Abstract: We included 11 studies including 414 participants in the review. Two trials compared therapeutic ultrasound with placebo, two compared one ultrasound regimen with another, two compared ultrasound with another non-surgical intervention, and six compared ultrasound as part of a multi-component intervention with another non-surgical intervention (for example, exercises and splint). The risk of bias was low in some studies and unclear or high in other studies, with only two reporting that the allocation sequence was concealed and six reporting that participants were blinded. Overall, there is insufficient evidence that one therapeutic ultrasound regimen is more efficacious than another. Only two studies reported the primary outcome of interest, short-term overall improvement (any measure in which patients indicate the intensity of their complaints compared with baseline, for example, global rating of improvement, satisfaction with treatment, within three months post-treatment). One low quality trial with 68 participants found that when compared with placebo, therapeutic ultrasound may increase the chance of experiencing short-term overall improvement at the end of seven weeks treatment (RR 2.36; 95% CI 1.40 to 3.98), although losses to follow-up and failure to adjust for the correlation between wrists in participants with bilateral CTS in this study suggest that this data should be interpreted with caution. Another low quality trial with 60 participants found that at three months post-treatment therapeutic ultrasound plus splint increased the chance of short-term overall improvement (patient satisfaction) when compared with splint alone (RR 3.02; 95% CI 1.36 to 6.72), but decreased the chance of short-term overall improvement when compared with low-level laser therapy plus splint (RR 0.87; 95% CI 0.57 to 1.33), though participants were not blinded to treatment, it was unclear if the random allocation sequence was adequately concealed, and there was a potential unit of analysis error. Differences between groups receiving different frequencies and intensities of ultrasound, and between ultrasound as part of a multi-component intervention versus other non-surgical interventions, were generally small and not statistically significant for symptoms, function, and neurophysiologic parameters. No studies reported any adverse effects of therapeutic ultrasound, but this outcome was only measured in three studies. More adverse effects data are required before any firm conclusions on the safety of therapeutic ultrasound can be made. There is only poor quality evidence from very limited data to suggest that therapeutic ultrasound may be more effective than placebo for either short- or long-term symptom improvement in people with CTS. There is insufficient evidence to support the greater benefit of one type of therapeutic ultrasound regimen over another or to support the use of therapeutic ultrasound as a treatment with greater efficacy compared to other non-surgical interventions for CTS, such as splinting, exercises, and oral drugs. More methodologically rigorous studies are needed to determine the effectiveness and safety of therapeutic ultrasound for CTS.

Plain-language summary: We searched for study reports and found 11 randomised controlled trials including 443 participants overall that assessed the safety and benefit of therapeutic ultrasound for people with carpal tunnel syndrome. The risk of bias of studies was low in some studies and unclear or high in others. There is only poor quality evidence from very limited data to suggest that therapeutic ultrasound may be more effective than placebo for either short- or long-term symptom improvement in people with carpal tunnel syndrome. There is insufficient evidence to support the greater benefit of one type of therapeutic ultrasound regimen over another or to support the use of therapeutic ultrasound as a treatment with greater efficacy compared with other non-surgical interventions for carpal tunnel syndrome, such as splinting, exercises, and oral drugs. Few studies measured adverse effects to therapeutic ultrasound. More research is needed to find out how effective and safe therapeutic ultrasound is for people with carpal tunnel syndrome, particularly in the long term.