Selection of Fusion Level for Adolescent Idiopathic Scoliosis Surgery : Selective Fusion versus Postoperative Decompensation

Abstract

Adolescent idiopathic scoliosis (AIS), which is associated with an extensive range of clinical and radiological presentations, is the one of the most challenging spinal disorders. The goals of surgery are to correct the deformity in 3 dimensions and to preserve motion segments while avoiding complications. Despite the ongoing evolution of classification systems and algorithms for the surgical treatment of AIS, there has been considerable debate regarding the selection of an appropriate fusion level in AIS. In addition, there is no consensus regarding the exact description, relationship, and risk factors of coronal decompensation following selective fusion. In this review, we summarize the current concepts of selection of the fusion level for AIS and review the available information about postoperative coronal decompensation.

Keywords: Adolescent idiopathic scoliosis; Coronal decompensation; Selective fusion; Spinal fusion.

Fig. 1.

Definition of the radiographic parameters. The Cobb angle of thoracic major curve and proximal thoracic curve is 57° and 45°, respectively. Upper end vertebra (UEV) means the upper vertebra that is most tilted from the horizontal apical vertebra. Apical vertebral translation (AVT) means the distance from the CSVL to the mid-point of the apical vertebra. Lower end vertebra (LEV) means the lower vertebra that is most tilted from the horizontal apical vertebra. Last touched vertebra (LTV) means the most proximal vertebra that are touched by the CSVL. Stable vertebra (SV) means the vertebra that are bisected or nearly bisected by the CSVL. Central sacral vertical line (CSVL) means the vertical line that bisects proximal sacrum. UIV : upper instrumented vertebra, LIV : lower instrumented vertebra.

Fig. 2.

A representative case of selective thoracic fusion for Lenke 3CN curves. Preoperative standing posteroanterior radiography showed a right-side major thoracic curve of 69.0° and a left-side structural lumbar curve of 48.6°, which was reduced by 28.9° on the side bending film. The thoracic apical vertebral translation (AVT) was 54.3 mm and the lumbar AVT was 25.5 mm. Considering that the upper end vertebra was T5 with level shoulders, T3 was chosen as the upper instrumented vertebra. The lower instrumented vertebra was located at L1, which was the last substantially touched vertebra by central sacral line. Therefore, the patient underwent selective thoracic fusion from T3 to L1.