Intra-observer reproducibility and interobserver reliability of the radiographic parameters in the Spinal Deformity Study Group's AIS Radiographic Measurement Manual.

Study Design: Retrospective cross-sectional assessment of the reproducibility and reliability of radiographic parameters.
Objective: To measure the intra-examiner and interexaminer reproducibility and reliability of salient radiographic features.
Summary of Background Data: The management and treatment of adolescent idiopathic scoliosis (AIS) depends on accurate and reproducible radiographic measurements of the deformity.
Methods: Ten sets of radiographs were randomly selected from a sample of patients with AIS, with initial curves between 20 degrees and 45 degrees. Fourteen measures of the deformity were measured from posteroanterior and lateral radiographs by 2 examiners, and were repeated 5 times at intervals of 3-5 days. Intra-examiner and interexaminer differences were examined. The parameters include measures of curve size, spinal imbalance, sagittal kyphosis and alignment, maximum apical vertebral rotation, T1 tilt, spondylolysis/spondylolisthesis, and skeletal age.
Results: Intra-examiner reproducibility was generally excellent for parameters measured from the posteroanterior radiographs but only fair to good for parameters from the lateral radiographs, in which some landmarks were not clearly visible. Of the 13 parameters observed, 7 had excellent interobserver reliability.
Conclusions: The measurements from the lateral radiograph were less reproducible and reliable and, thus, may not add value to the assessment of AIS. Taking additional measures encourages a systematic and comprehensive assessment of spinal radiographs.