Influence on lowest instrumented vertebra disc wedging by thoracolumbar/lumbar and thoracic Cobb ratio (TL/L:T Cobb ratio) after selective lumbar fusion in patients with adolescent idiopathic scoliosis Lenke type 5

Abstract

The purpose of this study was to evaluate whether selective lumbar fusion (SLF) for adolescent idiopathic scoliosis (AIS) Lenke type 5C based on thoracolumbar/lumbar and thoracic Cobb ratio (TL/L:T Cobb ratio) >1.25 index was appropriate in concerning postoperative coronal imbalance. This study included 56 AIS Lenke 5C patients (all female; mean age, 15.9 years old) who underwent posterior SLF with L3 as the lowest instrumented vertebra from 2007 to 2018. In 6 of 56 cases (10.7%), distal adjacent disc angle wedging of more than 10 degrees was observed. Even in patients with a TL/L:T Cobb ratio of 1.5 or greater, immature bone maturity may lead to a progressive thoracic curve and wedging of the distal disc angle during follow-up. In cases with a TL/L:T Cobb ratio of around 1.3, the residual thoracic curve may also cause wedging of the adjacent disc.