Risk factors for the development of DJK in AIS patients undergoing posterior spinal instrumentation and fusion

Typically, selection of lowest instrumented vertebra (LIV) in Adolescent Idiopathic Scoliosis (AIS) is based on the coronal radiograph; however, increasing evidence suggests that fusions proximal to the stable sagittal vertebrae (SSV) on the lateral radiograph can result in distal junctional kyphosis (DJK). The purpose of this study is to compare rates of DJK in patients with AIS that have a discordance between the Lowest Touched Vertebra (LTV) and the SSV and to identify risk factors for developing DJK. Patients with AIS Lenke type 1, 2 and 3 curves treated with a posterior spinal fusion were separated into two groups. Group 1 had SSV that was proximal to the LTV whereas group 2 had SSV that was distal to the LTV. Comparisons were made for patients that were fused to the SSV(a), LTV(b) or between(c). Distal junctional angle (DJA) > 5° and increasing kyphosis at the end of the fusion construct were evaluated as risk factors for DJK. The rate of DJK was 0.0% in group 1a, 1b, and 1c compared to 4.3%, 18.5% and 10.0% in groups 2a, 2b and 2c, respectively(p 5° versus 1.4% when the DJA