Fusions ending above the sagittal stable vertebrae in adolescent idiopathic scoliosis: does it matter?

Study design: Retrospective cohort study. Objective: To validate whether fusions that end proximal to the sagittal stable vertebrae are at risk for developing distal junctional kyphosis in adolescent idiopathic scoliosis. Background: Posterior spinal fusion is routinely used for the treatment of patients with adolescent idiopathic scoliosis. Fusions that end in either the lower thoracic or upper lumbar spine have the advantage of preserving motion segments. However, fusions ending proximal to the sagittal stable vertebrae has been shown to be at higher risk for developing distal junctional kyphosis. Methods: A multi-center database of prospectively enrolled subjects was queried for patients with adolescent idiopathic scoliosis that had Lenke type 1, 2 and 3 curves treated with posterior pedicle screw instrumentation. PA (posterior-anterior) and lateral full-length scoliosis films were obtained on each patient. PA radiographs were viewed to determine the coronal deformity and lateral radiographs to determine the sagittal deformity. Distal junctional kyphosis was defined as a greater than 10° increase in segmental kyphosis between the LIV and the LIV + 1 vertebra. Results: 346 patients were included with 85% being female and mean age of cohort 14.2 ± 2.08 years. At 5 years postoperatively, there was significant difference occurrence of distal junctional kyphosis dependent on whether the LIV relative to SSV with only 2.2% of fusions below the SSV developing DJK compared to 6.5% for fusions ending at the SSV and 15% for fusions with LIV above the SSV (p ' 0.001). There was no statistical difference in revision rates based on the relationship of LIV to SSV. Conclusion: There is an increased risk for development of DJK in patients with AIS treated with posterior fusion where the LIV was chosen proximal to the SSV. Level evidence: Level III.