Type I:

  • S-shaped curve in which both thoracic curve lumbar curve cross midline
  • Lumbar curve larger than thoracic curve on standing roentgenogram
  • Flexibility index a negative value (thoracic curve < lumbar curve on standing roentgenogram, but more flexible on side-bending)

Type II:

  • S-shaped curve in which thoracic curve and lumbar curve cross midline
  •  Thoracic curve < lumbar curve
  •  Flexibility index < 0

Type III

  • Thoracic curve in which lumbar curve does not cross midline (so-called overhang)

Type IV

  • Long thoracic curve in which L5 is centered over sacrum but L4 tilts into long thoracic curve

Type V

  • Double thoracic curve with T1 tilted into convexity of upper curve; upper curve structural on side-bending


Provide an explanation for key principles and pertinent aspects of the classification


Insert figures illustrating the classification


Provide the citation for the landmark article and recent review articles describing the classification