How to select the lowest instrumented vertebra in Lenke 5/6 adolescent idiopathic scoliosis patients with derotation technique

Abstract

Purpose: To introduce and evaluate our lowest instrumented vertebra (LIV) selection criteria for Lenke type 5/6 adolescent idiopathic scoliosis (AIS) patients with de-rotation technique.

Methods: There were 53 eligible Lenke 5/6 AIS patients with minimum 2-year follow-up enrolled in current study. The LIV selection criteria were: (1) the first vertebra touching the central sacral vertical line (CSVL) or the most cephalad vertebra which can return to stable zone under lateral bending position; (2) vertebral rotation no more than grade II by Nash-Moe rotation evaluation; (3) the lowest instrumented vertebra disc angle (LIVDA) could be reversed on lateral bending position. Demographic data, operation data and radiographic data were obtained and analyzed.

Results: Both clinical evaluation and radiographic data showed satisfactory outcome. The thoracolumbar/lumbar curve was improved from 53.4 ± 11.0° preoperatively to 6.9 ± 2.6° at the final follow-up. Two patients (3.8%) with adding on and two patients (3.8%) with coronal decompensation were identified at the final follow-up. LIV translation, LIV tilt and LIV disc angle were gradually improved after operation. The preoperative LIV tilt was positively correlated with Cobb angle (p = 0.010) and AVT (p = 0.030) at the final follow-up, and preoperative LIVDA was positively correlated with Cobb angle (p = 0.033) at the final follow-up.

Conclusion: In Lenke 5/6 scoliosis, the current LIV selection criteria with de-rotation technique contribute to satisfactory correction rate of 87.1% and minimal alignment complications of 7.6%. LIV could be spontaneously and progressively improved after operation. Preoperative LIV tilt and LIVDA could predict postoperative correction and coronal balance.

Keywords: Adolescent idiopathic scoliosis; Lenke 5/6; Lowest instrumented vertebrae selection; Lumbar and thoracolumbar curve; Selective fusion.