Evaluation of a three-dimensional reconstruction method of the rib cage of mild scoliotic patients

Study Design: Validation study. Objective: To evaluate a method of 3-dimensional (3D) reconstruction of the rib cage in a population of scoliotic patients. Summary of Background Data: Evaluation of the thoracic cage clinical parameters would be helpful in the management of spinal deformities. Methods: Biplanar X-rays were performed using the EOS system and the rib cage was reconstructed using a previously developed semi-automated method. Thoracic parameters were calculated from the 3D reconstructions: volume, frontal and sagittal diameters, 3D spinal penetration index (SPI), thoracic index, and rib hump. To test accuracy, the authors constructed biplanar projections from 3 computed tomography scans and then used these projected X-rays as material for stereoradiographic reconstructions. The models were then compared with volumetric objects reconstructed from these 3 computed tomography scans. To test intra-observer and interobserver reproducibility, 22 chests (mean Cobb angle, 28° [range, 17° to 45° ]) were reconstructed twice by 3 operators. The 95% confidence interval was calculated for the study parameters. Results: The mean signed point to surface distance was -1.6 mm. Interobserver reproducibility was 9 mm for maximum anteroposterior and lateral diameters, <0.8% for SPI, 5 for rib hump,.02 for thoracic index, and 450 cm3 for volume. Conclusions: The results of the reproducibility study were satisfactory. The 95% confidence interval was <6% for the transverse diameters and <10% for volume and SPI. The reported method of 3D reconstruction of the rib cage provides accurate and reproducible determinations of the investigated thoracic parameters in scoliotic patients. © 2013 Scoliosis Research Society.