Purpose: To assess the benefits of using the touched vertebra (TV) rule in Lenke classification for thoracic curves of adolescent idiopathic scoliosis (AIS).
Methods: A total of 141 AIS patients with thoracic curves determined by Suk classification were divided based on whether the lowest instrumented vertebra (LIV) matched the TV into groups of mTV (n = 84, LIV = TV), TV- (n = 21, LIV above TV), and TV+ (n = 36, LIV below TV) for 5-year follow-up. The radiological parameters were the central sacral vertical line (CSVL)-LIV distance, distal end vertebra rotation, coronal, and sagittal parameters. Complications included adding-on phenomenon, coronal imbalance, and distal junctional kyphosis.
Results: Adding-on phenomenon and coronal imbalance were significantly higher in the TV- group (P = 0.006) and TV + group (P = 0.006), respectively. The distal motion segments were significantly saved in the mTV group (P < 0.001). The CSVL-LIV distance was significantly improved in the mTV group compared to the others during the 5-year follow-up (P = 0.007). The 5-year follow-up CSVL-LIV distance correlated with LIV tilt angle (r = 0.442, P = 0.021) and coronal balance (r = 0.437, P = 0.023).
Conclusions: Selecting the TV as LIV minimizes the loss of the distal mobile segment and reduces the complications in the thoracic curves of AIS, which produces a more stable LIV on the CSVL. Therefore, TV is an ideal landmark for determining the distal fusion level using the Lenke classification or Suk classification.
Keywords: Adolescent idiopathic scoliosis; Lenke classification; Lowest instrumented vertebra; Suk classification; Touched vertebra.
© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.