Exposure to Low Amounts of Ultrasound Energy Does Not Improve Soft Tissue Shoulder Pathology: A Systematic Review

Abstract

Although therapeutic ultrasound is commonly used to treat shoulder injuries, research to date on the ability of ultrasound to improve outcomes for shoulder pathologies is conflicting. This study aimed to systematically and critically review available literature to ascertain whether beneficial effects of ultrasound were associated with certain shoulder pathologies or particular ultrasound treatment protocols. Five electronic databases were searched, and the included studies, identified through pair consensus, were randomized controlled trials (RCTs) that utilized ultrasound for soft tissue shoulder injury or pain. Eight studies included in this review (n=586 patients, median PEDro score=8.0/10) evaluated various parameters, including the duration of patients' symptoms (0-12 months), duty cycle (20% and 100%), intensity (0.1-2.0 W/cm2), treatment time per session (4.5-15.8 minutes), number of treatments (6-39), and total energy applied per treatment (181-8,152 J). Inconsistent outcome measures among studies precluded meta-analysis; however, 3 RCTs showed statistically significant benefits of ultrasound, 2 of which examined calcific tendinitis. Studies that showed beneficial effects of ultrasound typically had 4 times longer total exposure times and applied much greater ultrasound energy per session (average of 4,228 J) compared with studies that showed no benefit of ultrasound (average of 2,019 J). No studies that delivered < or = 720 J per session showed improvement in treatment groups. Current research involving ultrasound treatment protocols that delivered low levels of ultrasound energy do not adequately address whether ultrasound can improve outcomes for shoulder disorders. Determining whether therapeutic ultrasound can affect soft tissue shoulder pathologies will require further research and systematic reviews that involve appropriate ultrasound treatment protocols.