title: Distal adding-on in Lenke 1A scoliosis: how to more effectively determine the onset of distal adding-on.
abstract: METHODS
  A radiographical follow-up and analysis.
  
  
  OBJECTIVE
  To identify appropriate radiographical parameters for measuring the extent of distal adding-on and to discuss criteria for determining the onset of distal adding-on.
  
  
  BACKGROUND
  There is no consensus on how to determine the onset of distal adding-on in Lenke 1A scoliosis. Such questions as: "Which radiographical parameters should be used for measuring the extent of distal adding-on?" and "What criteria should be applied in determining the onset of distal adding-on?" need to be answered.
  
  
  METHODS
  We reviewed all the AIS cases surgically treated in an institution from 2003 through 2009. Inclusion criteria were as follows: (1) patients with Lenke 1A curves who were treated with selective thoracic fusion; (2) age less than 30 years; (3) 2-year radiographical follow-up. Eight radiographical parameters were tested to see if they are potential instruments in the detection of distal adding-on.
  
  
  RESULTS
  Fifty-three patients met the inclusion criteria. No pseudarthrosis or crankshaft phenomenon was observed in the current cohort. Five out of 8 radiographical parameters: thoracic Cobb, LIV-CSVL distance, LIV + 1-CSVL distance, thoracic AV-CSVL distance and LIV + 1 tilt angle, in the 2 years after surgery, showed significant increase. The remaining 3 parameters: LIV tilt angle, T1-CSVL distance and number of vertebrae within Cobb, however, did not show significant increase. In regard to the 5 parameters that have the potential to detect the onset of distal adding-on, we found a high correlation between every 2 of them. The correlation coefficients range from 0.504 to 0.962 (P = 0.001), suggesting that all of them are in a positive linear relationship. Regarding the criterion for determining the onset of distal adding-on, an increase of more than 10 mm in LIV-CSVL distance in the postoperative period can be considered as a the main criterion because it is unlikely to be induced by measurement errors.
  
  
  CONCLUSIONS
  LIV-CSVL distance could be an ideal parameter for measuring the extent of distal adding-on. Distal adding-on can be determined when the LIV-CSVL distance increases by 10 mm in the postoperative period.
authors.affiliation: Department of Orthopaedics E, Aarhus University Hospital, Aarhus 8000, Denmark. yu.wang@ki.au.dk
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Cody Eric
authors.initials: CE
authors.lastname: Bünger
authors.forename: Yanqun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Chunsen
authors.initials: C
authors.lastname: Wu
authors.forename: Haisheng
authors.initials: H
authors.lastname: Li
authors.forename: Ebbe Stender
authors.initials: ES
authors.lastname: Hansen
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D011184:Postoperative Period; D057234:Preoperative Period; D011859:Radiography; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult