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Updated: Oct 5 2016

# Lenke Classification of AIS

Introduction
•  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 PT** MT TL/L Type 1 MT - Structural (major*) - Type 2 Double thoracic (DT) Structural Structural (major*) - Type 3 Double major (DM) - Structural (major*) Structural Type 4 Triple major (TM) Structural Structural (major*) Structural (major*) Type 5 TL/L - - Structural (major*) Type 6 TL/L-MT - Structural 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°
Private Note

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