Determining the validity and reliability of spinopelvic parameters through comparing standing whole spinal...

Standing whole spinal radiographs are used to evaluate spinal alignment in adult spinal deformity (ASD), yet some studies have reported that pelvic incidence, pelvic tilt, and thoracic kyphosis (TK) intra- and inter-observer reliability is low. This study aimed to evaluate the accuracy of spinopelvic parameters through comparing standing whole spinal radiographs and upright CT images.

We enrolled 26 patients with ASD. All standing whole spinal posterior/anterior and lateral radiographs and upright whole spinal CT had been obtained in a natural standing position. Two examiners independently measured 13 radiographic parameters. Interclass correlation coefficients (ICCs) were used to analyze measurement intra- and inter-observer reliability. Paired t- and Pearson's correlation tests were used to analyze validity of the standing whole spinal radiographs.

ICCs of upright CT were excellent in both intra- and inter-observer reliability. However, intra-observer ICCs for TK2-12, TK1-5, TK2-5, and TK5-12 on standing lateral radiographs were relatively low, as were inter-observer ICCs for TK2-12, TK1-5, TK2-5, and TK5-12. Concerning TK values, the difference between the radiographs and CT in TK1-12 and TK2-12 were 4.4 ± 3.1 and 6.6 ± 4.6, respectively, and TK values from T2 showed greater measurement error (p < 0.05).

Upright CT showed excellent intra- and inter-observer reliability in the measurement of spinopelvic parameters. Measurement of TK with T2 on standing whole spinal radiographs resulted in a greater measurement error of up to 6.6°. Surgeons need to consider this when planning surgery and measuring postoperative TK changes in patients with ASD.