How to determine the upper level of instrumentation in thoracic adolescent idiopathic scoliosis:: A prospective study of 103 patients

Purpose of the study. - Determining the level of fusion remains a highly debated topic in adolescent isiopathic scoliosis. The King and Lenke classifications are used, but have their limitations, particularly the weak interobserver reproducibility. We describe the method we use which is independent of the anatomic classification, based on the predictable reduction of the different curvatures. The goal is to achieve good balance of T1 and the shoulders and reestablish spinal balance in the frontal and sagittal planes. The purpose of this work was to assess the midterm results of this strategy for determining the upper level of instrumentation. Material and methods. - The series included 103 adolescents who underwent surgery for idiopathic thoracic scoliosis using a posterior segmental instrumentation. The upper level of fusion was determined by analyzing the rigidity of the proximal curvature and the inclination of T1 and the shoulder. X-rays (preop, postop, last follow-up) were digitalized for computer processing. Comparisons were made with the t test for paired series. Results. - Mean age at surgery was 15.2 +/- 1.7 years (range 10.8-19.3). Mean follow-up was 30.2 months. The clavicular angle and T1 inclination were improved significantly, both for the unique thoracic curvatures and for double thoracic curvatures. No correlation could be found between T1 inclination and shoulder balance. At last follow-up, 86.5% of the patients satisfied all balance criteria. Discussion. - The results of our method, which was carried out fully in 97% of patients, are encouraging and show that systematic instrumentation of the entire proximal curvature is not warranted for double thoracic curvatures. The tong-term consequences for the residual. T1 inclination remain to be assessed. (C) 2008 Elsevier Masson SAS. Tous droits reserves.