Associations of pain sensitisation with tender and painful joint counts in people with hand osteoarthritis: results from the Nor-Hand study

ObjectiveTo examine associations of pain sensitisation with tender and painful joint counts and presence of widespread pain in people with hand osteoarthritis (OA).MethodsPressure pain thresholds (PPT) at a painful finger joint and the tibialis anterior muscle, and temporal summation (TS) were measured in 291 persons with hand OA. We examined whether sex-standardised PPT and TS values were associated with assessor-reported tender hand joint count, self-reported painful hand and total body joint counts and presence of widespread pain using linear and logistic regression analyses adjusted for age, sex, body mass index, education and OA severity.ResultsPeople with lower PPTs at the painful finger joint (measure of peripheral and/or central sensitisation) had more tender and painful hand joints than people with higher PPTs. PPT at tibialis anterior (measure of central sensitisation) was associated with painful total body joint count (beta=−0.82, 95% CI −1.28 to –0.35) and presence of widespread pain (OR=0.57, 95% CI 0.43 to 0.77). The associations between TS (measure of central sensitisation) and joint counts in the hands and the total body were statistically non-significant.ConclusionThis cross-sectional study suggested that pain sensitisation (ie, lower PPTs) was associated with joint counts and widespread pain in hand OA. This knowledge may be used for improved pain phenotyping of people with hand OA, which may contribute to better pain management through more personalised medicine. Further studies are needed to assess whether a reduction of pain sensitisation leads to a decrease in tender and painful joint counts.

Hypoalgesia after exercises with painful vs. non-painful muscles in healthy subjects – a randomized cross-over study

Objectives Exercise-induced hypoalgesia (EIH) is a decrease in the pain sensitivity after exercise. Individuals with chronic pain show less EIH after one exercise session compared with pain-free individuals possibly due to pain in exercising muscles. The primary aim of this randomized controlled cross-over study was to compare the EIH response at the exercising thigh muscle following exercises performed with painful vs. non-painful muscles. Secondary aims were to explore if a reduced EIH response was confined to the painful muscle, and whether the muscle pain intensity and the EIH responses were negatively associated. Methods In two sessions, 34 pain-free participants received a painful (hypertonic saline, 5.8%) injection and a control (isotonic saline, 0.9%) injection in the right thigh muscle before performing a 3 min isometric wall squat exercise. Pressure pain thresholds (PPTs) were assessed at both thighs and the left neck/shoulder at baseline, after injections and after exercise. Pain intensities in the thighs were rated on numerical rating scales (NRS: 0–10). Results Hypertonic saline induced moderate thigh pain at rest (NRS: 4.6 ± 2.1) compared to the control injection (NRS: 0.3 ± 0.4; p<0.001). EIH at the thighs and neck/shoulder were not different between sessions (Injected thigh: 0 kPa; 95% CI: −51 to 52; Contralateral thigh: −6 kPa; 95% CI: −42 to 30; neck/shoulder: 19 kPa; 95% CI: −6 to 44). No significant associations between pain intensity ratings immediately after the Painful injection and EIH responses at any assessment sites were found (right thigh: β=0.08, 95% CI: −12.95 to 20.64, p=0.64, left thigh: β=−0.33, 95% CI: −27.86 to 0.44, p=0.06; neck/shoulder: β=−0.18, 95% CI: −15.11 to 4.96, p=0.31). Conclusions Pain in the area of an exercising muscle did not reduce local or systemic EIH responses. Trial registration number NCT04354948.

The importance of the local twitch response during needling interventions in spinal pain associated with myofascial trigger points: a systematic review and meta-analysis

Objective: To compare the clinical effects of needling interventions eliciting local twitch responses (LTRs) versus needling without eliciting LTRs when applied to muscle trigger points (TrPs) associated with spinal pain of musculoskeletal origin. Databases and data treatment: Electronic databases were searched for randomized or non-randomized clinical trials where one group received needling intervention where LTRs were elicited and was compared with another group receiving the same intervention without elicitation of LTRs in spinal pain disorders associated with TrPs. Outcomes included pain intensity, pain-related disability, and pressure pain thresholds. The risk of bias (RoB) was assessed using the Cochrane risk of bias tool or ROBINS-I tool, methodological quality was assessed with the PEDro score, and quality of evidence was evaluated using the GRADE approach. Results: Six trials were included. The application of a needling intervention eliciting LTRs was associated with a significant reduction in pain intensity immediately after treatment (mean difference (MD): −2.03 points, 95% confidence interval (CI): −3.77 to −0.29; standardized MD (SMD): −1.35, 95% CI: −2.32 to −0.38, p = 0.02) when compared to the same needling intervention without elicitation of LTRs. No effect at short-term follow-up (MD: −0.20 points, 95% CI: −1.46 to 1.06, p = 0.75) was observed. No significant differences based on elicitation or non-elicitation of LTRs were found in related disability (SMD: −0.05, 95% CI: −0.41 to 0.30, p = 0.77) or pressure pain thresholds (MD: 23.39 kPa, 95% CI: −13.68 to 60.47, p = 0.22). Discussion: Low-level evidence suggests an immediate effect of obtaining LTRs during needling interventions on pain intensity, with no significant effects on related disability or pressure pain sensitivity in spinal pain disorders associated with muscle TrPs. Registration number: OSF Registry— https://doi.org/10.17605/OSF.IO/5ZX9N

Psychophysical testing in chronic migraine and chronic tension type headache: An observational study

Background Clinical presentation is the key to the diagnosis of patients with migraine and tension-type headache, but features may overlap when both become chronic. Psychophysical parameters may distinguish both conditions. We aimed to compare psychophysical aspects of patients with chronic migraine, chronic tension-type headache and headache-free controls, and to determine whether these can predict headache frequency. Methods An examiner blinded to the diagnosis assessed 100 participants (chronic migraine (n = 38), chronic tension-type headache (n = 31) and controls (n = 31)). Assessed variables included painful area, pressure pain thresholds, temporal summation, cervical range of motion, neck posture, headache and neck impact, quality of life, and kinesiophobia. Comparison between groups was performed with one-way ANOVA and multiple linear regression was used to assess the headache frequency predictors. Results We found differences of both headache groups compared to controls ( p < 0.01), but not between headache groups. Neck disability was a significant predictor of headache frequency for chronic tension-type headache (adjusted R2 = 0.14; β = 0.43; p = 0.03) and chronic migraine (adjusted R2 = 0.18; β = 0.51; p < 0.01). Conclusions Chronic tension-type headache and chronic migraine showed similar psychophysical results, but were significantly worse when compared to controls. The psychophysical examination did not discriminate between headache types. The variable best explaining headache frequency for both headache types was neck disability.

A mechanism-based proof of concept study on the effects of duloxetine in patients with painful knee osteoarthritis

Background The global burden of osteoarthritis (OA) is steadily increasing due to demographic and lifestyle changes. The nervous system can undergo peripheral and central neuroplastic changes (sensitization) in patients with OA impacting the options to manage the pain adequately. As a result of sensitization, patients with OA show lower pressure pain thresholds (PPTs), facilitated temporal summation of pain (TSP), and impaired conditioned pain modulation (CPM). As traditional analgesics (acetaminophen and non-steroidal anti-inflammatory drugs) are not recommended for long-term use in OA, more fundamental knowledge related to other possible management regimes are needed. Duloxetine is a serotonin-noradrenalin reuptake inhibitor, and analgesic effects are documented in patients with OA although the underlying fundamental mechanisms remain unclear. The descending pain inhibitory control system is believed to be dependent on serotonin and noradrenalin. We hypothesized that the analgesic effect of duloxetine could act through these pathways and consequently indirectly reduce pain and sensitization. The aim of this mechanistic study is to investigate if PPTs, TSP, CPM, and clinical pain parameters are modulated by duloxetine. Methods This proof of concept study is a randomized, placebo-controlled, double-blinded, crossover trial, which compares PPTs, TSP, and CPM before and after 18 weeks of duloxetine and placebo in forty patients with knee OA. The intervention periods include a titration period (2 weeks), treatment period (60 mg daily for 14 weeks), and a discontinuation period (2 weeks). Intervention periods are separated by 2 weeks. Discussion Duloxetine is recommended for the treatment of chronic pain, but the underlying mechanisms of the analgesic effects are currently unknown. This study will investigate if duloxetine can modify central pain mechanisms and thereby provide insights into the underlying mechanisms of the analgesic effect. Trial registration ClinicalTrials.govNCT04224584. Registered on January 6, 2020. EudraCT 2019-003437-42. Registered on October 22, 2019. The North Denmark Region Committee on Health Research Ethics N-20190055. Registered on October 31, 2019.

Foot and Lower Limb Clinical and Structural Changes in Overuse Injured Recreational Runners Using Floating Heel Shoes: Preliminary Results of a Randomised Control Trial

Foot-strike and the associated load rate are factors related to overuse injuries in runners. The purpose of this study was to analyse structural and functional changes in runners using floating heel running shoes, compared with runners using conventional footwear. A randomised control trial was conducted. Twenty runners with overuse injuries were followed over a 12-week gait retraining programme using floating heel running shoes or their conventional footwear. Pain was measured with pressure pain thresholds (PPTs), structural changes were measured with ultrasonography, and severity and impact of injury was scored on the Oslo Sports Trauma Research Centre Overuse Injury Questionnaire (OSTRC-O). Statistical differences were found between groups after the intervention (p < 0.001), with a medium size effect SE = 0.8, and the floating heel running shoes group reached higher PPTs values. Participants using floating heel running shoes showed higher OSTRC-O scores than those using their conventional footwear (p < 0.05), with higher scores after the intervention (p < 0.05). A 12-week gait retraining programme using floating heel running shoes had positive effects on the injury recovery process when compared to the use of conventional footwear, with significant differences in terms of pain and impact on sports activity.

Active Virtual Reality Games Reduce Pain Sensitivity in Young, Healthy Adults

Separately, both physical activity and virtual reality can attenuate pain sensitivity in healthy adults. What is unknown is whether virtual reality combined with physical activity (active virtual reality) could have a greater hypoalgesic effect compared to non-active virtual reality distraction (passive virtual reality engagement).Objective: The purpose of this study was to determine whether playing physically active virtual reality games exert a greater hypoalgesic effect than a non-active virtual reality game.Methods: Participants (n = 36) played three different active virtual reality games (Beat Saber, Holopoint, and Hot Squat) and one non-active virtual reality game (Relax Walk) for 15 min on four different visits. During gameplay, participants wore accelerometers on the thigh, wrist, and waist to measure movement intensity and quantity. Pressure pain thresholds were measured on the forearm and thigh immediately prior to gameplay (pretest) and immediately following each gaming bout (posttest).Results: Analysis of the accelerometer data indicated that Hot Squat elicited greater whole-body and lower body moderate to vigorous physical activity compared to the other games. The ANOVA revealed an overall hypoalgesic effect of the virtual reality games on the forearm, regardless of game type. Results also showed a significant hypoalgesic effect on the thigh following gameplay for Hot Squat, Holopoint, and Relax Walk VR. The magnitude of pain reduction was significantly greater during Hot Squat compared to the other games.Conclusion: Virtual reality gameplay exerted a hypoalgesic effect on experimental pressure pain. Additionally, the data provided evidence of a potential enhanced hypoalgesic effect of physically active virtual reality compared to non-active VR on pressure pain sensitivity.

Robotic Stroking on the Face and Forearm: Touch Satiety and Effects on Mechanical Pain

Background: Slow stroking touch is generally perceived as pleasant and reduces thermal pain. However, the tactile stimuli applied tend to be short-lasting and typically applied to the forearm. This study aimed to compare the effects of a long-lasting brushing stimulus applied to the facial region and the forearm on pressure pain thresholds (PPTs) taken on the hand. Outcome measurements were touch satiety and concurrent mechanical pain thresholds of the hand.Methods: A total of 24 participants were recruited and randomized to receive continuous stroking, utilizing a robotic stimulator, at C-tactile (CT) favorable (3 cm/s) and non-favorable (30 cm/s) velocities applied to the right face or forearm. Ratings of touch pleasantness and unpleasantness and PPTs from the hypothenar muscle of the right hand were collected at the start of stroking and once per minute for 5 min.Results: A reduction in PPTs (increased pain sensitivity) was observed over time (P &lt; 0.001). However, the increase in pain sensitivity was less prominent when the face was stroked compared to the forearm (P = 0.001). Continuous stroking resulted in a significant interaction between region and time (P = 0.008) on pleasantness ratings, with a decline in ratings observed over time for the forearm, but not on the face. Unpleasantness ratings were generally low.Conclusion: We observed touch satiety for 5 min of continuous robotic brushing on the forearm confirming previous studies. However, we did not observe any touch satiety for brushing the face. Mechanical pain sensitivity, measured in the hand, increased over the 5-min period but less so when paired with brushing on the face than with brushing on the forearm. The differential effects of brushing on the face and forearm on touch satiety and pain modulation may be by the differences in the emotional relevance and neuronal pathways involved.

Pain thresholds and suprathreshold pain after sleep restriction in migraine – A blinded crossover study

Objective There is an unexplained association between disturbed sleep and migraine. In this blinded crossover study, we investigate if experimental sleep restriction has a different effect on pain thresholds and suprathreshold pain in interictal migraineurs and controls. Methods Forearm heat pain thresholds and tolerance thresholds, and trapezius pressure pain thresholds and suprathreshold pain were measured in 39 interictal migraineurs and 31 healthy controls after two consecutive nights of partial sleep restriction and after habitual sleep. Results The effect of sleep restriction was not significantly different between interictal migraineurs and controls in the primary analyses. Pressure pain thresholds tended to be lower (i.e., increased pain sensitivity) after sleep restriction in interictal migraineurs compared to controls with a 48-hour preictal-interictal cut-off (p = 0.061). We found decreased pain thresholds after sleep restriction in two of seven migraine subgroup comparisons: heat pain thresholds decreased in migraineurs with lower pain intensity during attacks (p = 0.005) and pressure pain thresholds decreased in migraineurs with higher severity of photophobia during attacks (p = 0.031). Heat pain thresholds tended to decrease after sleep restriction in sleep-related migraine (p = 0.060). Sleep restriction did not affect suprathreshold pain measurements in either group. Conclusion This study could not provide strong evidence for an increased effect of sleep restriction on pain sensitivity in migraineurs compared to healthy controls. There might be a slightly increased effect of sleep restriction in migraineurs, detectable using large samples or more pronounced in certain migraine subgroups.