Spine and Thoracic Height Measurements Have Excellent Interrater and Intrarater Reliability in Patients with Early Onset Scoliosis

Study Design. Reproducibility of measurements. Objective. This study investigates the reliability and standard error of measurement of spine and thoracic height radiographic measurements in patients with early onset scoliosis (EOS). Summary of Background Data. Spine and thoracic height radiographic measurements are often used as a surrogate for pulmonary development in patients with EOS. There is limited literature validating the reliability of spine and thoracic height measurements in the EOS population. Methods. Using pilot data, we determined measuring 49 unique radiographs would provide 80% power to obtain a 95% confidence interval (CI) width of 0.05 for the interclass correlation coefficients (ICCs). A random sampling strategy, stratified by underlying diagnosis from the Classification of Early Onset Scoliosis (C-EOS), was used to distribute the diagnoses in the study sample. Two attending pediatric spine surgeons, two pediatric orthopedic fellows, and two research assistants measured coronal spine (T1-S1) and thoracic (T1-T12) height on digital radiographs using imaging software (Surgimap; Nemaris, Inc, New York) on two separate occasions at least 3 weeks apart. Order of images was randomized for the second iteration. Linear mixed model regression analyses were used to estimate interrater and intrarater reliability. Results. The study sample included subjects (N=48) with idiopathic (N=17, 35%), congenital (N=16, 33%, 1 patient excluded), neuromuscular (N=11, 23%), and syndromic (N=4, 8%) scoliosis. Overall interrater reliability estimates for spine height (ICC: 0.894, 95% CI: 0.847-0.932) and thoracic height (ICC: 0.890, 95% CI: 0.844-0.929) were excellent. Intrarater reliability estimates for spine height (ICC: 0.906, 95% CI: 0.830-0.943) and thoracic height (ICC: 0.898, 95% CI: 0.817-0.938) were also excellent. Conclusion. There is excellent interrater and intrarater reliability for radiographic measurements of spine and thoracic height in the EOS population at our institution.