Comparison of ischemic compression and lumbopelvic manipulation as trigger point therapy for patellofemoral pain syndrome in young adults: A double-blind randomized clinical trial

The Effect of Lumbopelvic Manipulation for Pain Reduction in Patellofemoral Pain Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Patellofemoral pain syndrome (PFPS) is one of the most common etiologies of knee pain and might be relieved with lumbopelvic manipulation (LPM). This meta-analysis aimed to investigate the effects of LPM on pain reduction in patients with PFPS. Electronic databases were searched from inception to December 2023 for randomized controlled trials (RCTs) investigating the effects of LPM on PFPS. The primary outcome was the change in visual analog or numeric rating scale scores assessing pain. Ten studies comprising 346 participants were included. Significant pain reduction was noted in the LPM group (Hedges' g = -0.706, 95% confidence interval [CI] = -1.197 to -0.214, p = 0.005, I2 = 79.624%) compared with the control group. Moreover, pain relief was more pronounced when LPM was combined with other physical therapies (Hedges' g = -0.701, 95% CI = -1.386 to -0.017, p = 0.045, I2 = 73.537%). No adverse events were reported during the LPM. The LPM appears to be a safe and effective adjuvant therapy for pain reduction in patients with PFPS. Clinicians should consider adding LPM to other physical therapies (e.g., quadriceps muscle strengthening) during the management of these patients.

Effects of high frequency strengthening on pain sensitivity and function in female runners with chronic patellofemoral pain

OBJECTIVE

To investigate the effects of a high frequency strengthening program on function, pain, and pain sensitization in female runners with chronic patellofemoral pain (PFP).

DESIGN

Cross-sectional study.

SETTING

University laboratory.

PARTICIPANTS

Thirty female runners (mean age 32 ± 8.1 years) with chronic PFP completed an 8-week home strengthening program.

MAIN OUTCOME MEASURES

Variables assessed at baseline, 8-weeks, and 12 weeks included single leg step down test (SLSD), pain, Anterior Knee Pain Scale (AKPS), University of Wisconsin Running Injury and Recovery Index (UWRI), and quantitative sensory testing.

RESULTS

There was large and statistically significant improvement at 8 and 12 weeks for average knee pain (ηp2 = 0.334, p < 0.001), worst knee pain (ηp2 = 0.351, p < 0.001), SLSD (ηp2 = 0.161, p = 0.001), AKPS (ηp2 = 0.463, p < 0.001), and UWRI (ηp2 = 0.366, p < 0.001). A medium to large effect and statistically significant improvement in pressure pain threshold testing was found for all local and remote structures (ηp2 range, 0.110 to 0.293, range p < 0.001 to p = 0.009) at 8 and 12 weeks.

CONCLUSIONS

There was a significant decrease in local and remote hyperalgesia via mechanical and thermal pain sensitivity testing in female runners with chronic PFP. There was a large effect and significant improvement in self-reported pain and function.

Does manual therapy meaningfully change quantitative sensory testing and patient reported outcome measures in patients with musculoskeletal impairments related to the spine?: A 'trustworthy' systematic review and meta-analysis

OBJECTIVES

To perform a 'trustworthy' systematic review (SR) with meta-analysis on the potential mechanisms of manual therapy used to treat spinal impairments.

DESIGN

SR with meta-analysis.

LITERATURE SEARCH

Articles published between January 2010 and October 2022 from CENTRAL, CINAHL, MEDLINE, PubMed, ProQuest, and PEDro.

METHODS

This SR included English-language randomized clinical trials (RCTs) involving manual therapy to treat spinal impairments in adults. The primary outcome was pressure pain thresholds (PPTs). To synthesize RCTs with high confidence in estimated effects using the GRADE, RCTs with questionable prospective, external, and internal validity, and high risk of bias (RoB) were excluded.

RESULTS

Following title and abstract screening, 89 full-text RCTs were reviewed. Twenty-two studies included the criteria of interest. Sixteen were not prospectively registered, two contained discussion/conclusions judged to be inconsistent with the registry, and one was rated as having a high RoB. Three studies met the inclusion criteria; heterogeneous interventions and locations for PPT testing prevented synthesis into practice recommendations. The two studies with high confidence in estimated effects had small effect sizes, and one study had confidence intervals that crossed zero for the outcome measures of interest.

DISCUSSION

Standardized PPT testing, as a potential measure of centrally mediated pain, could provide clues regarding the mechanisms of manual therapy or help identify/refine research questions.

CONCLUSION

High-quality RCTs could not be synthesized into strong conclusions secondary to the dissimilarity in research designs. Future research regarding quantitative sensory testing should develop RCTs with high confidence in estimated effects that can be translated into strong recommendations.

Six Treatments Have Positive Effects at 3 Months for People With Patellofemoral Pain: A Systematic Review With Meta-analysis

OBJECTIVE: To determine the effects of nonsurgical treatments on pain and function in people with patellofemoral pain (PFP). DESIGN: Systematic review with meta-analysis. LITERATURE SEARCH: We searched MEDLINE, Web of Science, and Scopus databases from their inception until May 2022 for interventional randomized controlled trials (RCTs) in people with PFP. STUDY SELECTION CRITERIA: We included RCTs that were scored ≥7 on the PEDro scale. DATA SYNTHESIS: We extracted homogenous pain and function data at short- (≤3 months), medium- (>3 to ≤12 months) and long-term (>12 months) follow-up. Interventions demonstrated primary efficacy if outcomes were superior to sham, placebo, or wait-and-see control. Interventions demonstrated secondary efficacy if outcomes were superior to an intervention with primary efficacy. RESULTS: We included 65 RCTs. Four interventions demonstrated short-term primary efficacy: knee-targeted exercise therapy for pain (standardized mean difference [SMD], 1.16; 95% CI: 0.66, 1.66) and function (SMD, 1.19; 95% CI: 0.51, 1.88), combined interventions for pain (SMD, 0.79; 95% CI: 0.26, 1.29) and function (SMD, 0.98; 95% CI: 0.47, 1.49), foot orthoses for global rating of change (OR = 4.31; 95% CI: 1.48, 12.56), and lower-quadrant manual therapy for function (SMD, 2.30; 95% CI: 1.60, 3.00). Two interventions demonstrated short-term secondary efficacy compared to knee-targeted exercise therapy: hip-and-knee-targeted exercise therapy for pain (SMD, 1.02; 95% CI: 0.58, 1.46) and function (SMD, 1.03; 95% CI: 0.61, 1.45), and knee-targeted exercise therapy and perineural dextrose injection for pain (SMD, 1.34; 95% CI: 0.72, 1.95) and function (SMD, 1.21; 95% CI: 0.60, 1.82). CONCLUSIONS: Six interventions had positive effects at 3 months for people with PFP, with no intervention adequately tested beyond this time point. J Orthop Sports Phys Ther 2022;52(11):750-768. Epub: 8 September 2022. doi:10.2519/jospt.2022.11359.

Effectiveness of local exercise therapy versus spinal manual therapy in patients with patellofemoral pain syndrome: medium term follow-up results of a randomized controlled trial

Background

Increasing evidence has shown benefits of spinal manipulations in patients with patellofemoral pain syndrome (PFPS). There is scarcity regarding medium term effects of spinal manual therapy on outcome measures in PFPS patients. Therefore, the aim of the present study was to compare the effectiveness of local exercise therapy and spinal manual therapy for knee pain, function and maximum voluntary peak force (MVPF) velocity of the quadriceps in PFPS patients.

Methods

Forty-three patients with PFPS were randomly assigned to a local exercise or spinal manual therapy group. The local exercise group received six sessions (one session per week) of supervised training of the knee-and hip muscles with mobilization of the patellofemoral joint. The spinal manual therapy group received six interventions (one intervention per week) of high velocity low thrust manipulations at the thoracolumbar region, sacroiliac joint, and/or hip. All patients were also asked to do home exercises. Maximum, minimum and current pain were measured using the visual analogue scale. Function was assessed with the anterior knee pain scale (AKPS) and MPFV was recorded using a Biodex System 3 dynamometer. Patients were assessed before intervention, after 6 weeks of intervention and after 6 weeks of follow-up. Between-group differences at assessments were analysed by way of analysis of covariance with Bonferroni correction.

Results

Pain and functionality improved more following spinal manipulative therapy than local exercise therapy. After 6 weeks of intervention the between-group difference (local versus spinal) for maximal pain was 23.4 mm [95% CI: 9.3, 37.6; effect size (ES): 1.04] and − 12.4 [95% CI: − 20.2, − 4.7; ES: 1.00] for the AKPS. At 6 weeks of follow-up the between-group difference for maximal pain was 18.7 mm [95% CI: 1.4, 36.0; ES: 0.68] and − 11.5 [95% CI: − 19.9, − 3.3; ES: − 0.87] for the AKPS.

Conclusions

This study suggests that spinal manual therapy is more effective than local exercise therapy in improving pain and function in patients with PFPS in the medium term. We suggest for future research to investigate whether combining local exercise therapy and spinal manual therapy is more effective than either single intervention on its own.

This clinical trial study was approved by the Medical Ethics Committee METC Z under registration number NL57207.096. and registered retrospectively in ClinicalTrials.gov PRS with registration ID number NCT04748692 on the 10th of February 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04310-9.

Criteria Used for the Diagnosis of Myofascial Trigger Points in Clinical Trials on Physical Therapy: Updated Systematic Review

OBJECTIVE

The objective of this study was to conduct an updated systematic review of diagnostic criteria for myofascial trigger points (MTrPs) used in clinical trials of physical therapy interventions from 2007 to 2019.

METHODS

MEDLINE and Physiotherapy Evidence Database (PEDro) were searched using the following MeSH keywords: "trigger points," "trigger point," "myofascial trigger point," "myofascial trigger points," "myofascial pain," and "myofascial pain syndrome." The MeSH keywords were combined by using Boolean operators "OR"/"AND." All physiotherapy clinical trials including patients with musculoskeletal conditions characterized by at least 1 active MTrP or latent MTrP in any body area were selected. We pooled data from an individual criterion and criteria combinations used to diagnose MTrPs. The protocol was developed in accordance with the PRISMA-P guidelines.

RESULTS

Of 478 possibly relevant publications, 198 met the inclusion criteria. Of these 198 studies, 129 studies (65.1%) stated specifically the diagnostic criteria used for MTrPs in the main text, 56 studies (28.3%) failed to report any method whereby MTrP was diagnosed, and 13 studies (6.6%) adopted expert-based definitions for MTrPs without specification. Of 129 studies, the 6 criteria applied most commonly were: "spot tenderness" (n=125, 96.9%), "referred pain" (95, 73.6%), "local twitch response" (63, 48.8%), pain recognition (59, 45.7%), limited range of motion" (29, 22.5%), and "jump sign" (10, 7.8%). Twenty-three combinations of diagnostic criteria were identified. The most frequently used combination was "spot tenderness," "referred pain," and "local twitch response" (n=28 studies, 22%).

CONCLUSIONS

A number of the included studies failed in properly reporting the MTrP diagnostic criteria. Moreover, high variability in the use of MTrP diagnostic was also observed. Spot tenderness, referred pain, and local twitch response were the 3 most popular criteria (and the most frequently used combination). A lack of transparency in the reporting of MTrP diagnostic criteria is present in the literature.

REGISTRY

This systematic review was registered under the Centre for Reviews and Dissemination, PROSPERO number: CRD42018087420.

Effects of Trigger Point Dry Needling on Neuromuscular Performance and Pain of Individuals Affected by Patellofemoral Pain: A Randomized Controlled Trial

Purpose

To investigate the effects of trigger point dry needling (TrP-DN) on exercise-induced patellofemoral pain syndrome (PFPS).

Patients and Methods

In this randomized, single-blind, parallel-group trial, 50 patients with PFPS were randomly allocated to the following two groups: the TrP-DN group (n = 25) and the Sham needling group (n = 25). Patients in both groups were asked to perform a stretching exercise of the quadriceps daily after needling. The needling group received a single session of TrP-DN to trigger points (TrPs) in the vastus medialis oblique (VMO), vastus lateralis (VL), and rectus femoris muscles (once a week for 6 weeks), and the Sham group received placebo needling. Visual analogue scale (VAS) for pain intensity and Kujala questionnaire for the functional status were assessed before treatment, 3 and 6 weeks after treatment, and at the 3-month follow-up. The ratio of the myoelectric amplitude of the vastus medialis oblique and vastus lateralis muscles (VMO/VL) was assessed before treatment and 6 weeks after treatment.

Results

There was no significant difference in the general data between the two groups. The VAS scores and Kujala scores in the TrP-DN group were significantly improved and increased at the 3-week treatment visit, 6-week treatment visit, and 3-month follow-up compared to the scores before treatment; and the scores in the Sham group were only significantly improved at the 3-week treatment visit, and 6-week treatment visit. VAS scores in the TrP-DN group were significantly lower and Kujala scores were significantly higher at the 6-week treatment visit and the 3-month follow-up compared to those in the Sham group. The VMO/VL ratio in the TrP-DN group was significantly increased at the 6-week treatment visit compared to that before treatment.

Conclusion

TrP-DN at the quadriceps combined with stretch can reduce the pain, and improves the clinical symptoms and function, the VMO/VL ratio, and the coordination of VMO and VL in patients with PFPS.

The Effectiveness of Ischemic Compression Technique on Pain and Function in Individuals With Shoulder Pain: A Systematic Review

OBJECTIVE

To systematically review current literature to determine the effectiveness of the ischemic compression (IC) technique on pain and function in individuals with shoulder pain.

METHODS

This review was conducted according to recommendations of Preferred Reporting Items for Systematic Reviews and Meta-Analyses and the Cochrane Collaboration for Systematic Reviews; a search was performed in the electronic databases PubMed, Cumulative Index to Nursing and Allied Health Literature, SPORTDiscus, Physiotherapy Evidence Database, and Web of Science. Randomized clinical trials and quasi-randomized clinical trials were included, and the methodological quality was evaluated through the Physiotherapy Evidence Database scale.

RESULTS

The search found 572 studies; of these, 71 were selected by title and, subsequently, 29 were selected through abstract analyses. After critical analyses, 5 studies were included. The methodological quality ranged from 4 (reasonable) to 9 (excellent) points. Pain was assessed by all studies using the visual analog scale, Global Perceived Effect scale, Numerical Rating Scale, pressure pain threshold, or Perceived Amelioration Numerical Scale. Function was evaluated by 3 studies through the Shoulder Pain and Disability Index; Neck Disability Index; American Shoulder and Elbow Surgeons Standardized Shoulder Assessment; and Disabilities of the Arm, Shoulder, and Hand questionnaires. The studies showed that the IC technique produces immediate and short-term positive effects for pain, and positive short-term effects for shoulder function in individuals with shoulder pain.

CONCLUSION

The IC technique seems to be beneficial for pain and shoulder function. However, caution is needed when considering this evidence owing to the limited quality of some studies, the few articles found, and the lack of standardization of the application parameters of the technique to facilitate its reproducibility.

Comparison of dry needling and ischaemic compression techniques on pain and function in patients with patellofemoral pain syndrome: a randomised clinical trial

BACKGROUND

To compare the effectiveness of ischaemic compression (IC) applied directly to the knee versus dry needling (DN) with respect to pain, functional status and sensitivity to mechanical stimulation of vastus medialis obliquus (VMO) myofascial trigger points (MTrPs) in patients with patellofemoral pain syndrome (PFPS).

METHODS

A total of 54 patients with unilateral PFPS aged 20-30 years were selected randomly from patients referred to physical therapy clinics of Babol University of Medical Sciences in Iran. Twenty-seven patients were allocated to either IC or DN groups. Three sessions of treatment were applied over 1 week with follow-up at 1 week, 1 month and 3 months. Primary outcome measures comprised the Kujala questionnaire score for functional status, numerical pain rating scale (NPRS) for pain intensity and pressure pain threshold (PPT) for sensitivity to mechanical stimulation; these were measured and recorded before treatment and 1 week, 1 month and 3 months after the last treatment session.

RESULTS

There were no statistically significant differences in the between-group comparisons of any variables at the various follow-up points. Both groups (n = 27 participants each) had significant improvements (p < 0.05) in pain, functional status and PPT values at follow-up.

CONCLUSIONS

There were no differences in markers of pain, function or pressure sensitivity over a 3-month follow-up period between patients with PFPS treated with DN and IC. Temporal improvements in both groups suggested that the two techniques may be similarly effective for the treatment of PFPS.

Assessment and Management of Somatic Dysfunctions in Patients With Patellofemoral Pain Syndrome

Context

Patellofemoral pain syndrome (PFPS) is one of the most common determinants of knee pain. The causes of PFPS are multifactorial, and most treatment approaches are conservative. There are many kinds of therapy for this syndrome, which are based on building strength, flexibility, proprioception, and endurance. Training is functional and progression is gradual. Our hypothesis is that total-body osteopathic manipulative therapy (OMTh; manipulative care provided by foreign-trained osteopaths) focused on the management of somatic dysfunctions could be useful for managing the pain of patients with PFPS.

Objective

To investigate the effect of OMTh on pain reduction in patients with PFPS.

Methods

This pilot study was randomized, controlled, and single-blinded with 2 months of follow-up. Qualified participants were randomly assigned to 1 of 2 groups: OMTh group or placebo group. Each participant received either 4 sessions of OMTh or 4 sessions of manual placebo intervention that consisted of passive touching without joint mobilization in a protocolled order. A visual analogue scale (VAS) was used to assess general knee pain, peripatellar pain, pain after prolonged sitting, pain during the patellar compression test, and pain during stair ascent and descent. Pain assessment was performed before the baseline (T0), second (T1), third (T2), and fourth (T3) sessions, and follow-up (T4) was performed 8 weeks after T3.

Results

Thirty-five participants were enrolled the study. The VAS score was significantly reduced and clinically relevant in the OMTh group after each treatment and after 2 months of follow-up. The change in the VAS score before each treatment indicates that the most improved areas at T1 compared with T0 were lumbar and sacral with improvements in 83% and 40% of patients, respectively. At T2 compared with T1, the most improved areas were cervical and sacral with improvements found in 58% and 36% of patients, respectively. The number of dysfunctions that were diagnosed decreased during the baseline to T3 period (40% change). The correlation analysis showed significant results for the dysfunction and the compression test at T2 (P=.01, ρ=0.543).

Conclusion

Significant differences in VAS scores were found between the OMTh and placebo groups. These findings underline how OMTh can lead to reduced pain in patients with PFPS.

Dry Cupping, Ischemic Compression, or Their Combination for the Treatment of Trigger Points: A Pilot Randomized Trial

Background: Chronic neck pain (NP) attributed to myofascial pain syndrome is one of the particularly common skeletal muscle disorder associated with the hyperirritable zone in the taut band of muscle. Trigger points (TPs) are the physical interpretation of the myofascial pain syndrome. In the United States, 30%–85% of pain patients have been affected by myofascial TPs.

Objectives: To reveal preliminary evidence on the clinical efficacy of ischemic compression therapy, dry cupping, and their combination on improving the TPs' pressure pain threshold (PPT), neck range of motion (NROM), and neck disability index (NDI) in patients with TPs and nonspecific NP. Besides, assess the feasibility of conducting a randomized clinical trial (RCT).

Design: A randomized pilot study was conducted on 24 patients with TPs and nonspecific NP. Patients were randomly assigned to three groups: the cupping group, the ischemic compression group, and the combination therapy group. PPT, NROM, and NDI were assessed before and after 4 weeks of treatment.

Results: The results showed a statistically significant improvement in NDI, PPT, and NROM compared with values before the treatment (p < 0.05) in all groups. Although no significant difference was detected between ischemic compression (IC) and dry cupping, the combination approach showed significantly higher and faster improvement (p < 0.05).

Conclusions: It is feasible to conduct a main RCT. Both IC and dry cupping may hold promise in treating TPs; a combination of the two therapies may provide superior improving rate.

2018 Consensus statement on exercise therapy and physical interventions (orthoses, taping and manual therapy) to treat patellofemoral pain: recommendations from the 5th International Patellofemoral Pain Research Retreat, Gold Coast, Australia, 2017

Patellofemoral pain affects a large proportion of the population, from adolescents to older adults, and carries a substantial personal and societal burden. An international group of scientists and clinicians meets biennially at the International Patellofemoral Research Retreat to share research findings related to patellofemoral pain conditions and develop consensus statements using best practice methods. This consensus statement, from the 5th International Patellofemoral Research Retreat held in Australia in July 2017, focuses on exercise therapy and physical interventions (eg, orthoses, taping and manual therapy) for patellofemoral pain. Literature searches were conducted to identify new systematic reviews and randomised controlled trials (RCTs) published since the 2016 Consensus Statement. The methodological quality of included systematic reviews and RCTs was graded using AMSTAR and PEDro, respectively. Evidence-based statements were developed from included papers and presented to a panel of 41 patellofemoral pain experts for consensus discussion and voting. Recommendations from the expert panel support the use of exercise therapy (especially the combination of hip-focused and knee-focused exercises), combined interventions and foot orthoses to improve pain and/or function in people with patellofemoral pain. The use of patellofemoral, knee or lumbar mobilisations in isolation, or electrophysical agents, is not recommended. There is uncertainty regarding the use of patellar taping/bracing, acupuncture/dry needling, manual soft tissue techniques, blood flow restriction training and gait retraining in patients with patellofemoral pain. In 2017, we launched the International Patellofemoral Research Network (www.ipfrn.org) to consolidate and grow our patellofemoral research community, facilitate collaboration and disseminate patellofemoral pain knowledge to clinicians and the general public. The 6th International Patellofemoral Research Retreat will be held in Milwaukee, Wisconsin, USA, in October 2019.

Effectiveness of Manual Therapy for Pain and Self-reported Function in Individuals With Patellofemoral Pain: Systematic Review and Meta-analysis

Study Design Systematic literature review with meta-analysis. Background Management of patellofemoral pain (PFP) may include the utilization of manual therapy (MT) techniques to the patellofemoral joint, surrounding soft tissues, and/or lumbopelvic region. Objectives To determine the effectiveness of MT, used alone or as an adjunct intervention, compared to standard treatment or sham for reducing pain and improving self-reported function in individuals with PFP. Methods An electronic literature search was conducted in the PubMed, Ovid, Cochrane Central Register of Controlled Trials, and CINAHL databases for studies investigating MT for individuals with PFP. Studies published through August 2017 that compared MT (local or remote to the knee), used alone or in combination with other interventions, to control or sham interventions were included. Patient-reported pain and functional outcomes were collected and synthesized. Trials were assessed via the Cochrane risk-of-bias tool, and a meta-analysis of the evidence was performed. Results Nine studies were included in the review, 5 of which were rated as having a low risk of bias. The use of MT, applied to the local knee structure, was associated with favorable short-term changes in self-reported function and pain in individuals with PFP, when compared to a comparison (control or sham) intervention. However, the changes were clinically meaningful only for pain (defined as a 2-cm or 2-point improvement on a visual analog scale or numeric pain-rating scale). The evidence regarding lumbopelvic manipulation was inconclusive for pain improvement in individuals with PFP, based on 3 studies. Conclusion The data from this review cautiously suggest that MT may be helpful in the short term for decreasing pain in patients with PFP. Several studies integrated MT into a comprehensive treatment program. Changes in self-reported function with the inclusion of MT were shown to be significant, but not clinically meaningful. The limitations in the studies performed to date suggest that future research should determine the optimal techniques and dosage of MT and perform longer follow-up to monitor long-term effects. Level of Evidence Therapy, level 1a. J Orthop Sports Phys Ther 2018;48(5):358-371. Epub 6 Jan 2018. doi:10.2519/jospt.2018.7243.

The effects of joint mobilization on individuals with patellofemoral pain: a systematic review

OBJECTIVE

To investigate and synthesize the effects of joint mobilization on individuals with patellofemoral pain syndrome.

DATA SOURCES

Five electronic databases (CINAHL, the Cochrane Central Register of Controlled Trials, PubMed, Scopus, and SPORTDiscus) were used.

REVIEW METHODS

Each database was searched from inception to 1 November 2017. Randomized controlled trials investigating a manual therapy intervention, with or without co-interventions, for persons with patellofemoral pain were included. Two reviewers independently screened the retrieved literature and appraised the quality of the selected studies using the PEDro rating scale. A third reviewer was used in cases of discrepancy to create a consensus.

RESULTS

A total of 361 articles were identified in the search. Twelve randomized trials with a total of 499 participants were selected for full review. Within-group improvements in pain and function were noted for the manual therapy groups. Between-group improvements for short-term outcomes (three months or less) were greatest when joint mobilization was directed to the knee complex and used as part of a comprehensive approach.

CONCLUSION

In the articles reviewed, joint mobilization appears to be most effective in improving pain and function when coupled with other interventions, although its discrete effect is unclear due to the reviewed studies' design and reporting.