Spine - 2026-03-12 - Journal Article
Sagittal Spinal Alignment 2 Years After Vertebral Body Tethering.
Ouchida J, Schupper A, Pahys J, Samdani A, Hwang S, Upasani VV, Newton PO, Gholami P, Kelly MP
Topics
Key Takeaway
VBT achieved 26° coronal correction (49° to 23°) while maintaining sagittal alignment, with T4-L1 mismatch falling within adult normal prediction intervals in 70.1% of patients at 2 years versus 56.3% preoperatively.
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Summary
This study examined whether VBT disrupts sagittal alignment in skeletally immature patients with thoracic idiopathic scoliosis using pelvic incidence-normalized vertebral pelvic angles (VPA) at T4 and L1. In 87 patients, main thoracic curves corrected from 49° to 23° (P<0.01), while T4PA increased from 3° to 6° and L1PA from 5° to 8°, both consistent with expected growth-related changes. T4-L1 mismatch correlated with PI postoperatively (R²=0.11, P<0.01), and the proportion of patients within adult normal 80% prediction intervals improved from 56.3% to 70.1%.
Key Limitation
The R²=0.11 for postoperative T4-L1 mismatch versus PI indicates that PI explains only 11% of sagittal variance, leaving the majority of individual sagittal outcomes unpredicted by this model.
Original Abstract
STUDY DESIGN
Retrospective cohort.
OBJECTIVE
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.
SUMMARY OF BACKGROUND DATA
VBT is a non-fusion option for the treatment of idiopathic scoliosis, though concern exists for derangement of the sagittal plane with skeletal growth.
METHODS
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.
RESULTS
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%.
CONCLUSION
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.