For type 2 DT curves, the general rule is to fuse both the PT and MT regions posteriorly.
The upper end vertebra of fusion is usually either T2 (left shoulder high before surgery) or T3 (shoulders level, or, rarely, right shoulder high before surgery), and the lower level of fusion is selected again based on the CSL, as noted above for type I MT curves. It is extremely important to assess the radiographic and clinical aspects of the PT curve and clinical shoulder balance preoperatively to obtain and maintain optimal shoulder balance postoperatively. This is especially true with newer instrumentation techniques such as thoracic pedical screws that afford much greater coronal correction of the main thoracic curve.
For type 3DM curves, the general rule is to fuse both the MT and TL/L regions posteriorly. The upper end vertebra is usually T3, T4, or T5, and the lower instrumented vertebra is usually L3 or L4. Most of these curve patterns will be type 3C, indicating complete translation of the apex of the lumbar spine off the midline. Rarely, for a type 3CN curve in which the thoracic surve is the major curve and much more structural in its radiographic parameters, a selective thoracic fusion can be performed. Typically, both thoracic and lumbar curves will need to be included in the instrumentation and fusion.
Scoliosis Double Major Curve