Fusions ending at the thoracolumbar junction in adolescent idiopathic scoliosis: comparison of lower instrumented vertebrae.

Abstract

Retrospective cohort study. To compare clinical outcomes and radiographic parameters between patients treated with a posterior spinal fusion that had a lower instrumented vertebra at T11, T12, and L1. Posterior instrumented fusions are well established for treating patients with adolescent idiopathic scoliosis (AIS). Fusions limited to the thoracic spine can adequately correct a spinal deformity while preserving lumbar segmental mobility. However, fusions that end at the thoracolumbar junction have been proposed to cause adjacent segment complications. Studies comparing outcomes between patients who were treated with fusions that end at the thoracolumbar junction with varying LIVs are limited. A multicenter database was queried for patients with AIS that had Lenke Type 1 and 2 curves treated with a fusion that had an LIV at T11, T12, or L1. Coronal curve magnitude, degree of junctional kyphosis, C7-central sacral line, thoracic apical translation, and sagittal stable vertebrae were measured. Clinical and functional outcomes were assessed using the Scoliosis Research Society-22 (SRS-22) questionnaire and lumbar flexibility testing. The lower instrumented level was below the sagittal stable vertebrae in 22.7%, 40%, and 66.2% of patients in the LIV-T11, T12, and L1 groups, respectively (p < 0.001). The 5-year postoperative lumbar curve magnitudes were 20.3°, 16.3°, and 14.0° for T11, T12, and L1-LIV, respectively (p < 0.001). No patients in the T11 group (0%), two patients in the T12 group (2.5%), and one patient in the L1 (0.8%) group developed distal junctional kyphosis (p = 0.5). The 5-year postoperative total SRS-22 scores were 4.21, 4.50, and 4.38 (p = 0.029). Lumbar flexion decreased by 0.78cm in the T11-LIV group, increased by 0.01cm in the T12-LIV group, and decreased by 0.15cm in the L1-LIV group (p = 0.434). There was no significant difference in SRS-22 scores, development of distal junctional kyphosis or loss of lumbar mobility between patients treated with a spinal fusion that had an LIV at T11, T12, or L1. Level III.