Therapeutic ultrasound for chronic low back pain

Background: This is an update of a Cochrane Review published in 2014. Chronic non-specific low back pain (LBP) has become one of the main causes of disability in the adult population around the world. Although therapeutic ultrasound is not recommended in recent clinical guidelines, it is frequently used by physiotherapists in the treatment of chronic LBP.

Objectives: The objective of this review was to determine the effectiveness of therapeutic ultrasound in the management of chronic non-specific LBP. A secondary objective was to determine the most effective dosage and intensity of therapeutic ultrasound for chronic LBP.

Search methods: We performed electronic searches in CENTRAL, MEDLINE, Embase, CINAHL, PEDro, Index to Chiropractic Literature, and two trials registers to 7 January 2020. We checked the reference lists of eligible studies and relevant systematic reviews and performed forward citation searching.

Selection criteria: We included randomised controlled trials (RCTs) on therapeutic ultrasound for chronic non-specific LBP. We compared ultrasound (either alone or in combination with another treatment) with placebo or other interventions for chronic LBP.

Data collection and analysis: Two review authors independently assessed the risk of bias of each trial and extracted the data. We performed a meta-analysis when sufficient clinical and statistical homogeneity existed. We determined the certainty of the evidence for each comparison using the GRADE approach.

Main results: We included 10 RCTs involving a total of 1025 participants with chronic LBP. The included studies were carried out in secondary care settings in Turkey, Iran, Saudi Arabia, Croatia, the UK, and the USA, and most applied therapeutic ultrasound in addition to another treatment, for six to 18 treatment sessions. The risk of bias was unclear in most studies. Eight studies (80%) had unclear or high risk of selection bias; no studies blinded care providers to the intervention; and only five studies (50%) blinded participants. There was a risk of selective reporting in eight studies (80%), and no studies adequately assessed compliance with the intervention. There was very low-certainty evidence (downgraded for imprecision, inconsistency, and limitations in design) of little to no difference between therapeutic ultrasound and placebo for short-term pain improvement (mean difference (MD) -7.12, 95% confidence interval (CI) -17.99 to 3.75; n = 121, 3 RCTs; 0-to-100-point visual analogue scale (VAS)). There was also moderate-certainty evidence (downgraded for imprecision) of little to no difference in the number of participants achieving a 30% reduction in pain in the short term (risk ratio 1.08, 95% CI 0.81 to 1.44; n = 225, 1 RCT). There was low-certainty evidence (downgraded for imprecision and limitations in design) that therapeutic ultrasound has a small effect on back-specific function compared with placebo in the short term (standardised mean difference -0.29, 95% CI -0.51 to -0.07 (MD -1.07, 95% CI -1.89 to -0.26; Roland Morris Disability Questionnaire); n = 325; 4 RCTs), but this effect does not appear to be clinically important. There was moderate-certainty evidence (downgraded for imprecision) of little to no difference between therapeutic ultrasound and placebo on well-being (MD -2.71, 95% CI -9.85 to 4.44; n = 267, 2 RCTs; general health subscale of the 36-item Short Form Health Survey (SF-36)). Two studies (n = 486) reported on overall improvement and satisfaction between groups, and both reported little to no difference between groups (low-certainty evidence, downgraded for serious imprecision). One study (n = 225) reported on adverse events and did not identify any adverse events related to the intervention (low-certainty evidence, downgraded for serious imprecision). No study reported on disability for this comparison. We do not know whether therapeutic ultrasound in addition to exercise results in better outcomes than exercise alone because the certainty of the evidence for all outcomes was very low (downgraded for imprecision and serious limitations in design). The estimate effect for pain was in favour of the ultrasound plus exercise group (MD -21.1, 95% CI -27.6 to -14.5; n = 70, 2 RCTs; 0-to-100-point VAS) at short term. Regarding back-specific function (MD - 0.41, 95% CI -3.14 to 2.32; n = 79, 2 RCTs; Oswestry Disability Questionnaire) and well-being (MD -2.50, 95% CI -9.53 to 4.53; n = 79, 2 RCTs; general health subscale of the SF-36), there was little to no difference between groups at short term. No studies reported on the number of participants achieving a 30% reduction in pain, patient satisfaction, disability, or adverse events for this comparison.

Authors' conclusions: The evidence from this systematic review is uncertain regarding the effect of therapeutic ultrasound on pain in individuals with chronic non-specific LBP. Whilst there is some evidence that therapeutic ultrasound may have a small effect on improving low back function in the short term compared to placebo, the certainty of evidence is very low. The true effect is likely to be substantially different. There are few high-quality randomised trials, and the available trials were very small. The current evidence does not support the use of therapeutic ultrasound in the management of chronic LBP.