Restoration of normal central pain processing following manual therapy in nonspecific chronic neck pain

OBJECTIVE

To determine if a 4-week manual therapy treatment restores normal functioning of central pain processing mechanisms in non-specific chronic neck pain (NSCNP), as well as the existence of a possible relationship between changes in pain processing mechanisms and clinical outcome.

DESIGN

Cohort study.

METHODS

Sixty-three patients with NSCNP, comprising 79% female, with a mean age of 45.8 years (standard deviation: 14.3), received four treatment sessions (once a week) of manual therapy including articular passive mobilizations, soft tissue mobilization and trigger point treatment. Pressure pain thresholds (PPTs), conditioned pain modulation (CPM) and temporal summation of pain (TSP) were evaluated at baseline and after treatment completion. Therapy outcome was measured using the Global Rating of Change Scale (GROC), the Neck disability Index (NDI), intensity of pain during the last 24 hours, Tampa Scale of Kinesiophobia (TSK) and Pain Catastrophizing Scale (PCS). Two sets of generalized linear mixed models with Gaussian response and the identity link were employed to evaluate the effect of the intervention on clinical, psychological and psychophysical measures and the association between psychophysical and clinical outcomes.

RESULTS

Following treatment, an increased CPM response (Coefficient: 0.89; 95% credibility interval = 0.14 to 1.65; P = .99) and attenuated TSP (Coefficient: -0.63; 95% credibility interval = -0.82 to -0.43; P = 1.00) were found, along with amelioration of pain and improved clinical status. PPTs at trapezius muscle on the side of neck pain were increased after therapy (Coefficient: 0.22; 95% credibility interval = 0.03 to 0.42; P = .98), but not those on the contralateral trapezius and tibialis anterior muscles. Only minor associations were found between normalization of TSP/CPM and measures of clinical outcome.

CONCLUSION

Clinical improvement after manual therapy is accompanied by restoration of CPM and TSP responses to normal levels in NSCNP patients. The existence of only minor associations between changes in central pain processing and clinical outcome suggests multiple mechanisms of action of manual therapy in NSCNP.

An international consensus on gaps in mechanisms of forced-based manipulation research: findings from a nominal group technique

Force-Based Manipulation (FBM) including light touch, pressure, massage, mobilization, thrust manipulation, and needling techniques are utilized across several disciplines to provide clinical analgesia. These commonly used techniques demonstrate the ability to improve pain-related outcomes; however, mechanisms behind why analgesia occurs with these hands-on interventions has been understudied. Neurological, neuroimmune, biomechanical, neurovascular, neurotransmitter, and contextual factor interactions have been proposed to influence response; however, the specific relationships to clinical pain outcomes has not been well established. The purpose of this study was to identify gaps present within mechanism-based research as it relates to FBM. An international multidisciplinary nominal group technique (NGT) was performed and identified 37 proposed gaps across eight domains. Twenty-three of these gaps met consensus across domains supporting the complex multisystem mechanistic response to FBM. The strength of support for gaps within the biomechanical domain had less overall support than the others. Gaps assessing the influence of contextual factors had strong support as did those associating mechanisms with clinical outcomes (translational studies). The importance of literature investigating how FBM differs with individuals of different pain phenotypes (pain mechanism phenotypes and clinical phenotypes) was also presented aligning with other analgesic techniques trending toward patient-specific pain management (precision medicine) through the use of pain phenotyping.

An overview of systematic reviews examining the quantitative sensory testing-derived hypoalgesic effects of manual therapy for musculoskeletal pain

BACKGROUND

Changes in quantitative sensory testing (QST) after manual therapy can provide insight into pain relief mechanisms. Prior systematic reviews have evaluated manual-therapy-induced QST change. This overview of systematic reviews aims to consolidate this body of literature and critically review evidence on the hypoalgesic effects of manual therapy in clinical populations.

METHODS

A comprehensive search was conducted on PubMed, CINAHL, PsycInfo, and Embase. Peer-reviewed systematic reviews with or without meta-analysis were eligible if the reviews examined the effect of manual therapy compared to non-manual therapy interventions on QST outcomes in clinical populations. Methodological quality was assessed with the AMSTAR 2 tool. Meta-analysis results and qualitative (non-meta-analysis) interpretations were summarized by type of manual therapy. Overlap of studies was examined with the corrected covered area (CCA) index.

RESULTS

Thirty systematic reviews, including 11 meta-analyses, met inclusion. There was a slight overlap in studies (CCA of 1.72% for all reviews and 1.69% for meta-analyses). Methodological quality was predominantly low to critically low. Eight (27%) reviews examined studies with a range of manual therapy types, 13 (43%) reviews focused on joint-biased manual therapy, 7 (23%) reviews focused on muscle-biased manual therapy, and 2 (7%) reviews focused on nerve-biased manual therapy. Twenty-nine (97%) reviews reported on pressure pain threshold (PPT). Meta-analytic results demonstrated conflicting evidence that manual therapy results in greater hypoalgesic effects compared to other interventions or controls.

CONCLUSION

Our overview of QST effects, which has relevance to mechanisms underlying hypoalgesia, shows conflicting evidence from mostly low to critically low systematic reviews.

Biopsychosocial contributors to irritability in individuals with shoulder or low back pain

OBJECTIVES

Irritability is a foundational clinical reasoning concept in rehabilitation to evaluate reactivity of the examination and treatment. While originally theorized to reflect tissue damage, a large body of evidence supports pain is a biopsychosocial experience impacted by pain sensitivity and psychological factors. Therefore, the purpose of this study was to examine biopsychosocial contributors to irritability.

METHODS

40 patients with shoulder (n = 20) and low back (n = 20) pain underwent Quantitative Sensory Testing (QST) (Pressure Pain Threshold, Heat Pain Threshold, Conditioned Pain Modulation, Temporal Summation), completed pain-related psychological questionnaires, an Exercise-Induced Hypoalgesia protocol, and standardized irritability assessment based on Clinical Practice Guidelines. Participants were then categorized as irritable or not irritable based on Maitland's criteria and by irritability level based on Clinical Practice Guidelines. An independent samples t-test examined for differences in QST and psychological factors by irritability category. A MANOVA examined for differences in QST and psychological factors by irritability level (high, moderate, low).

RESULTS

Significantly lower heat and pressure pain thresholds at multiple locations (p < 0.05), as well as less efficient conditioned pain modulation (p = 0.02), were demonstrated in individuals categorized as irritable. Heat and pressure pain thresholds were also significantly lower in patients with high irritability compared to other levels. Significantly higher depression and anger, as well as lower self-efficacy, were reported in individuals with an irritable presentation.

DISCUSSION/CONCLUSION

Biopsychosocial factors, including widespread hyperalgesia and elevated psychological factors, may contribute to an irritable presentation.

An international consensus definition for contextual factors: findings from a nominal group technique

Objective

Emerging literature suggests contextual factors are important components of therapeutic encounters and may substantially influence clinical outcomes of a treatment intervention. At present, a single consensus definition of contextual factors, which is universal across all health-related conditions is lacking. The objective of this study was to create a consensus definition of contextual factors to better refine this concept for clinicians and researchers.

Design

The study used a multi-stage virtual Nominal Group Technique (vNGT) to create and rank contextual factor definitions. Nominal group techniques are a form of consensus-based research, and are beneficial for identifying problems, exploring solutions and establishing priorities.

Setting

International.

Main outcome measures

The initial stages of the vNGT resulted in the creation of 14 independent contextual factor definitions. After a prolonged discussion period, the initial definitions were heavily modified, and 12 final definitions were rank ordered by the vNGT participants from first to last.

Participants

The 10 international vNGT participants had a variety of clinical backgrounds and research specializations and were all specialists in contextual factors research.

Results

A sixth round was used to identify a final consensus, which reflected the complexity of contextual factors and included three primary domains: (1) an overall definition; (2) qualifiers that serve as examples of the key areas of the definition; and (3) how contextual factors may influence clinical outcomes.

Conclusion

Our consensus definition of contextual factors seeks to improve the understanding and communication between clinicians and researchers. These are especially important in recognizing their potential role in moderating and/or mediating clinical outcomes.

Expectations affect pain sensitivity changes during massage

BACKGROUND

Pain-inducing massage produces comparable changes in pain sensitivity as a cold pressor task, suggesting shared neurophysiological mechanisms of conditioned pain modulation. Manual therapy and conditioned pain modulation are influenced by positive and negative expectations. Therefore, the purpose of this study was to examine the effects of positive and negative expectations on pain-free and pain-inducing massage.

METHODS

56 healthy participants were randomly assigned to receive a positive or negative expectation instructional set followed by a pain-inducing or a pain-free massage. Pressure pain threshold (PPT) was measured followed by each interval of massage. A repeated measures ANCOVA controlling for post-randomization differences in sex tested for massage x expectation set x PPT interaction effects, as well as two-way interaction effects.

RESULTS

A significant three-way interaction effect (p = 0.04) and time x expectation interaction effect was observed for individuals receiving pain inducing massage (p = 0.02). Individuals who received the positive expectation instructional set demonstrated significantly higher PPT at minutes 3 and 4 of massage compared to individuals who received the negative expectation instructional set.

CONCLUSIONS

Expectations impact pain sensitivity changes produced during massage. Clinicians planning to provide pain-inducing massage should consider the role of expectations in modulating pain sensitivity changes.

Pain phenotyping and investigation of outcomes in physical therapy: An exploratory study in patients with low back pain

Phenotypes have been proposed as a method of characterizing subgroups based on biopsychosocial factors to identify responders to analgesic treatments. This study aimed to, first, confirm phenotypes in patients with low back pain receiving physical therapy based on an a priori set of factors used to derive subgroups in other pain populations. Second, an exploratory analysis examined if phenotypes differentiated pain and disability outcomes at four weeks of physical therapy. Fifty-five participants completed psychological questionnaires and pressure pain threshold (PPT). Somatization, anxiety, and depression domains of the Symptom-Checklist-90-Revised, and PPT, were entered into a hierarchical agglomerative cluster analysis with Ward's method to identify phenotypes. Repeated measures ANOVAs assessed pain ratings and disability by phenotype at four weeks. Three clusters emerged: 1) high emotional distress and pain sensitivity (n = 10), 2) low emotional distress (n = 34), 3) low pain sensitivity (n = 11). As an exploratory study, clusters did not differentiate pain ratings or disability after four weeks of physical therapy (p's>0.05). However, trends were observed as magnitude of change for pain varied by phenotype. This supports the characterization of homogenous subgroups based on a protocol conducted in the clinical setting with varying effect sizes noted by phenotype for short-term changes in pain. As an exploratory study, future studies should aim to repeat this trial in a larger sample of patients.

Characteristics and Outcomes of Patients Receiving Physical Therapy for Low Back Pain with a Nociplastic Pain Presentation: A Secondary Analysis

Introduction

Individuals with low back pain (LBP) may be classified based on mechanistic descriptors, such as a nociplastic pain presentation (NPP). The purpose of this secondary analysis was to examine the frequency and characteristics of patients with a NPP referred to physical therapy with LBP. Additionally, we characterized patients with LBP meeting the criteria for NPP by demographic, clinical, psychological, and pain sensitivity variables. Finally, we examined short- and long-term clinical outcomes in patients with a NPP compared to those without a NPP.

Materials and Methods

Patients referred to physical therapy for LBP completed the Patient Self-report Survey for the Assessment of Fibromyalgia. Participants were categorized as "LBP with NPP" or "LBP without NPP" based on the threshold established in this measure. A rank sum test examined for differences in pain-related psychological factors and pressure-pain threshold between groups. Next, a Friedman test examined if LBP intensity and disability trajectories differed by groups at one and six months after initiation of physical therapy.

Results

22.2% of patients referred to physical therapy for LBP met the criteria for a NPP. Patients with a NPP reported significantly greater disability, pain catastrophizing, depression, anxiety, and somatization compared to individuals without a NPP (p < 0.05). Pressure-pain threshold did not differ between groups (p > 0.05). Individuals with LBP with a NPP demonstrated nonsignificant, small to medium reductions in pain and disability at one and six months. Individuals experiencing LBP without a NPP demonstrated significant reductions in pain and disability in the short- and long term.

Conclusion

Patients with LBP with a NPP displayed greater negative pain-related psychological factors but similar pain sensitivity compared to LBP without NPP.

Experimental Pain Phenotype Profiles in Community-dwelling Older Adults

OBJECTIVES

Pain sensitivity and the brain structure are critical in modulating pain and may contribute to the maintenance of pain in older adults. However, a paucity of evidence exists investigating the link between pain sensitivity and brain morphometry in older adults. The purpose of the study was to identify pain sensitivity profiles in healthy, community-dwelling older adults using a multimodal quantitative sensory testing protocol and to differentiate profiles based on brain morphometry.

MATERIALS AND METHODS

This study was a secondary analysis of the Neuromodulatory Examination of Pain and Mobility Across the Lifespan (NEPAL) study. Participants completed demographic and psychological questionnaires, quantitative sensory testing, and a neuroimaging session. A Principal Component Analysis with Varimax rotation followed by hierarchical cluster analysis identified 4 pain sensitivity clusters (the "pain clusters").

RESULTS

Sixty-two older adults ranging from 60 to 94 years old without a specific pain condition (mean [SD] age=71.44 [6.69] y, 66.1% female) were analyzed. Four pain clusters were identified characterized by (1) thermal pain insensitivity; (2) high pinprick pain ratings and pressure pain insensitivity; (3) high thermal pain ratings and high temporal summation; and (4) thermal pain sensitivity, low thermal pain ratings, and low mechanical temporal summation. Sex differences were observed between pain clusters. Pain clusters 2 and 4 were distinguished by differences in the brain cortical volume in the parieto-occipital region.

DISCUSSION

While sufficient evidence exists demonstrating pain sensitivity profiles in younger individuals and in those with chronic pain conditions, the finding that subgroups of experimental pain sensitivity also exist in healthy older adults is novel. Identifying these factors in older adults may help differentiate the underlying mechanisms contributing to pain and aging.

The healthcare buffet: preferences in the clinical decision-making process for patients with musculoskeletal pain

The preferences a person has for care are associated with outcomes for patients presenting with musculoskeletal pain conditions. These include preferences for differing levels of involvement in the decision-making process, preferences for the provider attributes, and preferences for particular interventions. In this paper, we discuss these various forms of preference, as well as how they influence clinical care within shared decision-making frameworks. We also present a conceptual framing for how patient preferences can be incorporated in clinical decision-making by orthopedic manual physical therapists. Finally, research implications for interpreting findings from clinical studies are discussed.

A psychophysical study comparing massage to conditioned pain modulation: A single blind randomized controlled trial in healthy participants

INTRODUCTION

Pain-inducing massage results in greater pain inhibition than pain free massage, suggesting a mechanism dependent on conditioned pain modulation (CPM). The purpose of this study was to test the hypothesis that pain inducing massage produces similar magnitude of reduction in pain sensitivity as a cold pressor task and that baseline conditioned pain modulation efficiency predicts pain inducing massage related hypoalgesia.

METHODS

Sixty healthy participants were randomly assigned to receive either pain inducing massage to the neck, cold pressor task to the hand, or pain free massage to the neck. Participants also underwent pre and immediate post-intervention quantitative sensory testing. A repeated measures ANCOVA determined between group differences in pain sensitivity changes.

RESULTS

Pain inducing massage used as a conditioning stimulus resulted in comparable experimental pain sensitivity changes as a cold pressor task (p > 0.05). Pain intensity during the intervention demonstrated a weak correlation (r = 0.20, p = 0.12) with changes in pain sensitivity at a remote site. Individuals with an efficient CPM at baseline who received the pain inducing massage displayed greater increases in pressure pain threshold compared to individuals with a less efficient CPM indicating the potential benefit of treatment stratification by mechanism.

CONCLUSION

Although pain inducing massage resulted in less self-reported pain than a cold pressor task, both resulted in similar magnitude of the CPM response, suggesting shared underlying mechanisms. Understanding mechanisms of interventions can move us closer to mechanistic based treatments for pain which is consistent with a personalized medicine approach to care.

Riding a Tiger: Maximizing Effects of Manual Therapies for Pelvic Pain

Manual therapy interventions are frequently used during the management of pelvic pain conditions. Pain relief after any intervention results from effects unrelated to the intervention, effects specific to the intervention, and effects of context in which the intervention is provided. Understanding these multiple mechanisms allows providers of manual therapy to maximize outcomes by deliberately harnessing each of these core elements of pain relief.

Musculoskeletal pain stakeholder engagement and partnership development: determining patient-centered research priorities

BACKGROUND

Musculoskeletal (MSK) pain is a global public health problem with increased societal burden. Increased attention has focused toward patient and other stakeholder perspectives when determining future MSK pain research priorities, however infrastructure and capacity building within the community are needed for individuals and organizations to participate in patient-centered outcomes research. The purpose of this manuscript is to describe our collaborative experiences with several MSK pain stakeholders and processes to identify a top priority research topic.

METHODS

Lunch meetings and formalized workshops were used to develop infrastructure for engaging patients and other stakeholders with early capacity building for partners to identify MSK pain research ideas based on their personal experiences. Additional capacity building and engagement through literature searching further prepared partners to contribute informed decisions about MSK pain research topics and subsequent selection of an important research question.

RESULTS

Several key deliverables (e.g., Governance Document, Communication Plan) were developed and completed over the course of this project to provide partnership structure. Other key deliverables included a list of preliminary comparative effectiveness research ideas (n = 8) and selection of shared decision making for MSK pain as the top priority research topic with patient partners identifying pain self-efficacy as an important outcome domain.

CONCLUSIONS

Our patient partners provided the catalyst for identifying shared decision making as a high priority research topic based on a wide spectrum of stakeholder perspectives and unique experiences. Patient partners were primarily identified using a single rehabilitation health system and clinician partners were heavily weighted by physical therapists which may have introduced selection bias.

Factors shaping expectations for complete relief from symptoms during rehabilitation for patients with spine pain

OBJECTIVE

Patient expectations are related to treatment outcome across a broad variety of patient conditions. Here we sought to examine factors associated with the expectation of complete relief from treatment for spinal pain.

DESIGN

Secondary analysis of data pooled from two randomized controlled trials of conservative rehabilitation interventions.

PATIENTS

252 patients (103 men, 149 women) with neck (n = 140) or back (n = 112) pain.

METHODS

We used logistic regression model with backward elimination to test which patient clinical or demographic factors were most related to the expectation of complete relief.

MAIN OUTCOME MEASURES

The expectation of complete recovery, which was collected at the baseline examination visit in the primary trials.

RESULTS

The final model examining the contributions of patient and clinical characteristics to the expectation of complete relief included two significant interactions. First, increasing disability was associated with increased odds of expecting complete recovery in women while there was very little change for men across levels of disability (OR 0.9 [95%CI 0.8, 0.9]). Second, patients with low fear and a sudden onset of pain had higher odds of expecting recovery than patients with a gradual onset of pain (OR 0.7 [95%CI 0.5, 0.97]). A main effect for education level of the patient was also significant with better odds for expecting complete recovery for college educated patients compared to those with graduate school education (OR 5.0 [95%CI 1.9, 13.4]).

CONCLUSION

The results should assist physical therapists to recognize patients who may have lower expectations of recovery and plan pre-treatment education interventions.

The influence of clinical equipoise and patient preferences on outcomes of conservative manual interventions for spinal pain: an experimental study

Background

Expected pain relief from treatment is associated with positive clinical outcomes in patients with musculoskeletal pain. Less studied is the influence on outcomes related to the preference of patients and providers for a specific treatment.

Objectives

We sought to determine how provider and patient preferences for a manual therapy intervention influenced outcomes in individuals with acutely induced low back pain (LBP).

Participants and methods

Pain-free participants were randomly assigned to one of two manual therapies (joint biased [JB] or constant touch [CT]) 48 hours after completing an exercise protocol to induce LBP. Expectations for pain relief and preferences for treatment were collected at baseline, prior to randomization. Pain relief was assessed using a 100 mm visual analog scale. All study procedures were conducted in a private testing laboratory at the University of Florida campus.

Results

Sixty participants were included in this study. After controlling for preintervention pain intensity, the multivariate model included only preintervention pain (B=0.12, p=0.07) and provider preference (B=3.05, p<0.0001) and explained 35.8% of the variance in postintervention pain. When determining whether a participant met his or her expected pain relief, receiving an intervention from a provider with a strong preference for that intervention increased the odds of meeting a participant’s expected pain relief 68.3 times (p=0.013) compared to receiving any intervention from a provider with no preference. Receiving JB intervention from any provider increased the odds of meeting expected relief 29.7 times (p=0.023). The effect of a participant receiving an intervention they preferred was retained in the model but did not meet the criteria for a significant contribution.

Conclusion

Our primary findings were that participant and provider preferences for treatment positively influence pain outcomes in individuals with acutely induced LBP, and joint-biased interventions resulted in a greater chance of meeting participants’ expected outcomes. This is contrary to our hypothesis that the interaction of receiving an intervention for which a participant had a preference would result in the best outcome.

Placebo disclosure does not result in negative changes in mood or attitudes towards health care or the provider

Objectives: The purposes of this study were to (1) determine whether disclosure of having received a placebo treatment following participation in a randomized manual therapy trial resulted in changes in negative mood or attitudes towards health care and the provider and (2) examine the association between changes in mood or attitude and changes in clinical outcomes over the two-week study period. Methods: Participants with low back pain (N = 110) were randomly assigned to receive a spinal manipulative therapy (SMT), a standard placebo SMT in which participants were aware of a chance of receiving a placebo, an enhanced placebo SMT in which participants were instructed 'the manual therapy technique you will receive has been shown to significantly reduce low back pain in some people,' or no treatment. Outcomes included pain (Numeric Rating Scale), disability (Oswestry Disability Index), and negative mood and attitudes towards health care and the provider (visual analog scales). Pain and disability were obtained at baseline and two weeks. Mood and attitude measures were assessed at baseline, at the start of the final session, and upon completion of the final session following disclosure of group assignment. Results: Disclosure of having received a placebo treatment was not associated with worsening of mood or attitudes towards health care or the provider (p > 0.05). A small, but significant (p < 0.05) association was observed between two-week changes in disability and immediate changes in mood (r = 0.31-0.36) upon disclosure of having received a placebo. This analysis indicates an association between larger improvements in disability and more positive changes in mood. Discussion: Placebo treatment use in clinical practice is common yet controversial due to the deceptive nature. Our findings suggest disclosure of having received a placebo treatment is not associated with adverse changes in negative mood or attitudes towards health care or the provider.

What effect can manual therapy have on a patient's pain experience?

Manual therapy (MT) is a passive, skilled movement applied by clinicians that directly or indirectly targets a variety of anatomical structures or systems, which is utilized with the intent to create beneficial changes in some aspect of the patient pain experience. Collectively, the process of MT is grounded on clinical reasoning to enhance patient management for musculoskeletal pain by influencing factors from a multidimensional perspective that have potential to positively impact clinical outcomes. The influence of biomechanical, neurophysiological, psychological and nonspecific patient factors as treatment mediators and/or moderators provides additional information related to the process and potential mechanisms by which MT may be effective. As healthcare delivery advances toward personalized approaches there is a crucial need to advance our understanding of the underlying mechanisms associated with MT effectiveness.

Spinal manipulative therapy-specific changes in pain sensitivity in individuals with low back pain (NCT01168999)

Spinal manipulative therapy (SMT) is effective for some individuals experiencing low back pain; however, the mechanisms are not established regarding the role of placebo. SMT is associated with changes in pain sensitivity, suggesting related altered central nervous system response or processing of afferent nociceptive input. Placebo is also associated with changes in pain sensitivity, and the efficacy of SMT for changes in pain sensitivity beyond placebo has not been adequately considered. We randomly assigned 110 participants with low back pain to receive SMT, placebo SMT, placebo SMT with the instructional set "The manual therapy technique you will receive has been shown to significantly reduce low back pain in some people," or no intervention. Participants receiving the SMT and placebo SMT received their assigned intervention 6 times over 2 weeks. Pain sensitivity was assessed prior to and immediately following the assigned intervention during the first session. Clinical outcomes were assessed at baseline and following 2 weeks of participation in the study. Immediate attenuation of suprathreshold heat response was greatest following SMT (P = .05, partial η(2) = .07). Group-dependent differences were not observed for changes in pain intensity and disability at 2 weeks. Participant satisfaction was greatest following the enhanced placebo SMT. This study was registered at www.clinicaltrials.gov under the identifier NCT01168999.

PERSPECTIVE

The results of this study indicate attenuation of pain sensitivity is greater in response to SMT than the expectation of receiving an SMT. These findings suggest a potential mechanism of SMT related to lessening of central sensitization and may indicate a preclinical effect beyond the expectations of receiving SMT.

Placebo response to manual therapy: something out of nothing?

The mechanisms through which manual therapy inhibits musculoskeletal pain are likely multifaceted and related to the interaction between the intervention, the patient, the practitioner, and the environment. Placebo is traditionally considered an inert intervention; however, the pain research literature suggests that placebo is an active hypoalgesic agent. Placebo response likely plays a role in all interventions for pain and we suggest that the same is true for the treatment effects associated with manual therapy. The magnitude of a placebo response may be influenced by negative mood, expectation, and conditioning. We suggest that manual therapists conceptualize placebo not only as a comparative intervention, but also as a potential active mechanism to partially account for treatment effects associated with manual therapy. We are not suggesting manual therapists include known sham or ineffective interventions in their clinical practice, but take steps to maximize placebo responses to reduce pain.

Patient expectations of benefit from common interventions for low back pain and effects on outcome: secondary analysis of a clinical trial of manual therapy interventions

OBJECTIVES

The purpose of this secondary analysis was 1) to examine patient expectations related to a variety of common interventions for low back pain (LBP) and 2) to determine the influence that specific expectations about spinal manipulation might have had on self-report of disability.

METHODS

We collected patients' expectations about the benefit of specific interventions for low back pain. We also collected patients' general expectations about treatment and tested the relationships among the expectation of benefit from an intervention, receiving that intervention and disability-related outcomes.

RESULTS

Patients expected exercise and manual therapy interventions to provide more benefit than surgery and medication. There was a statistical association between expecting relief from thrust techniques and receiving thrust techniques, related to meeting the general expectation for treatment (chi-square: 15.5, P  =  0.008). This was not the case for patients who expected relief from thrust techniques but did not receive it (chi-square: 6.9, P  = 0.4). Logistic regression modeling was used to predict change in disability at treatment visit 5. When controlling for whether the general expectations for treatment were met, intervention assignment and the interaction between intervention assignment and expectations regarding thrust techniques, the parsimonious model only included intervention as the significant contributor to the model (P < 0.001). The adjusted odds ratio of success comparing thrust techniques to non-thrust in this study was 41.2 (11.0, 201.7).

DISCUSSION

The findings of this secondary analysis indicate that patients seeking intervention for LBP expect active interventions and manual therapy to significantly help improve their pain more than interventions like traction, rest, surgery, or medication. Additionally, in patients who meet the clinical prediction rule for good prognosis when managed with thrust techniques, treating with thrust techniques is more important than matching treatment to patient expectation.

Temporal summation of second pain: variability in responses to a fixed protocol

BACKGROUND

Temporal summation of second pain (TSSP) is relevant for the study of central sensitization, and refers to increased pain evoked by repetitive stimuli at a constant intensity. While the literature reports on participants whose pain ratings increase with successive stimuli, response to a TSSP protocol can be variable. The aim of this study was to characterize the full range of responses to a TSSP protocol in pain-free adults.

METHOD

Three hundred twelve adults received a train of brief, repetitive heat stimuli at a fixed temperature and rated the intensity of second pain after each pulse. TSSP response (Δ in pain ratings) was quantified using the most common methods in the literature, and response groups were formed: TSSP (Δ > 0), no change (Δ = 0), and temporal decrease in second pain (TDSP) (Δ < 0). A cluster analysis was performed on the Δ values to empirically derive response groups.

RESULTS

Depending on how TSSP response was quantified, 61-72% of the sample demonstrated TSSP, 11-28% had no change in pain ratings and 0-20% demonstrated TDSP. The cluster analysis found that the majority (59%) of participants fell in the no change cluster, 29% clustered into the TSSP group and 12% in the TDSP cluster.

CONCLUSIONS

Using a fixed thermal paradigm, pain-free adults exhibit substantial variability in response to a TSSP protocol not well characterized by group-mean slopes. Studies are needed to determine TSSP response patterns in clinical samples, identify predictors of response and determine the clinical implications of response variability.

Changes in pain sensitivity following spinal manipulation: a systematic review and meta-analysis

Spinal manipulation (SMT) is commonly used for treating individuals experiencing musculoskeletal pain. The mechanisms of SMT remain unclear; however, pain sensitivity testing may provide insight into these mechanisms. The purpose of this systematic review is to examine the literature on the hypoalgesic effects of SMT on pain sensitivity measures and to quantify these effects using meta-analysis. We performed a systematic search of articles using CINAHL, MEDLINE, PsycINFO, and SPORTDiscus from each databases' inception until May 2011. We examined methodological quality of each study and generated pooled effect size estimates using meta-analysis software. Of 997 articles identified, 20 met inclusion criteria for this review. Pain sensitivity testing used in these studies included chemical, electrical, mechanical, and thermal stimuli applied to various anatomical locations. Meta-analysis was appropriate for studies examining the immediate effect of SMT on mechanical pressure pain threshold (PPT). SMT demonstrated a favorable effect over other interventions on increasing PPT. Subgroup analysis showed a significant effect of SMT on increasing PPT at the remote sites of stimulus application supporting a potential central nervous system mechanism. Future studies of SMT related hypoalgesia should include multiple experimental stimuli and test at multiple anatomical sites.

Basis for spinal manipulative therapy: a physical therapist perspective

Physical therapists internationally provide spinal manipulative therapy (SMT) to patients with musculoskeletal pain complaints. SMT has been a part of physical therapist practice since the profession's beginning. Early physical therapist clinical decision making for SMT was influenced by the approaches of osteopathic and orthopedic physicians at the time. Currently a segmental clinical decision making approach and a responder clinical decision making approach are two of the more common models through which physical therapist clinical use of SMT is directed. The focus of segmental clinical decision making is upon identifying a dysfunctional vertebral segment with the application of SMT to restore mobility and/or alleviate pain. The responder clinical decision making approach attempts to categorize individuals based on a pattern of signs and symptoms suggesting a likely positive response to SMT. The present manuscript provides an overview of common physical therapist clinical decision making approaches to SMT and presents areas requiring further study in order to optimize patient response.

Heightened pain sensitivity in individuals with signs and symptoms of carpal tunnel syndrome and the relationship to clinical outcomes following a manual therapy intervention

Neurophysiological responses related to lessening of pain sensitivity are a suggested mechanism of manual therapy. Prior studies have observed generalized lower pain thresholds associated with carpal tunnel syndrome (CTS) in comparison to healthy controls. The present study sought to determine whether similar findings were present in suprathreshold measures and measures specific to central integration of pain (temporal summation and after sensations). Additionally, we wished to determine whether measures of pain sensitivity were related to clinical outcomes in participants with signs and symptoms of CTS receiving a manual therapy intervention. Individuals with signs and symptoms of CTS reported greater pain sensitivity to suprathreshold measures of mechanical pain, temporal summation, and after sensation in comparison to healthy controls. Immediate lessening of mechanical pain sensitivity and after sensations in response to a manual therapy intervention and 3-week attenuation of temporal summation following a 3-week course of manual therapy were associated with 3-week changes in clinical pain intensity in participants with signs and symptoms of CTS. These findings suggest heightened pain sensitivity across several parameters may be associated with CTS. Furthermore, changes in mechanical pain, after sensation, and temporal summation may be related to improvements in clinical outcomes.

Stability of behavioral estimates of activity-dependent modulation of pain

Temporal sensory summation of pain (TSSP) is a proxy measure of windup in humans and results in increased ratings of pain caused by a repetitive, low-frequency noxious stimulus. Aftersensations (ASs) are pain sensations that remain after TSSP has been induced. We examined the within-session and across-session variability in TSSP and AS estimation in healthy participants and in participants with exercise-induced muscle pain in order to determine whether the presence of pain affected the stability of TSSP and ASs. TSSP was estimated by application of 10 repetitive, low-frequency (<0.33 Hz) thermal pulses and measured by the simple slope of pain ratings between the first and fifth pulses. ASs were measured by the presence of any remaining pain sensations up to 1 minute after TSSP was induced. TSSP estimation remained moderately stable in pain-free participants and in participants with pain within a single testing session but demonstrated low stability across sessions in pain-free participants. AS estimation was stable for all groups. Estimation of TSSP and ASs using these protocols appears to be a reliable single-session outcome measure in studies of interventions for acute muscle pain and in experimental studies with healthy participants. This article evaluates the reliability of a commonly used method of estimating TSSP and ASs in both healthy participants and in a clinically relevant model of acute pain. These protocols have the potential to be used as single-session outcome measures for interventional studies and in experimental studies.

The relationship of the audible pop to hypoalgesia associated with high-velocity, low-amplitude thrust manipulation: a secondary analysis of an experimental study in pain-free participants

OBJECTIVE

High-velocity, low-amplitude (HVLA) manipulation is an effective treatment of low back pain (LBP); however, the corresponding mechanisms are undetermined. Hypoalgesia is associated with HVLA manipulation and suggests specific mechanisms of action. An audible pop (AP) is also associated with HVLA manipulation; however, the influence of the AP on the hypoalgesia associated with HVLA manipulation is not established. The purpose of the current study was to observe the influence of the AP on hypoalgesia associated with HVLA manipulation.

METHODS

The current study represents a secondary analysis of 40 participants. All participants underwent thermal pain sensitivity testing to their leg and low back using protocols specific to A delta fiber-mediated pain and temporal summation. Next, participants received HVLA manipulation to their low back, and the examiner recorded whether an AP was perceived. Finally, participants underwent immediate follow-up thermal pain sensitivity testing using the same protocols. Separate repeated-measure analyses of variance (ANOVAs) were used to observe changes in pain sensitivity before and immediately after HVLA manipulation.

RESULTS

Hypoalgesia of A delta fiber-mediated pain was observed in the low back after HVLA (P < .05), and this was independent of whether an AP was perceived (P > .05). Hypoalgesia of temporal summation was observed in the lower extremity after HVLA (P < .05), and this was independent of whether an AP was perceived (P = .08). However, a moderate effect size for temporal summation was observed favoring participants in whom an AP was perceived.

CONCLUSION

The current study suggests hypoalgesia is associated with HVLA manipulation and occurs independently of a perceived AP. Inhibition of lower extremity temporal summation may be larger in individuals in whom an AP is perceived, but further study is necessary to confirm this finding.

Supra-threshold scaling, temporal summation, and after-sensation: relationships to each other and anxiety/fear

This study investigated the relationship of thermal pain testing from three types of quantitative sensory testing (ie, supra-threshold stimulus response scaling, temporal summation, and after-sensation) at three anatomical sites (ie, upper extremity, lower extremity, and trunk). Pain ratings from these procedures were also compared with common psychological measures previously shown to be related to experimental pain responses and consistent with fear-avoidance models of pain. Results indicated that supra-threshold stimulus response scaling, temporal summation, and after-sensation, were significantly related to each other. The site of stimulation was also an important factor, with the trunk site showing the highest sensitivity in all three quantitative sensory testing procedures. Supra-threshold response measures were highly related to measures of fear of pain and anxiety sensitivity for all stimulation sites. For temporal summation and after-sensation, only the trunk site was significantly related to anxiety sensitivity, and fear of pain, respectively. Results suggest the importance of considering site of stimulation when designing and comparing studies. Furthermore, psychological influence on quantitative sensory testing is also of importance when designing and comparing studies. Although there was some variation by site of stimulation, fear of pain and anxiety sensitivity had consistent influences on pain ratings.

The mechanisms of manual therapy in the treatment of musculoskeletal pain: a comprehensive model

Prior studies suggest manual therapy (MT) as effective in the treatment of musculoskeletal pain; however, the mechanisms through which MT exerts its effects are not established. In this paper we present a comprehensive model to direct future studies in MT. This model provides visualization of potential individual mechanisms of MT that the current literature suggests as pertinent and provides a framework for the consideration of the potential interaction between these individual mechanisms. Specifically, this model suggests that a mechanical force from MT initiates a cascade of neurophysiological responses from the peripheral and central nervous system which are then responsible for the clinical outcomes. This model provides clear direction so that future studies may provide appropriate methodology to account for multiple potential pertinent mechanisms.

Manipulation of pain catastrophizing: An experimental study of healthy participants

Pain catastrophizing is associated with the pain experience; however, causation has not been established. Studies which specifically manipulate catastrophizing are necessary to establish causation. The present study enrolled 100 healthy individuals. Participants were randomly assigned to repeat a positive, neutral, or one of three catastrophizing statements during a cold pressor task (CPT). Outcome measures of pain tolerance and pain intensity were recorded. No change was noted in catastrophizing immediately following the CPT (F((1,84)) = 0.10, p = 0.75, partial η(2) < 0.01) independent of group assignment (F((4,84)) = 0.78, p = 0.54, partial η(2) = 0.04). Pain tolerance (F((4)) = 0.67, p = 0.62, partial η(2) = 0.03) and pain intensity (F((4)) = 0.73, p = 0.58, partial η(2) = 0.03) did not differ by group. This study suggests catastrophizing may be difficult to manipulate through experimental pain procedures and repetition of specific catastrophizing statements was not sufficient to change levels of catastrophizing. Additionally, pain tolerance and pain intensity did not differ by group assignment. This study has implications for future studies attempting to experimentally manipulate pain catastrophizing.

Fear of pain, pain catastrophizing, and acute pain perception: relative prediction and timing of assessment

Pain-related fear and catastrophizing are important variables of consideration in an individual's pain experience. Methodological limitations of previous studies limit strong conclusions regarding these relationships. In this follow-up study, we examined the relationships between fear of pain, pain catastrophizing, and experimental pain perception. One hundred healthy volunteers completed the Fear of Pain Questionnaire (FPQ-III), Pain Catastrophizing Scale (PCS), and Coping Strategies Questionnaire-Catastrophizing scale (CSQ-CAT) before undergoing the cold pressor test (CPT). The CSQ-CAT and PCS were completed again after the CPT, with participants instructed to complete these measures based on their experience during the procedure. Measures of pain threshold, tolerance, and intensity were collected and served as dependent variables in separate regression models. Sex, pain catastrophizing, and pain-related fear were included as predictor variables. Results of regression analyses indicated that after controlling for sex, pain-related fear was a consistently stronger predictor of pain in comparison to catastrophizing. These results were consistent when separate measures (CSQ-CAT vs PCS) and time points (pretask vs "in vivo") of catastrophizing were used. These findings largely corroborate those from our previous study and are suggestive of the absolute and relative importance of pain-related fear in the experimental pain experience.

PERSPECTIVE

Although pain-related fear has received less attention in the experimental literature than pain catastrophizing, results of the current study are consistent with clinical reports highlighting this variable as an important aspect of the experience of pain.

Sex differences in pain drawing area for individuals with chronic musculoskeletal pain

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To (1) determine the association between pain severity and pain drawing area for men and women; (2) determine if sex differences exist in pain severity or pain drawing area; (3) determine the relative influence of pain severity, anatomical location of pain, personality, and psychological coping factors on pain drawing area for men and women.

BACKGROUND

Pain drawings have been postulated to assist in clinical decision making regarding classification and treatment of musculoskeletal pain. Prior studies have been ambiguous on this topic, possibly because they have not considered if sex differences exist for pain drawing area.

METHODS AND MEASURES

One hundred twenty-six subjects referred to a multidisciplinary chronic pain clinic with chronic musculoskeletal pain were included in this study. Subjects completed a pain drawing, the Multidimensional Pain Inventory (MPI), the Coping Strategies Questionnaire (CSQ), and the Minnesota Multiphasic Personality Inventory (MMPI-2). Pearson correlations investigated the associations of pain severity and pain drawing area, independent t tests investigated sex differences in pain severity and pain drawing area, and multiple regression investigated factors that influenced pain drawing area.

RESULTS

P a in severity w as positively correlated with pain drawing area for men (r = 0.38, P = .003) and women (r = 0.23, P = .052), accounting for approximately 14% and 5% of the total variance, respectively. There was no significant sex difference in pain severity ratings, but women reported a significantly larger area of symptoms on the pain drawings (effect size, 0.61; P = .002). The sex difference in pain drawing area was consistent across different anatomical locations of pain. In women, the final regression model accounted for 39% (P < .001) of the variance in pain drawing area, with anatomical location of pain (beta = .42, P < .001) and hypochondriasis (beta = .31, P = .005) as the only unique predictors in the final model. In men, the regression model accounted for 27% (P = .003) of the variance in pain drawing area, with pain severity (beta = .32, P = .021) and a coping style of ignoring pain (beta = -.32, P = .018) as the only unique predictors in the final model.

CONCLUSIONS

Women had larger pain drawing area and this area was significantly associated with anatomical location of pain and hypochondriasis. Men had smaller pain drawing area and this area was associated with pain severity and a coping style of ignoring pain. These findings suggest that clinicians interpreting pain diagram area should consider the sex of the individual.

Immediate effects of spinal manipulation on thermal pain sensitivity: an experimental study

Background

The underlying causes of spinal manipulation hypoalgesia are largely unknown. The beneficial clinical effects were originally theorized to be due to biomechanical changes, but recent research has suggested spinal manipulation may have a direct neurophysiological effect on pain perception through dorsal horn inhibition. This study added to this literature by investigating whether spinal manipulation hypoalgesia was: a) local to anatomical areas innervated by the lumbar spine; b) correlated with psychological variables; c) greater than hypoalgesia from physical activity; and d) different for A-delta and C-fiber mediated pain perception.

Methods

Asymptomatic subjects (n = 60) completed baseline psychological questionnaires and underwent thermal quantitative sensory testing for A-delta and C-fiber mediated pain perception. Subjects were then randomized to ride a stationary bicycle, perform lumbar extension exercise, or receive spinal manipulation. Quantitative sensory testing was repeated 5 minutes after the intervention period. Data were analyzed with repeated measures ANOVA and post-hoc testing was performed with Bonferroni correction, as appropriate.

Results

Subjects in the three intervention groups did not differ on baseline characteristics. Hypoalgesia from spinal manipulation was observed in lumbar innervated areas, but not control (cervical innervated) areas. Hypoalgesic response was not strongly correlated with psychological variables. Spinal manipulation hypoalgesia for A-delta fiber mediated pain perception did not differ from stationary bicycle and lumbar extension (p > 0.05). Spinal manipulation hypoalgesia for C-fiber mediated pain perception was greater than stationary bicycle riding (p = 0.040), but not for lumbar extension (p = 0.105).

Conclusion

Local dorsal horn mediated inhibition of C-fiber input is a potential hypoalgesic mechanism of spinal manipulation for asymptomatic subjects, but further study is required to replicate this finding in subjects with low back pain.

The centralization phenomenon and fear-avoidance beliefs as prognostic factors for acute low back pain: a preliminary investigation involving patients classified for specific exercise

STUDY DESIGN

Secondary analysis of a prospective cohort of patients with acute low back pain (LBP).

OBJECTIVES

To determine if the centralization phenomenon and fear-avoidance beliefs predict measurement of pain and disability 6 months after entering the study.

BACKGROUND

The centralization phenomenon and fear-avoidance are predictive of future pain and disability. However, previous prognostic studies have not routinely included both measures in homogenous subgroups of patients with acute LBP.

METHODS AND MEASURES

Patients completed self-report questionnaires and were evaluated and treated with treatment-based classification guidelines. Only the patients classified for specific exercise were included in this analysis (n = 28). Measures of disability and pain intensity were reassessed at 6 months by mail. Separate hierarchical regression models predicted measures of disability and pain intensity with the centralization phenomenon, fear-avoidance beliefs, and prespecified covariates.

RESULTS

There were no significant differences in duration of symptoms, fear-avoidance beliefs, and history of LBP based on the centralization phenomenon (P > .05). Patients reporting the centralization phenomenon were significantly more likely to have leg pain (P < .01). A regression model including initial disability, the centralization phenomenon, and fear-avoidance beliefs about work significantly predicted 6-month disability, explaining 49% of the total variance (P < .001). A regression model that included initial pain intensity and the centralization phenomenon significantly predicted 6-month pain intensity, explaining 29% of the total variance (P < .016). These factors also appeared to be clinically meaningful predictors of outcome, but lacked precision for immediate use in clinical settings. The following covariates were not included in the final regression models: presence of leg pain, history of LBP, and duration of LBP.

CONCLUSIONS

Baseline elevation in fear-avoidance beliefs about work and lack of centralization phenomenon predicted higher disability. Baseline lack of centralization phenomenon predicted higher pain intensity. These results can only be generalized to patients with acute LBP classified for specific exercise. It will be necessary to independently validate these prediction models before they can be implemented in clinical settings.

Physical therapist management of a patient with acute low back pain and elevated fear-avoidance beliefs

BACKGROUND AND PURPOSE

Elevated fear-avoidance beliefs are believed to be a precursor of chronic disability, yet effective intervention options have not been described in the literature. The purpose of this case report is to describe physical therapist management of a patient with acute low back pain and elevated fear-avoidance beliefs.

CASE DESCRIPTION

The patient was a 42-year-old sales manager with acute low back pain. The patient had no previous history of activity-limiting low back pain and initially had limitations in straight leg raising, limitations in lumbar movement, and elevated fear-avoidance beliefs.

INTERVENTION

Treatment-based classification and graded exercise were used.

OUTCOME

Disability, fear-avoidance beliefs, and pain decreased 4 weeks after starting physical therapy. Six months later, disability and fear-avoidance beliefs had increased, but were still improved when compared with the initial measurements.

DISCUSSION

Disability and fear-avoidance beliefs improved following a fear-avoidance-based physical therapy intervention. Research is warranted to investigate the effectiveness of this approach.

The effect of a fear-avoidance-based physical therapy intervention for patients with acute low back pain: results of a randomized clinical trial

STUDY DESIGN

A randomized clinical trial with 4-week and 6-month follow-up periods.

OBJECTIVE

To compare the effect of a fear-avoidance-based physical therapy intervention with standard care physical therapy for patients with acute low back pain.

SUMMARY OF BACKGROUND DATA

The disability reduction strategy of secondary prevention involves providing specific treatment for patients that are likely to have chronic disability from low back pain. Previous studies have indicated that elevated fear-avoidance beliefs are a precursor to chronic disability from low back pain. However, the effectiveness of physical therapy intervention based on a fear-avoidance model is unknown.

METHODS

Sixty-six consecutive patients referred to physical therapy with low back pain of less than 8 weeks' duration were randomly assigned to receive fear-avoidance-based physical therapy (n = 34) or standard care physical therapy (n = 32). The intervention period lasted 4 weeks for this study. Disability, pain intensity, and fear-avoidance beliefs measures were recorded before and after treatment. A 6-month follow-up of the same measures was obtained by mail.

RESULTS

An intention-to-treat principle (last value forward) was used for data analyses that tested the primary and secondary hypotheses. The prediction of disability at 4 weeks and 6 months after treatment was significantly improved by considering the interaction between the type of treatment and the initial level of fear-avoidance beliefs. Both groups had significant within group improvements for disability and pain intensity. The fear-avoidance treatment group had a significant improvement in fear-avoidance beliefs, and fear-avoidance beliefs about physical activity were significantly lower than the standard care group at 4 weeks and 6 months after treatment.

CONCLUSION

Patients with elevated fear-avoidance beliefs appeared to have less disability from fear-avoidance-based physical therapy when compared to those receiving standard care physical therapy. Patients with lower fear-avoidance beliefs appeared to have more disability from fear-avoidance-based physical therapy, when compared to those receiving standard care physical therapy. In addition, physical therapy supplemented with fear-avoidance-based principles contributed to a positive shift in fear-avoidance beliefs.