8 ng/mL, respectively; P = .002). Age- but not sex-related differences were observed for insulin-like growth factor-1 (IGF-1) ( P < .001). Age and sex interaction terms were not significant. While mean differences were significant, there was also substantial intragroup variability.

CONCLUSION

This study in healthy patients shows differences in the composition of PRP between men and women, with sex being a greater factor than age. There was also proteomic variability within the groups. These data support a personalized approach to PRP treatment and highlight the need for a greater understanding of the relationships between proteomic factors in PRP and clinical outcomes.

CLINICAL RELEVANCE

Variability in the proteomic profile of PRP may affect tissue and clinical responses to treatment. These data suggest that clinical studies should account for the composition of PRP used.

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.

The presence of Waddell signs depends on age and gender, not diagnosis

Aims

The aim of this study was to determine if positive Waddell signs were related to patients’ demographics or to perception of their quality of life.

Patients and Methods

This prospective cross-sectional study included 479 adult patients with back pain from a university spine centre. Each completed SF-12 and Oswestry Disability Index (ODI) questionnaires and underwent standard spinal examinations to elicit Waddell signs. The relationship between Waddell signs and age, gender, ODI, Mental Component Score (MCS), and Physical Component Score (PCS) scores was determined.

Results

Of the 479 patients, 128 (27%) had at least one positive Waddell sign. There were significantly more women with two or more Waddell signs than men. The proportion of patients with at least one positive Waddell sign increased with age until 55 years, and then declined rapidly; none had a positive sign over the age of 75 years. Functional outcome scores were significantly worse in those with a single Waddell sign (p < 0.01). With one or more Waddell signs, patients’ PCS and ODI scores indicated a perception of severe disability; with three or more Waddell signs, patients’ MCS scores indicated severe disability. With five Waddell signs, ODI scores indicated that patients perceived themselves as crippled.

Conclusion

Positive Waddell signs, a potential indicator of central sensitization, indicated a likelihood of having functional limitations and an impaired quality of life, particularly in young women. Cite this article: Bone Joint J 2018;100-B:219–25.

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.

Clinical and ultrasonographic features associated to response to intraarticular corticosteroid injection. A one year follow up prospective cohort study in knee osteoarthritis patient with joint effusion

OBJECTIVES

Intraarticular injection is used for pain relief in knee osteoarthritis (OA), but there is not a well defined profile of patient who could get more benefit from it. The purpose of this study was to evaluate the frequency of pain relief at one year after corticosteroids intraarticular injection and to identify clinical factors associated to response in patients with knee osteoarthritis with joint effusion.

METHODS

One-year prospective cohort study of patients with knee OA with joint effusion confirmed by ultrasound. An intraarticular injection was performed following a clinical protocol. Anthropometric measurements, laboratory parameters, clinical severity, ultrasound parameters and radiological severity were collected. Response regarding pain and presence of synovial fluid on ultrasound at one month and at one year were evaluated. Clinical responder were consider in subjects with enough improvement to carry out normal daily activities with pain VAS<40mm.

RESULTS

One hundred and thirty-two patients were included.A significant number of patients (61.4%) improved pain at one year following the protocol established in this study. Pain and ultrasound synovial fluid at one month appeared to predict the response at one year. The Lequesne index and the percentage of body fat were independently associated to pain at one year while the Lequesne index and ultrasound synovial hypertrophy were independently related to the presence of synovial fluid at one year.

CONCLUSIONS

The status regarding pain or ultrasound synovial fluid at one month after an intraarticular joint injection appeared to predict the status at one year in patients with knee osteoarthritis and synovial effusion.

Factors Leading to Persistent Postsurgical Pain in Adolescents Undergoing Spinal Fusion: An Integrative Literature Review

PROBLEM

Adolescent idiopathic scoliosis (AIS) is the most common spinal deformity among children and adolescents and the most frequent reason for corrective spinal fusion (SF). Of the children and adolescents who undergo SF, a significant number will experience persistent postoperative pain (PPP). This integrative literature review was conducted to identify and synthesize perioperative factors that may contribute to risk of developing PPP.

ELIGIBILITY CRITERIA

Articles which addressed PPP within the last 10years and primary research on postoperative pain outcomes in adolescents after SF were selected for review.

SAMPLE

15 articles which met eligibility criteria were included.

RESULTS

Preoperative pain intensity was the most significant factor identified in the development of PPP and increased postoperative pain. Social function and psychological factors also have role in the development of PPP. There were no theoretical models or frameworks for evaluating PPP incidence in adolescent with AIS after SF.

CONCLUSIONS

Perioperative factors such as, preoperative pain, correction magnitude, pain coping, anxiety and social functioning are vital to understanding a child's risk of PPP following SF. There is a need for theoretically-based studies to assess PPP among children and adolescents with AIS after SF surgery.

IMPLICATIONS

The Biobehavioral Pain Network (BPN) model was proposed, to encompass biological, social and psychological domains which may be responsible for incidence of PPP in children undergoing SF. Such a model can be used to systematically develop and evaluate personalized postoperative pain management strategies for this patient population.

Differences in pain intensity in anti- and pro-nociceptive pain profile subgroups in patients with knee osteoarthritis

Aim: Facilitated temporal summation is one component of central sensitization. The aim of this exploratory study was to classify pro-, eu- and antinociceptive subgroups based on wind-up ratio cut-off scores in patients with knee osteoarthritis (OA). Patients & methods: A total of 56 patients with knee OA met the inclusion criteria. Temporal summation was measured and wind-up ratio was calculated. Reference values of 180 healthy subjects were used to define wind-up ratio cut-off scores. Results: Twenty-seven percent of patients showed a pro-nociceptive pain profile. Sixteen percent of patients showed an anti-nociceptive pain profile. A eu-nociceptive pain profile was present in 57% of patients. Conclusion: Central pain sensitization was present in approximately a third of knee OA patients. The results should be confirmed in larger studies.

Classification and Treatment of Chronic Neck Pain: A Longitudinal Cohort Study

BACKGROUND AND OBJECTIVES

Neck pain exerts a steep personal and socioeconomic toll, ranking as the fourth leading cause of disability. The principal determinant in treatment decisions is whether pain is neuropathic or nonneuropathic, as this affects treatment at all levels. Yet, no study has sought to classify neck pain in this manner.

METHODS

One hundred participants referred to an urban, academic military treatment facility with a primary diagnosis of neck pain were enrolled and followed up for 6 months. Pain was classified as neuropathic, possible neuropathic, or nonneuropathic using painDETECT and as neuropathic, mixed, or nociceptive by s-LANSS (self-completed Leeds Assessment of Neuropathic Symptoms and Signs pain scale) and physician designation. Based on previous studies, the intermediate possible neuropathic pain category was considered to be a mixed condition. The final classification was based on a metric combining all 3 systems, slightly weighted toward physician's judgment, which is considered the reference standard.

RESULTS

Fifty percent of participants were classified as having possible neuropathic pain, 43% as having nonneuropathic pain, and 7% with primarily neuropathic pain. Concordance was high between the various classification schemes, ranging from a low of 62% between painDETECT and physician designation for possible neuropathic pain, to 83% concordance between s-LANSS and the 2 other systems for neuropathic pain. Individuals with neuropathic pain reported higher levels of baseline disability, were more likely to have a coexisting psychiatric illness, and underwent surgery more frequently than other pain categories, but were also more likely to report greater reductions in disability after 6 months.

CONCLUSIONS

Although pure neuropathic pain comprised a small percentage of our cohort, 50% of our population consisted of mixed pain conditions containing a possible neuropathic component. There was significant overlap between the various classification schemes.

Pain in osteoarthritis. Implications for optimal management

Pain is an ubiquitous symptom in osteoarticular diseases, occurring much more commonly than stiffness or disability. OA of the knee, hand, or hip affects around 20% of adults in various populations and is dramatically increasing in many countries, mostly related to age and obesity, leading to an increased number of people having OA pain, and creating a huge burden related to disability and health care costs. OA-related pain, has been classically considered to be a nociceptive pain condition. Clinicians have considered pain to be an alarm signal, correlated to the intensity of joint degradation. In OA, most authors have focused their studies on joint architecture and local degradation, considering pain as only a symptom, a consequence of joint damage. However, OA-related pain is a specific disease, with a complex pathophysiology, including neuropathic peripheral and central abnormalities, together with local inflammation involving all joint structures. Clinical findings emphasize that it is not a stable and linear condition, that pain experience is independent of structural modifications, and that the quality of pain in OA is important to consider, aside from its intensity. OA-related pain is modulated by many factors, including the individual patient's psychological and genetic factors, as well as the theoretical role of meteorological influences. Recent neuroimaging findings have improved our knowledge about central mechanisms of OA pain, especially in persistent cases.

Loss of Temporal Inhibition of Nociceptive Information Is Associated With Aging and Bodily Pain

An age-related decline in endogenous pain inhibitory processes likely places older adults at an increased risk for chronic pain. Limited research indicates that older adults may be characterized by deficient offset analgesia, an inhibitory temporal sharpening mechanism that increases the detectability of minor decreases in noxious stimulus intensity. The primary purpose of the study was to examine age differences in offset analgesia in community-dwelling younger, middle-aged, and older adults. An additional aim of the study was to determine whether the magnitude of offset analgesia predicted self-reported bodily pain. Eighty-seven younger adults, 42 middle-aged adults, and 60 older adults completed 4 offset analgesia trials and 3 constant temperature trials in which a noxious heat stimulus was applied to the volar forearm for 40 seconds. The offset trials consisted of 3 continuous phases: an initial 10-second painful stimulus, either a 1.0°C or .4°C increase in temperature from the initial 10-second painful stimulus for 10 seconds, and either a 1.0°C or .4°C decrease back to the initial testing temperature for 20 seconds. During each trial, subjects rated pain intensity continuously using an electronic visual analog scale (0-100). All subjects also completed the Short-Form Health Survey-36 including the Bodily Pain subscale. The results indicated that older and middle-aged adults showed reduced offset analgesia compared with younger adults in the 1.0°C and .4°C offset trials. Furthermore, the magnitude of offset analgesia predicted self-reported bodily pain, with those exhibiting reduced offset analgesia reporting greater bodily pain. Dysfunction of this endogenous inhibitory system could increase the risk of developing chronic pain for middle-aged and older adults.

PERSPECTIVE

Older and middle-aged adults showed reduced offset analgesia compared with younger adults. The significant association between reduced offset analgesia and pain in daily life supports the notion that pain modulatory deficits are associated with not just a chronic pain condition but with the experience of pain in general.

Cyclooxygenase Inhibition: Pain, Inflammation, and the Cardiovascular System

Inhibitors of the cyclooxygenases (COXs), the nonsteroidal antiinflammatory drugs (NSAIDs), relieve inflammatory pain, but are associated with gastrointestinal and cardiovascular complications. Given the widespread use of NSAIDs, there has been a longstanding interest in optimizing their risk-benefit ratio, for example by reducing their gastrointestinal risk. More recently, the focus has shifted toward the cardiovascular complications of NSAIDs and very large prospective studies have been performed to compare cardiovascular risk across distinct NSAIDs. Surprisingly, much less attention has been paid to the efficacy side of the risk-benefit ratio. There is marked variability in the degree of pain relief by NSAIDs due to the complex interplay of molecular mechanisms contributing to the pain sensation, variability in the disposition of NSAIDs, and imprecision in the quantification of human pain. Here we discuss how NSAIDs relieve pain, how molecular mechanisms relate to clinical efficacy, and how this may inform our interpretation of clinical trials.

Sex moderates the effects of positive and negative affect on clinical pain in patients with knee osteoarthritis

BACKGROUND AND AIMS

Sex differences in clinical pain severity and response to experimental pain are commonly reported, with women generally showing greater vulnerability. Affect, including state (a single rating) and stable (average daily ratings over two weeks) positive affect and negative affect has also been found to impact pain sensitivity and severity, and research suggests that affect may modulate pain differentially as a function of sex. The current study aimed to examine sex as a moderator of the relationships between affect and pain-related outcomes among participants with knee osteoarthritis (KOA).

METHODS

One hundred and seventy-nine participants (59 men) with KOA completed electronic diaries assessing clinical pain, positive affect, and negative affect. A subset of participants (n=120) underwent quantitative sensory testing, from which a single index of central sensitization to pain was derived. We used multiple regression models to test for the interactive effects of sex and affect (positive versus negative and stable versus state) on pain-related outcomes. We used mixed effects models to test for the moderating effects of sex on the relationships between state affect and pain over time.

RESULTS

Sex differences in affect and pain were identified, with men reporting significantly higher stable positive affect and lower central sensitization to pain indexed by quantitative sensory testing, as well as marginally lower KOA-specific clinical pain compared to women. Moreover, there was an interaction between stable positive affect and sex on KOA-specific clinical pain and average daily non-specific pain ratings. Post hoc analyses revealed that men showed trends towards an inverse relationship between stable positive affect and pain outcomes, while women showed no relationship between positive affect and pain. There was also a significant interaction between sex and stable negative affect and sex on KOA-specific pain such that men showed a significantly stronger positive relationship between stable negative affect and KOA-specific pain than women. Sex did not interact with state affect on pain outcomes.

CONCLUSIONS

Findings suggest that men may be particularly sensitive to the effects of stable positive affect and negative affect on clinical pain. Future work with larger samples is needed in order to identify potential mechanisms driving the sex-specific effects of affect on pain.

IMPLICATIONS

The current study provides novel data that suggesting that the association of positive affect, negative affect, and pain are different in men versus women with KOA. Further understanding of the difference in affective expression between men and women may lead to the development of novel therapeutic interventions and help to identify additional modifiable factors in the prevention and management of pain.

Increased spatial dimensions of repetitive heat and cold stimuli in older women

Protocols of temporal summation (TS) of pain typically involve the delivery of brief repetitive noxious pulses of a constant intensity while measuring the perceived intensity of pain after each pulse. The size percept of noxious repetitive stimulation has been poorly characterized. Furthermore, no studies have investigated age differences in TS of cold pain. The current study examined TS of pain intensity and the perceived size of the painful area during repetitive noxious heat and cold pulses in healthy younger (n = 104) and older adults (n = 40). Trials of 10 brief repetitive noxious heat or cold pulses were delivered to the upper extremities. Participants rated the perceived size of the painful area or intensity of pain after each pulse. The magnitude of change for the size percept and intensity for pain were calculated for each trial. The results indicated that older adults experienced greater TS of the size percept of cold stimuli compared with younger adults. Additionally, older women experienced greater TS of the size percept of heat stimuli compared with older men and all younger participants. No overall age or sex differences were found in the TS of pain intensity for cold or heat trials. These results suggest dysfunctional modulation of the spatial percept of the painful stimuli by older adults, and in particular older women, during repetitive noxious thermal pulses.

Pain sensitivity profiles in patients with advanced knee osteoarthritis

The development of patient profiles to subgroup individuals on a variety of variables has gained attention as a potential means to better inform clinical decision making. Patterns of pain sensitivity response specific to quantitative sensory testing (QST) modality have been demonstrated in healthy subjects. It has not been determined whether these patterns persist in a knee osteoarthritis population. In a sample of 218 participants, 19 QST measures along with pain, psychological factors, self-reported function, and quality of life were assessed before total knee arthroplasty. Component analysis was used to identify commonalities across the 19 QST assessments to produce standardized pain sensitivity factors. Cluster analysis then grouped individuals who exhibited similar patterns of standardized pain sensitivity component scores. The QST resulted in 4 pain sensitivity components: heat, punctate, temporal summation, and pressure. Cluster analysis resulted in 5 pain sensitivity profiles: a "low pressure pain" group, an "average pain" group, and 3 "high pain" sensitivity groups who were sensitive to different modalities (punctate, heat, and temporal summation). Pain and function differed between pain sensitivity profiles, along with sex distribution; however, no differences in osteoarthritis grade, medication use, or psychological traits were found. Residualizing QST data by age and sex resulted in similar components and pain sensitivity profiles. Furthermore, these profiles are surprisingly similar to those reported in healthy populations, which suggests that individual differences in pain sensitivity are a robust finding even in an older population with significant disease.

An over-the-counter central sensitization therapy: a chronic back pain registry study of pain relief, medication use and their adverse effects

Aim: Back pain, the most prevalent musculoskeletal chronic pain condition, is usually treated with analgesic medications of questionable efficacy and frequent occurrence of adverse side effects. Objective: The objective was to determine the effectiveness of the ActiPatch medical devices in reducing chronic back pain, document medication related adverse side effects and establish their impact on quality of life. Methods: Upon completing a 7-day trial, subjects were contacted via email with an assessment form using the Constant Contact email program. A total of 1394 responses were collected from subjects who used the device for back pain. Conclusion: Medication adverse effects are common and impact quality of life in the lay population. ActiPatch is an effective intervention for the majority of subjects for treating chronic back pain, although this requires further investigation in randomized clinical trials.

Sex-specific impact of early-life adversity on chronic pain: a large population-based study in Japan

BACKGROUND

Responses to early-life adversity may differ by sex. We investigated the sex-specific impact of early-life adversity on chronic pain, chronic multisite pain, and somatizing tendency with chronic pain.

METHODS

We examined 4229 respondents aged 20-79 years who participated in the Pain Associated Cross-Sectional Epidemiological Survey in Japan. Outcomes were: 1) chronic pain prevalence, 2) multisite pain (≥3 sites) prevalence, and 3) multiple somatic symptoms (≥3 symptoms) among respondents with chronic pain related to the presence or absence of early-life adversity. Multivariable-adjusted odds ratios (ORs) were calculated with 95% confidence intervals using a logistic regression model including age, smoking status, exercise routine, sleep time, body mass index, household expenditure, and the full distribution of scores on the Mental Health Inventory-5. We further adjusted for pain intensity when we analyzed the data for respondents with chronic pain.

RESULTS

The prevalence of chronic pain was higher among respondents reporting the presence of early-life adversity compared with those reporting its absence, with multivariable ORs of 1.62 (1.22-2.15, p<0.01) in men and 1.47 (1.13-1.90, p<0.01) in women. Among women with chronic pain, early-life adversity was associated with multisite pain and multiple somatic symptoms; multivariable ORs were 1.78 (1.22-2.60, p<0.01) for multisite pain and 1.89 (1.27-2.83, p<0.01) for ≥3 somatic symptoms. No associations were observed between early-life adversity and chronic multisite pain or multiple somatic symptoms among men with chronic pain.

CONCLUSION

Early-life adversity may be linked to a higher prevalence of chronic pain among both sexes and to multisite pain and somatizing tendency among women with chronic pain.

Frequency of Shoulder Corticosteroid Injections for Pain and Stiffness After Shoulder Surgery and Their Potential to Enhance Outcomes with Physiotherapy: A Retrospective Study

Introduction

What is the rate of injecting patients with shoulder corticosteroid injections to alleviate excessive stiffness and pain within 6 months after shoulder surgery?

Methods

Retrospective 10-year review of a shoulder surgeon’s practice. Participants included 754 patients who had 945 non-arthroplasty shoulder surgeries. Outcome measures included the rate of injections, diagnoses, patient characteristics, and efficacy via questionnaire.

Results

Approximately one in five patients received a subacromial and/or glenohumeral corticosteroid injection. Over 95% of patients stated that the injections helped reduce shoulder pain and increased function 6 weeks post-injection. Twenty-two percent of cases (208/945) received glenohumeral and/or subacromial injections. The 208 injected cases had these diagnoses: rotator cuff tear (28% of injected patients), subacromial impingement (20%), glenohumeral instability (16%), subacromial impingement with acromioclavicular osteoarthritis (10%), adhesive capsulitis (7%), SLAP lesion (5%), biceps tendinopathy (3%), glenohumeral instability with subacromial impingement (3%), proximal humerus fracture (2%), calcific tendinitis (2%), and less common conditions (4%). Diagnoses among those with the highest rates of injected patients per diagnosis included: SLAP lesions (40%), calcific tendinitis (40%), adhesive capsulitis (29%), subacromial impingement (28%), proximal humerus fracture (24%), rotator cuff tear (19%), and glenohumeral instability (16%). Significant differences (p < 0.03) were found between patients who did and did not receive injections with respect to age (more likely younger patients with cuff tear) and sex (more likely female with subacromial impingement and instability) but not for diabetes or arthroscopic vs. open procedures.

Conclusion

This is the first study to establish the rates of postoperative shoulder corticosteroid injections within the first 6 months after various non-arthroplasty shoulder surgeries for patients with high pain/stiffness. These data will be useful for establishing guidelines for using corticosteroid injections along with physiotherapy.

Expanded Distribution of Pain as a Sign of Central Sensitization in Individuals With Symptomatic Knee Osteoarthritis

BACKGROUND

Expanded distribution of pain is considered a sign of central sensitization (CS). The relationship between recording of symptoms and CS in people with knee osteoarthritis (OA) has been poorly investigated.

OBJECTIVE

The aim of this study was to examine whether the area of pain assessed using pain drawings relates to CS and clinical symptoms in people with knee OA.

DESIGN

This was a cross-sectional study.

METHODS

Fifty-three people with knee OA scheduled to undergo primary total knee arthroplasty were studied. All participants completed pain drawings using a novel digital device, completed self-administration questionnaires, and were assessed by quantitative sensory testing. Pain frequency maps were generated separately for women and men. Spearman correlation coefficients were computed to reveal possible correlations between the area of pain and quantitative sensory testing and clinical symptoms.

RESULTS

Pain frequency maps revealed enlarged areas of pain, especially in women. Enlarged areas of pain were associated with higher knee pain severity (rs=.325, P<.05) and stiffness (rs=.341, P<.05), lower pressure pain thresholds at the knee (rs=-.306, P<.05) and epicondyle (rs=-.308, P<.05), and higher scores with the Central Sensitization Inventory (rs=.456, P<.01). No significant associations were observed between the area of pain and the remaining clinical symptoms and measures of CS.

LIMITATIONS

Firm conclusions about the predictive role of pain drawings cannot be drawn. Further evaluation of the reliability and validity of pain area extracted from pain drawings in people with knee OA is needed.

CONCLUSION

Expanded distribution of pain was correlated with some measures of CS in individuals with knee OA. Pain drawings may constitute an easy way for the early identification of CS in people with knee OA, but further research is needed.

Sex differences in symptom severity and clusters in patients with stage C4 and stage C5 chronic venous disease

BACKGROUND

Multiple symptoms associated with chronic venous disease (CVD) are poorly understood, under-recognized, and ill-managed.

AIMS

The aim of this study was to determine whether there are differences in symptoms and symptom clusters between men and women with stage C4 and stage C5 CVD.

METHODS

Data were collected via interviews with 264 patients using a demographic survey and an 11-item VEINES-SYM questionnaire.

ANALYSIS

An intrinsic scoring algorithm was developed to calculate the overall t scores for each item by sex. Exploratory factor analysis identified symptom clusters using oblique rotation to account for correlations between factors.

RESULTS

The average age was 61.7 years; 54.5% of the patients were women, 58% were African American or black, and 60.6% had diabetes. The top three symptoms for women in order of frequency were achy legs, swelling, and pain; for men, these were swelling, achy legs, and heavy legs. For the total group, two symptom clusters emerged: distressful and discomfort. There was no statistically significant difference in factor score between the sexes. Different factor loadings for symptom clusters were observed: women reported hurting and annoying clusters; and men reported nagging and irritating clusters.

CONCLUSION

The data suggest differences in CVD symptoms and clusters by sex. Symptoms in the two clusters were different; however, there was consistency in the factors associated with each cluster. Co-morbid conditions and sex differences in pain responses may play a part in symptom presentation. This study supports the need for increased sex-delineated clinical assessment and consideration of the potential differences between the sexes in the management of CVD symptoms.