The lumbar multifidus (LM) muscle plays a crucial role in maintaining segmental lumbar stability and preventing recurrence of low back pain (LBP). 17,27,42 Studies have shown that patients with acute or chronic LBP have localized LM atrophy and reduced voluntary LM muscle contraction ipsilateral to the side of symptoms.14,17,38 Unfortunately, the resolution of LBP is not accompanied with spontaneous recovery in the function and morphology of the LM muscle, unless appropriate exercises are prescribed. 16,27 To evaluate the function of the LM muscle and to monitor the progress of treatment, a costeffective, noninvasive clinical assessment tool is needed.Brightness-mode (B-mode) rehabilitative ultrasound imaging (RUSI) has been advocated as a valid noninvasive tool to evaluate the size and dynamic behavior of trunk muscles 40 and to provide real-time feedback to LBP patients during motor control training. 24,35 Research has demonstrated measurement agreement of LM muscle thickness by RUSI and by magnetic resonance imaging.
15Indwelling electromyography studies have also validated the correlation between the myoelectric activity of the LM and the change in geometry of the LM as measured by RUSI. 21,36 Clinically, the role of RUSI biofeedback in facilitating LM muscle recruitment in patients with LBP during back-stabilizing exercises has been demonstrated. 13,16,24,35,40 To measure LM muscle thickness T T STUDY DESIGN: Reliability study.
T T OBJECTIVES:To compare the within-and between-day intrarater reliability of rehabilitative ultrasound imaging (RUSI) using static images (static RUSI) and video clips (video RUSI) to quantify multifidus muscle thickness at rest and while contracted. Secondary objectives were to compare the measurement precision of averaging multiple measures and to estimate reliability in individuals with and without low back pain (LBP).
T T BACKGROUND:Although intrarater reliability of static RUSI in measuring multifidus thickness has been established, using video RUSI may improve reliability estimates, as it allows examiners to select the optimal image from a video clip. Further, multiple measurements and LBP status may affect RUSI reliability estimates.
T T METHODS:Static RUSI and video RUSI were used to quantify multifidus muscle thickness at rest and during contraction and percent thickness change in 27 volunteers (13 without LBP and 14 with LBP). Three static RUSI images and 3 video RUSI video clips were collected in each of 2 sessions 1 to 4 days apart. Reliability and precision were assessed using intraclass correlation coefficients, standard error of measurement, minimal detectable change, bias, and 95% limits of agreement.
T T RESULTS:Using an average of 2 measures yielded optimal measurement precision for static RUSI and video RUSI. Based on the average of 2 measures obtained under the same circumstance, there was no significant difference in the reliability estimates between static RUSI and video RUSI across all testing conditions. Reliability point estimates (intraclass correlation co...