Preoperative Recognition of Vertebral Number Variations in Adolescent Idiopathic Scoliosis: A Series of Four Cases.

Numerical variations in thoracic and lumbar vertebrae in adolescent idiopathic scoliosis (AIS) are not uncommon but are often underrecognized. This case series highlights the impact of identifying these variations on operative planning and correct fusion level identification. We report four patients with AIS with thoracic and lumbar vertebral number variations that were identified on standing whole-spine radiographs. Vertebral counts, curve characteristics, Lenke classification, and planned fusion levels are presented to illustrate the impact of these variations on surgical planning and approach. Increasing surgeons' awareness of the importance of vertebral enumeration is essential to ensure accurate documentation and fusion level selection and to avoid unnecessary costs, prolonged operative time, and associated complications.