The effect of journal impact factor, reporting conflicts, and reporting funding sources, on standardized effect sizes in back pain trials: a systematic review and meta-regression
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Low back pain is a common and costly health complaint for which there are several moderately effective treatments. In some fields there is evidence that funder and financial conflicts are associated with trial outcomes. It is not clear whether effect sizes in back pain trials relate to journal impact factor, reporting conflicts of interest, or reporting funding.
We performed a systematic review of English-language papers reporting randomised controlled trials of treatments for non-specific low back pain, published between 2006-2012. We modelled the relationship using 5-year journal impact factor, and categories of reported of conflicts of interest, and categories of reported funding (reported none and reported some, compared to not reporting these) using meta-regression, adjusting for sample size, and publication year. We also considered whether impact factor could be predicted by the direction of outcome, or trial sample size.
We could abstract data to calculate effect size in 99 of 146 trials that met our inclusion criteria. Effect size is not associated with impact factor, reporting of funding source, or reporting of conflicts of interest. However, explicitly reporting ‘no trial funding’ is strongly associated with larger absolute values of effect size (adjusted β=1.02 (95 % CI 0.44 to 1.59), P=0.001). Impact factor increases by 0.008 (0.004 to 0.012) per unit increase in trial sample size (P<0.001), but does not differ by reported direction of the LBP trial outcome (P=0.270).
The absence of associations between effect size and impact factor, reporting sources of funding, and conflicts of interest reflects positively on research and publisher conduct in the field. Strong evidence of a large association between absolute magnitude of effect size and explicit reporting of ‘no funding’ suggests authors of unfunded trials are likely to report larger effect sizes, notwithstanding direction. This could relate in part to quality, resources, and/or how pragmatic a trial is.
KeywordsBack pain Impact factor Effect size Conflicts of interest Funding Reporting Publication bias Meta-regression REML
Consolidated standards of reporting trials
Conflict of interest
(Thomson Reuters) Institute for scientific information
Low back pain
Randomised controlled trial
Restricted maximum likelihood
Standardised mean difference
Re-standardised standard error
Years lived with disability
Low back pain (LBP) is a common and costly health complaint for which the life-time prevalence may be as high as 84 % . Each year approximately 4 % of the UK population take time off work because of LBP; this equates to around 90 million working days lost and between eight and 12 million GP consultations per year [2, 3]. Globally, LBP ranks number one for contributions to Years Lived with Disability (YLDs) . Several therapist-delivered interventions have been identified as useful for the early management of persistent non-specific LBP . It can be difficult to choose which interventions will suit which patients, so guidelines recommend taking account of patient preference . This is in part due to the different reporting methods used, the variance of reported effect sizes and a paradox that in the largest trials effect sizes tend to be quite similar irrespective of intervention and small to medium in magnitude [6, 7]. We are currently unable to determine for whom a particular treatment will be effective, as outcome has not often been shown to be dependent on participant characteristics . Notwithstanding these challenges, a great deal of trust is placed in authors’ work and their estimates of treatment effect sizes, which inform decision-making and policy .
Readers of LBP trial reports often look first at the abstract and conclusion . Some go on to look at potential known sources of bias such as lack of allocation concealment or lack of outcome assessment blinding . Fewer examine funding source or conflicts of interest, possibly because it is generally assumed that, except in exceptional circumstances, these are unlikely to materially affect results. However, in 2010, an additional item recommending the reporting of trial funding was added to the CONSORT statement following the emergence of evidence that studies sponsored by pharmaceutical companies were more likely to have outcomes favouring the sponsor than studies with other sponsors, with an odds ratio of 4.05, (95 % CI 2.98 to 5.51) [10, 11]. While CONSORT does not specifically recommend reporting conflicts of interest, this is a requirement for submission to most journals. Bekelman et al found, in a review of reviews, that those with financial conflicts of interest were more likely to report a result in favour of pro-industry conclusions, with an odds ratio of 3.60 (95 % CI 2.63 to 4.91) . Given the challenges to choosing between treatments for LBP, it is important to explore whether such an association is present in the field of LBP research. This will help to inform consumers’ interpretations of LBP trial results in the case a similarly large association exists.
Journal impact factors (IFs) quantify the average number of citations per article published in a particular journal over a specific time period; usually, the past two, or the past five-years. The Thomson Reuters Institute for Scientific Information (ISI), tracks both publications and citations of articles across journals. While use of IFs have been criticised, they are widely regarded as a proxy of output quality and journal esteem, and are commonly used for advertising and self-promotion by journals on the home pages of their websites [13, 14]. Consequently, many authors select a target journal publication in-part based on that journal’s IF . Effect sizes are known to become smaller as the quality of the study improves and we wanted to determine if a similar phenomenon occurred with IF, an established proxy for journal quality [16, 17]. It is not known whether the IF of a journal is associated with reported outcomes in LBP research. Submission and acceptance patterns could be influenced by several factors including perceived interest factor; perceived quality; how newsworthy a report is, especially if it is particularly novel, or goes against accepted practice in showing a null or negative result for a commonly used treatment; or how topical it is. We hypothesised that the direction or magnitude of treatment effect size is associated with journal IF.
We systematically reviewed trials of treatments for non-specific LBP to explore methodological factors as part of a larger project. In this paper, we test the null hypotheses that reported effect sizes in non-specific LBP trials are independent of (1) five-year journal IF, (2) reporting of conflicts of interest, and (3) reporting of funding sources. We also explored whether direction of outcome and trial sample size is associated with IF to find the extent to which these two factors are related to IF.
Our focus was on trials comparing any interventions for treating non-specific LBP, measuring any patient-reported continuous (or quasi-continuous) outcome, and published over a five-year period. We included all reports of trials for interventions for non-specific LBP unless they met one or more of the following exclusion criteria: reports that self-identified as pilot/feasibility studies; trials including mixed samples of back pain (e.g. including neck or thoracic pain in addition to LBP); LBP due to known pathology (e.g cancer, ankylosing spondylitis, or disc herniation); LBP associated with pregnancy; non-English language publications; samples that included participants with radiating leg pain, or referred pain extending past the knee; and because of limited utility: non-inferiority designs (i.e. trials of interventions that are hypothesised to be non-different with respect to a given delta); cross-over designs; secondary reports; trials using solely objective or psychological outcome measures; and multiple publications. In the case of multiple publications, we included the first published article and excluded subsequent publications.
We searched PubMed, EMBASE, and The Cochrane Register of Controlled Trials for non-specific LBP trials published between January 1, 2006 and January 1, 2012 using the non-specific LBP string from a Cochrane Back Pain Review group search strategy . Two reviewers (either TB, PB, or DR) working independently, identified all randomised controlled trial (RCT) reports for inclusion by combining all database hits in an Endnote (Version 14; Thomson Reuters, Philadelphia) library, removing duplicates, and short-listing by title and abstract. Full-texts were obtained if the titles and abstract alone contained insufficient information.
Using Microsoft Visual Basic 6.3 (Microsoft, Washington) and Microsoft Office Excel 2003 (Microsoft, Washington), we developed a front-end program to assist the data abstraction process and transfer abstracted data to a spread sheet. The program ensured consistency of data abstraction and comprehensive form completion as it insisted on correct completion of each field, producing error messages alerting reviewers to missed fields.
Two reviewers (either TB, PB, DR) independently abstracted all data. Disagreements were resolved through discussion and, if necessary, with arbitration and a fourth reviewer (RF). First the primary outcome was identified. An outcome measure was identified as ‘primary’ if (1) the outcome was nominated as the primary outcome by the authors; if no outcome was nominated, or multiple outcomes were nominated, we used (2) the outcome measure on which the sample size calculation was based; if this was not reported, we referred to (3) the first outcome measure referred to in the abstract; and if this was not identified in the abstract, we used (4) the first outcome mentioned in the paper. This approach has been used in other methodological reviews . We identified the primary end-point, or used the first follow-up time point in cases when this was not clear. We then abstracted data on standardised effect size according to a set protocol.
First, we identified whether the paper reported a between-group difference in the primary outcome, or change scores or baseline and follow-up scores for each group from which we could calculate the between-group difference. The difference was recorded as positive if it favoured the intervention and negative if it favoured the control or comparison intervention. If there were more than two groups (and therefore more than two comparisons) we included the comparison with the largest effect size. To obtain the standardised effect size, if it was not directly reported, we extracted a pooled baseline SD, if available, otherwise we extracted SDs from baseline or change scores from single arms and calculated a pooled SD. We then divided the between-group difference by the SD to obtain the standardised effect size (i.e the standardised mean difference (SMD)) .
where Upp=the upper limit of the 95% CI, and Lwr= the lower limit of the 95% CI; n=sample size, t=treatment group, c=control/comparator group, σ b =the pooled baseline SD.
If, during any of these steps, the required information could not be ascertained, we recorded the reason and did not analyse data from that paper. For consistency in this process we developed a flow chart for reviewers’ use (Additional file 1).
In addition, we abstracted data on the number of participants on whom data were analysed, COIs, classifying these as either ‘not reported’, ‘none reported’, or ‘some reported’; and funding status, which we classified in the same way. We used 2011 five-year IF for the corresponding journals, which we obtained from Thompson Reuters ISI Web of Knowledge (Thompson Reuters, Philadelphia).
We tested the null hypotheses that effect size is independent of (1) 5-year journal IF; (2) COI reporting category; and (3) funding reporting category. As high-magnitude departures from the null value regardless of direction of effect size might be equally attractive to some journals, we also explored relationships to the absolute value of effect size. We explored sample size by COI and funding reporting category compared to not reporting any details, whether sample size was independent of journal IF, and whether there was any difference in journal IF in journals publishing positive and negative trial reports.
We fitted random effects meta-regression models of effect size on IF, COI category, and funding status, using within-study SSEs (vide supra) to weight observations. We used a restricted maximum likelihood (REML) estimator for between-study variance [21, 22, 23]. Within the REML algorithm used, coefficients as well as between-study variance was estimated with weighted least squares, so error terms were unbiased by heteroschedasticity [24, 25]. In the case that a journal did not have an official IF, we imputed an IF value of zero. We performed sensitivity analyses, using log-transformed IF (involving small non-zero imputations for journals with no official impact factor) and sample size, to allay concerns that readers more familiar with transformations than REML estimation to overcome heteroschedasticity might have in relation to the heteroschedasticity.
We first fitted crude models, i.e. with only the outcome and predictor variable for each hypothesis, and subsequently fitted adjusted models including the other predictor variables; i.e IF, COI category, and funding category, as well as trial sample size, and publication year, in case relationships changed over time. If predictors appeared non-linear we explored fitting polynomial terms to the model.
Model fits were assessed by graphical examination of standardised predicted random effects. We did not dismiss models on the basis of a high proportion of residual error explained by heterogeneity (i.e. I2), since our focus was on the associations between effect size and characteristics across a number of different interventions and not on estimation of any one intervention effect in particular. All analyses were performed using Stata, version 12.1 for Unix (Statacorp, Texas) and we used the package metareg v2.6.1 to fit the meta-regression models [24, 26].
We could abstract the required effect size data on 99 trials [192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290] from the 146 articles that met inclusion criteria [192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317, 318, 319, 320, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337]. We could not abstract data on SD for the remaining 47 cases (Additional file 1). (Additional file 2: Table S1) shows the characteristics of included studies and (Additional file 3: Table S2) shows the characteristics of excluded studies.
Mean sample size, effect size (ES), absolute effect size, and IF, by categories of funding and reported COIs
Sample size (SD)
219.9 (277.6) ∗∗∗
Adjusted for trial sample size, there was no evidence of a difference in journal IF between positive or negative trials (P=0.270). Adjusted for direction of effect, there was very strong evidence of a linear association between IF and sample size, suggesting that the IF of the publishing journal increases by 0.008 (95 % CI 0.004 to 0.012) per unit increase in total sample size (P<0.0005).
Meta-regression: the effect of impact factor, COI, Funding category, year, and sample size on effect size
95 % CI for β
95 % CI for β
−0.04 to 0.05
−0.03 to 0.06
−0.55 to 0.39
−0.68 to 0.41
−0.70 to 0.76
−0.75 to 0.80
−0.49 to 0.86
−0.48 to 1.02
−0.39 to 0.45
−0.43 to 0.52
−0.16 to 0.07
−0.17 to 0.08
−0.001 to 0.0005
−0.002 to 0.0005
Meta-regression: the effect of impact factor, COI, Funding category, year, and sample size and on absolute values of effect size
95 % CI for β
95 % CI for β
−0.04 to 0.02
−0.03 to 0.04
−0.25 to 0.51
−0.55 to 0.28
−0.82 to 0.34
−0.78 to 0.36
0.42 to 1.45
0.44 to 1.59
−0.27 to 0.37
−0.24 to 0.48
−0.14 to 0.05
−0.14 to 0.05
−0.001 to 0.0002
−0.001 to 0.0003
As anticipated, residual variance due to heterogeneity was high (91.06 % >I2>85.76 %) across all models. Quadratic terms in IF and sample size were not significant in either unadjusted or adjusted models. Graphical inspection of standardised predicted random effects showed adequate model fits. Sensitivity analyses (not reported) showed near identical results.
Main findings, implications and comparisons to existing research
While no associations were found between effect size and IF, reporting sources of funding, or conflicts of interest, there was strong evidence of a large association between absolute magnitude of effect size and the explicit reporting of ‘no funding’. We first discuss IF and then COIs and funding.
The results show no evidence that IF is associated with effect size reported in LBP trials. Effect size is much more variable in journals with low IFs and since journals with higher IFs tend to publish larger trials this likely explains the relationship between effect size variance and journal IF. Journal IF was not associated with direction of result, although there was some evidence that trials reporting a funder had a higher IF than those who did not report funding status.
Suñé et al reviewed clinical trials evaluating drug therapy published between 1997 and 2004 and classified the outcomes of these trials as positive, negative, or descriptive (non-controlled) . They found no difference in IF based on trial direction, but they found the IF was significantly lower in trials classified as descriptive. Littner et al found that over a five-year period in the field of neonatology, articles with negative results were more likely than articles with positive results to be published in journals with lower IFs . Penel and Adenis found the same pattern of association in phase II trials investigating anticancer therapies . Outside of the medical fields, Murtaugh has explored the relationship between standardised effects and IFs in published meta-analyses of terrestrial plant competition, predation in streams, woody plant growth under elevated CO2, and marine nutrient enrichment experiments. Using raw data, he similarly applied weighted least squares regression analysis of study-specific means of the absolute values of the log response ratios on log of journal IFs and found some evidence that in two of the four areas studied (Nutrient enrichment experiments and predation in streams) that journal IF was associated with reported effects .
The presence or absence of associations differs across different research areas. It may be that there is less competition in high-impact journals in terms of newsworthiness of LBP trial results relative to other fields. As it is rare for individual treatments for LBP to stand out dramatically from others in terms of effect size, effect sizes in LBP trials may not be a big driver of an acceptance decision in higher-impact journals.
COI and funding status
We found no evidence that COI category or reported funding status is associated with effect size reported in LBP trials. However, we observed that absolute magnitudes of effect sizes tended to be about one SD larger for trials that declared no funding compared with trials that did not report funding status. The observed association is not due to confounding by sample size. Jacob Cohen, who originally defined standardised effect sizes, considered effect sizes of 0.2 or less to be small, 0.5 to be medium, and 0.8 and above to be large . Using Cohen’s categorisation, the effect size in the larger trials of interventions for LBP tend to be only small-to-medium in magnitude .
This relationship is in marked contrast to that observed in other fields, where evidence suggests industry-funded, industry-linked studies, or studies with an industry-funded author, report greater effect sizes than independently funded studies [11, 12, 342, 343]. In the authors’ experiences, LBP research trials tend to be more commonly funded by government and charitable organisations rather than by industry. It may be that, in the case of LBP trials, reporting larger effect sizes, may be higher amongst studies with fewer resources.
Our a priori approach was to compare categories of explicitly reporting no funding/COIs, and explicitly reporting funding/COIs with not reporting anything about funding/COIs, and it is these results that are reported. As a post hoc comparison to explore reporting of funding further, we compared trials that explicitly reported having funding with trials that explicitly reported not having funding, and found strong evidence of a large effect (β=−0.89 (95 % CI −1.46 to −0.33), P = 0.002), suggesting that those reporting receiving funding, report considerably smaller effect sizes than those reporting their trials were not funded.
Trial quality may partially explain the results. It has been previously shown that larger trials in non-specific LBP tend to be higher quality [17, 344]. We did not explore trial quality in our study. Another consideration may be that pragmatic trials tend to be done more often in LBP research, since many interventions under assessment are complex in nature and pharmacological interventions (which are usually of efficacy rather than effectiveness)  are comparatively rare. It may be that trials more toward the pragmatic end of the spectrum, which may be more difficult to do in the absence of funding given their typical requirement to be large in scale, may be associated with smaller effect sizes simply because the comparator is often another active intervention. Conversely, efficacy trials may have higher effect sizes in part due to more commonly utilising placebo/sham comparisons. We did not explicitly set out to explore this. However, as another post hoc comparison we looked at the intervention comparisons in our included trials, and those that were compared to sham/placebo had an effect size of 0.74 (large), in contrast with those compared to a non-sham/placebo interventions, which had an effect size of 0.29 (P = 0.077; i.e weak evidence of a small-to-moderate difference).
Strengths and limitations
Meta-regression modelling is most useful in this case as a tool to assess the role of chance in the observed results. We caution against use for prediction, since epistemologically this may not be entirely sensible: prediction may involve a reversal of the direction of causality; authors likely choose journals on the basis of publishing work they believe to be newsworthy, high-quality, or of interest to a particular journal’s readership. More robust and simpler solutions to establishing the role of chance, and whether relationships between effect size and IF are monotonic could be used (such as non-parametric correlation) but, as Murtaugh points out, such approaches are less able to incorporate study-specific weights and are ultimately less powerful . Also, such approaches are not as conducive to the inclusion of covariates. In this study we had sufficient power to detect a medium-to-large effect size in terms of funding category, but not in terms of COI, which were only reported in 7 % of trials.
COIs disclosure may or may not be insisted upon by a journal, or COI forms may have been completed but not reported with the article. Additionally, disclosed COIs may or may not be relevant to the trial. We explored only the presence or absence of such statements reported with the article and did not judge the relevance of disclosed COIs to the trial, nor whether the publishing journal required disclosure, and this as a limitation of our study.
The large I2 values for the models suggests that the residual variance explained by heterogeneity is very high. This is to be expected since the included trials featured many different interventions. In our analysis, other than having a detrimental effect on power, the high I2 is inconsequential to interpretation and does not present a limitation as it would in a meta-analysis of a specific treatment effect. We were not focused on estimating the effect of a specific intervention, but the association between effect size and IF, COIs, and funding across many different interventions for nsLBP, some of which will naturally have larger effects than others.
We imputed zero values for IF in the case of journals without an official IF. Many journals use unofficial IFs and including these could have been used to introduce more information into our models. We reasoned that the majority of journals without official IFs would likely have unofficial IFs of less than 1.00 and preferred to use only official values. We note that if IFs had been associated with effect size then our estimates may have been exaggerated. As we did not find any association with effect size, imputing values where there was no official IF was of limited consequence and does not affect conclusions.
In attempting to explain our results, we have hypothesised that there may be a link to study quality, which we did not explore. While there is some evidence of a small effect of poor quality on effect size in LBP trials from other work, we would welcome future investigations using the Cochrane Risk of Bias tool, since the judgement criteria in this tool can be applied to either pragmatic or efficacy trials without prejudice. Lower quality trials may have been associated with both absence of definition of primary outcome measure, where we would have used outcome measure selection method 3 or 4 (see Methods section), as well as with larger study effects. While we recorded and reported authors explicitly identifying an outcome as primary, for the trials in which this was not explicitly identified, we did not record how often primary outcome identification method 2, 3, or 4 needed to be used. So we caution that there may have been an unmeasured confounding factor.
We rejected trials from which we could not abstract population-specific SD data required for the meta-analysis. This resulted in 47 rejections and opens a possibility for bias, in the case that not reporting these data is also associated with reported effect size. While not specifically an item in the CONSORT statement, this is something one might reasonably expect to be discussed within a sample size calculation. For this reason, we suggest the absence of its reporting, is more likely to be associated with lower quality. Assuming this, and the premise that lower quality trials report larger effect sizes notwithstanding direction, are both correct, then our results will tend toward being conservative.
Finally, we restricted our systematic review to three large databases, reasoning that these index the majority of nsLBP RCTs. We acknowledge however, that the review of the period is unlikely to be exhaustive and that there may be further associations between trials indexed in other databases alone, and quality; and thus with the potential to alter results. However, our results cover most of the field and therefore provide a useful account of behaviour.
Based on our results we recommend that journal editors consider giving increased scrutiny at peer-review stage to unfunded LBP trials. Researchers need to carefully consider whether the trial in question can be adequately and appropriately conducted in the absence of funding, and whether the protocol should be subject to peer review. Consumers of LBP trial reports should note this relationship in the case trials are unfunded.
The causal pathway for the relationship between funding and effect size needs further exploration. If larger effect sizes yielded by unfunded trials are incorrect, these may add noise to data consumed by review work decreasing the precision of meta-analyses. If internal validity is a factor, one might raise the question of whether it is ethically justified to undertake unfunded trials of interventions for LBP. If the extent of the pragmatism of a trial is a driving factor, then absorption of the higher absolute effect sizes into specific review work is less of a concern, but a scale of pragmatism might aid interpretation of effect size from individual trials and be useful to reviewers.
Research into the relationship between funding status and effect size, and IF and effect size, appears to be dependent of the field of research and the nature of interventions under investigation. For this reason we suggest that investigations are conducted across different fields and interventions so that the relationships between COIs and funding and effect size can be better understood and consumers can take this into consideration, as appropriate.
Authors of LBP trials should explicitly report whether or not funding was attained, as only around two-thirds of all authors are currently doing this. Moreover, more authors need to be explicit about whether or not there were COIs as in our dataset only 29 % of authors are doing this. Journals and editors could consider taking steps to ensuring this information is reported.
While there is no evidence that reported funding status and reported conflicts of interest influence effect size, there is very strong evidence that authors who explicitly report that their LBP trial was unfunded tend to report larger absolute magnitudes of effect size. Journal editors, researchers, and consumers may have need to be cautious of large effect sizes in unfunded trials, possibly giving additional scrutiny to internal validity. Our results contrast with findings in pharmacological research and suggests relationships may vary by field. Further discipline-specific investigations would inform interpretation of trial reports and help identify causal pathways of associations between effect sizes and trial/report characteristics.
We thank Campus Kristiania, University of Warwick, and Monash University for funding this study, and the European School of Osteopathy for contributing additional reviewer time. A full research proposal for the project was prepared for the principal funder, Campus Kristiania, which was internally assessed by people not involved in the research prior to a funding decision being made. Additional funding was provided to senior co-authors by University of Warwick and Monash University for additional reviewer time to abstract some of the data required for this study (approximately 35 % of total). Thanks are due to Simon Gates and Gary Abel for useful conversations and comments relating to our analysis. RB is funded in-part by an Australian National Health and Medical Research Council (NHMRC) Practitioner Fellowship.
- 4.Vos T, Flaxman AD, Naghavi M, Lozano R, Michaud C, Ezzati M, et al.Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990-2010: a systematic analysis for the global burden of disease study 2010. Lancet. 2012; 380(9859):2163–96. doi:10.1016/S0140-6736(12)61729-2.PubMedGoogle Scholar
- 5.Savigny P, Watson P, Underwood M, Group GD. Early management of persistent non-specific low back pain: summary of nice guidance. BMJ. 2009; 338:1805.Google Scholar
- 6.Froud R, Eldridge S, Lall R, Underwood M. Estimating number needed to treat from continuous outcomes in randomised controlled trials: Methodological challenges and worked example using data from the UK back pain exercise and manipulation (BEAM) trial. BMC Med Res Meth. 2009; 9:35.Google Scholar
- 7.Froud R. Improving interpretation of patient-reported outcomes in low back pain trials. PhD Thesis. London: Queen Mary University of London : 2010.Google Scholar
- 8.Underwood MR, Morton V, Farrin A. Do baseline characteristics predict response to treatment for low back pain? Secondary analysis of the UK BEAM dataset [ISRCTN32683578]. Rheumatology (Oxford). 2007; 46(8):1297–302.Google Scholar
- 10.Schulz KF, Altman DG, Moher D, CONSORT. Consort 2010 statement: updated guidelines for reporting parallel group randomised trials. BMJ. 2010; 340:32.Google Scholar
- 13.Seglen P. Why the impact factor of journals should not be used for evaluating research. BMJ. 1997; 314:497.Google Scholar
- 16.Hempel S, Booth M, Miles J, Wang Z, Maglione M, Morton S, et al.Empirical evidence of associations between trial quality and effect size. Technical report, Agency for Healthcare Research and Quality. 2011.Google Scholar
- 17.van Tulder MW, Suttorp M, Morton S, Bouter LM, Shekelle P. Empirical evidence of an association between internal validity and effect size in randomized controlled trials of low-back pain. Spine (Phila Pa 1976). 2009; 34(16):1685–92.Google Scholar
- 18.Heymans MW, van Tulder MW, Esmail R, Bombardier C, Koes BW. Back schools for non-specific low-back pain. Cochrane Database Syst Rev. 2004; 30(19):2153–63.Google Scholar
- 24.Harbord R, Higgins J. Meta-regression in stata. Stata J. 2008; 8(4):493–519.Google Scholar
- 25.Stanley T, Doucouliagos H. Better than random: Weighted least squares meta-regression analysis. Technical report: Deakin University; 2013.Google Scholar
- 26.Sharp S. Meta-analysis regression. Stata Tech Bull. 1998; 42:16–22.Google Scholar
- 28.Anon. Erratum: Efficacy and safety of tapentadol extended release for the management of chronic low back pain: results of a prospective, randomized, double-blind, placebo- and active-controlled phase iii study. Expert Opin Pharmacother. 2010; 11(16):2773.Google Scholar
- 33.Bergholdt K, Fabricius RN, Bendix T. Better backs by better beds?Spine (Phila Pa 1976). 2008; 33(7):703–8.Google Scholar
- 40.Buynak R, Etropolski M, Lange B, Shapiro DY, Okamoto A, Steup A, et al.Dose stability of tapentadol er for the relief of chronic low back pain: Results of a randomized, active- and placebo-controlled study. Arthritis Rheum. 2009; 60:1494.Google Scholar
- 42.Casserley-Feeney SN, Bury G, Daly L, Hurley DA. The ACCESS trial - randomised controlled trial of public hospital-based versus private clinic-based physiotherapy for low back pain: clinical outcomes. J Bone Joint Surg Br. 2008; 90(SUPP III):492.Google Scholar
- 43.Cevik R, Bilici A, Gur A, Sarac AJ, Yildiz H, Nas K, et al.Effect of new traction technique of prone position on distraction of lumbar vertebrae and its relation with different application of heating therapy in low back pain. Journal of Back and Musculoskeletal Rehabilitation. 2007; 20(2-3):71–77.Google Scholar
- 45.Clark D, Chu L. Tolerance and opioid-induced hyperalgesia in clinical populations. Eur J Pain Suppl. 2010; 4(1):29.Google Scholar
- 46.Cleland J, Fritz J, Kulig K, Davenport TE, Eberhart S, Magel JS, et al.Comparison of the effectiveness of 3 manual physical therapy techniques in a subgroup of patients with low back pain who satisfy a clinical prediction rule: a randomized clinical trial. Spine. 2009; 34(25):2720–9.PubMedGoogle Scholar
- 47.Codding C, Levinsky D, Hale ME, Thomas JW, Lockhart E, Best A, et al.Efficacy and safety evaluation of 12 weeks extended-release hydrocodone/acetaminophen treatment in patients with chronic low back pain (clbp) by prior opioid use. Pain Med. 2009; 10(1):260.Google Scholar
- 51.Critchley DJ, Ratcliffe J, Noonan S, Jones RH, Hurley MV. Effectiveness and cost-effectiveness of three types of physiotherapy used to reduce chronic low back pain disability: a pragmatic randomized trial with economic evaluation. Spine (Phila Pa 1976). 2007; 32(14):1474–81.Google Scholar
- 56.Demoulin C, Maquet D, Tomasella M, Croisier J, Crielaard J, Vanderthommen M. Benefits of a physical training program after back school for chronic low back pain patients. Journal of Musculoskeletal Pain. 2006; 14(2):21–31.Google Scholar
- 58.Desmoulin GT, Yasin NI, Chen DW. Initial results using khan kinetic treatment(trademark) as a low back pain treatment option. J Musculoskelet Pain. 2007; 15(3):91–102.Google Scholar
- 60.Eisenberg DM, Post DE, Davis RB, Connelly MT, Legedza AT, Hrbek AL, et al.Addition of choice of complementary therapies to usual care for acute low back pain: a randomized controlled trial. Spine (Phila Pa 1976). 2007; 32(2):151–8.Google Scholar
- 62.Etropolski M, Rauschkolb-Loffler C, Shapiro D, Okamoto A, Lange C. A randomized, double-blind, placebo- and active-controlled phase iii study of tapentadol er for chronic low back pain: Analysis of efficacy endpoint sensitivity. J Pain. 2009; 10(4):51.Google Scholar
- 66.Fritz JM, Lindsay W, Matheson JW, Brennan GP, Hunter SJ, Moffit SD, et al.Is there a subgroup of patients with low back pain likely to benefit from mechanical traction? results of a randomized clinical trial and subgrouping analysis. Spine (Phila Pa 1976). 2007; 32(26):793–800.Google Scholar
- 68.George SZ, Childs JD, Teyhen DS, Wu SS, Wright AC, Dugan JL, et al.Brief psychosocial education, not core stabilization, reduced incidence of low back pain: results from the prevention of low back pain in the military (polm) cluster randomized trial. BMC Med. 2011; 9:128.PubMedPubMedCentralGoogle Scholar
- 76.Hancock MJ, Maher CG. Letter to editor re: Cleland JA, Fritz JM, Kulig K, et al. Comparison of the effectiveness of three manual physical therapy techniques in a subgroup of patients with low back pain who satisfy a clinical prediction rule. A randomized clinical trial. Spine. 2010; 35:839.PubMedGoogle Scholar
- 77.Hasegawa TM, Baptista AS, De Souza MC, Yoshizumi AM, Natour J. Acupuncture for acute non-specific low back pain: A randomized, controlled, placebo trial. Arthritis Rheum. 2009; 60:1497.Google Scholar
- 84.Hollinghurst S, Sharp D, Ballard K, Barnett J, Beattie A, Evans M, et al.Randomised controlled trial of alexander technique lessons, exercise, and massage (ateam) for chronic and recurrent back pain: economic evaluation. BMJ. 2008; 337:2656.Google Scholar
- 85.Hurley DA, O’Donoghue G, Tully MA, Moffett JK, van Mechelen W, Daly L, et al.A walking programme and a supervised exercise class versus usual physiotherapy for chronic low back pain: a single-blinded randomised controlled trial. (the supervised walking in comparison to fitness training for back pain (swift) trial). BMC Musculoskelet Disord. 2009; 10:79.PubMedPubMedCentralGoogle Scholar
- 88.Ikegami S, Kamimura M, Uchiyama S, Nakagawa H, Hashidate H, Takahara K, et al.Anti-nociceptive effects of elcatonin injection for postmenopausal women with back pain: A randomized controlled trial. Osteoporos Int. 2010; 21:197–8.Google Scholar
- 90.Jans MP, Korte d EM, Heinrich J, Hildebrandt VH. Intermittent follow-up treatment with Cesar exercise therapy in patients with subacute or chronic aspecific low back pain: results of a randomized, controlled trial with a 1.5-year follow-up. / Intermitterende vervolgbehandeling oefentherapie Cesar bij subacute of chronische aspecifieke lage-rugklachten: een RCT Cochrane Register of Controlled Trials. 2006: CN-00592636. 2006. http://www.ncbi.nlm.nih.gov/pubmed/15106234.
- 91.Kasis AG, Marshman LAG, Krishna M, Bhatia CK. Significantly improved outcomes with a less invasive posterior lumbar interbody fusion incorporating total facetectomy. Spine (Phila Pa 1976). 2009; 34(6):572–7.Google Scholar
- 92.Katz N, Borenstein D, Birbara C, Bramson C, Nemeth M, Smith M, et al.Tanezumab, an anti-nerve growth factor (ngf) antibody, for the treatment of chronic low back pain (clbp) - a randomized, controlled, double-blind, phase 2 trial. J Pain. 2009; 10(4):42.Google Scholar
- 94.Kavanagh S, Lange B, Ashworth J, Etropolski MS, McNeill M, Rauschkolb C. Tapentadol extended release (er) for chronic low back pain: Results of euroqol-5 dimension (eq-5d) and short form-36 (sf-36) health status questionnaires. Value Health. 2009; 12(7):376.Google Scholar
- 97.Kovacs F, Abraira V, Santos S, Diaz E, Gestoso M, Muriel A, et al.A comparison of two short education programs for improving low back pain-related disability in the elderly: a cluster randomized controlled trial. Spine (Phila Pa 1976). 2007; 32(10):1053–9.Google Scholar
- 98.Kullich W, Schwann H, Machreich K, Ausserwinkler M. Additional outcome improvement in the rehabilitation of chronic low back pain after nuclear resonance therapy. Rheumatologia. 2006; 20(1):7–12.Google Scholar
- 99.Kullich W, Schwann H, Walcher J, Machreich K. The effect of MBST-NuclearResonanceTherapy with a complex 3-dimensional electromagnetic nuclear resonance field on patients with low back pain 23. Journal of Back and Musculoskeletal Rehabilitation. 2006; 19:79–87.Google Scholar
- 104.Leichtfried V, Kantner-Rumplmair W, Raggautz M, Bartenbach C, Aigner M, Winkler D, et al.Can bright light therapy ameliorate symptoms associated with low back pain (LBP)? A randomized controlled trial. J Psychosom Res. 2010; 68(6):642.Google Scholar
- 109.Long A, May S, Fung T. The comparative prognostic value of directional preference and centralization: A useful tool for front-line clinicians?J Manual Manip Therapy. 2008; 16(4):248–54.Google Scholar
- 111.Magnusson ML, Chow DH, Diamandopoulos Z, Pope MH. Motor control learning in chronic low back pain. Spine (Phila Pa 1976). 2008; 33(16):532–8.Google Scholar
- 112.Mandara A, Fusaro A, Musicco M, Bado F. A randomised controlled trial on the effectiveness of osteopathic manipulative treatment of chronic low back pain. Int J Ost Med. 2008; 11(4):156.Google Scholar
- 113.Mattila R, Malmivaara A, Kastarinen M, Kivela SL, Nissinen A. The effects of lifestyle intervention for hypertension on low back pain: a randomized controlled trial. Spine (Phila Pa 1976). 2007; 32(26):2943–7.Google Scholar
- 114.Mehling WE. Breath therapy for chronic low back pain. J Bodyw Mov Ther. 2006; 10(2):96–8.Google Scholar
- 115.Mehta S, Chopra A, Goregaonkar A, Chandanwale A, Medhi B, Shah V, et al.Evaluation of efficacy and safety of eperisone hydrochloride in treatment of acute musculoskeletal spasm associated with low back pain: A randomized, doubleblind, placebo-controlled trial. Pain Pract. 2009; 9:123.Google Scholar
- 116.Meng K, Seekatz B, Roband H, Worringen U, Vogel H, Faller H. Intermediate and long-term effects of a standardized back school for inpatient orthopedic rehabilitation on illness knowledge and self-management behaviors: a randomized controlled trial. Clin J Pain. 2011; 27(3):248–57.PubMedGoogle Scholar
- 117.Mirovsky Y, Grober A, Blankstein A, Stabholz L. The effect of ambulatory lumbar traction combined with treadmill on patients with chronic low back pain. J Back Musculoskeletal Rehabil. 2006; 19(2-3):73–8.Google Scholar
- 120.Najm WI. German acupuncture trials (gerac) for chronic low back pain. Med Acupunct. 2008; 20(2):131–2.Google Scholar
- 121.Nath S, Nath CA, Pettersson K. Percutaneous lumbar zygapophysial (facet) joint neurotomy using radiofrequency current, in the management of chronic low back pain: a randomized double-blind trial. Spine (Phila Pa 1976). 2008; 33(12):1291–71298.Google Scholar
- 124.O’Brien N, Hanlon M, Meldrum D. Randomised, controlled trial comparing physiotherapy and Pilates in the treatment of ordinary low back pain. Concrans Register of Controlled Trials. 2006; 452:3165. http://pesquisa.bvsalud.org/evidences/resource/en/CN-00592705.Google Scholar
- 125.O’Donnell JB, Ekman EF, Spalding WM, Bhadra P, McCabe D, Berger MF. The effectiveness of a weak opioid medication versus a cyclo-oxygenase-2 (cox-2) selective non-steroidal anti-inflammatory drug in treating flare-up of chronic low-back pain: results from two randomized, double-blind, 6-week studies. J Int Med Res. 2009; 37(6):1789–802.PubMedGoogle Scholar
- 127.Padua R, Bondi R, Ceccarelli E, Alviti F. Re: A randomized study of back school in women with chronic low back pain. quality of life at three, six, and twelve months follow-up. Spine (Phila Pa 1976). 2009; 34(12):1336.Google Scholar
- 128.Pareek A, Chandurkar N, Chandanwale AS, Ambade R, Gupta A, Bartakke G. Aceclofenac-tizanidine in the treatment of acute low back pain: a double-blind, double-dummy, randomized, multicentric, comparative study against aceclofenac alone. Eur Spine J. 2009; 18(12):1836–42.PubMedPubMedCentralGoogle Scholar
- 131.Perrot S, Krause D, Crozes P, Naim C. Efficacy and tolerability of paracetamol/tramadol (325 mg/37.5 mg) combination treatment compared with tramadol (50 mg) monotherapy in patients with subacute low back pain: a multicenter, randomized, double-blind, parallel-group, 10-day treatment study. Clin Ther. 2006; 28(10):1592–606.PubMedGoogle Scholar
- 132.Petersen T, Larsen K, Jacobsen S. One-year follow-up comparison of the effectiveness of mckenzie treatment and strengthening training for patients with chronic low back pain: outcome and prognostic factors. Spine (Phila Pa 1976). 2007; 32(26):2948–56.Google Scholar
- 133.Petersen T, Larsen K, Nordsteen J, Olsen S, Fournier G, et al.The mckenzie method compared with manipulation when used adjunctive to information and advice in low back pain patients presenting with centralization or peripheralization: a randomized controlled trial. Spine (Phila Pa 1976). 2011; 36(24):1999–2010.Google Scholar
- 134.Petrofsky JS, Batt J, Brown J, Stacey L, Bartelink T, Le Moine M, et al.Improving the outcomes after back injury by a core muscle strengthening program. J Appl Res. 2008; 8(1):62–75.Google Scholar
- 135.Podichetty VK, Varley ES, Oleske dm, lavender sa, andersson gb, et al.are back supports plus education more effective than education alone in promoting recovery from low back pain? results from a randomized clinical trial. spine 2007; 32:2050-7. Spine (Phila Pa 1976). 2008; 33(3):349–50.Google Scholar
- 141.Ralph L, Wheeler B, Sacks H. Improvement in functional status with carisoprodol 250-mg tablets in patients with acute lower back spasm: A randomized, double-blind, placebo-controlled trial. Pain Med. 2009; 10(1):258.Google Scholar
- 142.Rauck RL, Bookbinder SA, Bunker TR, Alftine CD, Ghalie R, Negro-Vilar A, et al.The action study: a randomized, open-label, multicenter trial comparing once-a-day extended-release morphine sulfate capsules (avinza) to twice-a-day controlled-release oxycodone hydrochloride tablets (oxycontin) for the treatment of chronic, moderate to severe low back pain. J Opioid Manag. 2006; 2(3):155–66.PubMedGoogle Scholar
- 143.Rauck RL, Bookbinder SA, Bunker TR, Alftine CD, Ghalie R, Negro-Vilar A, et al.A randomized, open-label study of once-a-day avinza (morphine sulfate extended-release capsules) versus twice-a-day oxycontin (oxycodone hydrochloride controlled-release tablets) for chronic low back pain: the extension phase of the action trial. J Opioid Manag. 2006; 2(6):325–83313.PubMedGoogle Scholar
- 146.Rusinyol FC, Perice RV, Boronat ER, Bosch FF. Effects of two different doses of eperisone in the treatment of acute low back pain. J Appl Res. 2009; 9(1-2):23–9.Google Scholar
- 148.Schimmel JJ, de Kleuver M, Horsting PP, Spruit M, Jacobs WC, van Limbeek J. No effect of traction in patients with low back pain: a single centre, single blind, randomized controlled trial of intervertebral differential dynamics therapy. Eur Spine J. 2009; 18(12):1843–50.PubMedPubMedCentralGoogle Scholar
- 150.Schwarz I, Lawrence DJ. Relative responsiveness of 3 different types of clinical outcome measures on chiropractic patients with low back pain. J Manip Physiol Ther. 2007; 30(1):77–8.Google Scholar
- 153.Shakoor MA, Salek AKM, Islam MT, Moyeenuzzaman M. Evaluation of the effects of selective rehabilitation on the patients with chronic low back pain. Int J Rheum Dis. 2010; 13:221.Google Scholar
- 155.Sherman KJ, Cherkin DC, Ichikawa L, Avins AL, Delaney K, Barlow WE, et al.Treatment expectations and preferences as predictors of outcome of acupuncture for chronic back pain. Spine (Phila Pa 1976). 2010; 35(15):1471–7.Google Scholar
- 158.Skljarevski V, Zhang S, Desaiah D, Palacios S, Miazgowski T, Patrick K. Efficacy and safety of duloxetine 60 mg once-daily in patients with chronic low back pain. J Pain. 2010; 11(4):38.Google Scholar
- 159.Skljarevski V, Zhang S, Desaiah D, Palacios S, Miazgowski T, Patrickm K. Effect of duloxetine 60 mg once daily versus placebo in patients with chronic low back pain: A 12-week, randomized, double-blind trial. Pain Med. 2010; 11(2):322.Google Scholar
- 164.Smeets RJEM, Vlaeyen JWS, Hidding A, Kester ADM, Van Der Heijden GJMG, Van Geel ACM, et al.Active rehabilitation for chronic low back pain: Cognitive-behavioral, physical, or both? first direct post-treatment results from a randomized controlled trial [ISRCTN22714229]. BMC Musculoskelet Disord. 2006; 7:5.PubMedPubMedCentralGoogle Scholar
- 166.Smith AL, Kolt GS, McConville JC. The effect of the felenkrais method on pain and anxiety in people experiencing chronic low back pain 3136. N Z J Physiother. 2007; 29(1):6–14.Google Scholar
- 170.Steiner D, Munera C, Hale M, Ripa S, Landau C. The efficacy and safety of buprenorphine transdermal system (BTDS) in subjects with moderate to severe low back pain: A double-blind study. J Pain. 2009; 10(4):51.Google Scholar
- 172.Steiner DJ, Sitar S, Wen W, Sawyerr G, Munera C, Ripa SR, et al.Efficacy and safety of the seven-day buprenorphine transdermal system in opioid-naive patients with moderate to severe chronic low back pain: an enriched, randomized, double-blind, placebo-controlled study. J Pain Symptom Manag. 2011; 42(6):903–17.Google Scholar
- 176.Tavafian SS, Jamshidi AR, Montazeri A. A randomized study of back school in women with chronic low back pain: quality of life at three, six, and twelve months follow-up. Spine (Phila Pa 1976). 2008; 33(15):1617–21.Google Scholar
- 181.Underwood M, Mistry D, Lall R, Lamb S. Predicting response to a cognitive-behavioral approach to treating low back pain: Secondary analysis of the best data set. Arthritis Care Res (Hoboken). 2011; 63(9):1271–9.Google Scholar
- 185.Wheeler WJ, Gever LN. Functional status of patients with acute low back pain following treatment with carisoprodol 250-mg tablets assessed by the roland-morris disability questionnaire (rmdq). Pain Med. 2010; 11(2):305.Google Scholar
- 188.Wilson-MacDonald J, Fairbank J, Frost H, Yu LM, Barker K, Collins R, et al.The mrc spine stabilization trial: surgical methods, outcomes, costs, and complications of surgical stabilization. Spine (Phila Pa 1976). 2008; 33(21):2334–40.Google Scholar
- 189.Worth SGA, Henry SM, Bunn JY. Real-time ultrasound feedback and abdominal hollowing exercises for people with low back pain. NZ J Physiother. 2007; 35(1):4–11.Google Scholar
- 191.Zaina F, Vismara L, Menegoni F, Galli M, Negrini S, Villa V. Clinical and kinematic evaluation of osteopathy vs specific exercises in obese non-specific chronic low back pain females patients: A randomized controlled trial. Spine. 2010; 2010:244.Google Scholar
- 194.Akbari A, Khorashadizadeh S, Abdi G. The effect of motor control exercise versus general exercise on lumbar local stabilizing muscles thickness: Randomized controlled trial of patients with chronic low back pain. J Back Musculoskelet Rehabil. 2008; 21(2):105–12.Google Scholar
- 195.Becker A, Leonhardt C, Kochen MM, Keller S, Wegscheider K, Baum E, et al.Effects of two guideline implementation strategies on patient outcomes in primary care: a cluster randomized controlled trial. Spine (Phila Pa 1976). 2008; 33(5):473–80.Google Scholar
- 196.Bello AI, Kalu NH, Adegoke BOA, Agyepong-Badu S. Hydrotherapy versus land-based exercises in the management of chronic low back pain: A comparative study. J Musculoskelet Res. 2010; 13(4):159–65.Google Scholar
- 201.Calmels P, Queneau P, Hamonet C, Le Pen C, Maurel F, Lerouvreur C, et al.Effectiveness of a lumbar belt in subacute low back pain: an open, multicentric, and randomized clinical study. Spine (Phila Pa 1976). 2009; 34(3):215–0.Google Scholar
- 202.Cecchi F, Molino-Lova R, Chiti M, Pasquini G, Paperini A, Conti AA, et al.Spinal manipulation compared with back school and with individually delivered physiotherapy for the treatment of chronic low back pain: a randomized trial with one-year follow-up. Clin Rehabil. 2010; 24(1):26–36.PubMedGoogle Scholar
- 209.Chown M, Whittamore L, Rush M, Allan S, Stott D, Archer M. A prospective study of patients with chronic back pain randomised to group exercise, physiotherapy or osteopathy. Physiotherapy. 2008; 94(1):21–8.Google Scholar
- 211.Cuesta-Vargas AI, Garcia-Romero JC, Arroyo-Morales M, Diego-Acosta AM, Daly DJ. Exercise, manual therapy, and education with or without high-intensity deep-water running for nonspecific chronic low back pain: a pragmatic randomized controlled trial. Am J Phys Med Rehabil. 2011; 90(7):526–345358.PubMedGoogle Scholar
- 212.Demirel R, Ucok K, Kavuncu V, Gecici O, Evcik D, Dundar U, et al.Effects of balneotherapy with exercise in patients with low back pain. J Back Musculoskelet Rehabil. 2008; 21(4):263–72.Google Scholar
- 213.Di Cesare A, Giombini A, Di Cesare M, Ripani M, Vulpiani MC, Saraceni VM. Comparison between the effects of trigger point mesotherapy versus acupuncture points mesotherapy in the treatment of chronic low back pain: a short term randomized controlled trial. Complement Ther Med. 2011; 19(1):19–26.PubMedGoogle Scholar
- 214.Diaz Arribas MJ, Ramos Sanchez M, Pardo Hervas P, Lopez Chicharro J, Angulo Carrere T, Ortega Molina P, et al.Effectiveness of the physical therapy godelive denys-struyf method for nonspecific low back pain: primary care randomized control trial. Spine (Phila Pa 1976). 2009; 34(15):1529–38.Google Scholar
- 215.Dufour N, Thamsborg G, Oefeldt A, Lundsgaard C, Stender S. Treatment of chronic low back pain: a randomized, clinical trial comparing group-based multidisciplinary biopsychosocial rehabilitation and intensive individual therapist-assisted back muscle strengthening exercises. Spine (Phila Pa 1976). 2010; 35(5):469–76.Google Scholar
- 216.Dundar U, Solak O, Yigit I, Evcik D, Kavuncu V. Clinical effectiveness of aquatic exercise to treat chronic low back pain: a randomized controlled trial. Spine (Phila Pa 1976). 2009; 34(14):1436–40.Google Scholar
- 217.Durmus D, Akyol Y, Alayli G, Tander B, Zahiroglu Y, Canturk F. Effects of electrical stimulation program on trunk muscle strength, functional capacity, quality of life, and depression in the patients with low back pain: a randomized controlled trial. Rheumatol Int. 2009; 29(8):947–54.PubMedGoogle Scholar
- 218.Durmus D, Durmaz Y, Canturk F. Effects of therapeutic ultrasound and electrical stimulation program on pain, trunk muscle strength, disability, walking performance, quality of life, and depression in patients with low back pain: a randomized-controlled trial. Rheumatol Int. 2010; 30(7):901–10.PubMedGoogle Scholar
- 219.Engbert K, Weber M. The effects of therapeutic climbing in patients with chronic low back pain: a randomized controlled study. Spine (Phila Pa 1976). 2011; 36(11):842–9.Google Scholar
- 224.Field T, Hernandez-Reif M, Diego M, Fraser M. Lower back pain and sleep disturbance are reduced following massage therapy. J Bodyw Mov Ther. 2007; 11(2):141–5.Google Scholar
- 226.Franca FR, Burke TN, Hanada ES, Marques AP. Segmental stabilization and muscular strengthening in chronic low back pain: a comparative study. Clinics (Sao Paulo). 2010; 65(10):1013–7.Google Scholar
- 227.Gladwell V, Head S, Haggar M, Beneke R. Does a program of pilates improve chronic non-specific low back pain?J Sport Rehabil. 2006; 15(4):338–50.Google Scholar
- 231.Hall AM, Maher CG, Lam P, Ferreira M, Latimer J. Tai chi exercise for treatment of pain and disability in people with persistent low back pain: a randomized controlled trial. Arthritis Care Res (Hoboken). 2011; 63(11):1576–83.Google Scholar
- 234.Henchoz Y, de Goumoens P, Norberg M, Paillex R, So AK. Role of physical exercise in low back pain rehabilitation: a randomized controlled trial of a three-month exercise program in patients who have completed multidisciplinary rehabilitation. Spine (Phila Pa 1976). 2010; 35(12):1192–9.Google Scholar
- 235.Henchoz Y, de Goumoens P, So AK, Paillex R. Functional multidisciplinary rehabilitation versus outpatient physiotherapy for non specific low back pain: randomized controlled trial. Swiss Med Wkly.2010;140. doi:10.4414/smw.2010.13133.
- 237.Hsieh LL, Kuo CH, Lee LH, Yen AM, Chien KL, Chen TH. Treatment of low back pain by acupressure and physical therapy: randomised controlled trial. BMJ (Clin Res ed.) 2006; 332(7543):696–700.Google Scholar
- 240.Johnson RE, Jones GT, Wiles NJ, Chaddock C, Potter RG, Roberts C, et al.Active exercise, education, and cognitive behavioral therapy for persistent disabling low back pain: a randomized controlled trial. Spine (Phila Pa 1976). 2007; 32(15):1578–85.Google Scholar
- 253.Leonardt C, Keller S, Chenot J, Luckmann J, Basler H, Wegscheider B, et al.Ttm-based motivational counselling does not increase physical activity of low back pain patients in a primary care setting-a cluster-randomized controlled trial. Patient Educ Couns. 2008; 70:50–60.Google Scholar
- 256.Mackawan S, Eungpinichpong W, Pantumethakul R, Chatchawan U, Hunsawong T, Arayawichanon P. Effects of traditional thai massage versus joint mobilization on substance p and pain perception in patients with non-specific low back pain. J Bodyw Mov Ther. 2007; 11(1):9–16.Google Scholar
- 257.Marshall P, Murphy B. Self-report measures best explain changes in disability compared with physical measures after exercise rehabilitation for chronic low back pain. Spine (Phila Pa 1976). 2008; 33(3):326–8.Google Scholar
- 262.Muller-Schwefe GHH, Uberall MA. Dysport(registered trademark) for the treatment of myofascial back pain: Results from an open-label, phase ii, randomized, multicenter, dose-ranging study. Scand J Pain. 2011; 2(1):25–33.Google Scholar
- 270.Roche-Leboucher G, Petit-Lemanac’h A, Bontoux L, Dubus-Bausiere V, Parot-Shinkel E, Fanello S, et al.Multidisciplinary intensive functional restoration versus outpatient active physiotherapy in chronic low back pain: a randomized controlled trial. Spine (Phila Pa 1976). 2011; 36(26):2235–42.Google Scholar
- 272.Santaella Da Fonseca Lopes De Sousa K, Garcia Orfale A, Mara Meireles S, Roberto Leite J, Natour J. Assessment of a biofeedback program to treat chronic low back pain. J Musculoskelet Pain. 2009; 17(4):369–77.Google Scholar
- 273.Schiltenwolf M, Buchner M, Heindl B, Reumont J, Müller A, Eich W. Comparison of a biopsychosocial therapy (BT) with a conventional biomedical therapy (mt) of subacute low back pain in the first episode of sick leave: a randomized controlled trial. Eur Spine J. 2006; 15(7):1083–92.PubMedGoogle Scholar
- 274.Senna MK, Machaly SA. Does maintained spinal manipulation therapy for chronic nonspecific low back pain result in better long-term outcome?Spine (Phila Pa 1976). 2011; 36(18):1427–37.Google Scholar
- 277.Skljarevski V, Zhang S, Chappell AS, Detke MJ, Murray I, Backonja M. Maintenance of effect of duloxetine in patients with chronic low back pain. European J Pain. 2009; 13:195.Google Scholar
- 279.Sorensen PH, Bendix T, Manniche C, Korsholm L, Lemvigh D, Indahl A. An educational approach based on a non-injury model compared with individual symptom-based physical training in chronic lbp. a pragmatic, randomised trial with a one-year follow-up. BMC Musculoskelet Disord. 2010; 11:212.PubMedPubMedCentralGoogle Scholar
- 282.Thomas KJ, MacPherson H, Thorpe L, Brazier J, Fitter M, Campbell MJ, et al.Randomised controlled trial of a short course of traditional acupuncture compared with usual care for persistent non-specific low back pain. BMJ: Br Med J. 2006; 333(7569):1–6.Google Scholar
- 284.Vasseljen O, Unsgaard-Tondel M, Westad C, Mork PJ. Effect of core stability exercises on feedforward activation of deep abdominal muscles in chronic low back pain: A randomized controlled trial. Spine (Phila Pa 1976). 2011; 37(13):1101–8.Google Scholar
- 289.Williams K, Abildso C, Steinberg L, Doyle E, Epstein B, Smith D, et al.Evaluation of the effectiveness and efficacy of iyengar yoga therapy on chronic low back pain. Spine (Phila Pa 1976). 2009; 34(19):2066–76.Google Scholar
- 291.Albaladejo C, Kovacs FM, Royuela A, del Pino R, Zamora J. The efficacy of a short education program and a short physiotherapy program for treating low back pain in primary care: a cluster randomized trial. Spine (Phila Pa 1976). 2010; 35(5):483–96.Google Scholar
- 292.Anema JR, Steenstra IA, Bongers PM, de Vet HC, Knol DL, Loisel P, et al.Multidisciplinary rehabilitation for subacute low back pain: graded activity or workplace intervention or both? a randomized controlled trial. Spine (Phila Pa 1976). 2007; 32(3):291–8.Google Scholar
- 293.Attanayake AMP, Somarathna K, Vyas GH, Dash SC. Clinical evaluation of selected yogic procedures in individuals with low back pain. Ayu. 2010; 31(2):245–50.Google Scholar
- 295.Bishop PB, Quon JA, Fisher CG, Dvorak MF. The chiropractic hospital-based interventions research outcomes (chiro) study: a randomized controlled trial on the effectiveness of clinical practice guidelines in the medical and chiropractic management of patients with acute mechanical low back pain. Spine J. 2010; 10(12):1055–64.PubMedGoogle Scholar
- 297.Cairns MC, Foster NE, Wright C. Randomized controlled trial of specific spinal stabilization exercises and conventional physiotherapy for recurrent low back pain. Spine. 2006; 31(19):670–81.Google Scholar
- 298.Cleland JA, Fritz JM, Kulig K, Davenport TE, Eberhart S, Magel J, et al.Comparison of the effectiveness of three manual physical therapy techniques in a subgroup of patients with low back pain who satisfy a clinical prediction rule: a randomized clinical trial. Spine (Phila Pa 1976). 2009; 34(25):2720–9.Google Scholar
- 301.Donzelli S, Domenica E, Cova AM, Galletti R, Giunta N. Two different techniques in the rehabilitation treatment of low back pain: a randomized controlled trial. Eura. 2006; 42(3):205–10.Google Scholar
- 302.Durmus D, Akyol Y, Cengiz K, Terzi T, Canturk F. Effects of therapeutic ultrasound on pain, disability, walking performance, quality of life, and depression in patients with chronic low back pain: A randomized, placebo controlled trial. Turkish J Rheumatol. 2010; 25(2):82–7.Google Scholar
- 303.Ergun H, Polat O, Demirkan NA, Gunalp M, Gurler S. The efficacy, safety, and pharmacokinetics of intramuscular and oral phenyramidol in patients with low back pain in an emergency department. Turkish J Med Sci. 2010; 40(1):71–6.Google Scholar
- 305.Friedrich M, Gittler G. Long-term effects of a combined exercise and motivation program in patients with chronic low back pain: A five-year follow-up. Pain Pract. 2009; 9:121.Google Scholar
- 313.Lambeek LC, van Mechelen W, Knol DL, Loisel P, Anema JR. Randomised controlled trial of integrated care to reduce disability from chronic low back pain in working and private life. BMJ. 2010; 340:1035.Google Scholar
- 314.Little P, Lewith G, Webley F, Evans M, Beattie A, Middleton K, et al.Randomised controlled trial of alexander technique lessons, exercise, and massage (ateam) for chronic and recurrent back pain. BMJ. 2008; 337:884.Google Scholar
- 318.Mohseni-Bandpei MA, Critchley J, Staunton T, Richardson B. A prospective randomised controlled trial of spinal manipulation and ultrasound in the treatment of chronic low back pain. Physiotherapy. 2006; 92(1):34–42.Google Scholar
- 319.Muthukrishnan R, Shenoy SD, Jaspal SS, Nellikunja S, Fernandes S. The differential effects of core stabilization exercise regime and conventional physiotherapy regime on postural control parameters during perturbation in patients with movement and control impairment chronic low back pain. Sports Med Arthrosc Rehabil Ther Technol. 2010; 2:13.PubMedPubMedCentralGoogle Scholar
- 322.Oleske DM, Lavender SA, Andersson GB, Kwasny MM. Are back supports plus education more effective than education alone in promoting recovery from low back pain?: Results from a randomized clinical trial. Spine (Phila Pa 1976). 2007; 32(19):2050–7.Google Scholar
- 324.Perez-Palomares S, Olivan-Blazquez B, Magallon-Botaya R, De-La-Torre-Beldarrain MML, Gaspar-Calvo E, Romo-Calvo L, et al.Percutaneous electrical nerve stimulation versus dry needling: Effectiveness in the treatment of chronic low back pain. J Musculoskelet Pain. 2010; 18(1):23–30.Google Scholar
- 326.Rasmussen-Barr E, Ang B, Arvidsson I, Nilsson-Wikmar L. Graded exercise for recurrent low-back pain: a randomized, controlled trial with 6-, 12-, and 36-month follow-ups. Spine (Phila Pa 1976). 2009; 34(3):221–8.Google Scholar
- 329.Shirado O, Doi T, Akai M, Hoshino Y, Fujino K, Hayashi K, et al.Multicenter randomized controlled trial to evaluate the effect of home-based exercise on patients with chronic low back pain: the japan low back pain exercise therapy study. Spine (Phila Pa 1976). 2010; 35(17):811–9.Google Scholar
- 332.Skljarevski V, Zhang S, Desaiah D, Palacios S, Miazgowski T, Patrick K. Efficacy and safety of duloxetine 60 mg once-daily in patients with chronic low back pain. J Pain. 2010; 11(4):38.Google Scholar
- 334.Suni J, Rinne M, Natri A, Statistisian MP, Parkkari J, Alaranta H. Control of the lumbar neutral zone decreases low back pain and improves self-evaluated work ability: a 12-month randomized controlled study. Spine. 2006; 31(18):611–20.Google Scholar
- 335.Szczurko O, Cooley K, Busse JW, Seely D, Bernhardt B, Guyatt GH, et al.Naturopathic care for chronic low back pain: a randomized trial. PLoS One. 2007; 2(9):919.Google Scholar
- 339.Littner Y, Mimouni F, Dollberg S, Mandel D. Negative results and impact factor a lesson from neonatology. 2005; (159):1036–7.Google Scholar
- 340.Penel N, Adenis A. Publication biases and phase ii trials investigating anticancer targeted therapies. Invest New Drug. 2009; 27(3):287–288.Google Scholar
- 341.Murtaugh P. Journal quality, effect size, and publication bias in meta-analysis. Ecology. 2002; 83(4):1162–1166.Google Scholar
- 344.Hempel S, Miles J, Suttorp M, Wang Z, Johnsen B, Morton S, et al.Detection of associations between trial quality and effect sizes. Technical report, Methods Research Report. Prepared by the Southern California Evidence-based Practice Center under Contract No. 290-2007-10062-I. AHRQ Publication No. 12-EHC010-EF. Rockville, MD: Agency for Healthcare Research and Quality January 2012.Google Scholar
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