131. Sagittal profile modifications in vertebral body tethering (VBT) versus posterior spinal fusion (PSF) in adolescent idiopathic scoliosis (AIS)

BACKGROUND CONTEXTSagittal alignment is integral to a patient's quality of life. Posterior spinal fusion (PSF) is currently the standard for correcting adolescent idiopathic scoliosis (AIS). Vertebral body tethering (VBT) is a fusionless growth modulating surgical technique used to treat AIS. It relies on the Hueter-Volkmann Law. Indications for this procedure include patients who have coronal curves up to 50°, growth remaining, and no excessive thoracic kyphosis. VBT has been shown to have good coronal plane deformity correction. There have been fewer examinations of the sagittal effects of VBT.PURPOSETo determine if VBT is a non-inferior treatment for correction of AIS with regard to sagittal alignment compared to PSF.STUDY DESIGN/SETTINGMulticenter retrospective cohort study.PATIENT SAMPLEPatients with AIS who underwent correction surgeries with LIV in the lumbar spine from 2013 to 2021 with pre- and minimum two-year postoperative standing full spine plain films.OUTCOME MEASURESSagittal vertical axis (SVA), cervical SVA (cSVA), pelvic tilt (PT), thoracic kyphosis (TK), cervical lordosis (CL), L4-S1 lordosis (L4L), T1 pelvic angle (TPA) and pelvic incidence lumbar lordosis mismatch (PI-LL).METHODSRadiographic analyses was completed with independent samples t-test with significance set to p <0.05.RESULTSA total of 99 patients were included, 49 VBT and 50 PSF. There were no differences in age or levels instrumented between groups. The VBT cohort Lenke class breakdown is 23% 1A, 13% 1C, 31% 3C. 18% 5C, and 15% 6C, while the PSF cohort consisted of 42% 1A, 6% 1B, 2% 2C, 2% 3B, 12% 3C, 2% 5B, 24% 5C, and 10% 6C. At Baseline, the VBT cohort had lower SVA (-0.7mm±3.7 vs 2.2mm±5.0, p=0.001), CL (-0.9°±18.2 vs 11.6°±12.8, p=0.001), L4-S1 Lordosis (20.7°±16.0 vs 41.6°±10.2, p=0.001), and higher cSVA (3.3mm±1.6 vs -0.95mm±3.1, p=0.001) than those who were fused. Postoperatively, VBT patients have an overall higher L4-S1 Lordosis (36.0°±10.1vs 18.3°±12.5, p=0.001), cSVA (3.4mm±1.4 vs -3.7mm±2.1, p=0.001), and lower CL (-4.3°±18.4 vs 7.0°±12.2, p=0.001). The PSF cohort had a larger change in cSVA (2.8mm±4.0 vs 0mm±1.6, p=0.001) from baseline to 2-year follow-up compared to VBT. No differences in the change of L4-S1 Lordosis (VBT 1.5°±12.3 vs 4.1°±10.9, p=0.3), TPA (VBT -1.6°±6.8 vs -1.4°±8.5, p=0.89), PT (VBT -0.5°±7.8 vs -1.9°±8.5, p=0.42), or PI-LL (0.2°±12.0 vs -0.5°±14.0, p=0.81) were observed.CONCLUSIONSVBT and PSF for AIS result in statistically similar changes in sagittal alignment parameters. The fact that we showed similar results comparing sagittal alignment in fusion and VBT groups indicates that VBT is non-inferior from a sagittal perspective. It is important to maintain sagittal alignment when correcting AIS. Future work can examine the long-term effect of VBT on sagittal alignment.FDA DEVICE/DRUG STATUSThis abstract does not discuss or include any applicable devices or drugs.