Efficacy of Pulsed Electromagnetic Therapy for Chronic Lower Back Pain: A Randomized, Double-blind, Placebo-controlled Study

Efficacy of Pulsed Electromagnetic Field Therapy for Pain Management After Impacted Mandibular Third Molar Surgery. A Randomized Clinical Trial

BACKGROUND

Postoperative pain and swelling associated with the removal of the third molar (M3) adversely affect the patient's quality of life.

PURPOSE

The study aims to measure pain reduction and analgesic use in patients treated with pulsed electromagnetic field (PEMF) therapy following M3 removal and compares it to patients who did not receive PEMF.

STUDY DESIGN, SETTING, SAMPLE

The single-center study was designed as a randomized, prospective, controlled, double-blinded trial on a sample of patients with impacted mandibular M3 ascertained by x-ray orthopantomography and computed tomography.

PREDICTOR/EXPOSURE/INDEPENDENT VARIABLES

The predictor variable is postoperative pain management. It was assigned randomly to each subject who received either PEMF or standard therapy.

MAIN OUTCOME VARIABLES

The pain was quantified using a 100 mm visual analog scale and the number of analgesics taken. Each subject kept a daily clinical diary for 7 days, recording the amount of pain using the visual analog scale and the number of analgesic tablets taken.

COVARIATES

The study covariates were age, sex, tobacco use, and Pell and Gregory's classification of M3s.

ANALYSES

Student t test was used, placing the statistical significance for P value < .05. The primary planned analysis was a 2-group, continuity-corrected, χ2 test of equality of proportions.

RESULTS

The study sample included 90 patients, 47 men and 43 women, with an average age of 32.43 ± 8.80 years. PEMF was statistically associated with improved pain reduction (2.08 vs 5.04 with a P value = .0002) and consumption of fewer analgesics than the control group (2.6 vs 5.8 with a P value = .0062).

CONCLUSIONS AND RELEVANCE

The study's results attest to the effectiveness of PEMF therapy in pain control after M3 surgery.

Spinal magnetic stimulation to treat chronic back pain: a feasibility study in veterans

Aim: Chronic low back pain represents a significant societal problem leading to increased healthcare costs and quality of life. This study was designed to evaluate the feasibility and effectiveness of non-invasive spinal electromagnetic simulation (SEMS) to treat nonspecific chronic low back pain (CLBP). Methods: A single-site prospective study was conducted to evaluate SEMS in reducing pain and improving disability. A total of 17 patients received SEMS two to three sessions a week. The Numeric Rating Scale and the Modified Oswestry Disability Questionnaire were used to assess pain and disability. Results: Participants receiving SEMS exhibited statistically significant reductions in pain and disability. Conclusion: Current results suggest that non-invasive SEMS can be an effective treatment in reducing pain and improving disability associated with CLBP.

[Physiotherapy in rehabilitation of patients with degenerative disk diseases from positions of evidence-based medicine: a literature review]

Back pain is one of the most urgent problems of rehabilitation. Patients with this pathology have a leading place among neurological patients in terms of the number of days of disability. The high economic costs in society are explained by the need for lumbar surgery (discectomy, spinal fusion and disc prosthesis) and rehabilitation after it. The effectiveness of rehabilitative measures is determined both by the patient's rehabilitative potential and by the choice of rehabilitative methods.

OBJECTIVE

To evaluate the effectiveness of physiotherapy in patients with degenerative disk diseases from positions of evidence-based medicine according to the scientific and technical literature.

MATERIAL AND METHODS

The analysis of scientific and technical literature sources and the study of materials of meta-analyses, systematic reviews (depth of search was 20 years) on the evaluation of effectiveness of physiotherapeutical methods in the rehabilitation of patients with degenerative disk diseases have been conducted.

RESULTS

The ability of pulsed magnetic field to reduce the intensity of pain and improve the functional capacities of the spine in patients with low back pain has been identified. There was a pronounced analgesic end-point of low-level laser therapy in acute and chronic back pain at short and medium-term (up to 12 months) observation, as well as the ability of the method to reduce temporary disability in degenerative disk diseases.

CONCLUSION

The use of magnetotherapy and low-level laser therapy can be recommended for the treatment of patients with degenerative disk diseases (C grade of recommendations, 3rd level of evidence). The recommendation is based on the results of 10 RCTs (1.111 patients with degenerative disk diseases), 3 meta-analyses, 1 systematic review and 1 Cochrane review (a total of 3.431 patients).

Efficacy of pulsed electromagnetic field therapy on pain and physical function in patients with non-specific low back pain: a systematic review

INTRODUCTION

Non-specific low back pain is a common and clinically significant condition with substantial socioeconomic implications. Pulsed electromagnetic field (PEMF) therapy has shown benefits in pain reduction and improvement of physical function in patients with pain-associated disorders like osteoarthritis. However, studies had heterogeneous settings. The aim of this study was to assess the effects of PEMF on pain and function on patients with non-specific low back pain.

METHODS

A systematic literature search of randomized controlled trials in PubMed, MEDLINE, EMBASE, Cochrane Library, and PEDro was performed (from inception until 15/5/2023). Outcome measures assessed pain and function.

RESULTS

Nine randomized controlled trials with 420 participants (n = 420) were included. The studies compared PEMF vs. placebo-PEMF, PEMF and conventional physical therapy vs. conventional physical therapy alone, PEMF and conventional physical therapy vs. placebo-PEMF and conventional physical therapy, PEMF vs. high-intensity laser therapy (HILT) vs. conventional physical therapy, and osteopathic manipulative treatment (OMT) and PEMF vs. PEMF alone vs. placebo-PEMF vs. OMT alone. Five of the nine included studies showed statistically significant pain reduction and improvement in physical function in comparison to their control groups (p < 0.05). There was substantial heterogeneity among the groups of the study, with a wide range of duration (10-30 min), treatments per week (2-7/week), applied frequencies (3-50 Hz), and intensities (2mT-150mT). No serious adverse event had been reported in any study. The included studies showed solid methodological quality, with an overall score of 7.2 points according to the PEDro scale.

CONCLUSION

PEMF therapy seems to be a safe and beneficial treatment option for non-specific low back pain, particularly if used as an addition to conventional physical therapy modalities. Future research should focus on standardized settings including assessment methods, treatment regimens, frequencies, and intensities.

Evaluation of the Analgesic Efficacy of a Bioelectronic Device in Non-Specific Chronic Low Back Pain with Neuropathic Component. A Randomized Trial

Low energy pulsed electromagnetic signals (PEMS) therapy, in the field of bioelectronics, has been suggested as a promising analgesic therapy with special interest in treating conditions with poor response to pharmacotherapy. This study evaluated the effectiveness of PEMS therapy on the treatment of chronic low back pain patients with a neuropathic component. A group of 64 individuals with such condition was allocated to a 2-week treatment period (10 twenty-minute sessions on consecutive days) with an active PEMS therapy device or an inactive device in random order. The pain was assessed on a visual analog scale, and the functional status was assessed using the SF-12 questionnaire. The visual analog scale scores were lower after treatment than at baseline but only in the group treated with the active device. According to the DN4 score, neuropathic pain decreased in both experimental groups with respect to baseline, but this was only significant for the group treated with the active device. Similarly, an improvement in the SF-12 and Medical Outcomes Study (MOS) sleep scale components was reported. The study demonstrated that low-energy PEMS therapy was efficient in reducing pain and improving function in chronic low back pain patients with a neuropathic component.

Translational Insights into Extremely Low Frequency Pulsed Electromagnetic Fields (ELF-PEMFs) for Bone Regeneration after Trauma and Orthopedic Surgery

The finding that alterations in electrical potential play an important role in the mechanical stimulation of the bone provoked hype that noninvasive extremely low frequency pulsed electromagnetic fields (ELF-PEMF) can be used to support healing of bone and osteochondral defects. This resulted in the development of many ELF-PEMF devices for clinical use. Due to the resulting diversity of the ELF-PEMF characteristics regarding treatment regimen, and reported results, exposure to ELF-PEMFs is generally not among the guidelines to treat bone and osteochondral defects. Notwithstanding, here we show that there is strong evidence for ELF-PEMF treatment. We give a short, confined overview of in vitro studies investigating effects of ELF-PEMF treatment on bone cells, highlighting likely mechanisms. Subsequently, we summarize prospective and blinded studies, investigating the effect of ELF-PEMF treatment on acute bone fractures and bone fracture non-unions, osteotomies, spinal fusion, osteoporosis, and osteoarthritis. Although these studies favor the use of ELF-PEMF treatment, they likewise demonstrate the need for more defined and better controlled/monitored treatment modalities. However, to establish indication-oriented treatment regimen, profound knowledge of the underlying mechanisms in the sense of cellular pathways/events triggered is required, highlighting the need for more systematic studies to unravel optimal treatment conditions.

Short-Term impacts of pulsed electromagnetic field therapy in middle-aged university's employees with non-specific low back pain: A pilot study

Objective:

Non-specific low back pain (non-specific LBP) is common problem between office-work employees. This study aimed to evaluate the short-term impacts of Pulsed Electromagnetic Field (PEMF) therapy in the treatment of non-specific LBP symptoms as pain, back mobility, LBP disabilities, and Health–Related Quality of Life (HRQOL).

Methods:

Forty-two University’s employees with non-specific LBP and aged from 35 to 55 years who participated in this study from January to June 2018 were divided into two groups: group A; received PEMF therapy and group B; received sham treatment. The outcome measures were; numerical rating scale, Modified Oswestry LBP Disability Score, Modified Schober test, and the Short Form-36 questionnaire. Evaluations were performed for both groups before and after finishing treatment.

Results:

All outcome measures were significantly improved statistically in the experimental group at the end of the intervention (p<0.05). On the other hand, there were non-significant differences in all outcome measures in the sham group (p>0.05).

Conclusions:

PEMT therapy may decrease pain, LBP disability, increase lumbar spine mobility, and improve HRQOL in middle-aged university’s employees with nonspecific LBP.

Effects of pulsed low-frequency magnetic field therapy on pain intensity in patients with musculoskeletal chronic low back pain: study protocol for a randomised double-blind placebo-controlled trial

INTRODUCTION

The aim of the present study is to investigate the effectiveness of pulsed low-frequency magnetic field (PLFMF) on the management of chronic low back pain (CLBP).

METHODS AND ANALYSIS

A randomised double-blinded controlled clinical trial will be conducted, involving 200 patients with CLBP. Participants will be randomised in a 1:1 ratio to receive either active PLFMF (experimental arm) or sham treatment (control arm) using a permuted-block design which will be stratified according to three subtypes of musculoskeletal CLBP (nociceptive, peripheral neuropathic or central sanitisation). The intervention consists of three sessions/week for 6 weeks. The primary outcome is the percentage change in Numerical Rating Scale (NRS) pain at week 24 after treatment completion with respect to the baseline. Secondary outcomes include percentage NRS pain during treatment and early after treatment completion, short form 36 quality of life, Roland and Morris Disability Questionnaire; Depression Anxiety Stress Scale 21, Patient Specific Functional Scale, Global perceived effect of condition change, Pittsburgh Sleep Quality Index and Modified Fatigue Impact Scale. Measures will be taken at baseline, 3 and 6 weeks during the intervention and 6, 12 and 24 weeks after completing the intervention. Adverse events between arms will be evaluated. Data will be analysed on an intention-to-treat basis.

ETHICS AND DISSEMINATION

The study is funded by Imam Abdulrahman Bin Faisal University (IAU). It has been approved by the institutional review board of IAU (IRB- 2017-03-129). The study will be conducted at King Fahd Hospital of the University and will be monitored by the Hospital monitoring office for research and research ethics. The trial is scheduled to begin in September 2018. Results obtained will be presented in international conferences and will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ACTRN12618000921280, prospectively.

The effect of pulsed electromagnetic frequency therapy on health-related quality of life in military service members with chronic low back pain

BACKGROUND

In the U.S. military, chronic low back pain is among the most frequent complaints for medical visits, lost work time, and attrition from active duty and the deployed setting by service members.

PURPOSE

The aim of this pilot study was to determine whether adjunctive treatment with pulsed electromagnetic frequency (PEMF) produced significant variability in chronic low back pain symptoms and secondary health-related quality of life, mental health and disability outcomes.

METHODS

Prospective, randomized pilot study with repeated measures at baseline, post-treatment, and 1 month follow-up for two groups: usual care (UC) vs. UC + PEMF.

FINDINGS

In a convenience sample of 75 service members, health-related quality of life mental and physical component scores were significant: F(2, 104) = 4.20, p = .018 (η² = .075) and F(2, 104) = 4.75, p = .011 (η² = .084), respectively; as was anxiety symptom severity: F(2, 104) = 5.28, p = .007 (η² = .092).

DISCUSSION AND RECOMMENDATIONS

Adjunctive treatment with PEMF demonstrated improvements in service members' overall physical health-related quality of life with expected, yet statistically nonsignificant improvements in reported pain and LBP-related disability. There were significant between group differences in anxiety symptom severity with higher symptoms reported by the UC + PEMF group, surprising findings that warrant further investigation.

Pulsed magnetic field versus ultrasound in the treatment of postnatal carpal tunnel syndrome: A randomized controlled trial in the women of an Egyptian population

The aim of this study was to compare the effects of pulsed electromagnetic field versus pulsed ultrasound in treating patients with postnatal carpal tunnel syndrome. The study was a randomized, double-blinded trial. Forty postnatal female patients with idiopathic carpal tunnel syndrome were divided randomly into two equal groups. One group received pulsed electromagnetic field, with nerve and tendon gliding exercises for the wrist, three times per week for four weeks. The other group received pulsed ultrasound and the same wrist exercises. Pain level, sensory and motor distal latencies and conduction velocities of the median nerve, functional status scale and hand grip strength were assessed pre- and post-treatment. There was a significant decrease (P < 0.05) in pain level, sensory and motor distal latencies of the median nerve, and significant increase (P < 0.05) in sensory and motor conduction velocities of the median nerve and hand grip strength in both groups, with a significant difference between the two groups in favour of pulsed electromagnetic field treatment. However, the functional status scale showed intergroup no significant difference (P > 0.05). In conclusion, while the symptoms were alleviated in both groups, pulsed electromagnetic field was more effective than pulsed ultrasound in treating postnatal carpal tunnel syndrome.

Pulsed electromagnetic field therapy effectiveness in low back pain: A systematic review of randomized controlled trials

Background

Low back pain is a worldwide prevalent musculoskeletal condition in the general population. In this sense, the pulsed electromagnetic fields (PEMF) therapy has shown significant clinical benefits in several musculoskeletal conditions.

Objective

To assess the effectiveness of the PEMF therapy in reducing pain and clinical symptomatology in patients with low back pathological conditions.

Methods

It was performed a comprehensive database search using Pubmed, Scopus, Cochrane Library and PEDro databases to assess the effectiveness of the PEMF therapy in reducing pain and clinical symptomatology in patients with low back pathological conditions. The search was performed from January 2005 to August 2015 and conducted by two independent investigators, which scrutinize the reference list of most relevant studies. The methodological quality was assessed by the PEDro scale and the level of evidence was set according Oxford Center for Evidence-Based Medicine scale.

Results

Six studies were eligible inclusion on the qualitative analysis and five into the quantitative analysis, scoring an overall 6.8 points according the PEDro scale. The studies showed heterogeneity concerning the intervention protocols. Nevertheless, the effect sizes' indicated a clear tendency to reduction of the pain intensity favoring the PEMF groups, reaching a minimal clinically important difference.

Conclusion

PEMF therapy seems to be able to relieve the pain intensity and improve functionality in individuals with low back pain conditions. Further research is needed regarding PEMF effects on the different conditions of low back pain, with standardized protocols, larger samples and adjustment for low back pain confounders in order to achieve stronger conclusions.

Disruption of the ovarian follicle reservoir of prepubertal rats following prenatal exposure to a continuous 900-MHz electromagnetic field

The effects on human health of electromagnetic field (EMF) have begun to be seriously questioned with the entry into daily life of devices establishing EMF, such as cell phones, wireless fidelity, and masts. Recent studies have reported that exposure to EMF, particularly during pregnancy, affects the developing embryo/fetus. The aim of this study was therefore to examine the effects of exposure to continuous 900-Megahertz (MHz) EMF applied in the prenatal period on ovarian follicle development and oocyte differentiation. Six pregnant Sprague Dawley rats were divided equally into a non-exposed control group (CNGr) and a group (EMFGr) exposed to continuous 900-MHz EMF for 1 h daily, at the same time every day, on days 13-21 of pregnancy. New groups were established from pups obtained from both groups after birth. One group consisting of female pups from CNGr rats was adopted as newborn CNGr (New-CNGr, n = 6), and another group consisting of female pups from EMFGr rats was adopted as newborn EMFGr (New-EMFGr, n = 6). No procedure was performed on New-CNGr or New-EMFGr rats. All rat pups were sacrificed on the postnatal 34th day, and their ovarian tissues were removed. Follicle count, histological injury scoring and morphological assessment with apoptotic index criteria were performed with sections obtained following routine histological tissue preparation. Follicle count results revealed a statistically significant decrease in primordial and tertiary follicle numbers in New-EMFGr compared to New-CNGr (p < 0.05), while atretic follicle numbers and apoptotic index levels increased significantly (p < 0.05). Histopathological examination revealed severe follicle degeneration, vasocongestion, a low level of increased stromal fibrotic tissue and cytoplasmic vacuolization in granulosa cell in New-EMFGr. Prenatal exposure to continuous 900-MHz EMF for 1 h each day from days 13-21 led to a decrease in ovarian follicle reservoirs in female rat pups at the beginning of the prepubertal period.

Mechanisms and therapeutic applications of electromagnetic therapy in Parkinson's disease

Electromagnetic therapy is a non-invasive and safe approach for the management of several pathological conditions including neurodegenerative diseases. Parkinson's disease is a neurodegenerative pathology caused by abnormal degeneration of dopaminergic neurons in the ventral tegmental area and substantia nigra pars compacta in the midbrain resulting in damage to the basal ganglia. Electromagnetic therapy has been extensively used in the clinical setting in the form of transcranial magnetic stimulation, repetitive transcranial magnetic stimulation, high-frequency transcranial magnetic stimulation and pulsed electromagnetic field therapy which can also be used in the domestic setting. In this review, we discuss the mechanisms and therapeutic applications of electromagnetic therapy to alleviate motor and non-motor deficits that characterize Parkinson's disease.

Treatment of failed back surgery syndrome in a forty-three-year-old man with high-dose oxycodone/naloxone

Introduction:

Failed back surgery syndrome (FBSS) is an increasing cause of chronic pain in most countries. This poses high costs to both patients and National Health Organizations.

Case Presentation:

In this report, multimodal pain management based on daily high-dose oxycodone/naloxone (OXN 180/90 mg) led to reduced patient's pain score and improved quality of life.

Conclusions:

Oxycodone/naloxone can be a good alternative for the management of FBSS when other interventional or pharmacologic strategies have failed. In this case report, higher doses than those recommended as a maximum daily ceiling (80/40 mg) were safely used in one selected patient with noncancer severe pain.

A literature review reveals that trials evaluating treatment of non-specific low back pain use inconsistent criteria to identify serious pathologies and nerve root involvement

OBJECTIVES

The broad aim of this study was to assess the homogeneity of patients included in trials of non-specific low back pain (NSLBP). To do this, we investigated the consistency and clarity of criteria used to identify and exclude participants with serious pathologies and nerve root compromise in randomized controlled trials, investigating interventions for NSLBP.

METHODS

We searched Medline database for randomized controlled trials of low back pain (LBP). published between 2000 and 2009. We then randomly selected and screened trials for inclusion until we had 50 eligible trials. Data were extracted on the criteria used to identify cases of serious conditions (e.g. cancer, fracture) and nerve root involvement.

RESULTS

The majority of papers (35/50) explicitly excluded patients with serious pathology. However, the terminology used and examples given were highly variable. Nerve root involvement was an exclusion criterion in the majority but not all studies. The criteria used for excluding patients with nerve root involvement varied greatly between studies. The most common criteria were 'motor, sensory or reflex changes' (nine studies), followed by 'pain radiating below the knee' (five studies) and 'reduced straight leg raise which reproduces leg pain' (five studies). In half of the included studies, the criteria used, while alluding to nerve root involvement, were not explained adequately for us to determine the types of patients included or excluded.

DISCUSSION

The inconsistent and unclear criteria used to identify cases of serious pathology and nerve root compromise means that published trials of LBP likely include heterogeneous patient populations. This trait limits our ability to make comparisons across trials or pool studies. Standardization and consensus is important for future research.

[Medical relevance of magnetic fields in pain therapy]

BACKGROUND

Magnetic and electromagnetic fields have been accepted as real physical entities in medicine and are believed to achieve pain relief. Magnetic field therapy has been acknowledged as a non-invasive, safe and simple method for treatment of the site of injury, source of pain or inflammation, or other types of illnesses and pathologies. However, a consensus regarding the statistical relevance of the effects has not been established.

MATERIALS AND METHODS

A detailed literature research was performed and the results were evaluated. Inclusion criteria were that the studies had to be randomized, double-blind and placebo-controlled, and no additional forms of treatment other than magnetic effects were allowed to be used.

RESULTS

The evaluation of 17 studies with static magnetic fields showed on average no significant difference in pain relief between the group treated with magnetic fields and the placebo group. All studies using magnetic fields showed that forms of treatment conducted over a period of 30 min and at intervals of 1 week have no effects. In 10 studies with dynamic magnetic fields different effects were registered, which ranged from no effect to significant differences regarding pain relief between the treated and the control groups.

CONCLUSIONS

Static magnetic fields are ineffective with respect to pain therapy. Dynamic magnetic fields show diverse effects. Hence, this therapy should be researched in depth.

Evaluation of the efficacy of pulsed electromagnetic field in the management of patients with diabetic polyneuropathy

AIM

The study was carried out to evaluate and compare the effect of low power, low frequency pulsed electromagnetic field (PEMF) of 600 and 800 Hz, respectively, in management of patients with diabetic polyneuropathy.

SETTINGS AND DESIGNS

The study was a randomized controlled trial performed in Guru Nanak Dev University and Medical College, Amritsar, India with different subject experimental design.

MATERIALS AND METHODS

Thirty subjects within an age group of 40-68 years with diabetic polyneuropathy stages N1a, N1b, N2a were randomly allocated to groups 1, 2, 3 with 10 subjects in each. Group 1 and 2 were treated with low power 600 and 800-Hz PEMF for 30 min for 12 consecutive days. Group 3 served as control on usual medical treatment of diabetic polyneuropathy (DPN). The subjects with neuropathy due to any cause other than diabetes were excluded. The pain and motor nerve conduction parameters (distal latency, amplitude, nerve conduction velocity) were assessed before and after treatment.

STATISTICAL ANALYSIS

Related t-test and unrelated t-test were used for data analysis.

RESULTS

Significant reduction in pain and statistically significant (P<0.05) improvement in distal latency and nerve conduction velocity were seen in experimental group 1 and 2.

CONCLUSIONS

Low-frequency PEMF can be used as an adjunct in reducing neuropathic pain as well as for retarding the progression of neuropathy in a short span of time.

Analgesic effects of treatments for non-specific low back pain: a meta-analysis of placebo-controlled randomized trials

OBJECTIVE

Estimates of treatment effects reported in placebo-controlled randomized trials are less subject to bias than those estimates provided by other study designs. The objective of this meta-analysis was to estimate the analgesic effects of treatments for non-specific low back pain reported in placebo-controlled randomized trials.

METHODS

Medline, Embase, Cinahl, PsychInfo and Cochrane Central Register of Controlled Trials databases were searched for eligible trials from earliest records to November 2006. Continuous pain outcomes were converted to a common 0-100 scale and pooled using a random effects model.

RESULTS

A total of 76 trials reporting on 34 treatments were included. Fifty percent of the investigated treatments had statistically significant effects, but for most the effects were small or moderate: 47% had point estimates of effects of <10 points on the 100-point scale, 38% had point estimates from 10 to 20 points and 15% had point estimates of >20 points. Treatments reported to have large effects (>20 points) had been investigated only in a single trial.

CONCLUSIONS

This meta-analysis revealed that the analgesic effects of many treatments for non-specific low back pain are small and that they do not differ in populations with acute or chronic symptoms.

Imperfect placebos are common in low back pain trials: a systematic review of the literature

The placebo is an important tool to blind patients to treatment allocation and therefore minimise some sources of bias in clinical trials. However, placebos that are improperly designed or implemented may introduce bias into trials. The purpose of this systematic review was to evaluate the adequacy of placebo interventions used in low back pain trials. Electronic databases were searched systematically for randomised placebo-controlled trials of conservative interventions for low back pain. Trial selection and data extraction were performed by two reviewers independently. A total of 126 trials using over 25 different placebo interventions were included. The strategy most commonly used to enhance blinding was the provision of structurally equivalent placebos. Adequacy of blinding was assessed in only 13% of trials. In 20% of trials the placebo intervention was a potentially genuine treatment. Most trials that assessed patients' expectations showed that the placebo generated lower expectations than the experimental intervention. Taken together, these results demonstrate that imperfect placebos are common in low back pain trials; a result suggesting that many trials provide potentially biased estimates of treatment efficacy. This finding has implications for the interpretation of published trials and the design of future trials. Implementation of strategies to facilitate blinding and balance expectations in randomised groups need a higher priority in low back pain research.