title: Are Thoracic Curves With a Low Apex (T11 or T11/T12) Really Thoracic Curves?
abstract: METHODS
  Multicenter; review of prospectively collected data.
  
  
  OBJECTIVE
  To determine whether curves with an apex at T11 or T11/T12 represent a combination of thoracic and thoracolumbar curves or constitute their own class of curves.
  
  
  BACKGROUND
  Curves with an apex at T11 and T11/T12 are classified by the Scoliosis Research Society and Lenke classification as thoracic curves.
  
  
  METHODS
  We reviewed 1,835 adolescent idiopathic scoliosis cases from a multicenter database. Based on the most common curve apex levels (thoracic [TH] curves, T9; thoracolumbar/lumbar [TL/L] curves, L1), we created 2 comparison groups that represented classic examples of TH and TL/L curves. We identified 66 cases with an apex at T11-T11/T12 and compared them with 320 cases with a T9 apex, and 126 cases with an L1 apex. We compared characteristics of these 3 groups (p < .05) and completed a radiographic review of the T11-T11/T12 group.
  
  
  RESULTS
  The curve direction of the 3 groups was significantly different (TL/L, 84% left; TH, 3% left; and T11-T11/T12, 16% left) (p < .001). The mean number of vertebrae in curves for the T11-T11/T12 group (7.1 ± 1.2) fell between the value for the TL/L (5.7 ± 0.8) and TH (7.3 ± 1.0) groups. The T11-T11/T12 curves had a greater trunk shift than TL/L (p = .002) and TH (p = .011) curves. There was no difference among the 3 groups in terms of major curve Cobb magnitude (p = .09) or age at surgery (p = .76). Radiographic review of the T11-T11/T12 curves revealed 3 curve patterns: 21 long single curves (32%), 28 short single curves (42%), and 17 double thoracic curves (26%).
  
  
  CONCLUSIONS
  We suggest caution in lumping curves with an apex at T11 or T11-12 disc together with other thoracic apices in studies involving primary thoracic curves, because some of these curves have features much more typical of thoracolumbar curves.
authors.affiliation: University of California, School of Medicine, 9500 Gilman Dr., La Jolla, CA 92093, USA.
authors.forename: Milad
authors.initials: M
authors.lastname: Alam
authors.affiliation: Rady Children's Hospital, Department of Orthopedics, 3020 Children's Way MC 5062, San Diego, CA 92123, USA. Electronic address: pnewton@rchsd.org.
authors.forename: Peter O
authors.initials: PO
authors.lastname: Newton
authors.affiliation: Rady Children's Hospital, Department of Orthopedics, 3020 Children's Way MC 5062, San Diego, CA 92123, USA.
authors.forename: Burt
authors.initials: B
authors.lastname: Yaszay
authors.affiliation: Rady Children's Hospital, Department of Orthopedics, 3020 Children's Way MC 5062, San Diego, CA 92123, USA.
authors.forename: Tracey P
authors.initials: TP
authors.lastname: Bastrom
keywords: Adolescent idiopathic scoliosis; Classification; Curve types; Lenke classification; Radiographs