Reliability of Rehabilitative Ultrasound Imaging of the Lumbar Multifidus

Abstract

[Purpose] The purpose of this study was to evaluate the intra-examiner reliability of rehabilitative ultrasound imaging (RUSI) in obtaining thickness measurements of the lumbar multifidus (LM) with intraclass correlation coefficients (ICC) and minimum detectable change (MDC). [Subjects] Ten healthy volunteers participated in the study. [Method] We measured thickness measurements of LM at 3 angles of pelvic tilt (moderate anterior-tilt, neutral position and moderate posterior-tilt) and different percentages of voluntary isometric contraction. The task was static muscle contraction of LM during pelvic anterior-tilt with nutation of the sacrum in a prone position on the edge of the bed and hanging subject’s legs. Thickness measurements of left LM were obtained by using RUSI during 2 sessions, 1 to 4 weeks apart. ICC and measurement error by 95% confidence intervals of MDC (MDC₉₅) were used to estimate reliability. [Result] Intra-examiner reliability estimates ranged from 0.73-0.96 for same-day comparisons and from 0.67-0.93 for between-day comparisons, except for maximum effort in the neutral pelvic position. MDC₉₅ of thickness measurements were 0.8-2.7 mm for same-day and 1.5-3.0 mm for between-day measurements. [Conclusion] We suggest that RUSI thickness measurements of LM are highly reliable at the 3 angles of pelvic tilt and different percentages of voluntary isometric contraction.