Retrospective analysis of anterior correction and fusion for adolescent idiopathic thoracolumbar/lumbar scoliosis: the relationship between preserving mobile segments and trunk balance.

The objective of this paper was to investigate the surgical strategy of the selection of the lowest instrumented vertebrae (LIV) in anterior correction for adolescent idiopathic scoliosis (AIS) and to discuss the relationship between the LIV and trunk balance. From 1998 to 2004, 28 patients with thoracolumbar/lumbar AIS (Lenke 5 type) were treated by anterior correction and fusion with a mean follow-up of 1.5 years. Specific radiographic parameters were observed respectively and the correlation between disc wedging immediately below the LIV and these parameters was analysed. The mean corrective rate of major curves was 74.84%. The preoperative disc angle distal to LIV was 2.96 +/- 1.43 degrees and postoperatively it was -3.60 +/- 1.75 degrees . The postoperative disc wedging was most correlated with LIV obliquity. The postoperative LIV-CSVL (centre sacral vertical line) distance, which reflects regional balance, was correlated with various preoperative parameters. LIV determination was correlated with multiple preoperative radiographic parameters. Disc wedging distal to LIV occurs most often when a short fusion excluding the lower end vertebra (LEV) and the subjacent disc are nearly parallel.