Reliability of B-mode ultrasonography for abdominal muscles in asymptomatic and patients with acute low back pain

SummaryThe purpose of this methological study was to develop a reliable method for measuring transversus abdominis, rectus abdominis, external oblique and internal oblique muscles in asymptomatic human subjects and patients with acute low back pain (ALBP). This was a single operator reliability design study using ultrasound imaging to measure muscle thickness in 27 subjects on three separate occasions. Intra-class correlation coefficients (ICC) and standard error of measurement (SEM) were used to analyze muscle thickness. The mean, SD, ICC and SEM for external oblique, internal oblique, transversus abdominis and rectus abdominis muscles in asymptomatic subjects were (5.38, 1.64, 0.96, 0.33), (9.35, 3.42, 0.97, 0.073), (4.36, 1.93, 0.81, 0.45), (10.8, 2.18, 0.85, 0.84), respectively. The mean, SD, ICC, SEM for external oblique, internal oblique and transversus abdominis muscles in patients with ALBP were (5.58, 0.97, 0.87, 0.35), (9.72, 1.92, 0.87, 0.31), (4.36, 1, 0.91, 0.3), respectively. Earlier study on ultrasonographic measurement for neck multifidus muscles has suggested that the reliability of muscle thickness is higher in asymptomatic subjects compared with those in the symptomatic subjects. However, the present study showed high reliability for both symptomatic and asymptomatic subjects. This difference may be related to non-atrophic changes in abdominal muscles in acute low back patients. The results of this study indicate that the measurement of abdominal muscle thickness with B-mode ultrasonography can be performed reliably even in patients with ALBP.