title: Do discs "open" anteriorly with posterior-only correction of Scheuermann's kyphosis?
abstract: METHODS
  Retrospective radiographic analysis.
  
  
  OBJECTIVE
  To investigate where and to what degree the correction of Scheuermann's kyphosis occurred in two different procedures: posterior instrumentation/fusion with an anterior release and posterior-only instrumentation/fusion with Ponte procedure.
  
  
  BACKGROUND
  Controversy remains regarding the outcome for these two procedures. The postoperative segmental disc shape change that account for deformity correction has not been described for either procedure.
  
  
  METHODS
  Eleven patients undergoing a thoracoscopic anterior release followed by posterior instrumentation (A + P) and 11 patients having posterior-only (PO) instrumentation/fusion were retrospectively reviewed. In addition to conventional Cobb measurements, segmental measures of intradiscal angulation as well as anterior and posterior disc heights were made before and after surgery.
  
  
  RESULTS
  The thoracic hyperkyphosis was corrected to similar degrees in both groups (A + P vs. PO, P = 0.87). The PO group averaged 82.7° ± 6.4° before surgery and corrected to 47.9° ± 5.4° after surgery; while the A + P group averaged 84.9° ± 10.2° before surgery and corrected to 48.6° ± 5.7° after surgery. The segmental analysis demonstrated similar degrees of intradiscal angular changes between the two surgical procedures. The majority of the correction occurred at and below the apex and was independent of an anterior release. The changes in both anterior and posterior disc thicknesses were also similar between the two groups. Both groups' anterior disc spaces opened at T8 and below, whereas maximum anterior disc opening occurred at the thoracolumbar junction. To a lesser extent, the posterior disc heights were reduced, but also to similar degrees for both surgical approaches.
  
  
  CONCLUSIONS
  For both surgical procedures, the majority of the kyphosis correction occurred in the lower thoracic levels and anterior disc heights increased up to twice as much as posterior disc heights shortened. The addition of the anterior release did not significantly alter the degree of correction or the disc shape changes.
authors.affiliation: Department of Orthopedic Surgery, Rady Children's Hospital, San Diego, CA, USA.
authors.forename: Shunji
authors.initials: S
authors.lastname: Tsutsui
authors.forename: Jeff B
authors.initials: JB
authors.lastname: Pawelek
authors.forename: Tracey P
authors.initials: TP
authors.lastname: Bastrom
authors.forename: Suken A
authors.initials: SA
authors.lastname: Shah
authors.forename: Peter O
authors.initials: PO
authors.lastname: Newton
mesh_terms: D000293:Adolescent; D001863:Bone Screws; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000601:surgery; D008297:Male; D019637:Orthopedic Procedures / Q000295:instrumentation / Q000379:methods*; D011859:Radiography; D012189:Retrospective Studies; D012544:Scheuermann Disease / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D016896:Treatment Outcome