Ultrasound image measurements of erector spinae muscle thickness at four spinal levels in adolescents with idiopathic scoliosis: reliability and concave-convex comparison

Methods Nine patients with AIS (8 females) with a single thoracic curve, aged 13.5±1.8 years old, with mean Cobb angles of 39.4±9.1o, under observation or undergoing brace treatment were included. In a prone position, three ultrasound images of erector thickness were obtained on each side at L3, the upper end vertebra, lower-end vertebra and the apex of the curve in random order. A 5cm curvilinear probe was used to capture images of the erectors parasagittally over the facets. Thickness was measured using ImageJ as the distance from the facet to the first fascia line by an examiner blinded to image location and measurements. Reliability was estimated using Intraclass Correlation Coefficients (ICC2,1 and 2,2) and standard error of measurement (SEM). Differences between sides were determined using paired t-tests at each level.