title: The position of the aorta relative to the spine before and after anterior instrumentation in right thoracic scoliosis.
abstract: METHODS
  Preoperative magnetic resonance images (MRI) and postoperative axial computed tomography (CT) scans in 25 consecutive patients with idiopathic right thoracic adolescent scoliosis (AIS) and anterior correction and fusion with a dual rod system were analyzed in a prospective study.
  
  
  OBJECTIVE
  Evaluation of the spatial relations between the vertebral body and the aorta and the relative migration of the aorta due to the anterior correction and instrumentation in right thoracic scoliosis patients.
  
  
  BACKGROUND
  In anterior scoliosis surgery, bicortical screw purchase is performed to increase pullout strength. However, impingement of the aorta due to excessive contralateral screw penetration has been reported, especially after endoscopic instrumentation. For a safe screw placement, knowledge of both the preoperative topographic relation of aorta and vertebral body and its changes due to surgical correction is crucial. Recent studies reported on a more lateral and posterior position of the aorta in AIS patients. However, there are hardly any data on the changes of the aortic position after anterior curve correction available in the current literature.
  
  
  METHODS
  All 25 patients underwent an identical anterior surgical technique with standard open approach and dual rod instrumentation of the primary curve. Preoperative MRI and postoperative sequential CT scans of 180 vertebrae were analyzed with respect to following parameters: vertebral body width and depth, diameter of the aorta, closest distance between aorta and the vertebral body, the aorta-vertebral angle, and the position of the aorta in relation to the spinal canal.
  
  
  RESULTS
  Before surgery, the aorta is positioned posterolaterally with an aorta-vertebral angle of between 78 degrees and 92 degrees (between T5 and T10). Between T11 and L2, the aorta is positioned more anteromedially with an aorta-vertebral angle from 62 degrees (T11) to 16 degrees (L2). After surgery, the aorta has migrated from a posterolateral to a more anteromedial position. This migration is maximal at the apex vertebra with an average change of the aorta-vertebral angle of 31.4 degrees . Whereas the distance between the aorta and the vertebral body increases at the upper and lower fusion levels, the aorta moves significantly closer to the vertebral body at the curve apex due to surgical correction. In patients with thoracic hypokyphosis, the aorta is positioned significantly more posterior than in patients with hyperkyphosis.
  
  
  CONCLUSIONS
  This MRI and CT based study of 25 patients with thoracic AIS treated by standard open dual rod and dual screw instrumentation demonstrates a migration of the aorta by 31 degrees from a more posterolateral position before surgery to a more anteromedial position after surgery at the curve apex. Scoliosis surgeons should be aware of these changes; any excessive contralateral screw penetration must be avoided at any level.
authors.affiliation: Department of Orthopaedics, University Hospital of Muenster, Muenster, Germany. bullmanv@uni-muenster.de
authors.forename: Viola
authors.initials: V
authors.lastname: Bullmann
authors.forename: Eva M
authors.initials: EM
authors.lastname: Fallenberg
authors.forename: Norbert
authors.initials: N
authors.lastname: Meier
authors.forename: Roman
authors.initials: R
authors.lastname: Fischbach
authors.forename: Thomas
authors.initials: T
authors.lastname: Lerner
authors.forename: Tobias L
authors.initials: TL
authors.lastname: Schulte
authors.forename: Nani
authors.initials: N
authors.lastname: Osada
authors.forename: Ulf R
authors.initials: UR
authors.lastname: Liljenqvist
mesh_terms: D000293:Adolescent; D000328:Adult; D001013:Aorta, Thoracic / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D001858:Bone Nails; D001863:Bone Screws; D002648:Child; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011183:Postoperative Complications / Q000517:prevention & control; D011300:Preoperative Care; D011446:Prospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D013904:Thoracic Vertebrae / Q000473:pathology / Q000601:surgery*; D014057:Tomography, X-Ray Computed