Comparison of the Reliability of Sonographic Measurements of Diaphragm Thickness and Mobility in Individuals with and without Pelvic Girdle Pain

Background: Various studies have reported that the pelvic girdle and lumbar spine are reflexively stabilized and braced prior to the initiation of extremity movements. Objectives: The present study aimed to assess the reliability of the diaphragm muscle thickness and excursion measured by rehabilitative ultrasound imaging (RUSI). Methods: This is a cross-sectional study that was done in the physiotherapy department of the Faculty of Rehabilitation at the Shahid Beheshti University of Medical Sciences (Tehran, Iran) in 2019. Images of diaphragm thickness were taken using RUSI in the intercostal space between the 7th and 8th, or 8th and 9th ribs, at which the diaphragm was more easily visualized. The diaphragm motion assessment was performed by applying the transducer on the abdomen at the right midclavicular line. Imaging was conducted in 10 participants with pelvic girdle pain (PGP) and 10 asymptomatic women and men aged 20 - 44 years. Images were obtained by one examiner, muscle thickness was measured using B mode RUSI, and the motion was assessed using M mode RUSI. All assessments were performed in quiet breathing and deep breathing states. Intraclass correlation coefficients (ICC), standard error of measurement (SEM), and minimal detectable change (MDC) were used for reliability assessment. Results: The ICC, SEM, andMDCvalues revealed an excellent intrarater reliability for RUSI in both groups to measure the diaphragm thickness (ICC between 0.88 to 0.92). Measurement of diaphragm excursion demonstrated excellent reliability in the asymptomatic group (ICC between 0.80 to 0.90) and less reliability, between good and excellent, in the PGP group (ICC between 0.74 to 0.79). Conclusions: The method of RUSI employed in the present study is recommended for measuring diaphragm thickness and motion in patients with PGP.