Selection of the lowest instrumented vertebra (LIV) in patients undergoing selective fusion for Lenke type 1 or 2 adolescent idiopathic scoliosis (AIS) varies widely across centres around the world.

Lenke, Suk, and Dubousset criteria show moderate agreement for LIV selection.

Sixty-eight patients with Lenke type 1 or 2 AIS managed by selective posterior fusion and followed-up for at least 2 years were included in a retrospective observational study. Agreement among Lenke, Suk, and Dubousset criteria for LIV selection was assessed. For surgery, the LIV was selected based on Dubousset criteria. Retrospectively, in each patient, the LIV selected by the Lenke and Suk criteria sets was identified on the preoperative images. The patients were then divided into two groups based on whether the Dubousset LIV was identical versus more distal than the LIV identified retrospectively by the Lenke or Suk criteria. The primary evaluation criterion was coronal balance.

The LIVs selected by the Lenke, Suk, and Dubousset criteria were identical in 57% of cases. The LIV selected by the Dubousset criteria were identical to that selected by the Lenke or Suk criteria in 70% of patients. No significant between-group differences were found for any of the evaluation criteria assessed preoperatively, postoperatively, or at last follow-up.

Agreement among the Lenke, Suk, and Dubousset criteria was moderate, confirming the working hypothesis. No coronal malalignment developed in the patients whose actual LIV was distal to the LIV selected by the Lenke or Suk criteria, supporting the validity of Dubousset criteria for LIV selection. When selecting the LIV, all three criteria sets should be assessed. The LIV is the vertebra selected by all three if they agree or by the Dubousset criteria if they do not.

IV, retrospective cohort study.