Reliability of Rehabilitative Ultrasonography to Measure Transverse Abdominis and Multifidus Muscle Dimensions

BACKGROUND: Lumbar paraspinal muscles play an important role in providing both mobility and stability during dynamic tasks. Among paraspinal muscles, transverse abdominis and lumbar multifidus have been of particular interest as active stabilizers of the lumbar spine. These muscles may become dysfunctional in chronic low back pain (CLBP). Low back injury can result in muscle inhibition and control loss that cannot recover spontaneously, and specific exercises are required to stimulate their recovery. OBJECTIVES: The purpose of this study was to test the reliability of ultrasonography to measure muscle dimensions and to present a reliable method for measuring transverse abdominis and lumbar multifidus as stabilizing muscles of the lumbar spine. SUBJECTS AND METHODS: Fifteen healthy participants (18-55 year olds) were evaluated by a radiologist using ultrasonography (ES500) with two probes (50mm linear 7.5 MHZ and 70 mm curvilinear 3.5 MHz). The muscle thickness of transverse abdominis and the anterior-posterior diameter and cross sectional area of the LMF were measured. To determine within and between days reliabilities, second and third measurements were repeated with half an hour and one week intervals, respectively. RESULTS: Intraclass correlation coefficient for left and right showed good to high reliability for the cross sectional area of lumbar multifidi (0.74 and 0.88, respectively) as well as the anterior-posterior dimensions of lumbar multifidi (0.89 and 0.91, respectively) and transverse abdomini thickness (0.73 and 0.85, respectively). CONCLUSIONS: Rehabilitative ultrasonography is a reliable and non-invasive instrument to measure muscle thickness. The method used in this study is a reliable way to measure lumbar stabilizing muscles.