Outcomes of Single-Sided Thoracic vs. Bilateral Thoracic and Lumbar Anterior Vertebral Body Tethering in Lenke 1 Curves with Lumbar C Modifier

Study Design: Retrospective review of a prospectively collected single-center adolescent idiopathic scoliosis (AIS) database. Objective: To evaluate the outcomes of single-sided thoracic anterior vertebral body tethering (VBT) versus bilateral thoracic/thoracolumbar VBT for the treatment of Lenke 1C type curves, as well as the outcomes of Lenke 1A/B curves compared to 1C curves. Background: Lenke 1C curves can be successfully treated with selective thoracic fusion alone. However, there are few data to support whether this classification scheme holds true for VBT in Lenke 1C curves. Materials and Methods: A total of 242 consecutive AIS patients with Lenke 1 curves and a minimum two-year follow-up were grouped based on preoperative lumbar modifier A/B (n=163) or C (n=79). The total C group (CTot) was further subdivided into single-sided thoracic VBT (CSing, n=49) and bilateral thoracic and thoracolumbar VBT (CBil, n=30). Results: The preoperative lumbar Cobb angle was larger for CBil (47°) than for CSing (36°, P =0.04), but similar at two years postoperative (CBil, 19°; CSing, 19°). Patients with preoperative open triradiate cartilage (TRC) had significantly increased revision rates, primarily for overcorrection, in all groups (A/B, 38%; CSing, 29%; CBil, 89%; P =0.01), compared to preoperative closed TRC (A/B, 10%; CSing, 17%; CBil, 19%). A similar percentage of patients in both groups required subsequent fusion (A/B, 5% vs. CTot, 10%; P =0.1). Conclusion: The mean lumbar Cobb angle (19°) and percentage of patients with a lumbar Cobb angle > 35° (10%) were similar for CSing and CBil groups at the latest follow-up. Thus, performing a bilateral VBT did not significantly improve the postoperative lumbar curve magnitude compared with thoracic-only VBT (CSing) in our cohort. There was a non-significant difference in revision rates for A/B vs. C groups (18% vs. 28%), and CSing vs. CBil (20% vs. 40%). Revision rates were threefold higher in all patients with preoperative open TRC.