Rib Cage Measurement Reproducibility Using Biplanar Stereoradiographic 3D Reconstructions in Adolescent Idiopathic Scoliosis.

BACKGROUND: A reproducibility study of preoperative rib cage three-dimensional (3D) measurements was conducted for patients with Adolescent Idiopathic Scoliosis (AIS). No prior reliability study has been performed for preoperative 3D reconstructions of the rib cage by using stereoradiography in patients with preoperative AIS. Our objective was to assess the reliability of rib cage 3D reconstructions using biplanar stereoradiography in patients with AIS before surgery.

METHODS: This series includes 21 patients with Lenke 1 or 2 scoliosis (74±20 degrees). All patients underwent low-dose standing biplanar radiographs. Two operators performed reconstructions twice each. Intraoperator repeatability, interoperator reproducibility, and intraclass coefficients (ICC) were calculated and compared between groups.

RESULTS: The average rib cage volume was 4.71 L (SD±0.75 L). Two SD was 0.19 L with a coefficient of variation of 4.1%; ICC was 0.968. The thoracic index was 0.6 (SD±0.1). Two SD was 0.03 with a coefficient of variation of 4.7% and a ICC of 0.820. As for the Spinal Penetration Index (6.4%; SD±2.4), 2SD was 0.9% with a coefficient of variation of 14.3% and a ICC of 0.901. The 3D rib hump 2SD (average 27±8 degrees) was 1.4 degrees. The coefficient of variation and ICC were respectively 5.1% and 0.991.

CONCLUSIONS: Three-dimensional reconstruction of the rib cage using biplanar stereoradiography is a reliable method to estimate preoperative thoracic parameters in patients with AIS.

LEVEL OF EVIDENCE: Level IV-diagnostic study.