The use of 3D freehand ultrasound to determine muscle volume of the lumbar multifidus: preliminary results of a reliability study in people with low back pain   — The International Society for the Study of the Lumbar Spine
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The use of 3D freehand ultrasound to determine muscle volume of the lumbar multifidus: preliminary results of a reliability study in people with low back pain   (#1045)

Sofie Rummens 1 2 , Sofie Dierckx 3 , Zafeiris Louvaris 3 , Koen Peers 1 2 , Simon Brumagne 3 , Kaat Desloovere 3
  1. Department of Physical Medicine & Rehabilitation, University Hospitals Leuven, Leuven, Belgium
  2. Department of Development & Regeneration, KU Leuven - University of Leuven, Leuven, Belgium
  3. Department of Rehabilitation Sciences, KU Leuven - University of Leuven, Leuven, Belgium

Introduction
Impairment of the lumbar multifidus has been associated with segmental instability and the pathogenesis of low back pain. However, the relation between macroscopic structure of the multifidus and low back pain remains unclear. This may be explained by the use of single-level cross-sectional area measurements that do not represent the entire muscle. Therefore, we aim to establish the inter- and intra-rater reliability of a 3D freehand ultrasound system (3DfUS) for the assessment of the lumbar multifidus in people with low back pain.
Methods
3DfUS is achieved by combining conventional 2D ultrasound with a synchronized motion-tracking system that obtains the position and orientation of the ultrasound probe during acquisition. Images were processed using Stradwin software. Muscle volume is obtained by manually tracing the contours of the lumbar multifidus, after which the software automatically interpolates these contours to obtain a 3D image. To evaluate intra- and interrater processing reliability, 3DfUS images were processed twice by investigator 1 (SR) and once by investigator 2 (SD).
Results
Data collected in 7 patients with low back pain (mean multifidus volume= 92.65±16.07ml) showed excellent intra-rater reliability (ICC 0.93, 95% CI 0.83-0.97; SEM 4.67ml, MDC 12.92ml) and good interrater reliability for imaging processing (ICC 0.88, 95% CI 0.46-0.98; SEM 8.68ml; MDC 24.07 ml).
Discussion
The repeatability indices for 3DfUS processing are promising. Yet, the observed processing errors suggest that repeated 3DfUS measures in clinical studies should be performed by the same assessor, until processing guidelines are further improved.
 

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