Thoracoscopic Vertebral Body Tethering for Adolescent Idiopathic Scoliosis Follow-up Curve Behavior According to Sanders Skeletal Maturity Staging

Study Design. Retrospective analysis of prospectively collected data. Objective. To report the follow-up curve behaviors in different Sanders staging groups. Summary of Background Data. Vertebral body tethering (VBT) is a growth modulation technique that allows gradual spontaneous follow-up curve correction as the patient grows. There is a lack of scientific evidence regarding appropriate patient selection and timing of implantation. Methods. Patients were grouped into five as: Sanders 1, 2, 3, 4- 5, and 6- 7. Data were collected preoperatively, at the day before discharge, and at each follow-up. Outcome measures were pulmonary and mechanical complications, readmission, and reoperation rates. Demographic, perioperative, clinical, radiographic, and complication data were compared using Fisher- Freeman- Halton exact tests for categorical variables and Kruskal-Wallis tests for the continuous variables. Results. Thirty-one (29 F, 2 M) consecutive patients with a minimum of 12 months of follow-up were included. The mean age at surgery was 12.1 (10- 14). The mean follow-up was 27.1 (12- 62) months. The mean preoperative main thoracic curve magnitude was 47 degrees +/- 7.6 degrees. For all curves, preoperative and first erect curve magnitudes, bending flexibility, and operative correction percentages were similar between groups (for all comparisons, P> 0.05). The median height gained during follow-up was different between groups (P< 0.001), which was reflected into median curve correction during follow-up. Total curve correction percentage was different between groups (P = 0.009). Four (12.9%) patients had pulmonary and six (19.4%) had mechanical complications. One (3.2%) patient required readmission and two (6.5%) required reoperation. Occurrence of pulmonary complications was similar in Sanders groups (P = 0.804), while mechanical complications and over-correction was significantly higher in Sanders 2 patients (P = 0.002 and P = 0.018). Conclusion. Follow-up curve behavior after VBT is different in patients having different Sanders stages. Sanders 2 patients experienced more overcorrection, thus timing and/or correction should be adjusted, since Sanders 3, 4, and 5 patients displayed a lesser risk of mechanical complications.