Lenke Classification of AIS


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  •  Note: To our knowledge the Lenke classifcation has never appeared on the OITE or on the the ABOS Part I.
  • The Lenke classication for adolescent idiopathic scoliosis has gained popularity and consists of three steps
    1. Label primary curve at Type 1-6
    2. Assign lumbar modifier (A,B,C)
    3. Assign sagittal modifier (-,N,+)
Step 1: Identification of primary curve (Type 1-6)
  1. Measure regional curves
    • proximal thoracic (PT)
    • main thoracic (MT)
    • thoracolumbar/lumbar (TL/L)
  2. Identify major curve (biggest curve)
    • always either MT (Type 1-4) or .MT/L (Type 4*,5,6)
  3. Determine if minor curve is structural or not
    • definition of structural
    • > 25° in coronal plane on standing AP and do not bend out to < 25° on bending films
    • OR > 20° in sagital plane
  4. Assign Type 1-6 based on chart below
Curve Type
Curve Name
Type 1 MT
Structural (major*)
Type 2 Double thoracic (DT)
Structural (major*)
Type 3 Double major (DM)
Structural (major*)
Type 4 Triple major (TM)
Structural (major*)
Structural (major*)
Type 5 TL/L
Structural (major*)
Type 6 TL/L-MT
Structural (major*)
Structural (major*) - has largest cobb angle and is always structural. In Type 4 can be either MT or FL/L depending on which Cobb is larger
**If PT is the largest curve, then by default assign major curve to MT

Step 2: Assignment of Lumbar modifiers (A,B,C)
  • Identify apical lumbar vertebrae (ALV)
    • is the inferior lumbar body that falls outside of the curve
  • Draw centeral sacral vertical line (CSVL) and see where it sits in relationship to pedicles of ALV
  • Assign modifer
    • A if CSVL passes between pedicles of apical lumbar vertebrae (ALV)
      • CSVL falls between pedicles of the lumbar spine up to stable vertebra
    • B modifier if CSVL touches pedicle of apical lumbar vertebrae (ALV)
    • C modifier if CSVL does not touch apical lumbar vertebrae (ALV)
      • apex of lumbar curve falls completely off the midline depicting a curve with complete apical translation off the CSVL
Step 3: Assignment of Sagittal thoracic modifier (-, N, +)
  • Measure sagital Cobb from T5 to T12
  • Assign modifier
    • hypokyphotic (-) if < 10°
    • normal if 10-40°
    • hyperkyphotic (+) if >40°

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