Lenke 1

Lenke 1 curves are one where the major curve (the curve with the largest Cobb angle) is in the main thoracic region while the proximal thoracic and thoracolumbar are non-structural.

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 13 year old female with Lenke 1A curve consisting of a:

• 40° minor PT curve, correcting to 3° on side bending
• 74° major MT curve, correcting to 49° on side bending
• 42° minor TL/L curve, correcting to 2° on side bending

As the residual PT and TL/L curves are less than 25° in bending radiographs they are non-structural.

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

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 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 "+".