Risk factors for coronal decompensation after posterior spinal instrumentation and fusion in adolescent idiopathic scoliosis

Study Design Retrospective review of multicenter data set with adolescent idiopathic scoliosis (AIS) patients with at least 2 years of follow-up after posterior spinal instrumentation and fusion (PSIF). Objectives The purpose of this study is to investigate risk factors for coronal decompensation 2 years after PSIF for AIS. Summary of Background Data Coronal decompensation is a potential complication of spinal instrumentation for AIS. This can result in problems requiring revision surgery. Methods Demographic, clinical, and radiographic measures were reviewed on 890 identified patients. Coronal decompensation was defined as a change farther away from midline from 6 weeks postoperatively to 2 years in any one of the following radiographic parameters: change in coronal balance >2 cm; change in coronal position of the lowest instrumented vertebra (LIV) >2 cm; change in thoracic trunk shift >2 cm; or change in LIV tilt angle >10°. Patients with decompensation were compared to those without. The relationship between the LIV and lowest end vertebra (LEV) was examined as an independent variable. Results Two years postoperation, 6.4% (57/890) of patients exhibited coronal decompensation. Multivariate regression revealed that decompensated patients were twice as likely to be male, have lower preoperative Risser score, and lower percentage major curve correction. The relationship between the LIV and LEV as well as quality of life surveys were not significantly different between decompensated and nondecompensated patients at 2 years. Conclusions Two years after PSIF, 6.4% of patients with AIS exhibit radiographic coronal decompensation. Although this study did not demonstrate a significant association between the relationship of LIV and LEV and decompensation 2 years postoperation, results of this study indicate that skeletal immaturity, male gender, and less correction of the major curve may be related to higher rates of coronal decompensation.