Mechanisms and manifestations in musculoskeletal pain: from experimental to clinical pain settings

Yoga, Physical Therapy and Home Exercise Effects on Chronic Low Back Pain: Pain Perception, Function, Stress, and Quality of Life in a Randomized Trial

Low back pain is a common health problem. In this study, we investigated the effects of yoga, physical therapy (PT), and home exercise (HE) on pain perception, function, stress, and quality of life in chronic low back pain (cLBP). We randomly assigned 54 participants to three distinct treatment groups: (a) a physical therapy group (PT) who received spinal stabilization exercises (SSE) combined with local heat and transcutaneous electrical stimulation; (b) a home exercise group (HE) who received SSE as part of the home program; and (c) a yoga group who received yoga exercises. The primary outcome measures were a Visual Analog Scale (VAS) for measuring pain, and the Oswestry Disability Index (ODI) to measure function. Secondary outcome measures were the Tampa Kinesiophobia Scale (TKS), Central Sensitization Inventory (CSI), pain sensitivity (L3 and deltoid R/L PPTs), Spielberger State-Trait Anxiety Inventory (STAI), plasma cortisol and DHEA-S levels, Transversus Abdominis (TrA) muscle activation, and the Nottingham Health Profile (NHP). Assessments were conducted before and after a six-week intervention period. All three groups demonstrated improvements in pain on the VAS, function on the ODI, pain sensitivity on the L3 and deltoid R/L PPTs, CSI, anxiety on the STAI, TrA muscle activation, and quality of life on the NHP (p < .05). The PT group exhibited a more pronounced improvement on the ODI score (p < .05) than the other groups. Cortisol levels only decreased in the PT group (p < .05). The exercises did not impact DHEA-S and NHP-S parameters. Thus, all interventions resulted in decreased stress, pain intensity, pain sensitivity, central sensitization, and improved function and quality of life; there was no singularly superior approach between interventions. These findings will aid in tailoring treatment programs for managing cLBP according to individual needs.

Quantitative Sensory Testing - From bench to bedside

The methodology of Quantitative Sensory Testing (QST) comprises standardized testing procedures, which provide information of the integrity of the somatosensory nervous system. Over the years, different protocols have been established, which utilize similar but distinct testing procedures. They pursue the same overall objective to identify loss or gain of function of the respective sensory parameter to better understand the degree of abnormal nervous function and thereby improve patient care in the long-term. Laboratory-based QST protocols, which apply highly standardized testing procedures in pre-defined order and body regions, are considered as the gold standard in sensory testing. However, those protocols often require specifically trained personal, high equipment investment, and are time consuming. Thus, in recent years several attempts have been made to simplify testing protocols as well as reduce high costs of testing equipment such as thermal probe systems. These attempts have culminated in an array of sensory bedside testing protocols subserving the need for protocols that are easy to implement in and provide a standardized assessment within clinical trials. While laboratory and bedside QST that focus on static responses of single stimuli, protocols for testing dynamic QST focus on the functional response to pain also exist. Conditioned pain modulation (CPM) is often applied, which offers the ability to study endogenous inhibition of pain. All of these mentioned methodologies are considered as psychophysical measures and thus rely heavily on the cooperation of the patient or participant. In this chapter we provide an overview of QST along three main lines: (i) laboratory QST, (ii) bedside QST and (iii) dynamic QST. In addition, we discuss advantages and pitfalls of each modality. While we discuss along these lines, it should be noted that methodologies are overlapping: some bedside tests are similar or identical to lab-QST, many lab-QST protocols include a dynamic component, and assessment of dynamic QST requires to start with static assessments.

Spatiotemporal characterization of an experimental model of muscle pain in humans based on short-wave diathermy

BACKGROUND

Commonly used models for eliciting muscle pain involve the injection of algesic substances or the induction of delayed onset muscle soreness. The former require invasive procedures, and the time frame for pain induction and subsidence in the latter can be inconvenient. This study presents a detailed spatiotemporal characterization of a new experimental model of muscle pain based on short-wave diathermy (SWD), developed to overcome the limitations of existing models.

METHODS

The shoulder was selected as target site and the effects of the model were tested in two sessions to assess its reliability. Pain intensity profiles were recorded during the application of SWD, and changes in pressure pain threshold (PPT) in the infraspinatus muscle, together with pain intensity, duration, and quality were assessed 30 min after induction.

RESULTS

SWD-induced pain intensity scores averaged 4 points on a visual analogue scale, whereas PPT showed a consistent decrease of about 25% relative to baseline values. Pain was localized in the shoulder area, and was described as continuous, dull, well-delimited, heavy, and bearable. Pain lasted for an average of 145 min without requiring reinduction and was reliably elicited in both experimental sessions.

CONCLUSION

SWD can be used to elicit experimental muscle pain in a non-invasive, long-lasting, and reliable way and allows for repeated within- and between-session testing in the shoulder.

SIGNIFICANCE STATEMENT

SWD produces deep heating in muscles by converting electromagnetic energy to thermal energy. It was previously shown that it can be used to elicit experimental pain in the forearm muscles, and the present study demonstrates that this can be reliably generalized to other body sites, such as the shoulder. Furthermore, SWD application is non-invasive and presents a convenient time frame for pain induction and subsidence, thus overcoming limitations associated with traditional muscle pain models.

Assessing Pain Levels Using Bioelectrical Impedance in Low Back Pain Patients: Clinical Performance Evaluation

BACKGROUND/OBJECTIVES

Musculoskeletal pain is one of the leading causes of years lived with disability worldwide and has a negative impact on daily life and quality of life.

METHODS

The purpose of this study was to analyze the electrical characteristics of back pain by measuring and calculating bioelectrical impedance variables (R, Z, PA) in 85 subjects (45 in the Healthy group and 40 in the LBP group). Additionally, impedance measurements were conducted on 20 subjects (10 in the Young group and 10 in the Older group) to assess the impact of aging.

RESULTS

Bioelectrical impedance parameter values were higher in cases of back pain, and correlation analysis showed that there was a statistically significant difference between the Healthy and LBP groups (p < 0.05). A positive correlation was found between impedance parameters and pain related indices (ODI, RMDQ, VAS) (mean R, Z, PA: 0.68, 0.54, 0.75), with BMI positively correlating only with PA (0.493). Diagnostic accuracy for detecting back pain exceeded 95% (R, Z, PA: 0.984, 0.984, 0.963).

CONCLUSIONS

Results indicated that aging did not significantly affect impedance values. The bioelectrical impedance measurement device used in this study, with its simultaneous diagnostic and therapeutic capabilities, proved useful for real-time pain diagnosis and treatment monitoring, highlighting its potential clinical utility.

Automated Pain Spots Recognition Algorithm Provided by a Web Service-Based Platform: Instrument Validation Study

Background

Understanding the causes and mechanisms underlying musculoskeletal pain is crucial for developing effective treatments and improving patient outcomes. Self-report measures, such as the Pain Drawing Scale, involve individuals rating their level of pain on a scale. In this technique, individuals color the area where they experience pain, and the resulting picture is rated based on the depicted pain intensity. Analyzing pain drawings (PDs) typically involves measuring the size of the pain region. There are several studies focusing on assessing the clinical use of PDs, and now, with the introduction of digital PDs, the usability and reliability of these platforms need validation. Comparative studies between traditional and digital PDs have shown good agreement and reliability. The evolution of PD acquisition over the last 2 decades mirrors the commercialization of digital technologies. However, the pen-on-paper approach seems to be more accepted by patients, but there is currently no standardized method for scanning PDs.

Objective

The objective of this study was to evaluate the accuracy of PD analysis performed by a web platform using various digital scanners. The primary goal was to demonstrate that simple and affordable mobile devices can be used to acquire PDs without losing important information.

Methods

Two sets of PDs were generated: one with the addition of 216 colored circles and another composed of various red shapes distributed randomly on a frontal view body chart of an adult male. These drawings were then printed in color on A4 sheets, including QR codes at the corners in order to allow automatic alignment, and subsequently scanned using different devices and apps. The scanners used were flatbed scanners of different sizes and prices (professional, portable flatbed, and home printer or scanner), smartphones with varying price ranges, and 6 virtual scanner apps. The acquisitions were made under normal light conditions by the same operator.

Results

High-saturation colors, such as red, cyan, magenta, and yellow, were accurately identified by all devices. The percentage error for small, medium, and large pain spots was consistently below 20% for all devices, with smaller values associated with larger areas. In addition, a significant negative correlation was observed between the percentage of error and spot size (R=-0.237; P=.04). The proposed platform proved to be robust and reliable for acquiring paper PDs via a wide range of scanning devices.

Conclusions

This study demonstrates that a web platform can accurately analyze PDs acquired through various digital scanners. The findings support the use of simple and cost-effective mobile devices for PD acquisition without compromising the quality of data. Standardizing the scanning process using the proposed platform can contribute to more efficient and consistent PD analysis in clinical and research settings.

Conditioned Pain Modulation and Temporal Summation of Pain in Patients With Traumatic and Non-Specific Neck Pain: A Systematic Review and Meta-Analysis

In patients with neck pain, it is unclear whether pain inhibition and facilitation endogenous pain mechanisms are altered. This systematic review and meta-analysis aimed to improve their understanding by assessing conditioned pain modulation (CPM) and temporal summation of pain (TSP) in patients with neck pain associated with whiplash-associated disorders (WAD) or of a nonspecific neck pain (NSNP) nature compared to pain-free controls. Very low certainty evidence suggests: impaired CPM when assessed remotely in chronic WAD patients (n = 7, 230 patients and 204 controls, standardized mean differences (SMD) = -.47 [-.89 to -.04]; P = .04) but not locally (n = 6, 155 patients and 150 controls; SMD = -.34 [-.68 to .01]; P = .05), impaired CPM in chronic NSNP patients when assessed locally (n = 5, 223 patients and 162 controls; SMD = -.55 [-1.04 to -.06]; P = .04) but not remotely (n = 3, 72 patients and 66 controls; SMD = -.33 [-.92 to .25]; P = .13), TSP not facilitated in either chronic WAD (local TSP: n = 4, 90 patients and 87 controls; SMD = .68 [-.62 to 1.99]) (remote TSP: n = 8, 254 patients and 214 controls; SMD = .18 [-.12 to .48]) or chronic NSNP (local TSP: n = 2, 139 patients and 92 controls; SMD = .21 [-1.00 to 1.41]), (remote TSP: n = 3; 91 patients and 352 controls; SMD = .60 [-1.33 to 2.52]). The evidence is very uncertain whether CPM is impaired and TSP facilitated in patients with WAD and NSNP. PERSPECTIVE: This review and meta-analysis present the current evidence on CPM and TSP in patients with WAD and NSNP. Standardization of measurement methodology is needed to draw clear conclusions. Subsequently, future studies should investigate the clinical relevance of these measurements as prognostic variables or predictors of treatment success.

Referred sensations in the orofacial region are associated with a decreased descending pain inhibition and modulated by remote noxious stimuli and local anesthesia

ABSTRACT

Referred sensation (RS) as a specific clinical phenomenon has been known for a long time, although the underlying mechanisms remain unclear. The aims of this study were to assess if (1) healthy individuals who experienced RS had a less active endogenous pain system when compared with those who did not; (2) activation of descending pain inhibition mechanisms can modulate RS parameters; and finally, (3) a transient decrease in peripheral afferent input because of a local anesthetic (LA) block in the masseter muscle can modulate RS parameters. To assess these, 50 healthy participants were assessed in 3 different sessions. In the first session, conditioned pain modulation (CPM) as well as mechanical sensitivity and RS at the masseter muscle were assessed. In the same session, participants who experienced RS had their mechanical sensitivity and RS assessed again while undergoing a CPM protocol. In the second and third sessions, participants had their mechanical sensitivity and RS assessed before and after receiving an injection of 2 mL of LA and isotonic saline into the masseter muscle. The main findings of this study were (1) participants who experienced RS during standardized palpation exhibited increased mechanical sensitivity ( P < 0.05, Tukey post hoc test) and decreased CPM ( P < 0.05, Tukey post hoc test) when compared with those who did not; RS incidence ( P < 0.05, Cochran Q test), frequency ( P < 0.05; Friedman test), intensity ( P < 0.05, Tukey post hoc test), and area ( P < 0.05, Tukey post hoc test) were all significantly reduced when assessed (2) during a painful conditioning stimulus and (3) after LA block. These novel findings highlight that RS in the orofacial region are strongly modified by both peripheral and central nervous system factors.

Mechanisms of chiropractic spinal manipulative therapy for patients with chronic primary low back pain: protocol for a mechanistic randomised placebo-controlled trial

INTRODUCTION

Chronic low back pain (CLBP) is a highly prevalent and disabling condition. Identifying subgroups of patients afflicted with CLBP is a current research priority, for which a classification system based on pain mechanisms was proposed. Spinal manipulative therapy (SMT) is recommended for the management of CLBP. Yet, little data are available regarding its mechanisms of action, making it difficult to match this intervention to the patients who may benefit the most. It was suggested that SMT may influence mechanisms associated with central sensitisation. Therefore, classifying patients with CLBP according to central sensitisation mechanisms may help predict their response to SMT.

METHODS AND ANALYSIS

This protocol describes a randomised placebo-controlled trial aiming to examine which variables linked to central sensitisation may help predict the clinical response to SMT in a cohort of patients with CLBP. One hundred patients with chronic primary low back pain will be randomised to receive 12 sessions of SMT or placebo SMT over a 4-week period. Pain intensity and disability will be assessed as primary outcomes after completing the 4-week treatment (primary endpoint), and at 4-week and 12-week follow-ups. Baseline values of two pain questionnaires, lumbar pressure pain thresholds, concentrations of an inflammatory cytokine and expectations of pain relief will be entered as predictors of the response to SMT in a multiple regression model. Changes in these variables after treatment will be used in a second multiple regression model. The reference values of these predictors will be measured from 50 age and sex-matched healthy controls to allow interpretation of values in patients. Mixed analyses of variance will also be conducted to compare the primary outcomes and the predictors between groups (SMT vs placebo) over time (baseline vs post-treatment).

ETHICS AND DISSEMINATION

Ethical approval was granted by the Fundación Jiménez Díaz Clinical Research Ethics Committee.

TRIAL REGISTRATION NUMBER

NCT05162924.