title: Upright, prone, and supine spinal morphology and alignment in adolescent idiopathic scoliosis.
abstract: BACKGROUND
  Patients with adolescent idiopathic scoliosis (AIS) are usually investigated by serial imaging studies during the course of treatment, some imaging involves ionizing radiation, and the radiation doses are cumulative. Few studies have addressed the correlation of spinal deformity captured by these different imaging modalities, for which patient positioning are different. To the best of our knowledge, this is the first study to compare the coronal, axial, and sagittal morphology of the scoliotic spine in three different body positions (upright, prone, and supine) and between three different imaging modalities (X-ray, CT, and MRI).
  
  
  METHODS
  Sixty-two AIS patients scheduled for scoliosis surgery, and having undergone standard pre-operative work-up, were included. This work-up included upright full-spine radiographs, supine bending radiographs, supine MRI, and prone CT as is the routine in one of our institutions. In all three positions, Cobb angles, thoracic kyphosis (TK), lumbar lordosis (LL), and vertebral rotation were determined. The relationship among three positions (upright X-ray, prone CT, and supine MRI) was investigated according to the Bland-Altman test, whereas the correlation was described by the intraclass correlation coefficient (ICC).
  
  
  RESULTS
  Thoracic and lumbar Cobb angles correlated significantly between conventional radiographs (68° ± 15° and 44° ± 17°), prone CT (54° ± 15° and 33° ± 15°), and supine MRI (57° ± 14° and 35° ± 16°; ICC ≥0.96;P< 0.001). The thoracic and lumbar apical vertebral rotation showed a good correlation among three positions (upright, 22° ± 12° and 11° ± 13°; prone, 20° ± 9° and 8° ± 11°; supine, 16° ± 11° and 6° ± 14°; ICC ≥0.82;P< 0.001). The TK and LL correlated well among three different positions (TK 26° ± 11°, 22° ± 12°, and 17° ± 10°;P≤ 0.004; LL 49° ± 12°, 45° ± 11°, and 44° ± 12°;P <0.006; ICC 0.87 and 0.85).
  
  
  CONCLUSIONS
  Although there is a generalized underestimation of morphological parameters of the scoliotic deformity in the supine and prone positions as compared to the upright position, a significant correlation of these parameters is still evident among different body positions by different imaging modalities. Findings of this study suggest that severity of scoliotic deformity in AIS patients can be largely represented by different imaging modalities despite the difference in body positioning.
authors.affiliation: Department of Orthopaedic Surgery, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, The Netherlands.
authors.forename: Rob C
authors.initials: RC
authors.lastname: Brink
authors.affiliation: Department of Orthopaedic Surgery, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, The Netherlands.
authors.forename: Dino
authors.initials: D
authors.lastname: Colo
authors.affiliation: Department of Orthopaedic Surgery, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, The Netherlands.
authors.forename: Tom P C
authors.initials: TPC
authors.lastname: Schlösser
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Koen L
authors.initials: KL
authors.lastname: Vincken
authors.affiliation: Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Marijn
authors.initials: M
authors.lastname: van Stralen
authors.affiliation: Department of Imaging and Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Steve C N
authors.initials: SCN
authors.lastname: Hui
authors.affiliation: Department of Diagnostic Radiology and Organ Imaging, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Lin
authors.initials: L
authors.lastname: Shi
authors.affiliation: Department of Imaging and Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Winnie C W
authors.initials: WCW
authors.lastname: Chu
authors.affiliation: Department of Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Jack C Y
authors.initials: JCY
authors.lastname: Cheng
authors.affiliation: Department of Orthopaedic Surgery, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, The Netherlands.
authors.forename: René M
authors.initials: RM
authors.lastname: Castelein
keywords: Adolescent idiopathic scoliosis; Body positioning; Computed tomography; Magnetic resonance imaging; Three-dimensional morphology; Upright radiographs