Ultrasound Imaging as a Visual Biofeedback Tool in Rehabilitation: An Updated Systematic Review.

Rehabilitative ultrasound imaging (RUSI) is used by physical therapists as a feedback tool for measuring changes in muscle morphology during therapeutic interventions such as motor control exercises (MCE). However, a structured overview of its efficacy is lacking. We aimed to systematically review the efficacy of RUSI for improving MCE programs compared with no feedback and other feedback methods. MEDLINE, PubMed, SCOPUS and Web of Science databases were searched for studies evaluating efficacy data of RUSI to improve muscular morphology, quality, and/or function of skeletal muscles and MCE success. Eleven studies analyzing RUSI feedback during MCE were included. Most studies showed acceptable methodological quality. Seven studies assessed abdominal wall muscles, one assessed pelvic floor muscles, one serratus anterior muscle, and two lumbar multifidi. Eight studies involved healthy subjects and three studies clinical populations. Eight studies assessed muscle thickness and pressure differences during MCE, two assessed the number of trials needed to successfully perform MCE, three assessed the retain success, seven assessed the muscle activity with electromyography and one assessed clinical severity outcomes. Visual RUSI feedback seems to be more effective than tactile and/or verbal biofeedback for improving MCE performance and retention success, but no differences with pressure unit biofeedback were found.