Lenke et al. developed and validated a new three-component classification system for adolescent idiopathic scoliosis (AIS) to replace the unreliable King classification. The system assigns a curve type (1–6), a lumbar spine modifier (A/B/C), and a sagittal thoracic modifier (−/N/+) to directly guide fusion level selection. Reliability was tested by two independent surgeon groups on 27 radiograph sets and validated against 315 consecutive surgical patients.
The King classification — built for Harrington rods and coronal-plane-only analysis. Had an interobserver kappa of just 0.49, meaning surgeons were barely agreeing beyond chance when describing the same curve. That made multicenter outcome comparisons functionally impossible.
When you evaluate an AIS patient for surgery, the Lenke system gives you a direct operative prescription: fuse the major curve plus any structural minor curves, leave nonstructural curves alone. For a Type 1 curve (main thoracic, nonstructural lumbar), a selective thoracic fusion is appropriate as long as the lumbar curve corrects to under 25° on side-bending and no thoracolumbar kyphosis is present. For a Type 5 or 6 curve, the TL/lumbar region is the major curve. Do not fuse the thoracic spine if it is nonstructural (Type 5) but you must include the main thoracic in a Type 6.
Lumbar modifier A or B means the lumbar spine stays out of the fusion unless TL kyphosis reaches +20°. Modifier C means the lumbar spine is almost always in.
Lenke et al. developed and validated a new three-component classification system for adolescent idiopathic scoliosis (AIS) to replace the unreliable King classification. The system assigns a curve type (1–6), a lumbar spine modifier (A/B/C), and a sagittal thoracic modifier (−/N/+) to directly guide fusion level selection. Reliability was tested by two independent surgeon groups on 27 radiograph sets and validated against 315 consecutive surgical patients.
The King classification — built for Harrington rods and coronal-plane-only analysis. Had an interobserver kappa of just 0.49, meaning surgeons were barely agreeing beyond chance when describing the same curve. That made multicenter outcome comparisons functionally impossible.
When you evaluate an AIS patient for surgery, the Lenke system gives you a direct operative prescription: fuse the major curve plus any structural minor curves, leave nonstructural curves alone. For a Type 1 curve (main thoracic, nonstructural lumbar), a selective thoracic fusion is appropriate as long as the lumbar curve corrects to under 25° on side-bending and no thoracolumbar kyphosis is present. For a Type 5 or 6 curve, the TL/lumbar region is the major curve. Do not fuse the thoracic spine if it is nonstructural (Type 5) but you must include the main thoracic in a Type 6.
Lumbar modifier A or B means the lumbar spine stays out of the fusion unless TL kyphosis reaches +20°. Modifier C means the lumbar spine is almost always in.