Changes of Deformity due to the Position and Anesthesia in Adolescent Idiopathic Scoliosis

Study Design: Restrospective case series. Objective: To determine changes in the end vertebra and neutral vertebra, and in the magnitudes of coronal and rotational deformities according to position and anesthesia in patients with adolescent idiopathic scoliosis. Summary of Background Data: Although it is known that coronal deformity of scoliosis has a tendency to decrease by position and anesthesia, there have been few reports on the effects of position and anesthesia on the rotational deformity of scoliosis. End vertebra and neutral vertebra can change after positioning and anesthesia, but little is known about it. Methods: Sixty-two structural curves in 31 patients were evaluated using standing, supine, side bending, postanesthesia, and postoperative anteroposterior plain radiographs. Cobb angles and rotation angles by Perdriolle torsionmeter were measured, and the end vertebra and neutral vertebra were identified in each radiograph. Results: Coronal Cobb angles decreased significantly with the correction rates of 25.0%, 31.7%, 59.5%, and 74.0%, and rotational deformities decreased with the correction rates of 6.1%, 24.5%, 6.2%, and 25.7% by supine position, anesthesia, side bending, and surgery, respectively. The end vertebrae changed in 18 patients (58.1%) in both supine and postanesthesia radiographs, and the neutral vertebrae changed in 10 patients (32.3%) in supine radiographs and in 20 patients (64.5%) in postanesthesia radiographs. Conclusions: Coronal deformities are significantly corrected by supine position and anesthesia. Anesthesia significantly corrects axial rotation, but further correction cannot be achieved by rod derotation. The end vertebra and neutral vertebra have a tendency to vary by position and anesthesia, which gives rise to confusion in the determination of fusion levels.