Posterior techniques for correcting deformity in adolescent idiopathic scoliosis––How much correction is optimal?

Abstract

The optimal surgical treatment of adolescent idiopathic scoliosis is heavily debated in the literature. This study aimed to review posterior surgical techniques in the treatment of adolescent idiopathic scoliosis. Literature review was performed. In treating adolescent idiopathic scoliosis with posterior spine fusion, there are many factors to consider when determining where to start and end the fusion construct: skeletal maturity, stress/bending radiographs, and assessment of vertebral rotation and translation. When considering selective thoracic fusion, the relative magnitudes of the main thoracic (MT) and thoracolumbar/lumbar (TL/L) curves and the overall sagittal profile of the thoracolumbar junction are assessed. Selective thoracic fusion can be appropriate if two of the three are found to be true: the MT-to-TL/L Cobb angle ratio is >1.2, the MT-to-TL/L apical vertebral translation (AVT) ratio is >1.2, and/or the MT-to-TL/L apical vertebral rotation (AVR) ratio is >1.2. Moreover, selective thoracic fusion can be an option in the presence of a nonstructural lumbar curve (bending Cobb angle <25°) with thoracolumbar (T10-L2) kyphosis <20°. When choosing the uppermost and lowest instrumented vertebra, one must consider standing coronal balance and regional kyphosis to lessen risk of postoperative complication. The uppermost instrumented vertebra should be a stable, neutral vertebra with <5° of junctional kyphosis; and the lowest instrument vertebra should be touched by the central sacral vertical line and within two vertebrae proximal to the neutral vertebra. To aid in correction, the addition of posterior surgical releases improves the mobility of spine, especially in more rigid curves, but may increase intraoperative blood loss and operative time. Rod derotation and vertebral translation appear to have similar results in correcting coronal and sagittal deformities. The addition of direct vertebral rotation and segmental rotation plays a role in surgical correction as well.