The Influence of Relative Curve Correction and Upper Instrumented Vertebra (UIV) Tilt Angle on Post-operative Shoulder Balance Following Posterior Spinal Fusion (PSF) in Lenke Type 1 and 2 Adolescent Idiopathic Scoliosis (AIS) Patients.

Study Design: Retrospective study.

Objective: To investigate the relative curve correction of Proximal Thoracic (PT) and Main Thoracic (MT) scoliosis curves and their relationship with post-operative UIV tilt angle as well as post-operative shoulder imbalance.

Methods: 151 AIS patients with Lenke type 1 and 2 curves who underwent PSF were reviewed.

A mathematical model for estimating the intraoperative lowest instrumented vertebra (LIV) tilt angle using preoperative supine left side-bending (LSB) radiographs in adolescent idiopathic scoliosis (AIS) patients with lenke type 1 and 2 non-AR curves.

Purpose: To devise a mathematical model for estimating the intraoperative lowest instrumented vertebra (LIV) tilt angle using preoperative supine left side-bending (LSB) radiographs in adolescent idiopathic scoliosis (AIS) patients with Lenke type 1 and 2 (non-AR curves), and to review its clinical and radiological outcomes.

Methods: The mathematical model for the adjusted LSB LIV tilt angle (α) measured preoperatively, was expressed as the sum of preoperative LSB LIV tilt angle (x) and LIV displacement angle (y) (α = x + y). This model was validated through inter-rater and intra-rater analysis in Part I of the study.