The operative goals of surgery in adolescent idiopathic scoliosis are to prevent progression while providing safe and optimal coronal correction, sagittal alignment, and axial derotation. The aim of this retrospective clinical study was to evaluate the outcome of selective thoracic fusion for adolescent idiopathic scoliosis in the presence of compensatory lumbar curve of more than 50 in terms of if the Kingʼs criteria are still valid or not.

Between the years of 1991 and 2000, 122 consecutive patients with major thoracic and compensatory lumbar AIS curves undergoing selective thoracic fusion were retrospectively identified from our surgical database. Twenty-nine of those patients were determined to have compensatory lumbar curves of more than 50 degrees in magnitude and included in the study.

All patients were female and the average age at the time of surgery was 16.5 years, range 13–19. The mean duration of radiographic follow-up was 12 years, range 7–16. Curve types according to the Lenke system were: 1C in 23 patients and 3C in 6 patients. The average preoperative main thoracic curve measured 65° (range 55°–90°) and decreased to 26° on side bending. The average preoperative compensatory lumbar curve measured 55° (50°–75°) and decreased to 13.2° on side bending. The per cent main thoracic curve operative correction was meanly 61 % and the per cent compensatory lumbar curve operative correction was meanly 50 %. There was no radiographic evidence of correction loss, implant loosening, dislodgement, low back pain complaint or fracture during the follow-up period. There were neither decompensation seen during follow-up period nor re-operations applied in the patient group.

One simple principle different from Kingʼs criteria is that if the neutral vertebra and the stable vertebra is not the same vertebra and if the stable vertebra is within the lumbar curve, it is better to stop instrumentation and fusion distally at the neutral vertebra to obtain better spontaneous compensatory lumbar curve correction even the CSVL does not touch neutral vertebra as it will be centered over the sacrum to achieve a balanced, stable spine after correction.

Keywords: Idiopathic scoliosis, Lenke classification, posterior instrumentation, decompenzation