The Lenke classification is a triad classification system consisting of:
An example of the classification may be Lenke 2A-
It provides a classification that is:
To determine the components of the triad the following radiographs are required:
The spine is divided into the 3 regions.
In the AP view Cobb angles are measured from cranial end vertebra to caudal end vertebra. End vertebra is defined as the vertebra that is most tilted from the horizontal apical vertebra. For a given curve the cranial end plate is used for the proximal end vertebra while the caudal end-plate is used for the distal end-vertebra.
The curve with the largest cobb angle is by definition the major curve.
Other curves are by definition minor curves.
Using the left and right supine bending, as well as the lateral radiographs, it is determined whether the minor curves are structural or non-structural.
A minor proximal thoracic curve is defined as structural if one of the two criteria are met:
A minor main thoracic curve is defined as structural if one of the two criteria are met:
A minor thoracolumbar/lumbar curve is defined as structural if one of the two criteria are met:
The minor/major and structural /non-structural information for each curve is then used together with the table below to identify the curve type.
The lumbar modifier is determined by drawing a vertical line from the center of the sacrum (CSVL).
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 apical vertebral body or pedicle.
The sagittal modifiers are determined from the lateral radiograph from T5-T12. A measurement less than 10° is designated as "-" or hypokyphosis.
Measurements between 10°- 40° is designated as "N"or Normokyphosis.
A measurement larger than 40° is designated as "+"or hyperkyphosis.