Sagittal Spinal Alignment 2 Years After Vertebral Body Tethering.

Abstract

Retrospective cohort. To investigate the change of sagittal spinal alignment after anterior vertebral body tethering (VBT) in skeletally immature patients with idiopathic scoliosis using pelvic incidence-based measures of alignment. VBT is a non-fusion option for the treatment of idiopathic scoliosis, though concern exists for derangement of the sagittal plane with skeletal growth. A retrospective analysis was conducted on 87 patients with thoracic idiopathic scoliosis who underwent VBT. Preoperative and 2-year postoperative radiographs were reviewed, recording coronal radiographic measures, sagittal pelvic parameters, and vertebral pelvic angles (VPA) at T4 and L1. Linear regression modeled T4PA and L1PA by pelvic incidence and the coefficient of determinations assessed model fit. The difference between T4PA and L1PA (T4-L1 mismatch) was modeled by pelvic incidence and compared with normal, healthy adults. After VBT, the thoracic main scoliotic curve significantly improved from 49 degrees (43-56) to 23 degrees (17-34) (P <.01). Accompanying growth-related pelvic parameter changes, T4PA increased from 3 (1, 8) to 6 (1, 11) degrees (P <0.01) and L1PA from 5 (2, 11) to 8 (3, 13) degrees (P <0.01). T4-L1 mismatch by PI showed significant correlation postoperatively (R²=0.11, P <0.01), with cases within the adult 80% prediction interval increasing from 56.3% to 70.1%. Patients who underwent VBT maintained sagittal alignment when measured by VPA while achieving coronal plane correction. These data offer evidence against concerns for sagittal plane malalignment with VBT.