Lenke Class 4B-

Therefore, Classification is Type 4B-

Lenke Type IV describes a triple major curve pattern. The main thoracic curve is considered the major curve as the greatest coronal plane deformity is present between T2 and the T11-12 disc. In Lenke Type IV curves, both the proximal thoracic and the thoracolumbar/ lumbar regions are also considered structural. By definition, the proximal thoracic spine is structural if the deformity is greater than 25 degrees on side-bending radiographs or if the T2-T5 kyphosis is greater than 20 degrees in the sagittal plane, and the thoracolumbar/ lumbar spine is structural if the deformity is greater than 25 degrees on side-bending radiographs or if the T10-L2 kyphosis is greater than 20 degrees in the sagittal plane. All lumbar and sagittal modifiers remain applicable in Lenke Type IV curves. A majority of patients with this pattern undergo instrumentation and fusion from T2 or T3 to L3 or L4. The LIV should be L3 if the L3-4 disc is parallel or wedged open opposite to the side of the apex of the curve. The LIV should be L4 if the L3-4 disc is wedged open in the same direction as the apex of the curve (i.e. L4 is the end vertebra). The disc below the lowest instrumented vertebra should be made as horizontal as possible. Rarely, selective fusion of only the main thoracic or the proximal and main thoracic curves may be performed if the Cobb angle, apical vertebral translation, and apical vertebral rotation ratios (MT:ThL/L) are greater than 1.2.

Preop: 4B- Examples