Basic aspects of musculoskeletal pain: from acute to chronic pain

Effects of Nutritional Interventions in the Control of Musculoskeletal Pain: An Integrative Review

Food consumption has significant positive effects on an individual’s health status, including the reduction of symptoms associated with musculoskeletal pain. However, specific food groups indicated for the treatment of pain are not yet determined. Hence, this review aimed to analyze the effects of nutritional interventions with specific diets, oils and/or fatty acids, and foodstuffs in natura in the reduction of musculoskeletal pain. An integrative review was conducted in the following databases: Embase, PubMed, LILACS, and Google Scholar. Clinical trials written in English, Spanish, and Portuguese and published between 2000 and March 2020 were included in this review. Seventeen studies were included. Among these, a reduction of musculoskeletal pain with different types of nutritional interventions, such as vegan and Mediterranean diets and the consumption of blueberry, strawberry, passion fruit peel extract, argan oil, fish oil (omega-3), olive oil, and undenatured type II collagen and vitamin D gel capsules, was observed in 14 studies. Eight studies evaluated the profiles of several inflammatory markers, and of these, decreased interleukin (IL)-6, IL-1β, and tumor necrosis factor-α levels were observed in two studies. This review suggests that different nutritional interventions with specific diets, oils and/or fatty acids, and foodstuffs in natura reduce musculoskeletal pain, specifically in adults with osteoarthritis. Besides pain improvement, nutritional interventions, including the consumption of strawberry and vitamin D gel capsules, decrease the levels of several inflammatory markers.

Psychosocial factors, disability and quality of life in chronic shoulder pain patients with central sensitization

Chronic shoulder pain is a complex and multidimensional phenomenon with multiple causative factors involved in its perpetuation. Alteration of central nervous system processing along with the central sensitization is a predominant feature in chronic pain. Reduction in physical function has an impact on the psychological well-being of an individual. The aim of the study was to compare pain, kinesiophobia, catastrophizing, disability and quality of life in chronic shoulder pain patients with and without central sensitization. Eighty chronic unilateral shoulder pain patients in the age group of 40 to 60 years were recruited. Of them, 38 were chronic shoulder pain with central sensitization and 42 without central sensitization, classified on the basis of central sensitization inventory. Pain catastrophizing was measured using the pain catastrophizing scale, kinesiophobia using Tampa scale of kinesiophobia, disability using Shoulder pain and disability index and quality of life using 36-Item Short Form Health Survey questionnaire was evaluated in both the groups. Increased pain catastrophizing (p=0.000), kinesiophobia (p=0.000) and disability (p=0.000) was observed in centrally sensitized chronic shoulder pain patients. Also, physical component summary (p=0.000) and mental component summary (p=0.000) of SF-36 quality of life were reduced in chronic shoulder pain with central sensitization as compared to without central sensitization. Hence, these components should be included during assessment which will provide a holistic and multimodal approach towards the understanding, planning and management of chronic shoulder pain patients.

The Association of Diabetes With Knee Pain Locations, Pain While Walking, and Walking Speed: Data From the Osteoarthritis Initiative

OBJECTIVE

Osteoarthritis (OA) and diabetes mellitus (DM) often coexist and can result in negative outcomes. DM can affect pain and walking speed in people with knee OA; however, the impact of DM on OA is understudied. The purpose of this study was to investigate the association between diabetes and knee pain locations, pain severity while walking, and walking speed in people with knee OA.

METHODS

A cross-sectional analysis was used. Data from 1790 individuals from the Osteoarthritis Initiative (mean [SD] age = 69 [8.7] years) with knee pain were included and grouped into knee OA and diabetes (n = 236) or knee OA only (n = 1554). Knee pain locations were categorized as no pain, localized pain, regional pain, or diffuse pain. Knee pain during a 20-m walk test was categorized as no pain, mild, moderate, or severe knee pain. Walking speed was measured using the 20-m walk test. Multinomial and linear regression analyses were performed.

RESULTS

Diabetes was associated with regional knee pain (odds ratio [OR] = 1.77; 95% CI = 1.01-3.11). Diabetes was associated only with moderate (OR = 1.78; 95% CI = 1.02-3.10) or severe (OR = 2.52; 95% CI = 1.01-6.28) pain while walking. Diabetes was associated with decreased walking speed (B = -0.064; 95% CI = -0.09 to -0.03).

CONCLUSIONS

Diabetes was associated with regional knee pain but not with localized or diffuse knee pain and was associated with moderate to severe knee pain while walking and slower walking speed in people with knee OA.

IMPACT

Clinicians can use a knee pain map for examining knee pain locations for people with diabetes and knee OA. Knee pain during walking and walking speed should be screened for people with knee OA and diabetes because of the influence of diabetes on these parameters in this population.

LAY SUMMARY

Diabetes might be associated with specific knee pain locations, pain during activities such as walking, and reduced walking speed in people with knee OA.

Relationships Between Psychological, Sleep, and Physical Activity Measures and Somatosensory Function in People With Peripheral Joint Pain: A Systematic Review and Meta-Analysis

OBJECTIVE

Alteration in somatosensory function has been linked to pain experience in individuals with joint pain. In this systematic review we aimed to establish the level of evidence of associations between psychological, social, physical activity, and sleep measures and somatosensory function that were assessed via quantitative sensory testing (QST) among individuals with joint pain.

METHODS

A comprehensive literature search was conducted in 6 electronic databases from their inception to July 2019. Two reviewers independently assessed the methodological quality using a modified Quality in Prognostic Studies (QUIPS) tool and supplemented with recommendations from the Critical Appraisal and Data Extraction for Systematic Review of Prediction Modelling Studies (CHARMS) checklist and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. The level of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. Data were pooled to evaluate the strength of the relationships of interest.

RESULTS

Seventeen studies related to joint pain were included. Pain catastrophizing, depression, anxiety, and physical activity level have been shown to have a significant (small to fair) association with several QST measures. Pressure pain threshold (PPT) is the only measure that was found to be consistently correlated with all the domains. The overall quality of evidence for all factors ranged from very low to moderate. Subgroup analysis revealed a stronger association for depression and pain catastrophizing and PPT and temporal pain summation in individuals with shoulder pain.

CONCLUSION

Psychological factors and physical activity levels are associated with somatosensory function in people with joint pain. These factors need to be adjusted when establishing predictive relationships between somatosensory function and pain outcomes in individuals with joint pain.

Understanding central sensitization for advances in management of carpal tunnel syndrome

Carpal tunnel syndrome is the most common nerve compression disorder of the upper extremity, and it is traditionally considered a peripheral neuropathy associated with a localized compression of the median nerve just at the level of the carpal tunnel. Surgery and physiotherapy are treatment approaches commonly used for this condition; however, conflicting clinical outcomes suggest that carpal tunnel syndrome may be more complex. There is evidence supporting the role of peripheral nociception from the median nerve in carpal tunnel syndrome; however, emerging evidence also suggests a potential role of central sensitization. The presence of spreading pain symptoms (e.g. proximal pain), widespread sensory changes, or bilateral motor control impairments in people presenting with strictly unilateral sensory symptoms supports the presence of spinal cord changes. Interestingly, bilateral sensory and motor changes are not directly associated with electrodiagnostic findings. Other studies have also reported that patients presenting with carpal tunnel syndrome exhibit neuroplastic brainstem change supporting central sensitization. Current data would support the presence of a central sensitization process, mediated by the peripheral drive originating in the compression of the median nerve, in people with carpal tunnel syndrome. The presence of altered nociceptive gain processing should be considered in the treatment of carpal tunnel syndrome by integrating therapeutic approaches aiming to modulate long-lasting nociceptive barrage into the central nervous system (peripheral drive) and strategies aiming to activate endogenous pain networks (central drive).

Electromagnetic Field Therapy: A Rehabilitative Perspective in the Management of Musculoskeletal Pain - A Systematic Review

Electromagnetic fields (EMFs) provide a non-invasive, safe, and easy method to treat pain with respect to musculoskeletal diseases. The purpose of this systematic review was to describe the use of electromagnetic therapy in the rehabilitation field by investigating the efficacy in acute and chronic pain in the musculoskeletal disorders. A database search was conducted using the following resources: PubMed, Cochrane, PEDro, SCOPUS, and WoS. The following MESH terms were used: [Electromagnetic field AND/OR Rehabilitation], [Electromagnetic field AND/OR Pain], [Pulsed Magnetic field AND/OR Rehabilitation] and [Pulsed Magnetic field AND/OR Pain], [Pulsed Electromagnetic field AND/OR Rehabilitation] and [Pulsed Electromagnetic field AND/OR Pain], per the guidelines of the PRISMA statement. Articles published between January 1, 2009 and December 31, 2018 were included as assessment of musculoskeletal pain conditions, randomized clinical trial including crossover and prospective design studies, full English text available, population age > 18 years; instead were excluded neurological randomized clinical trials, transcranial magnetic stimulation application, neuropathic pain, animal/in vitro studies, and articles without English abstract or English full text. Three independent investigators (AMC, NG, and LP) retrieved all the information. Twenty-one RTC (N=21) were considered for the inclusion and exclusion criteria. The results showed as pulsed magnetic fields at low intensity and frequency (from 1 Hz up to 100 Hz) are commonly used with efficacy in resolving musculoskeletal pain. EMFs therapy is a well tolerated, effective with no negative side effects, which can be integrated with rehabilitation for the treatment of chronic and acute pain in musculoskeletal diseases, but further studies are needed to examine the use of more standardized protocols.

The Use of Massage Therapy as a Nonpharmacological Approach to Relieve Postlaparoscopic Shoulder Pain: a Pediatric Case Report

INTRODUCTION

Postlaparoscopic shoulder pain (PLSP) has been well documented to effect patients following an abdominal or thoracic laparoscopic surgery. PLSP is characterized by referred pain that can occur both unilaterally or bilaterally, and is typically caused by phrenic nerve irritation. Current literature has focused on pharmacological treatment; however, there is limited evidence for the use of nonpharmacological management of PLSP in the pediatric population.

CASE DESCRIPTION

This retrospective case report study explores the use of a single-session massage therapy treatment for a 17-year-old patient with PLSP following laparoscopic abdominal surgery.

INTERVENTION AND RESULTS

Therapy intervention included a 25 min Swedish massage involving the effected shoulder with an emphasis on passive touch to the shoulder and at the level of the diaphragm. Pain was assessed using the Visual Analog Scale (VAS) pre- and postintervention. Following therapy the patient reported 0/10 pain.

CONCLUSION

This case report provides evidence for the use of massage therapy treatment as a noninvasive, nonpharmacological approach to reducing or eliminating PLSP in a pediatric patient.

Pressure pain sensitivity in patients with traumatic first-time and recurrent anterior shoulder dislocation: a cross-sectional analysis

Background and aims Traumatic anterior shoulder dislocation (ASD) is frequent in active populations and associated with a 39% higher risk of recurrent dislocation, which may cause persistent shoulder problems, pain, and impaired shoulder-related quality of life. While local and distant pressure pain sensitivity has been demonstrated in other shoulder conditions, little is known about the link between pressure pain sensitivity and ASD. The interesting aspect is whether recurrent dislocation - resulting in symptoms of longer duration - is associated with more pronounced pressure pain sensitivity, or if presence of pressure pain sensitivity may be part of the reasons why patients develop recurrent dislocation. Therefore, this study aimed at evaluating whether patients with recurrent ASD display greater pressure pain sensitivity and more painful body sites than patients with first-time ASD. Methods This was a cross-sectional analysis of baseline data from a randomized controlled trial including 34 patients with first-time ASD [82% male, mean (SD) age 26 (7) years] and 22 patients with recurrent ASD [96% male, mean (SD) age 25 (5) years]. Patients were assessed as follows: (1) assessment of local and distant pressure pain sensitivity evaluated by pressure pain thresholds (PPTs) using a handheld algometer on mm. trapezius superior, levator scapula, pectorales major, deltoideus, and tibialis anterior, (2) pain intensity at rest during the previous 24 h, (3) number of ASD, and (4) number of painful body sites on a region-divided body chart. Results The PPTs were not significantly different between first-time and recurrent ASD [mean (SD) kPa for m. trapezius superior 264 (110) vs. 261 (88), m. levator scapula 301 (157) vs. 325 (163), m. pectorales major 234 (163) vs. 269 (130), m. deltoideus 290 (166) vs. 352 (173), m. tibialis anterior 420 (202) vs. 449 (184)], two-way ANCOVA, adjusted for sex and age, F (4,263) = 0.29, p = 0.88. For both groups, the PPTs were lower at the shoulder sites than at m. tibialis anterior (difference 117-184 kPa, 95% CI range 33-267). Females had lower PPTs than males (difference 124 kPa, 95% CI 64-183). The number (SD) of painful body sites were 2.2 (1.9) for first-time ASD and 2.6 (5.4) for recurrent ASD, with no between-group differences, one-way ANCOVA, adjusted for sex and age, F (1, 52) = 0.24, p = 0.63. There was a strong correlation between PPTs at the shoulder and lower leg, r = 0.84, p < 0.01. Conclusions This study demonstrated no differences in local and distant pressure pain sensitivity or number of painful body sites between patients with first-time and recurrent ASD. Females had lower PPTs than males, and a strong correlation was found between PPTs at the shoulder and lower leg. Implications Patients with first-time and recurrent ASD seem to have similar pressure pain sensitivity, but lower PPTs compared to existing normative data, suggesting that it is relevant to evaluate the status of the pain system in these patients to prevent triggering or worsening of their symptoms. However, it remains unanswered how these changes affect the patients' ability to undergo rehabilitation, symptom response and long-term shoulder function.

The effect of manual therapy to the thoracic spine on pain-free grip and sympathetic activity in patients with lateral epicondylalgia humeri. A randomized, sample sized planned, placebo-controlled, patient-blinded monocentric trial

Background

The treatment of first choice for lateral epicondylalgia humeri is conservative therapy. Recent findings indicate that spinal manual therapy is effective in the treatment of lateral epicondylalgia. We hypothesized that thoracic spinal mobilization in patients with epicondylalgia would have a positive short–term effect on pain and sympathetic activity.

Methods

Thirty patients (all analyzed) with clinically diagnosed (physical examination) lateral epicondylalgia were enrolled in this randomized, sample size planned, placebo-controlled, patient-blinded, monocentric trial. Pain-free grip, skin conductance and peripheral skin temperature were measured before and after the intervention. The treatment group (15 patients) received a one-time 2-min T5 costovertebral mobilization (2 Hz), and the placebo group (15 patients) received a 2-min one-time sham ultrasound therapy.

Results

Mobilization at the thoracic spine resulted in significantly increased strength of pain-free grip + 4.6 kg ± 6.10 (p = 0.008) and skin conductance + 0.76 μS ± 0.73 (p = 0.000004) as well as a decrease in peripheral skin temperature by − 0.80 °C ± 0.35 (p < 0.0000001) within the treatment group.

Conclusion

A thoracic costovertebral T5 mobilization at a frequency of 2 Hz shows an immediate positive effect on pain-free grip and sympathetic activity in patients with lateral epicondylalgia.

Clinical trial registration

German clinical trial register DRKS00013964, retrospectively registered on 2.2.2018.

Sleep, Experimental Pain and Clinical Pain in Patients with Chronic Musculoskeletal Pain and Healthy Controls

Purpose

Everyday variations in night sleep in healthy pain-free subjects are at most weakly associated with pain, whereas strong alterations (eg, sleep deprivation, insomnia) lead to hyperalgesic pain changes. Since it remains unclear how substantial sleep alterations need to be in order to affect the pain system and lead to a coupling of both functions, the present study aimed at providing sufficient variance for co-variance analyses by examining a sample consisting of both healthy subjects and chronic pain patients.

Methods

A sample of 20 chronic musculoskeletal pain patients and 20 healthy controls was examined. This sample was assumed to show high inter-individual variability in sleep and pain, as pain patients frequently report sleep disturbances, whereas healthy subjects were required to be pain-free and normal sleepers. Sleep of two non-consecutive nights was measured using portable polysomnography and questionnaires. Experimental pain parameters (pressure pain thresholds (PPT), temporal summation of pain (TSP), conditioned pain modulation (CPM)) and situational pain catastrophizing (SCQ) were assessed in laboratory sessions before and after sleep. Pain patients’ clinical pain was assessed via questionnaire.

Results

As expected, both groups differed in several sleep parameters (reduced total sleep time and sleep efficiency, more time awake after sleep onset, lower subjective sleep quality in the patients) and in a few pain parameters (lower PPTs in the patients). In contrast, no differences were found in TSP, CPM, and SCQ. Contrary to our expectations, regression analyses indicated no prediction of overnight pain changes by sleep parameters.

Conclusion

Since sleep parameters were hardly apt to predict overnight pain changes, this leaves the association of both systems mainly unproven when using between-subject variance for verification.

Investigation of the Development of Hypersensitivity and Hyperalgesia After Repeated Application of Platelet-Rich Plasma in Rats: An Experimental Study

BACKGROUND

Hyperalgesia, defined as hypersensitivity to pain, refers to sensitization of nociceptors to normal levels of pain.

OBJECTIVES

We aimed to determine whether hyperalgesia occurs due to the development of sensitization following repeated applications of platelet-rich plasma (PRP), and to ascertain the mechanism responsible for inducing hyperalgesia.

METHODS

This study, performed between 2016 and 2017, involved 32 rats. A 2 cm × 2 cm area was shaved on the back of 10 experimental and 10 sham control animals. In the experimental animals this area was divided into 4 equal squares of 1 cm × 1 cm, and these squares were numbered 1 (no treatment; only the needle was inserted), 2 (0.2 mL, saline), 3 (0.2 mL, nonactivated PRP), and 4 (0.2 mL, activated PRP). The response of the animals to painful stimuli in these areas was investigated with Von Frey filaments, immediately before application and 4 weeks after the last application. Skin biopsies were taken, and growth factors were evaluated pathologically and biochemically.

RESULTS

Hyperalgesia developed in all 4 areas of each experimental rat but not in the sham group. However, areas 3 and 4 had smaller Von Frey g values than areas 1 and 2. When growth hormones were assessed histopathologically and biochemically, nerve growth factor (NGF) levels were found to be higher in areas 3 and 4 than in areas 1 and 2 and the sham group.

CONCLUSIONS

Both nonactivated and activated PRP resulted in greater hypersensitivity than saline and sham treatment. Development of hyperalgesia may be associated with an increase in NGF as well as increased inflammatory mediators.

The Influence of Glenohumeral Joint Posterior Capsule Tightness and Impingement Symptoms on Shoulder Impairments and Kinematics

BACKGROUND

Posterior capsule tightness (PCT) and shoulder impingement syndrome (SIS) symptoms are both associated with altered shoulder biomechanics and impairments. However, their combined effect on kinematics, pain, range of motion (ROM), strength, and function remain unknown.

OBJECTIVE

The purpose of this study was to determine if the combination of PCT and SIS affects scapular and humeral kinematics, glenohumeral joint ROM, glenohumeral joint external rotation strength, pain, and function differently than does either factor (PCT or SIS) alone.

DESIGN

The design was a cross-sectional group comparison.

METHODS

Participants were placed into 1 of 4 groups based on the presence or absence of SIS and PCT: control group (n = 28), PCT group (n = 27), SIS group (n = 25), and SIS + PCT group (n = 25). Scapular kinematics and humeral translations were quantified with an electromagnetic motion capture system. Shoulder internal rotation and external rotation ROM, external rotation strength, and pain and Shoulder Pain and Disabilities Index scores were compared between groups with ANOVA.

RESULTS

The SIS group had greater scapular internal rotation (mean difference = 5.13°; 95% confidence interval [CI] = 1.53°-8.9°) and less humeral anterior translation (1.71 mm; 95% CI = 0.53-2.9 mm) than the other groups. Groups without PCT had greater internal rotation ROM (16.05°; 95% CI = 5.09°-28.28°). The SIS + PCT group had lower pain thresholds at the levator scapulae muscle (108.02 kPa; 95% CI = 30.15-185.88 kPa) and the highest Shoulder Pain and Disabilities Index score (∼ 44.52; 95% CI = 33.41-55.63).

LIMITATIONS

These results may be limited to individuals with impingement symptoms and cannot be generalized to other shoulder conditions.

CONCLUSIONS

Decreased ROM and lower pain thresholds were found in individuals with both impingement symptoms and PCT. However, the combination of factors did not influence scapular and humeral kinematics.

Comparison of knee sonography and pressure pain threshold after anterior cruciate ligament reconstruction with quadriceps tendon versus hamstring tendon autografts in soccer players

Objective

The aim of this study was to compare the pressure pain threshold and muscle architecture after an anatomic single bundle reconstruction with quadriceps tendon and hamstring tendon autografts of the anterior cruciate ligament in competitive soccer players. We hypothesized that both procedures will obtain similar outcomes.

Methods

Fifty-one participants were enrolled in this secondary analysis of a randomized controlled trial and were categorised into two groups: quadriceps tendon (QT) group (23 men and 3 women; mean age 18.7 ± 3.6; BMI 23.0 ± 2.2) or hamstring tendon (HT) group (16 men and 9 women; mean age 19.2 ± 3.6 BMI 23.5 ± 3.5). Both groups followed the same rehabilitation staged protocol. Pressure pain threshold (PPT), as a measure of perceived pain, was obtained in several points of quadriceps and hamstring muscles. Ultrasound imaging measurements were obtained in quadriceps tendon and knee cartilage thickness. Four measurements were taken in this study: baseline, 1, 3, 6, and 12 months after the anterior cruciate ligament (ACL) reconstruction.

Results

The analysis of PPT did not find significant differences in both groups × interaction time in the points evaluated: epicondyle (QT = 421.1 ± 184.1 vs HT = 384.7 ± 154.1 kPa), vastus lateralis (QT = 576.2 ± 221.3 vs HT = 560.1 ± 167.7 kPa), vastus medialis (QT = 544.7 ± 198.8 vs HT = 541.1.1 ± 181.77 kPa), patellar tendon (QT = 626.3 ± 221.1 vs HT = 665.0 ± 205.5 kPa), QT (QT = 651.1 ± 276.9 vs HT = 660.0 ± 195.2 kPa).

(QT = 667.8 ± 284.7 vs HT = 648.2 ± 193.4 kPa) injured knee (all P > 0.05). The results of ultrasound imaging did not show significant differences in both groups × interaction time in the thickness of the QT (QT = 9.9 ± 2.4 vs HT = 9.4 ± 1.7 kPa) and patellar cartilage (QT = 3.2 ± 0.6 vs HT = 3.2 ± 0.4 kPa) (P > 0.05).

Conclusion

A QT autograft produces similar results to a HT autograft in ACL reconstructions in terms of pressure pain threshold and ultrasound muscle architecture during the 1-year follow-up.

Level of Evidence

Level I, Therapeutic Study.

Conditioning pain modulation reduces pain only during the first stimulation of the temporal summation of pain paradigm in healthy participants

BACKGROUND

Pro-nociceptive and anti-nociceptive mechanisms are commonly assessed in clinical and experimental pain studies, but their potential interaction is not well understood.

OBJECTIVES

Investigate the effect of conditioning pain modulation (CPM) on temporal summation of pain (TSP).

METHODS

Twenty healthy participants underwent cuff algometry assessment on the lower legs to establish the pressure pain tolerance threshold (PTT). For the TSP assessment, ten stimuli at the level of the PTT were delivered by computerised cuff inflations (1-s stimulation, 1-s break) while participants rated pain intensity on a 10-cm electronic visual analogue scale (VAS). This TSP paradigm was then repeated with a simultaneous conditioning stimulus induced by a cuff on the contralateral leg, inflated to a constant pressure corresponding to 30% (mild), 70% (moderate) or 100% (severe) of the PTT. These were assessed in a randomised order, with a fifteen-minute break between tests. A final TSP test without conditioning was reassessed at the end (post-recording).

RESULTS

An interaction between stimuli (1-10) and repetition (p < 0.05) was found for VAS scores. VAS scores for the first stimulus were decreased during 30%, 70%, and 100% conditioning intensities, compared to baseline and post-recordings (p < 0.05). There was a significant increase in TSP during conditioning (p < 0.05). There were no significant differences between baseline and post-recordings for any stimuli (p > 0.05).

CONCLUSIONS

The current study indicates that mild to severe stimuli administered by cuff algometry does not modulate summation effect of temporal summation of pain, which could indicate that pain facilitatory mechanisms are more potent compared with pain inhibitory mechanisms.

SIGNIFICANCE

Current knowledge on the interaction effect of pro and anti-nociceptive paradigms are the lacking. The current study indicates that conditioning pain modulation does not modulate the summation effect of temporal summation of pain, when evaluated by computerized pressure algometry. This finding was independent of the mild, moderate and severe painful conditioning intensities.

Anti-nerve growth factor monoclonal antibodies for the control of pain in dogs and cats

Nerve growth factor (NGF) is essential for the survival of sensory and sympathetic neurons during development. However, in the adult, NGF and its interaction with tropomyosin receptor kinase A receptor (TrkA) has been found to play a critical role in nociception and nervous system plasticity in pain conditions. Thus, various monoclonal antibody (mAb) therapies targeting this pathway have been investigated in the development of new pharmacotherapies for chronic pain. Although none of the mAbs against NGF are yet approved for use in humans, they look very promising for the effective control of pain. Recently, species-specific anti-NGF mAbs for the management of osteoarthritis (OA)-associated pain in dogs and cats has been developed, and early clinical trials have been conducted. Anti-NGF therapy looks to be both very effective and very promising as a novel therapy against chronic pain in dogs and cats. This review outlines the mechanism of action of NGF, the role of NGF in osteoarthritis, research in rodent OA models and the current status of the development of anti-NGF mAbs in humans. Furthermore, we describe and discuss the recent development of species-specific anti-NGF mAbs for the treatment of OA-associated pain in veterinary medicine.

A subgroup analysis to compare patients with acute low back pain classified as per treatment-based classification

OBJECTIVES

The evidence for the effectiveness of interventions targeting acute low back pain (LBP) is suboptimal. It is difficult to identify those patients who are more likely to develop chronic pain and disability after an acute episode of LBP. These shortcomings may be attributed to considering LBP as one homogenous condition.

METHODS

In this quasi-experimental study, we examined and analysed a prospective cohort of 267 patients with first-onset LBP and classified them into one of the groups based on treatment-based classification: direction-specified exercises (Group 2), manipulation (Group 3), stabilization exercises (Group 4), traction (Group 5), and a physician care group (Group 1). Disability and pain were assessed at baseline, after treatment, and at 6 months using the Oswestry Disability Index and the Numerical Rating Scale, respectively. Comparisons were made between the groups, and we predicted measures of disability and pain intensity at 6 months with age, gender, fear avoidance behaviour, centralization phenomenon (CP), expectations about recovery, CP, group classification, baseline pain, and disability.

RESULTS

Analysis showed that all the heterogeneous groups of LBP improved their outcomes with the respective treatment provided. However, when the entire sample was considered as one homogenous group of LBP, the results showed improvement with time (p < 0.05) only and no difference was found between groups (p > 0.05). None of the studied factors, except baseline pain (R = 0.227, R²  = 0.051, p < 0.05), were able to accurately predict the development of chronic pain in our study sample.

CONCLUSION

Though our results showed no differences between the subgroups in the reduction of pain and disability, we conclude that classifying and treating patients with LBP into subgroups based on signs and symptoms produce better outcomes. Baseline pain alone may predict a small percentage of people who may develop chronic pain.

Pain chronification: what should a non-pain medicine specialist know?

OBJECTIVE

Pain is one of the most common reasons for an individual to consult their primary care physician, with most chronic pain being treated in the primary care setting. However, many primary care physicians/non-pain medicine specialists lack enough awareness, education and skills to manage pain patients appropriately, and there is currently no clear, common consensus/formal definition of "pain chronification".

METHODS

This article, based on an international Change Pain Chronic Advisory Board meeting which was held in Wiesbaden, Germany, in October 2016, provides primary care physicians/non-pain medicine specialists with a narrative overview of pain chronification, including underlying physiological and psychosocial processes, predictive factors for pain chronification, a brief summary of preventive strategies, and the role of primary care physicians and non-pain medicine specialists in the holistic management of pain chronification.

RESULTS

Based on currently available evidence, we propose the following consensus-based definition of pain chronification which provides a common framework to raise awareness among non-pain medicine specialists: "Pain chronification describes the process of transient pain progressing into persistent pain; pain processing changes as a result of an imbalance between pain amplification and pain inhibition; genetic, environmental and biopsychosocial factors determine the risk, the degree, and time-course of chronification."

CONCLUSIONS

Early intervention plays an important role in preventing pain chronification and, as key influencers in the management of patients with acute pain, it is critical that primary care physicians are equipped with the necessary awareness, education and skills to manage pain patients appropriately.

Cuff Pressure Algometry in Patients with Chronic Pain as Guidance for Circumferential Tissue Compression for Wearable Soft Exoskeletons: A Systematic Review

In this article, we report on a systematic review of the literature on pressure-pain thresholds induced and assessed by computerized cuff pressure algometry (CPA). The motivation for this review is to provide design guidance on pressure levels for wearable soft exoskeletons and similar wearable robotics devices. In our review, we focus on CPA studies of patients who are candidates for wearable soft exoskeletons, as pain-related physiological mechanisms reportedly differ significantly between healthy subjects and patients with chronic pain. The results indicate that circumferential limb compression in patients most likely becomes painful at ∼10-18 kPa and can become unbearable even below 25 kPa. The corresponding ranges for healthy control subjects are 20-42 kPa (painful limits) and 34-84 kPa (unbearable levels). In addition, the increase of pain with time tends to be significantly higher, and the adaptation to pain significantly lower, than in healthy subjects. The results of this review provide guidance to designers of wearable robotics for populations with chronic pain regarding rates and magnitudes of tissue compression that may be unacceptable to users.

Carpal tunnel syndrome: just a peripheral neuropathy?

Carpal tunnel syndrome (CTS) is considered just a peripheral neuropathy of the upper extremity associated to the compression of the median nerve. There is evidence suggesting the presence of complex sensitization mechanisms in CTS. These processes are manifested by symptoms in extra-median regions and the presence of bilateral sensory and motor impairments. These sensory and motor changes are not associated to electrodiagnostic findings. The presence of sensitization mechanisms suggests that CTS should not be considered just as a peripheral neuropathy. The presence of altered nociceptive gain processing should be considered for therapeutic management of CTS by considering the application of therapeutic interventions that modulate nociceptive barrage into the CNS.

Effects of Chronic Musculoskeletal Pain on Fertility Potential in Lean and Overweight Male Patients

Both chronic pain and obesity are known to affect reproductive hormone profiles in male patients. However, the effect of these conditions, alone or in combination, on male fertility potential has received less attention. 20 chronic musculoskeletal pain patients and 20 healthy controls were divided into lean and overweight subgroups according to their BMI. Current level of chronic pain (visual analogue scale) and pressure pain thresholds (PPTs) in 16 predefined sites, classically described and tested as painful points on the lower body, were measured. Levels of reproductive hormone and lipid profiles were assessed by ELISA. Sperm concentration and motility parameters were analyzed using a computer-aided sperm analysis system. Sperm concentration, progressive motility, and percentage of hyperactivated sperm were generally lower in the chronic pain patients in both lean and overweight groups. The overweight control and the lean chronic pain groups demonstrated a significantly lower percentage of progressively motile sperm compared with the lean control group, suggesting that musculoskeletal chronic pain may have a negative influence on sperm quality in lean patients. However, due to the potential great negative influence of obesity on the sperm parameters, it is difficult to propose if musculoskeletal chronic pain also influenced sperm quality in overweight patients. Further research in chronic pain patients is required to test this hypothesis.

Scapholunate interosseous ligament dysfunction as a source of elbow pain syndromes: Possible mechanisms and implications for hand surgeons and therapists

Elbow pain syndromes are common upper extremity musculoskeletal disorders, and they are usually associated with repetitive occupational exposure. Ligaments are often one of the sources of musculoskeletal disorders because of their mechanical and neurological properties. The wrist ligaments are some of the ligaments most vulnerable to occupational exposure. Since most occupational tasks require wrist extension for handling tools and loading, the scapholunate interosseous ligament (SLIL) bears greater strain during loading, which results in creep deformation and hysteresis. Ligamentous creep may result in diminished ability to detect signal changes during joint movements, which impairs neuromuscular control established by ligamentomuscular reflex arcs elicited from mechanoreceptors in the ligaments. Changes in muscle activation patterns of forearm muscles due to diminished ligamentomuscular reflexes may initiate a positive feedback loop, leading to musculoskeletal pain syndromes. The relationship between elbow pain syndromes and SLIL injury will be presented through two hypotheses and relevant pain mechanisms: 1. Repetitive tasks may cause creep deformation of the SLIL, which then impairs ligamentomuscular reflexes, leading to elbow pain disorders. 2. Lateral epicondylalgia may increase the risk of SLIL injury through the compensation of the lower extensor carpi radialis muscle activity by higher extensor carpi ulnaris muscle activity, which may alter carpal kinematics, leading to SLIL degeneration over time. The differential diagnosis is usually complicated in musculoskeletal pain disorders. The failure of treatment methods is one of the issues of concern for many researchers. A key element in developing treatment strategies is to understand the source of the disorder and the nature of the injury. We proposed that the differential diagnosis include SLIL injuries when describing elbow pain syndromes, particularly, lateral epicondylalgia.

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

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

PERSPECTIVE

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

Ambroxol for the treatment of fibromyalgia: science or fiction?

Fibromyalgia appears to present in subgroups with regard to biological pain induction, with primarily inflammatory, neuropathic/neurodegenerative, sympathetic, oxidative, nitrosative, or muscular factors and/or central sensitization. Recent research has also discussed glial activation or interrupted dopaminergic neurotransmission, as well as increased skin mast cells and mitochondrial dysfunction. Therapy is difficult, and the treatment options used so far mostly just have the potential to address only one of these aspects. As ambroxol addresses all of them in a single substance and furthermore also reduces visceral hypersensitivity, in fibromyalgia existing as irritable bowel syndrome or chronic bladder pain, it should be systematically investigated for this purpose. Encouraged by first clinical observations of two working groups using topical or oral ambroxol for fibromyalgia treatments, the present paper outlines the scientific argument for this approach by looking at each of the aforementioned aspects of this complex disease and summarizes putative modes of action of ambroxol. Nevertheless, at this point the evidence basis for ambroxol is not strong enough for clinical recommendation.

Short stem total hip arthroplasty: Potential explanations for persistent post-surgical thigh pain

Short stem uncemented femoral implants were developed with the aim of preserving proximal bone stock for future revisions, improving biomechanical reconstruction, aiding insertion through smaller incisions and potentially decreasing or limiting the incidence of thigh pain. Despite all the advantages of short stem designs, it remains unclear whether they are able to limit post-surgical thigh pain. In patients with short stem hip arthroplasty and persistent thigh pain, it is of the utmost importance to understand the potential etiologies of this chronic pain for selecting the appropriate treatment strategy. Therefore, this manuscript explores the hypothetical etiologies of persistent thigh pain in short stem total hip arthroplasty, including both peripheral factors (structural or biomechanical causes) and central factors (involvement of the central nervous system). First, intrinsic causes (e.g. aseptic femoral loosening and prosthetic joint infection) and extrinsic sources (e.g. muscle pathology or spinal pathology) of persistent thigh pain related to hip arthroplasty are explained. In addition, other specific peripheral causes for thigh pain related to the short stem prosthetic reconstruction (e.g. stem malalignment and micro-motion) are unraveled. Second, the etiology of persistent thigh pain after short stem hip arthroplasty is interpreted in a broader concept than the biomechanical approach where peripheral structural injury is believed to be the sole driver of persistent thigh pain. Over the past decades evidence has emerged of the involvement of sensitization of central nervous system nociceptive pathways (i.e. central sensitization) in several chronic pain disorders. In this manuscript it is explained that there might be a relevant role for altered central nociceptive processing in patients with persistent pain after joint arthroplasty or revision surgery. Recognition of a potential role for centrally-mediated changes in pain processing in total hip replacement surgery has important implications for treatment. Comprehensive treatment addressing peripheral factors as well as neurophysiological changes occurring in the nervous system may help to improve outcomes in patients with short stem hip arthroplasty and chronic thigh pain. Working within a biopsychosocial approach in orthopaedic surgery, specifically in relation to total hip arthroplasty, could be very important and may lead to more satisfaction. Further research is warranted.

GEDOS-SECOT consensus on the care process of patients with knee osteoarthritis and arthoplasty

OBJECTIVE

To develop recommendations on the evaluation and management procedure in patients undergoing total knee replacement based on best evidence and the experience of a panel of experts.

METHODS

A multidisciplinary group of 12 experts was selected that defined the scope, users and the document parts. Three systematic reviews were performed in patients undergoing knee replacement: (i)efficacy and safety of fast-tracks; (ii)efficacy and safety of cognitive interventions in patients with catastrophic pain, and (iii) efficacy and safety of acute post-surgical pain management on post-surgical outcomes. A narrative review was conducted on the evaluation and management of pain sensitization, and about the efficacy and safety of pre-surgical physiotherapy. The experts generated the recommendations and explicative text. The level of agreement was evaluated in a multidisciplinary group of 85 experts with the Delphi technique. The level of evidence was established as well for each recommendation.

RESULTS

A total of 20 recommendations were produced. An agreement higher than 80% was reached in all of them. We found the highest agreement on the need for a full discharge report, on providing proper information about the process and on following available guidelines.

CONCLUSIONS

There is consensus among professionals involved in the management of patients undergoing total knee replacement, in that it is important to protocolize the replacement process, performing a proper, integrated and coordinated patient evaluation and follow-up, paying special attention to the surgical procedure and postoperative period.

Detection of peripheral and central sensitisation at acupoints in patients with unilateral shoulder pain in Beijing: a cross-sectional matched case-control study

OBJECTIVE

To investigate the pattern of experimental pain responses at acupoints in patients with unilateral shoulder pain.

DESIGN

A cross-sectional matched study.

SETTING

Acupuncture and Moxibustion Department, Beijing Hospital of Traditional Chinese Medicine Affiliated to Capital Medical University.

PARTICIPANTS

Volunteer samples of 60 participants (30 patients with unilateral shoulder pain, 30 healthy controls).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Pressure pain thresholds (PPTs) were measured at four acupoints-namely, Tianzong (SI 11), Jianliao (SJ 14), Jianyu (LI 15) and Jianzhen (SI 9), on the painful/non-painful side in patients with unilateral shoulder pain or healthy controls, respectively. The correlations between the Peripheral Sensitisation Index (PSI) and Central Sensitisation Index (CSI) were compared.

RESULTS

Analysis showed significantly lower PPT values at acupoints on the painful side compared with the non-painful side in patients with shoulder pain (p<0.025). Meanwhile, PPTs on the non-painful side of these patients were lower than those on the ipsilateral side of healthy controls (p<0.025). No significant differences in PPT values were found between the non-acupoint of the painful/non-painful side in patients with shoulder pain and the ipsilateral side of healthy controls (p>0.05). Additionally, it was observed that the pressure pain assessment acupoints have a strong association with PSI and CSI; three acupoints, in particular, SJ 14, LI 15 and SI 9, showed a correlation with PSI and CSI.

CONCLUSION

The results suggest the presence of peripheral and central sensitisation at acupoints in participants with unilateral shoulder pain. There exists an obvious relationship among the three acupoints SJ 14, LI 15 and SI 9, which are usually chosen to treat shoulder pain. The results provide evidence for the selection of acupoints to treat shoulder pain by acupuncture.

Evaluation of Pressure Pain Threshold as a Measure of Perceived Stress and High Job Strain

OBJECTIVE

To investigate whether pressure pain threshold (PPT), determined by pressure algometry, can be used as an objective measure of perceived stress and job strain.

METHODS

We used cross-sectional base line data collected during 1994 to 1995 within the Project on Research and Intervention in Monotonous work (PRIM), which included 3123 employees from a variety of Danish companies. Questionnaire data included 18 items on stress symptoms, 23 items from the Karasek scale on job strain, and information on discomfort in specified anatomical regions was also collected. Clinical examinations included pressure pain algometry measurements of PPT on the trapezius and supraspinatus muscles and the tibia. Associations of stress symptoms and job strain with PPT of each site was analyzed for men and women separately with adjustment for age body mass index, and discomfort in the anatomical region closest to the point of pressure algometry using multivariable linear regression.

RESULTS

We found significant inverse associations between perceived stress and PPT in both genders in models adjusting for age and body mass index: the higher level of perceived stress, the lower the threshold. For job strain, associations were weaker and only present in men. In men all associations were attenuated when adjusting for reported discomfort in regions close to the site of pressure algometry. The distributions of PPT among stressed and non-stressed persons were strongly overlapping.

CONCLUSIONS

Despite significant associations between perceived stress and PPT, the discriminative capability of PPT to distinguish individuals with and without stress is low. PPT measured by pressure algometry seems not applicable as a diagnostic tool of a state of mental stress.

Chronic Osteoporotic Pain in Mice: Cutaneous and Deep Musculoskeletal Pain Are Partially Independent of Bone Resorption and Differentially Sensitive to Pharmacological Interventions

Although the pathological changes in osteoporotic bones are well established, the characterization of the osteoporotic pain and its appropriate treatment are not fully elucidated. We investigated the behavioral signs of cutaneous and deep musculoskeletal pain and physical function; time-dependent changes in bone mineral density (BMD) and the emergence of the behavioral phenotype; and the effects of pharmacological interventions having different mechanisms of action (chronic intraperitoneal administration of pamidronate [0.25 mg/kg, 5x/week for 5 weeks] versus acute treatment with intraperitoneal morphine [10 mg/kg] and pregabalin [100 mg/kg]) in a mouse model of ovariectomized or sham-operated mice 6 months following surgery. We observed reduced BMD associated with weight gain, referred cutaneous hypersensitivity, and deep musculoskeletal pain that persisted for 6 months. Chronic bisphosphonate treatment, 6 months after ovariectomy, reversed bone loss and hypersensitivity to cold, but other behavioral indices of osteoporotic pain were unchanged. While the efficacy of acute morphine on cutaneous pain was weak, pregabalin was highly effective; deep musculoskeletal pain was intractable. In conclusion, the reversal of bone loss alone is insufficient to manage pain in chronic osteoporosis. Additional treatments, both pharmacological and nonpharmacological, should be implemented to improve quality of life for osteoporosis patients.

Intra-articular onabotulinumtoxinA in osteoarthritis knee pain: effect on human mechanistic pain biomarkers and clinical pain

OBJECTIVES

OnabotulinumtoxinA (onabotA) attenuates peripheral nociceptive transduction and consequently neuronal firing. The aim of this mechanistic study was to evaluate the effect of intra-articular (IA) onabotA in patients with painful knee osteoarthritis (OA).

METHOD

We conducted a double-blind, randomized, placebo-controlled, 12-week trial using a single ultrasound-guided IA injection of onabotA (200 U). Patients (N = 121) were randomized to receive onabotA (n = 61) or placebo (n = 60). Mechanistic pain biomarkers and clinical outcomes were used for profiling the effect. The biomarkers were pressure pain thresholds (PPTs) from the knee joint (localized sensitization) and extra-articular sites (widespread sensitization), and wind-up pain (central sensitization). Clinical assessments included the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), average daily pain (ADP), patient global impression of change (GIC), and rescue medication. The painDETECT questionnaire (PD-Q) was used for subgrouping patients (nociceptive, neuropathic, and mixed/uncertain).

RESULTS

The nociceptive and non-nociceptive groups were identical with respect to all baseline data. No significant differences in clinical efficacy parameters were found between onabotA and placebo in the entire population. The nociceptive group showed significant improvement after IA onabotA at week 8 for all WOMAC outcomes, ADP at weeks 9 and 10, and patient GIC at week 12, and significant reduction in rescue medication counts within each 14-day period at weeks 9 and 10. After 4, 8, and 12 weeks, significant correlations were obtained in the onabotA group between ADP (both the entire group and the nociceptive group) and various sensitization parameters. The nociceptive group showed pronounced effects on widespread sensitization.

CONCLUSIONS

Intra-articular onabotA given to patients with nociceptive knee OA reduced pain sensitization together with improvement in pain and function.

ASICs Mediate Pain and Inflammation in Musculoskeletal Diseases

Chronic musculoskeletal pain is debilitating and affects ∼ 20% of adults. Tissue acidosis is present in painful musculoskeletal diseases like rheumatoid arthritis. ASICs are located on skeletal muscle and joint nociceptors as well as on nonneuronal cells in the muscles and joints, where they mediate nociception. This review discusses the properties of different types of ASICs, factors affecting their pH sensitivity, and their role in musculoskeletal hyperalgesia and inflammation.

Cross friction algometry (CFA): Comparison of pressure pain thresholds between patients with chronic non-specific low back pain and healthy subjects

Palpation is widely used to assess muscular sensitivity in clinical settings but still remains a subjective evaluation. This cross-sectional study assessed a newly developed cross-friction algometry making palpation measurable. The objective was to investigate the reliability of pressure pain thresholds obtained using Cross-Friction Algometry (CFA-PPTs) measured at the level of Erector spinae and Gluteus maximus central muscle parts, and to compare the CFA-PPTs between patients with chronic nonspecific low back pain (nCLBP) and matching healthy subjects.

PARTICIPANTS

Patients presenting nCLBP to GP's and send into a Pain Center and healthy subjects recruited via university ad valvas & flyers distribution.

OUTCOME MEASURES

30 patients with nCLBP were measured for cross-friction algometry. Other evaluations consisted of the Visual Analogue Scale (VAS) and the Oswestry Disability Index (ODI).

RESULTS

The inter- and intra-reliability were tested and found to be sufficient. The mean CFA-PPT values of the Erector spinae at levels T8, T10, L1 & L3 and the Gluteus maximus of the nCLBP group were significantly lower (p ≤ 0.001) when compared to the CFA-PPT values of the healthy group. The greatest difference (-58%) was found at L1 Erector spinae level and at the superior part of the Gluteus maximus measuring point (-59%). Within the group of patients with nCLBP it was surprising to notice that there was no significant correlation between all the reference points measured using CFA-PPTs and the outcomes of the VAS and ODI scores.

CONCLUSIONS

With the aid of CFA, the importance of local muscular disorder in the lumbar part of the Erector spinae and Gluteus maximus in patients with nCLBP is obviously demonstrated, but also reveals the very large inter-individual differences in muscular fibrosis sensitivity and/or pain behavior in daily life. This possibly re-opens the debate on which influences can be put forward as the most important: the central or the peripheral sensitization system.

Chronic postoperative pain after primary and revision total knee arthroplasty

OBJECTIVES

Clinical experience suggests that patients with osteoarthritis (OA) undergoing revision total knee arthroplasty (TKA) experience more chronic complications after surgery compared with patients receiving primary TKA. This study aimed to investigate the difference in pain, mobility, and quality of life (QoL) in patients after revision TKA compared with patients after primary TKA.

METHODS

A total of 99 OA patients after revision TKA surgery and 215 patients after primary TKA surgery were investigated in a cross-sectional study using: a pain description of current pain (non-existent, mild, moderate, severe, or unbearable), the pain intensity visual analogue scale, the Knee Society Score, and the Osteoarthritis Research Society International questionnaire.

RESULTS

Nineteen percent after primary TKA surgery and 47% after revision TKA surgery experienced severe to unbearable chronic postoperative pain. After revision TKA surgery patients reported higher pain intensities during rest (P=0.039), while walking (P=0.008), and on average over the last 24 hours (P=0.050) compared with the patients after primary TKA surgery. Patients after revision TKA surgery had reduced walking distance (P=0.001), increased use of walking aids (P=0.015), and showed an overall decreased QoL (P<0.001) compared with patients after primary TKA surgery. No significant improvement was found in walking distance (P=0.448) for patients before revision TKA surgery compared with after revision TKA surgery.

DISCUSSION

More than twice as many patients have pain after revision surgery compared with patients after primary TKA. Patients after revision TKA surgery have reduced function, poorer QoL, and higher pain intensity compared with patients after primary TKA surgery.

The role of sensitization in musculoskeletal shoulder pain

INTRODUCTION

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

METHOD

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

RESULTS

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

DISCUSSION

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

Altered Central Sensitization and Pain Modulation in the CNS in Chronic Joint Pain

Musculoskeletal pain disorders are the second largest contributor to global disability underlining the significance of effective treatments. However, treating chronic musculoskeletal pain, and chronic joint pain (osteoarthritis (OA)) in particular, is challenging as the underlying peripheral and central pain mechanisms are not fully understood, and safe and efficient analgesic drugs are not available. The pain associated with joint pain is highly individual, and features from radiological imaging have not demonstrated robust associations with the pain manifestations. In recent years, a variety of human quantitative pain assessment tools (quantitative sensory testing (QST)) have been developed providing new opportunities for profiling patients and reaching a greater understanding of the mechanisms involved in chronic joint pain. As joint pain is a complex interaction between many different pain mechanisms, available tools are important for patent profiling and providing the basic knowledge for development of new drugs and for developing pain management regimes.

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

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

The common link between functional somatic syndromes may be central sensitisation

OBJECTIVES

Functional somatic syndromes are common and disabling conditions that all include chronic pain, and which may be related to central nervous system sensitisation. Here, we address the concept of central sensitisation as a physiological basis for the functional somatic syndromes.

METHODS

A narrative review of the current literature on central sensitisation and physiological studies in the functional somatic syndromes.

RESULTS

Central sensitisation may be a common neurophysiological process that is able to explain non-painful as well as painful symptoms in these disorders. Furthermore, central sensitisation may represent an endophenotypic vulnerability to the development of these syndromes that potentially explains why they cluster together.

CONCLUSIONS

Further research is needed to verify these findings, including prospective studies and the standardisation of combined methods of investigation in the study of central sensitisation in functional somatic syndromes. In turn, this may lead to new explanatory mechanisms and treatments being evaluated. Our conclusions add to the debate over the nomenclature of these syndromes but importantly also provide an explanation for our patients.

Stem cells for the treatment of musculoskeletal pain

Musculoskeletal-related pain is one of the most disabling health conditions affecting more than one third of the adult population worldwide. Pain from various mechanisms and origins is currently underdiagnosed and undertreated. The complexity of molecular mechanisms correlating pain and the progression of musculoskeletal diseases is not yet fully understood. Molecular biomarkers for objective evaluation and treatment follow-up are needed as a step towards targeted treatment of pain as a symptom or as a disease. Stem cell therapy is already under investigation for the treatment of different types of musculoskeletal-related pain. Mesenchymal stem cell-based therapies are already being tested in various clinical trials that use musculoskeletal system-related pain as the primary or secondary endpoint. Genetically engineered stem cells, as well as induced pluripotent stem cells, offer promising novel perspectives for pain treatment. It is possible that a more focused approach and reassessment of therapeutic goals will contribute to the overall efficacy, as well as to the clinical acceptance of regenerative medicine therapies. This article briefly describes the principal types of musculoskeletal-related pain and reviews the stem cell-based therapies that have been specifically designed for its treatment.

Roles of ASIC3, TRPV1, and NaV1.8 in the transition from acute to chronic pain in a mouse model of fibromyalgia

Background

Tissue acidosis is effective in causing chronic muscle pain. However, how muscle nociceptors contribute to the transition from acute to chronic pain is largely unknown.

Results

Here we showed that a single intramuscular acid injection induced a priming effect on muscle nociceptors of mice. The primed muscle nociceptors were plastic and permitted the development of long-lasting chronic hyperalgesia induced by a second acid insult. The plastic changes of muscle nociceptors were modality-specific and required the activation of acid-sensing ion channel 3 (ASIC3) or transient receptor potential cation channel V1 (TRPV1). Activation of ASIC3 was associated with increased activity of tetrodotoxin (TTX)-sensitive voltage-gated sodium channels but not protein kinase Cϵ (PKCϵ) in isolectin B4 (IB4)-negative muscle nociceptors. In contrast, increased activity of TTX-resistant voltage-gated sodium channels with ASIC3 or TRPV1 activation in Na_V1.8-positive muscle nociceptors was required for the development of chronic hyperalgesia. Accordingly, compared to wild type mice, Na_V1.8-null mice showed briefer acid-induced hyperalgesia (5 days vs. >27 days).

Conclusion

ASIC3 activation may manifest a new type of nociceptor priming in IB4-negative muscle nociceptors. The activation of ASIC3 and TRPV1 as well as enhanced Na_V1.8 activity are essential for the development of long-lasting hyperalgesia in acid-induced, chronic, widespread muscle pain.

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

BACKGROUND

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

OBJECTIVE

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

DESIGN

A cross-sectional design was used.

METHODS

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

RESULTS

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

LIMITATIONS

The cross-sectional design was a limitation.

CONCLUSIONS

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