title: Cervical sagittal plane decompensation after surgery for adolescent idiopathic scoliosis: an effect imparted by postoperative thoracic hypokyphosis.
abstract: OBJECTIVE
  Several studies have characterized the relationship among postoperative thoracic, lumbar, and pelvic alignment in the sagittal plane. However, little is known of the relationship between postoperative thoracic kyphosis and sagittal cervical alignment in patients with adolescent idiopathic scoliosis (AIS) treated with all pedicle screw constructs. The authors examined this relationship and associated factors.
  
  
  METHODS
  A prospective database of pediatric patients with AIS undergoing spinal fusion between 2003 and 2005 was reviewed for those who received predominantly pedicle screw constructs for Lenke Type 1 or Type 2 curves. Parameters analyzed on pre- and postoperative radiographs were the fusion levels; cervical, thoracic, and lumbar sagittal balance; and C-2 and C-7 plumb lines.
  
  
  RESULTS
  Preoperatively, 6 (Group A) of the 22 patients included in the study had frank cervical kyphosis (mean angle 13.0°) with mean associated thoracic kyphosis of 27.2° (range 16°-37°). Postoperatively, cervical kyphosis (13.0°) remained in the patients in Group A along with mean thoracic kyphosis of 17.7° (range 4°-26°, p < 0.05). Preoperatively, the remaining 16 of 22 patients had neutral to lordotic cervical alignment (mean -13.8°) with thoracic kyphosis (mean 45°, range 30°-76°). Postoperatively, 8 (Group B) of these 16 patients demonstrated cervical sagittal decompensation (> 5° kyphosis), with 6 showing frank cervical kyphosis (10.5°, p < 0.05). In Group B, the mean postoperative thoracic kyphosis was 25.6° (range 7°-49°, p < 0.05). The other 8 patients (Group C) had mean postoperative thoracic kyphosis of 44.1° (range 32°-65°), and there was no cervical decompensation (p < 0.05).
  
  
  CONCLUSIONS
  The sagittal profile of the thoracic spine is related to that of the cervical spine. The surgical treatment of Lenke Type 1 and 2 curves by using all pedicle screw constructs has a significant hypokyphotic effect on thoracic sagittal plane alignment (19 [86%] of 22 patients). If postoperative thoracic kyphosis is excessively decreased (mean 25.6°, p < 0.05), the cervical spine may decompensate into significant kyphosis.
authors.affiliation: Department of Orthopedic Surgery, Shriner's Hospital for Children, Philadelphia, Pennsylvania 19140, USA. stevenhwang@hotmail.com
authors.forename: Steven W
authors.initials: SW
authors.lastname: Hwang
authors.forename: Amer F
authors.initials: AF
authors.lastname: Samdani
authors.forename: Mark
authors.initials: M
authors.lastname: Tantorski
authors.forename: Patrick
authors.initials: P
authors.lastname: Cahill
authors.forename: Jason
authors.initials: J
authors.lastname: Nydick
authors.forename: Anthony
authors.initials: A
authors.lastname: Fine
authors.forename: Randal R
authors.initials: RR
authors.lastname: Betz
authors.forename: M Darryl
authors.initials: MD
authors.lastname: Antonacci
mesh_terms: D000293:Adolescent; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D002648:Child; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000000981:diagnostic imaging / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D011446:Prospective Studies; D011859:Radiography; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D016896:Treatment Outcome