Lenke 4

Type 4 curves have structural proximal thoracic, main thoracic, and thoracolumbar/lumbar curves (triple major).

A minor curve is defined as structural if at least one of the two below criteria are met:

• Residual curve greater than or equal to 25 ° on supine bending radiograph
• T2 – T5, T10-L2 kyphosis greater than or equal to 20 ° (regardless of coronal flexibility)

The left X-rays show a 15 year old female with Lenke 4C curve consisting of a:

• 40° minor PT curve, correcting to 29° on side bending
• 68° major MT curve, correcting to 46° on side bending
• 57° minor TL/L curve, correcting to 26° on side bending

Both the PT and the TL/L curves are structural.

Lumbar modifier A is designated if this line lies between the pedicles at the apical level of the lumbar curve.

Lumbar modifier B is designated if this line touches the apical vertebral pedicle.

Lumbar modifier C is designated if this line does not touch any part of the vertebral body or pedicle at the apex.

The lumbar modifier is determined by drawing a vertical line from the center of the sacrum.

The sagittal modifiers are determined from the lateral radiograph from T5-T12. A measurement less than 10° is designated as "-".

Measurements between 10°-40° is designated as "N".

A measurement larger than 40° is designated as "+".