The clinical course of acute, subacute and persistent low back pain: a systematic review and meta-analysis.

BACKGROUND: Understanding the clinical course of low back pain is essential to informing treatment recommendations and patient stratification. Our aim was to update our previous systematic review and meta-analysis to gain a better understanding of the clinical course of acute, subacute and persistent low back pain. METHODS: To update our 2012 systematic review and meta-analysis, we searched the Embase, MEDLINE and CINAHL databases from 2011 until January 2023, using our previous search strategy. We included prospective inception cohort studies if they reported on participants with acute (< 6 wk), subacute (6 to less than 12 wk) or persistent (12 to less than 52 wk) nonspecific low back pain at study entry. Primary outcome measures included pain and disability (0-100 scale). We assessed risk of bias of included studies using a modified tool and assessed the level of confidence in pooled estimates using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) tool. We used a mixed model design to calculate pooled estimates (mean, 95% confidence interval [CI]) of pain and disability at 0, 6, 12, 26 and 52 weeks. We treated time in 2 ways: time since study entry (inception time uncorrected) and time since pain onset (inception time corrected). We transformed the latter by adding the mean inception time to the time of study entry. RESULTS: We included 95 studies, with 60 separate cohorts in the systematic review (n = 17 974) and 47 cohorts (n = 9224) in the meta-analysis. Risk of bias of included studies was variable, with poor study attrition and follow-up, and most studies did not select participants as consecutive cases. For the acute pain cohort, the estimated mean pain score with inception time uncorrected was 56 (95% CI 49-62) at baseline, 26 (95% CI 21-31) at 6 weeks, 22 (95% CI 18-26) at 26 weeks and 21 (95% CI 17-25) at 52 weeks (moderate-certainty evidence). For the subacute pain cohort, the mean pain score was 63 (95% CI 55-71) at baseline, 29 (95% CI 22-37) at 6 weeks, 29 (95% CI 22-36) at 26 weeks and 31 (95% 23-39) at 52 weeks (moderate-certainty evidence). For the persistent pain cohort, the mean pain score was 56 (95% CI 37-74) at baseline, 48 (95% CI 32-64) at 6 weeks, 43 (95% CI 29-57) at 26 weeks and 40 (95% CI 27-54) at 52 weeks (very low-certainty evidence). The clinical course of disability was slightly more favourable than the clinical course of pain. INTERPRETATION: Participants with acute and subacute low back pain had substantial improvements in levels of pain and disability within the first 6 weeks ( moderate-certainty evidence); however, participants with persistent low back pain had high levels of pain and disability with minimal improvements over time (very low-certainty evidence). Identifying and escalating care in individuals with subacute low back pain who are recovering slowly could be a focus of intervention to reduce the likelihood of transition into persistent low back pain. PROTOCOL REGISTRATION: PROSPERO - CRD42020207442.

Exploring Patient Perceptions of Noninvasive Brain Stimulation: A Systematic Review.

OBJECTIVE: To synthesize and critically appraise literature exploring patient perceptions regarding the therapeutic use of noninvasive brain stimulation. MATERIAL AND METHODS: A systematic search of CINHAL, PUBMED, Web of Science, and Medline was performed. Reference lists of relevant articles were also screened. Studies exploring participant perceptions regarding the therapeutic use of noninvasive brain stimulation were eligible for inclusion. Perceptions were divided into three domains: knowledge, experience, and attitudes. Noninvasive brain stimulation was defined as any neuromodulation technique that alters brain activity but does not require invasive methods such as surgery. No restrictions were placed upon study design or participant population. Two reviewers performed data extraction and risk of bias assessment. Data relating to methodological characteristics, participant demographics, type of noninvasive brain stimulation, and nature of perceptions (knowledge, experience, or attitudes) were extracted. RESULTS: Four studies comprising data from 163 participants met the inclusion criteria. All studies investigated perceptions of repetitive transcranial magnetic stimulation (rTMS) in psychiatric populations. Most participants perceived rTMS to be safe and beneficial, demonstrated low levels of fear, and were willing to recommend the intervention to others. No studies were found investigating patient perception of transcranial direct current stimulation (tDCS). CONCLUSION: The findings from this review suggest that rTMS is well accepted as a therapeutic treatment among psychiatric populations, providing support for its clinical utility. Future work is needed to determine if similar findings exist for other conditions (eg, chronic pain) and for other therapeutic forms of brain stimulation (eg, tDCS).

The Relationship Between Corticomotor Reorganization and Acute Pain Severity: A Randomized, Controlled Study Using Rapid Transcranial Magnetic Stimulation Mapping.

OBJECTIVE: Although acute pain has been shown to reduce corticomotor excitability, it remains unknown whether this response resolves over time or is related to symptom severity. Furthermore, acute pain research has relied upon data acquired from the cranial "hotspot," which do not provide valuable information regarding reorganization, such as changes to the distribution of a painful muscle's representation within M1. Using a novel, rapid transcranial magnetic stimulation (TMS) mapping method, this study aimed to 1) explore the temporal profile and variability of corticomotor reorganization in response to acute pain and 2) determine whether individual patterns of corticomotor reorganization are associated with differences in pain, sensitivity, and somatosensory organization. METHODS: Corticomotor (TMS maps), pain processing (pain intensity, pressure pain thresholds), and somatosensory (two-point discrimination, two-point estimation) outcomes were taken at baseline, immediately after injection (hypertonic [n = 20] or isotonic saline [n = 20]), and at pain resolution. Follow-up measures were recorded every 15 minutes until 90 minutes after injection. RESULTS: Corticomotor reorganization persisted at least 90 minutes after pain resolution. Corticomotor depression was associated with lower pain intensity than was corticomotor facilitation (r = 0.47 [P = 0.04]). These effects were not related to somatosensory reorganization or peripheral sensitization mechanisms. CONCLUSIONS: Individual patterns of corticomotor reorganization during acute pain appear to be related to symptom severity, with early corticomotor depression possibly reflecting a protective response. These findings hold important implications for the management and potential prevention of pain chronicity. However, further research is required to determine whether these adaptations relate to long-term outcomes in clinical populations.

Fear of movement is associated with corticomotor depression in response to acute experimental muscle pain.

Acute musculoskeletal pain is associated with reductions in corticomotor output that persists even after pain resolves. Factors that contribute to corticomotor depression following acute pain are unknown. This study examined whether psychological factors, including pain catastrophising, kinesiophobia, and implicit theories of pain, were associated with corticomotor depression following acute experimental muscle pain. Forty-two healthy individuals participated. Participants completed three questionnaires: Pain Catastrophising Scale, Tampa Scale of Kinesiophobia, and Implicit Theories of Pain Scale. Acute pain was induced into the right extensor carpi radialis brevis (ECRB) muscle by injection of hypertonic saline. Corticomotor depression was assessed as a reduction in motor-evoked potentials measured from ECRB muscle in response to transcranial magnetic stimulation before, immediately after, and at 10, 20, and 30 min following pain resolution. Corticomotor depression was present at each time point relative to baseline (p < 0.001). Higher levels of kinesiophobia were associated with less corticomotor depression 10-min post pain resolution (r = 0.32, p = 0.03), but not at any other time point (p > 0.11). When corticomotor depression was compared between individuals with 'high' and 'low' kinesiophobia, a similar relationship was observed: Individuals with high compared to low kinesiophobia displayed less corticomotor depression immediately after (p = 0.02) and 10 min post pain (p = 0.02), but not at 20 or 30 min (p = 0.05 for both). No relationship was observed with any other psychological variable (p > 0.15). These data provide preliminary support for a relationship between pain-related fear of movement and corticomotor depression in response to acute pain. These findings may have implications for clinical musculoskeletal pain disorders.

Cerebral peak alpha frequency reflects average pain severity in a human model of sustained, musculoskeletal pain.

Heightened pain sensitivity, the amount of pain experienced in response to a noxious event, is a known risk factor for development of chronic pain. We have previously reported that pain-free, sensorimotor peak alpha frequency (PAF) is a reliable biomarker of pain sensitivity for thermal, prolonged pains lasting tens of minutes. To test whether PAF can provide information about pain sensitivity occurring over clinically relevant timescales (i.e., weeks), EEG was recorded before and while participants experienced a long-lasting pain model, repeated intramuscular injection of nerve growth factor (NGF), that produces progressively developing muscle pain for up to 21 days. We demonstrate that pain-free, sensorimotor PAF is negatively correlated with NGF pain sensitivity; increasingly slower PAF is associated with increasingly greater pain sensitivity. Furthermore, PAF remained stable following NGF injection, indicating that the presence of NGF pain for multiple weeks is not sufficient to induce the PAF slowing reported in chronic pain. In total, our results demonstrate that slower pain-free, sensorimotor PAF is associated with heightened sensitivity to a long-lasting musculoskeletal pain and also suggest that the apparent slowing of PAF in chronic pain may reflect predisease pain sensitivity.NEW & NOTEWORTHY Pain sensitivity, the intensity of pain experienced after injury, has been identified as an important risk factor in the development of chronic pain. Biomarkers of pain sensitivity have the potential to ease chronic pain burdens by preventing disease emergence. In the current study, we demonstrate that the speed of pain-free, sensorimotor peak alpha frequency recorded during resting-state EEG predicts pain sensitivity to a clinically-relevant, human model of prolonged pain that persists for weeks.

Dry needling perceptions and experiences: A survey of Australian physiotherapists.

BACKGROUND: There is a lack of information on the use of dry needling in Australian physiotherapy practice. OBJECTIVES: Our primary aim was to enhance the understanding of why Australian physiotherapists use dry needling in clinical practice. The secondary aim was to explore Australian physiotherapists experiences with adverse events caused by dry needling. DESIGN: Cross-sectional online survey. METHOD: We developed a survey and disseminated it through email to physiotherapists from all states and territories in Australia. Participant demographics and responses were reported as frequencies and percentages. RESULTS/FINDINGS: We invited 1006 Australian physiotherapists, of which 232 (23%) viewed the online survey and 203 (20%) consented to participate, of which nearly all completed the survey (n = 198, 98%). Most respondents worked in private practice (n = 164, 83%), with 127 (64%) reporting using dry needling as an intervention within the previous 12 months. Physiotherapists typically used dry needling to decrease pain intensity (n = 105, 85%) and reduce muscle tension (n = 100, 81%). Reports of minor adverse events were common and included discomfort during the treatment (n = 77, 62%) and bruising (n = 69, 56%). Some respondents reported experiencing major adverse events including prolonged aggravation of symptoms (n = 10, 8%) and syncope (n = 16, 13%). CONCLUSIONS: We found that many Australian physiotherapists in private practice use dry needling, usually to decrease pain intensity and muscle tension. Minor adverse events were experienced by more than half the respondents and between 8 and 13% of the Australian physiotherapists surveyed reported experiencing a major adverse event due to dry needling.

The Relationship Between Pain and Interoception: A Systematic Review and Meta-Analysis.

Interoception refers to the ability to sense internal bodily sensations. Research suggests that dysfunctions in interoception may be implicated in the transition to chronic pain, however, little work has examined interoceptive ability in pain states. Therefore, this systematic review aimed to assess whether interoception is altered in individuals experiencing pain. Following a systematic search of 4 electronic databases from inception to February 2023, 28 studies were included. Outcomes of interoceptive accuracy, interoceptive sensibility, and interoceptive awareness were meta-analysed. The risk of bias was assessed, and the certainty of the evidence was evaluated. Meta-analyses indicated that those with chronic pain display reduced interoceptive accuracy and increased interoceptive sensibility. Subgroup analyses indicated that the change in interoceptive sensibility is dependent on the measure used, with those with chronic pain scoring higher on measures focusing on attention to bodily sensations, while also scoring lower on emotional reactivity. No difference in interoceptive awareness was observed between individuals with chronic pain and pain-free controls. Only one study was found that measured interoception in those experiencing acute pain, while another study recruited those experiencing recurrent pain. These findings suggest that while those with chronic pain self-report as more interoceptively aware, they are less accurate at detecting internal bodily signals. Further research investigating domains of interoception in those experiencing acute and recurrent pain is needed. Data should be interpreted with caution as the certainty of evidence was very low for all completed analyses. This review was registered on the PROSPERO International Prospective Register of Systematic Reviews (Registration ID = CRD42022318843). PERSPECTIVE: This review considered the relationship between interoception and pain and found that an individual's ability to accurately sense internal signals is decreased in those with chronic pain, despite them reporting being more aware of internal sensations. However, there remains little research examining interoception in non-chronic pain states.

Bilateral Corticomotor Reorganization and Symptom Development in Response to Acute Unilateral Hamstring Pain: A Randomized, Controlled Study.

Accumulating evidence demonstrates that pain induces adaptations in the corticomotor representations of affected muscles. However, previous work has primarily investigated the upper limb, with few studies examining corticomotor reorganization in response to lower limb pain. This is important to consider, given the significant functional, anatomical, and neurophysiological differences between upper and lower limb musculature. Previous work has also focused on unilateral corticomotor changes in response to muscle pain, despite an abundance of literature demonstrating that unilateral pain conditions are commonly associated with bilateral motor dysfunction. For the first time, this study investigated the effect of unilateral acute hamstring pain on bilateral corticomotor organization using transcranial magnetic stimulation (TMS) mapping. Corticomotor outcomes (TMS maps), pain, mechanical sensitivity (pressure pain thresholds), and function (maximal voluntary contractions) were recorded from 28 healthy participants at baseline. An injection of pain-inducing hypertonic (n = 14) or pain-free isotonic (n = 14) saline was then administered to the right hamstring muscle, and pain ratings were collected every 30 seconds until pain resolution. Follow-up measures were taken immediately following pain resolution and at 25, 50, and 75 minutes post-pain resolution. Unilateral acute hamstring pain induced bilateral symptom development and changes in corticomotor reorganization. Two patterns of reorganization were observed-corticomotor facilitation and corticomotor depression. Corticomotor facilitation was associated with increased mechanical sensitivity and decreased function bilaterally (all P < .05). These effects persisted for at least 75 minutes after pain resolution. PERSPECTIVE: These findings suggest that individual patterns of corticomotor reorganization may contribute to ongoing functional deficits of either limb following acute unilateral lower limb pain. Further research is required to assess these adaptations and the possible long-term implications for rehabilitation and reinjury risk in cohorts with acute hamstring injury.

Higher intensity exercise reduces disability more than lower intensity exercise in adults with chronic low back pain: A systematic review and meta-analysis.

BACKGROUND: Intensity is an important determinant of physiological adaptations and health benefits of exercise, but the role of exercise intensity on improving outcomes in people with chronic low back pain (CLBP) is unclear. This systematic review aimed to determine the effect of higher versus lower intensity exercise intensity on pain, disability, quality of life and adverse events in people with CLBP. METHODS: Six databases and four clinical trial registries were searched from inception to 21 December 2022, for randomised controlled trials that compared two or more exercise intensities in adults with CLBP. Data were analysed using random-effects meta-analysis for disability and synthesised narratively for pain, quality of life and adverse events due to limited studies. Risk of bias was assessed using the Cochrane tool and certainty of evidence was evaluated using Grading of Recommendations, Assessment, Development and Evaluations framework. RESULTS: Four trials (n = 214 participants, 84% male) reported across five studies were included. Higher intensity exercise reduced disability more than lower intensity exercise at end-treatment (SMD [95% CI] = -0.39 [-0.56 to -0.22]; very low certainty) but not at 6-month follow-up (SMD [95% CI] = -0.20 [-0.53 to 0.13]; very low certainty). Higher intensity exercise did not reliably improve pain and quality of life more than lower intensity exercise. Adverse events did not differ between exercise intensities. All studies were at high risk of bias. CONCLUSION: Based on very low certainty evidence from a limited number of studies, exercise intensity does not appear to meaningfully influence clinical outcomes in people with CLBP.

Investigating interindividual variability in corticomotor reorganization during sustained hamstring pain: A randomized experimental study.

BACKGROUND: Increasing evidence suggests that pain drives maladaptive corticomotor changes that may increase susceptibility to injury and promote symptom recurrence. However, few studies have evaluated the influence of interindividual corticomotor responses to musculoskeletal pain. Existing research in this area has also been limited largely to the upper limb. This is a pertinent point, given the functional and neurophysiological differences between upper and lower limb muscles, as well as the fact that most acute sporting injuries occur in the lower limb. Accordingly, this study explored the variability of corticomotor responses to experimentally-induced sustained hamstring pain and whether specific patterns of corticomotor reorganization were associated with poorer outcomes (mechanical sensitivity, pain, or functional limitation). METHOD: Thirty-six healthy individuals participated. Following random allocation on Day 0, the experimental group performed an eccentric exercise protocol of the right hamstring muscles to induce delayed onset muscle soreness. The control group performed repetition-matched concentric exercise that did not induce soreness. Measures of mechanical sensitivity, pain, function, and corticomotor organization were collected at baseline and on Day 2. RESULTS AND CONCLUSIONS: Corticomotor responses to sustained hamstring pain were variable. Individuals who developed corticomotor facilitation in response to hamstring pain experienced greater mechanical sensitivity than those who developed corticomotor depression. These novel data could have implications for rehabilitation following lower limb pain or injury.

The Effect of Theta Burst Stimulation Over the Primary Motor Cortex on Experimental Hamstring Pain: A Randomized, Controlled Study.

Theta burst stimulation (TBS) over the primary motor cortex (M1) is an emerging technique that may have utility in the treatment of musculoskeletal pain. However, previous work exploring the analgesic effects of noninvasive brain stimulation has been limited largely to the arm or hand, despite 80% of acute musculoskeletal injuries occurring in the lower limb. This is a pertinent point, given the functional and neurophysiological differences between upper and lower limb musculature, as well as evidence suggesting that reorganization of corticomotor pathways is region-specific. This study investigated the effect of excitatory TBS on pain, function, and corticomotor organization during experimentally induced lower limb pain. Twenty-eight healthy participants attended 2 experimental sessions. On Day 0, participants completed 10 sets of 10 maximal eccentric contractions of the right hamstring muscles to induce delayed onset muscle soreness. Four consecutive blocks of either active or sham TBS were delivered on Day 2. Measures of mechanical sensitivity, pain (muscle soreness, pain intensity, pain area) function (single-leg hop distance, maximum voluntary isometric contraction, lower extremity functional scale), and corticomotor organization were recorded before and after TBS on Day 2. Pain and function were also assessed daily from Days 2 to 10. Active TBS reduced mechanical sensitivity compared to sham stimulation (P = .01). Corticomotor organization did not differ between groups, suggesting that improvements in mechanical sensitivity were not mediated by changes in M1. Subjective reports of pain intensity and function did not change following active TBS, contrasting previous reports in studies of the upper limb. PERSPECTIVE: M1 TBS reduces mechanical sensitivity associated with experimentally induced hamstring pain. Though further work is needed, these findings may hold important implications for those seeking to expedite recovery or reduce muscle sensitivity following hamstring injury.

Reliability and learning effects of repeated exposure to the Bertec Balance Advantage sensory organisation test in healthy individuals.

BACKGROUND: The Sensory Organisation Test (SOT) of computerised dynamic posturography (CDP) is a well-established clinical test used to measure postural control. Advances in technology have enabled new CDP systems to use immersive virtual reality, such as the Bertec® Balance Advantage®. While the Bertec provides an innovative approach to posturography, the reliability and learning effects of the Bertec in administering the SOT has not been thoroughly investigated. RESEARCH QUESTION: To evaluate the reliability and performance during repeated administration of the Bertec® Balance Advantage® SOT. METHODS: Fourteen healthy adults (age 27.17 ± 5.5years; 10 females) participated. Each participant performed five SOTs over three sessions. The first two sessions were approximately two days apart and the third one month later. In the first two sessions, two SOTs were conducted, and in the third session, one was performed. Composite, equilibrium, and ratio scores were used for analysis. RESULTS: Poor within-session reliability was found in the first session for the composite score (ICC: 0.73, 95% CI: 0.32-0.91), which improved by the second session (ICC: 0.84, 95% CI: 0.58-0.94). Poor within-session reliability (ICC <0.5) was found for all ratio and equilibrium scores, except for the equilibrium score of condition 3, which demonstrated moderate reliability (ICC: 0.84, 95% CI: 0.57-0.95). Poor between-session reliability was found for all outcomes. There was an increase in the composite and equilibrium scores for conditions 5 and 6 over the 5 tests, which plateaued after the fourth test, and were retained at 1 month. SIGNIFICANCE: The data demonstrate a steady increase in performance with repeated exposure to the Bertec SOT, which was maintained one month later, indicating a learning effect. We recommend that a minimum of two familiarisation sessions should be administered to establish baseline performance and improve reliability.

Exploring patient perceptions of repetitive transcranial magnetic stimulation as a treatment for chronic musculoskeletal pain: a qualitative study.

OBJECTIVE: Repetitive transcranial magnetic stimulation (rTMS), a form of non-invasive brain stimulation, is a novel avenue for the management of chronic musculoskeletal pain. Despite evidence for the effectiveness of rTMS in chronic pain conditions, the clinical uptake of rTMS remains limited and little is known regarding patient perceptions of this therapeutic technique. DESIGN: Qualitative study using a phenomenological approach, reported in accordance with the Consolidated criteria for Reporting Qualitative research checklist. SETTING: Sydney, Australia. PARTICIPANTS: Fifteen participants were recruited from the community and completed the study. All participants had a diagnosis of chronic musculoskeletal pain, a history of seeking treatment and no prior experience with rTMS. METHODS AND ANALYSIS: All participants completed a semistructured interview to explore overall knowledge, preconceived concerns and attitudes regarding rTMS as a treatment for chronic musculoskeletal pain. The interviews were transcribed verbatim and analysed thematically. RESULTS: The key themes that influenced an individual's hypothetical acceptance of rTMS for chronic pain management were (1) the individual's initial impression of the equipment appearance, (2) the participant's individual history and familiarity with technology, (3) the accessibility and availability of rTMS and (4) knowledge regarding pain physiology and rTMS. CONCLUSIONS: This was the first qualitative study to explore the perception of rTMS as a treatment among people with chronic musculoskeletal pain. RTMS appears to be accepted as a treatment option among individuals with chronic musculoskeletal pain. Developing targeted strategies to address accessibility, funding support and medical endorsements may encourage use of rTMS in a clinical chronic pain setting.

Short-term impact of combining pain neuroscience education with exercise for chronic musculoskeletal pain: a systematic review and meta-analysis.

ABSTRACT: Exercise and pain neuroscience education (PNE) have both been used as standalone treatments for chronic musculoskeletal pain. The evidence supporting PNE as an adjunct to exercise therapy is growing but remains unclear. The aim of this systematic review and meta-analysis was to evaluate the effect of combining PNE and exercise for patients with chronic musculoskeletal pain, when compared with exercise alone. A systematic search of electronic databases was conducted from inception to November 6, 2020. A quality effects model was used to meta-analyze outcomes where possible. Five high-quality randomized controlled studies (n = 460) were included in this review. The PEDro scale was used to assess the quality of individual studies, and Grading of Recommendations, Assessment, Development, and Evaluation analysis was conducted to determine the quality of evidence for each outcome. Meta-analyses were performed for pain intensity, disability, kinesiophobia, and pain catastrophizing using data reported between 0 and 12 weeks postintervention. Long-term outcomes (>12 weeks) were only available for 2 studies and therefore were not suitable for meta-analysis. Meta-analysis revealed a significant difference in pain (weighted mean differences, -2.09/10; 95% confidence interval [CI], -3.38 to -0.80; low certainty), disability (standardized mean difference, -0.68; 95% CI, -1.17 to -0.20; low certainty), kinesiophobia (standardized mean difference, -1.20; CI, -1.84 to -0.57; moderate certainty), and pain catastrophizing (weighted mean differences, -7.72; 95% CI, -12.26 to -3.18; very low certainty) that favoured the combination of PNE and exercise. These findings suggest that combining PNE and exercise in the management of chronic musculoskeletal pain results in greater short-term improvements in pain, disability, kinesiophobia, and pain catastrophizing relative to exercise alone.

The role of the social determinants of health in outcomes of surgery for low back pain: a systematic review and narrative synthesis.

BACKGROUND CONTEXT: Low back pain is a major cause of morbidity and disability worldwide and is responsible for vast societal impact. Rates of surgical intervention for lumbar spine disorders continue to rise but poor outcomes remain common. Understanding how the social determinants of health (SDH) influence spinal surgical outcomes stands to inform appropriately tailored care practices and lead to better patient outcomes. PURPOSE: To determine the relationships between the SDH and pain, opioid use, disability and work absenteeism following lumbar spine surgery. STUDY DESIGN: Systematic review and narrative synthesis. METHODS: We searched Embase, the Cochrane Library, Medline, and Web of Science from inception to April 21, 2020. Studies eligible for inclusion involved participants receiving lumbar spine surgery and investigated the relationship between at least one SDH and post-surgical pain, opioid use, disability or work absenteeism. We evaluated the risk of bias of included studies and used the PROGRESS-Plus framework to organize a narrative synthesis of findings. RESULTS: Relevant data was extracted from twenty-three studies involving 30,987 adults from 12 countries. A total of 107 relationships between the SDH and post-surgical outcomes were evaluated, 67 in multivariate analyses. Education was investigated in 23 analyses (14 studies): 70% revealed significant independent relationships between lower education and poorer outcomes. Socioeconomic status was investigated in nine analyses (four studies): 67% revealed independent relationships between lower socioeconomic status and poorer outcomes. Gender was investigated in 40 analyses (22 studies): indications that male versus female sex was associated with poorer outcomes were equivocal. Place of residence, race/ethnicity, and social capital were infrequently investigated. CONCLUSIONS: Low educational attainment and low-income status are clear independent contributors to poorer outcomes following lumbar spine surgery. Occupational factors and work context are likely to be influential. Further research is critical to guide best-practice spinal surgery through a health equity lens. STUDY REGISTRATION: PROSPERO registration number CRD42015015778.

Transcranial Direct Current Stimulation Accelerates The Onset of Exercise-Induced Hypoalgesia: A Randomized Controlled Study.

Exercise-induced hypoalgesia (EIH) describes acute reductions in pain that occur following exercise. Current evidence suggests that the magnitude of EIH is small-to-moderate at best, warranting exploration of novel avenues to bolster these effects. Transcranial direct current stimulation (tDCS) has been shown to relieve pain and represents a promising intervention that may enhance EIH. This study aimed to determine whether anodal tDCS of the primary motor cortex (M1) can augment EIH in healthy individuals experiencing experimentally-induced musculoskeletal pain. Twenty-four healthy subjects attended 2 experimental sessions ("Day 0" and "Day 2"). On Day 0, subjects were injected with nerve growth factor into their right extensor carpi radialis brevis to induce persistent elbow pain. On Day 2, each subject received active or sham tDCS over M1 followed by an isometric grip exercise. Pain intensity, muscle soreness, sensitivity (pressure pain thresholds), and conditioned pain modulation were assessed prior to the nerve growth factor injection, on Day 2 before tDCS, immediately post-exercise, and 15 minutes post-exercise. Active tDCS expedited the onset of EIH, inducing immediate reductions in pain intensity that were not present until 15 minutes post-exercise in the sham group. However, active tDCS did not reduce muscle soreness or sensitivity when compared to sham tDCS. PERSPECTIVE: These findings suggest that active tDCS accelerates the onset of EIH in healthy individuals experiencing experimentally-induced pain. This may represent a promising means of enhancing adherence to exercise protocols. However, larger randomised controlled trials in persistent pain populations are required to confirm the clinical impact of these findings.

The Acute Readiness Monitoring Scale: Assessing Predictive and Concurrent Validation.

To complement and enhance readiness-monitoring capability, the Acute Readiness Monitoring Scale (ARMS) was developed: a widely applicable, simple psychometric measure of perceived readiness. While this tool may have widespread utility in sport and military settings, it remains unknown if the ARMS demonstrates predictive and concurrent validity. Here, we investigated whether the ARMS is: (1) responsive to an acute manipulation of readiness using sleep deprivation, (2) relates to biological markers of readiness [cortisol/heart-rate variability (HRV)], and (3) predicts performance on a cognitive task. Thirty young adults (aged 23 ± 4 years; 18 females) participated. All participants engaged in a 24-h sleep deprivation protocol. Participants completed the ARMS, biological measures of readiness (salivary cortisol, HRV), and cognitive performance measures (psychomotor vigilance task) before, immediately after, 24-, and 48-h post-sleep deprivation. All six of the ARMS subscales changed in response to sleep deprivation: scores on each subscale worsened (indicating reductions in perceived readiness) immediately after sleep deprivation, returning to baseline 24/48 h post. Lower perceived readiness was associated with reduced awakening responses in cortisol and predicted worse cognitive performance (slower reaction time). No relationship was observed between the ARMS and HRV, nor between any biological markers of readiness (cortisol/HRV) and cognitive performance. These data suggest that the ARMS may hold practical utility in detecting, or screening for, the wide range of deleterious effects caused by sleep deprivation; may constitute a quick, cheap, and easily interpreted alternative to biological measures of readiness; and may be used to monitor or mitigate potential underperformance on tasks requiring attention and vigilance.

Prevalence and incidence of phantom limb pain, phantom limb sensations and telescoping in amputees: A systematic rapid review.

BACKGROUND AND OBJECTIVE: This systematic, rapid review aimed to critically appraise and synthesize the recent literature (2014-2019) evaluating the incidence and prevalence of post-amputation phantom limb pain (PLP) and sensation (PLS). DATABASES AND DATA TREATMENT: Five databases (Medline, Embase, Emcare, PsychInfo, Web of Science) and Google Scholar were searched, with two independent reviewers completing eligibility screening, risk of bias assessment and data extraction. RESULTS: The search identified 1,350 studies with 12 cross-sectional and 3 prospective studies included. Studies evaluated traumatic (n = 5), atraumatic (n = 4), and combined traumatic/atraumatic (n = 6) amputee populations, ranging from 1 month to 33 years post-amputation. Study heterogeneity prevented data pooling. The majority of studies had a high risk of bias, primarily due to limited generalizability. Three studies evaluated PLP incidence, ranging from 2.2% (atraumatic; 1 month) to 41% (combined; 3 months) and 82% (combined; 12 months). Only one study evaluated PLS/telescoping incidence. Across contrasting populations, PLP point prevalence was between 6.7%-88.1%, 1 to 3-month period prevalence was between 49%-93.5%, and lifetime prevalence was high at 76%-87%. Point prevalence of PLS was 32.4%-90%, period prevalence was 65% (1 month) and 56.9% (3 months), and lifetime prevalence was 87%. Telescoping was less prevalent, highest among traumatic amputees (24.6%) within a 1-month prevalence period. Variations in population type (e.g. amputation characteristics) and incidence and prevalence measures likely influence the large variability seen here. CONCLUSIONS: This review found that lifetime prevalence was the highest, with most individuals experiencing some type of phantom phenomena at some point post-amputation. SIGNIFICANCE: This systematic rapid review provides a reference for clinicians to make informed prognosis estimates of phantom phenomena for patients undergoing amputation. Results show that most amputees will experience phantom limb pain (PLP) and phantom limb sensations (PLS): high PLP incidence 1-year post-amputation (82%); high lifetime prevalence for PLP (76%-87%) and PLS (87%). Approximately 25% of amputees will experience telescoping. Consideration of individual patient characteristics (cause, amputation site, pre-amputation pain) is pertinent given their likely contribution to incidence/prevalence of phantom phenomena.

Interrogating cortical representations in elite athletes with persistent posterior thigh pain - New targets for intervention?

OBJECTIVES: Hamstring injuries in athletes can lead to significant time away from competition as a result of persistent posterior thigh pain. These cases are often difficult to treat as the state of the tissues alone cannot explain symptoms. In non-athletic populations with persistent pain, disruptions to tactile, proprioceptive, and spatial cortical representations exist, which has led to promising brain-based treatments. Here, we explored whether athletes with persistent posterior thigh pain also display impairments in these cortical representations. DESIGN: Cross-sectional study. METHODS: Fourteen male professional athletes with persistent posterior thigh pain ('Patients') and 14 pain-free age, sport, body mass index and level-matched controls ('Controls') participated. The tactile cortical representation was assessed using two-point discrimination (TPD) threshold and accuracy of tactile localisation; the proprioceptive cortical representation was assessed using a left/right judgement task; spatial processing was assessed using an auditory detection task. RESULTS: TPD thresholds were similar for Patients and Controls (p=0.70). Patients were less accurate at localising tactile stimuli delivered to their affected leg, slower to make left/right judgements when the lower limb image corresponded to the side of their affected leg, and less accurate at detecting auditory stimuli delivered near their affected leg, when compared to their healthy leg or to the leg of Controls (p<0.01 for all). CONCLUSIONS: Leg-specific tactile, proprioceptive, and spatial processing deficits exist in athletes with persistent posterior thigh pain. That these processing deficits exist despite rehabilitation and normal tissue healing time suggests they may play a role in the persistence of posterior thigh pain.

Repetitive transcranial magnetic stimulation of the primary motor cortex expedites recovery in the transition from acute to sustained experimental pain: a randomised, controlled study.

Repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex (M1) is increasingly being investigated as a means of alleviating chronic pain. However, rTMS interventions are typically initiated once pain has already become chronic and maladaptive patterns of neural activity are likely to have been established. A critical question is whether M1 rTMS applied soon after pain onset can prevent the development of maladaptive neural activity and promote recovery. This study investigated the effect of 5 consecutive days of excitatory M1 rTMS on pain, functional limitation, mechanical hyperalgesia, descending inhibitory pain control, and M1 organisation in the transition from acute to sustained pain. Thirty healthy participants attended 8 sessions over a 16-day period. On days 0, 2, and 4, nerve growth factor was injected into the right forearm to induce progressively developing muscle soreness and mechanical hyperalgesia. Active or sham excitatory rTMS was delivered on days 4 to 8. Clinical and neurophysiological outcomes were recorded on days 0, 2, 4, 6, 8, 11, and 14. Active rTMS promoted recovery of muscle soreness, pain, and mechanical hyperalgesia when compared with sham rTMS (all between-group P < 0.05). Corticomotor excitability and descending inhibitory pain control did not differ between groups. These findings suggest that active excitatory M1 rTMS promotes recovery of muscle soreness, pain, and mechanical hyperalgesia in the transition from acute to sustained experimental pain. The analgesic effects of M1 rTMS do not seem to be modulated by descending inhibitory pain control or local changes in corticomotor excitability.