title: Flatback Revisited: Reciprocal Loss of Lumbar Lordosis Following Selective Thoracic Fusion in the Setting of Adolescent Idiopathic Scoliosis.
abstract: METHODS
  Retrospective review of prospective multicenter adolescent idiopathic scoliosis (AIS) database.
  
  
  OBJECTIVE
  To investigate the relationship between iatrogenic loss of thoracic kyphosis (TK) after selective thoracic posterior spinal instrumentation and fusion (PSIF) for AIS with straightening of lumbar lordosis (LL).
  
  
  BACKGROUND
  Segmental PSIF has become the standard of care for surgical treatment of severe AIS. Studies show that adults with flattening of TK and LL can develop pain and dysfunction associated with flatback syndrome. Analysis of post-fusion sagittal alignment is lacking in the AIS population.
  
  
  METHODS
  Query of prospective multicenter database for AIS patients with Lenke 1, 2, or 3 curves who underwent selective thoracic PSIF (lowest instrumented vertebra equal or cephalad to L1) identified 123 patients with a minimum of 2 years' follow-up. Thoracic kyphosis (T5-T12), LL (T12-S1), and global sagittal alignment were measured preoperatively and at 2 years postoperatively. Health-related quality of life measures were examined.
  
  
  RESULTS
  A total of 31% of patients had loss of TK and 42% lost LL. Patients with decreased TK had significantly higher rates of decreased LL (68%) than patients without decreased TK (31%). Multivariate regression confirmed that TK had significant predictive effect on LL (p < .001). Specifically, change in TK of 2° was associated with roughly 3° change in LL. There were no significant associations between changes in TK or LL and health-related quality of life.
  
  
  CONCLUSIONS
  Loss of TK occurs commonly in selective fusion for AIS. This loss of kyphosis is strongly associated with reciprocal loss of LL. Spinal fusion can have unintended effects on sagittal alignment; these effects may have consequences that remain to be fully elucidated.
authors.affiliation: Department of Orthopaedic Surgery, Columbia University Medical Center, 3959 Broadway, 800 North, New York, NY 10032, USA; Department of Epidemiology, Mailmen School of Public Health at Columbia University, 722 West 168th Street, New York, NY 10032, USA. Electronic address: hm2174@columbia.edu.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Matsumoto
authors.affiliation: Department of Orthopaedics, Tufts University Medical Center, Boston, MA, USA.
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Colacchio
authors.affiliation: Department of Orthopaedic Surgery, New York University Medical School, 301 East 17th Street, New York, NY 10003, USA.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Schwab
authors.affiliation: Department of Orthopaedic Surgery, New York University Medical School, 301 East 17th Street, New York, NY 10003, USA.
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafage
authors.affiliation: Department of Orthopaedic Surgery, Columbia University Medical Center, 3959 Broadway, 800 North, New York, NY 10032, USA.
authors.forename: David P
authors.initials: DP
authors.lastname: Roye
authors.affiliation: Department of Orthopaedic Surgery, Columbia University Medical Center, 3959 Broadway, 800 North, New York, NY 10032, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Vitale
keywords: Adolescent idiopathic scoliosis; Flatback syndrome; Post-fusion sagittal alignment; Posterior spinal instrumentation and fusion