203. Cobb angle measurement reliability using low-dose radiographs in early-onset idiopathic scoliosis

Abstract

BACKGROUND CONTEXT Early-onset idiopathic scoliosis (EOIS) management needs a long follow-up during the entire patient growth. The very young patient's age at the diagnosis can expose them to high cumulated radiation doses. Low-dose radiographs allow high-quality view of the spine in standing position. Accuracy and reproducibility of digital measurements of Cobb angle have already been assessed in adults and adolescents. Nevertheless, reliability of Cobb angle measurement has not been evaluated in EOIS follow-up PURPOSE Low dose stereoradiography could be a minimally invasive way to evaluate early-onset scoliosis before six years of age. STUDY DESIGN/SETTING Prospective data collection. PATIENT SAMPLE Forty-one patients younger than 6 years with thoracic or thoracolumbar scoliosis were evaluated. Patients with spine congenital abnormalities were excluded. OUTCOME MEASURES Intra- and interoperator reliability of 2D Cobb angle measurement in EOIS low-dose radiographs. METHODS Patients underwent low-dose standing radiographs. Three operators independently measured Cobb angles on two separate occasions. A fourth trained operator had previously labeled the superior and inferior limits vertebrae to avoid a potential source of uncertainty unrelated to low-dose radiography. Interoperator reproducibility, intraoperator repeatability and intraclass correlation coefficients (ICC) were calculated. Bland-Altmann plot was used to present the limits of agreement. RESULTS The mean age was 4.4 years (SD 0.8 years, range 2.2-5.8). Average Cobb angle was 22° (SD 9°, range 11-80°). ICCs were higher than 0.98 for all three operators, showing an excellent agreement. Reproducibility and repeatability were respectively of 1.2° (coefficient of variation: 4.5 %) and 0.8° (coefficient of variation 3.2%). Measurements were easily feasible in all cases. There was no effect of age or curve severity on uncertainty. CONCLUSIONS EOIS management includes bracing or surgical growth-friendly techniques. These require multiple radiological assessments responsible for a significant cumulative radiation exposure. Cobb angle measurements on low-dose radiographs showed an excellent reproducibility despite bone immaturity. Clinical follow-up could be done with this low-dose technique. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.