Measurement of Abdominal Muscle Thickness Using Ultrasound: A Reliability Study on Patients with Chronic Non-Specific Low Back Pain

Background and The purpose of this study was to assess the Within-day and Between-days reliability of abdominal muscles size measurement in patients with chronic non-specific low back pain (LBP) using ultrasound (US). In this study, 15 patients with chronic non-specific LBP (20-50 years old) were recruited. The reliability of the abdominal muscle size (External and Internal oblique, and Transversus abdominis) was assessed in a relaxed and contraction state by a real time US. Two images were taken on the same day with an hour interval to assess the within day reliability and the third image was taken a week later to determine the between- days reliability. Within-day and between-days reliability of abdominal muscles thickness measurements using US in patients with nonspecific chronic LBP in both rest and contraction state found to be high, ICC = 0.90 for within and ICC=0.85 for between-days of Transversus abdominis muscle in rest state and ICC= 0.82 and 0.86 in contraction state, respectively. For Internal oblique muscle, ICC=0.90 (82%) and ICC=0.88 (88%) were found for within-day and between-days in rest and contraction state, respectively. Within-day and between-days reliability at rest of ICC=0.86 (79%) and in contraction state of ICC=0.79 (75%) were demonstrated for External Oblique muscle. Results of the present study suggest US as a reliable method to evaluate the thickness of the abdominal muscles which could be used as a reliable tool in the assessment of patients and also in evaluating the effect of different therapeutic interventions.