Influence of Inward Pressure of the Transducer on Lateral Abdominal Muscle Thickness During Ultrasound Imaging

STUDY DESIGN: Controlled laboratory study, technical note. OBJECTIVES: The purpose of this study was to quantify changes in the thickness of the transversus abdominis, internal oblique, and external oblique muscles induced by different inward pressures of the transducer during ultrasound imaging (USI). BACKGROUND: USI of the lateral abdominal muscles is increasingly used in managing musculoskeletal dysfunction. However, to the best of our knowledge, no study has evaluated the influence of different inward pressures of the transducer on the lateral abdominal muscle thickness during USI. METHODS: Thirty healthy male volunteers participated in this study. The thickness of the transversus abdominis, internal oblique, and external oblique muscles was measured with USI by the same rater in 4 conditions of inward pressures of 0.5, 1.0, 2.0, and 4.0 N. Intraclass correlation coefficients (ICC1.1), with 95% confidence intervals, were calculated, and a repeated-measures analysis of variance was used to assess the influence of inward pressure on the thickness of the lateral abdominal muscles. RESULTS: The thickness of the transversus abdominis, internal oblique, and external oblique muscles was significantly different among the 4 conditions (P<.038). The mean difference between the 0.5-N and 4.0-N conditions was greater than the minimal detectable change of the 0.5-N condition in the lateral abdominal muscles. CONCLUSION: The difference in magnitude produced by the forces under different conditions was meaningful. When using a technique that involves a handheld transducer, the examiner should attempt to maintain consistent inward pressure of the transducer during USI to quantify the thickness of lateral abdominal muscles. J Orthop Sports Phys Ther 2012;42(9):815-818, Epub 19 April 2012. doi:10.2519/jospt.2012.4064