title: Characterizing the differences between the 2D and 3D measurements of spine in adolescent idiopathic scoliosis.
abstract: Although adolescent idiopathic scoliosis (AIS) is known to impact the 3D orientation of the spine and pelvis, the impact of the vertebral position relative to the X-ray scanner on the agreement between 2D and 3D measurements of a curve has not been evaluated. The purpose of this study was to investigate the agreement between 2D and 3D measurements of the scoliotic curve as a function of the 3D spinal parameters in AIS.
  
  
  
  Three independent observers measured the thoracic and lumbar Cobb angles, Kyphosis, and lordosis on the posterior-anterior and lateral X-rays of AIS patients. The 3D reconstructions were created from bi-planar X-rays and the 3D spinal parameters were calculated in both radio and patient planes using SterEOS software. The degree of agreement between the 2D and 3D measurements was tested and its relationship with the curve axial rotation was determined.
  
  
  
  2D and 3D measurements of the sagittal plane spinal parameters were significantly different (p < 0.05). The differences between the 2D and 3D measurements were related to the apical vertebrae rotation, the orientation of the plane of maximum curvature, pelvic axial rotation, and the curve magnitude. Differences between the radio plane and patient plane measurements were related to the pelvic axial rotation, Cobb angles, and apical vertebrae rotation, p < 0.05.
  
  
  
  Clinically and statistically significant differences were observed between the 2D and 3D measurements of the scoliotic spine. The differences between the 2D and 3D techniques were significant in sagittal plane and were related to the spinal curve and pelvic rotation in transverse plane.
authors.affiliation: Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, 2nd Floor, Wood Center, 34th Street and Civic Center Boulevard, Philadelphia, PA, 19104-4399, USA. pashas@email.chop.edu.
authors.forename: Saba
authors.initials: S
authors.lastname: Pasha
authors.affiliation: Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, 2nd Floor, Wood Center, 34th Street and Civic Center Boulevard, Philadelphia, PA, 19104-4399, USA.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Cahill
authors.affiliation: Pediatric Orthopaedic Surgery, Texas Children's Hospital, 6621 Fannin Street, Houston, TX, 77030, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Dormans
authors.affiliation: Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, 2nd Floor, Wood Center, 34th Street and Civic Center Boulevard, Philadelphia, PA, 19104-4399, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Flynn
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D002648:Child; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007738:Kyphosis / Q000000981:diagnostic imaging; D008141:Lordosis / Q000000981:diagnostic imaging; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male; D011859:Radiography / Q000379:methods*; D012189:Retrospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging*
keywords: 3D reconstruction; Adolescent idiopathic scoliosis; Axial rotation; Interrater reliability; Spine