P103. Sagittal alignment after mini open vertebral body tether versus posterior fusion for adolescent idiopathic scoliosis

Abstract

BACKGROUND CONTEXT Sagittal 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 less examinations of the sagittal effects of VBT. Sagittal alignment is significantly associated with a patient's quality of life. This underscores the importance of sagittal alignment when correcting the coronal deformity in these patients. PURPOSE We show that VBT for correction of AIS is non-inferior with regards to sagittal alignment compared to PSF. STUDY DESIGN/SETTING Retrospective review of AIS patient treated by VBT and PSF at a single medical center. PATIENT SAMPLE Data was collected from our AIS database of VBT and PSF fusion patients. OUTCOME MEASURES Our outcome measures are sagittal vertical axis (SVA), cervical SVA (cSVA), pelvic tilt (PT), thoracic kyphosis (TK), cervical lordosis (CL), L4-S1 lordosis, L5 slope, T1 pelvic angle (TPA) and pelvic incidence lumbar lordosis mismatch (PI-LL). METHODS We propensity matched by age, Risser score and Lenke classification. We compared preoperative and postoperative sagittal parameters measured by Surgimap with statistical significance set at p<0.050. RESULTS Comparing PSF to VBT there was no statistically significant difference in change between preoperative and postoperative cSVA (-.45, SD=6.85 vs .97, SD=5.59, P=.48); PT (4.12, SD=6.49 vs 3.41, SD=4.50, P=.68); TK (1.65, SD=12.12 vs -1.59, SD=10.49, P=.35); CL (3.62, SD=8.87 vs 9.04, SD=13.82, P=.16); L4-S1 lordosis (3.25, SD=7.78 vs 6.09, SD=10.19 , P=.34); SVA (-14.95, SD=30.92 vs -26.82, SD=35.76, P=.34); L5 slope (-1.36, SD=5.91vs -2.95, SD=5.43, P=.44); TPA (4.42, SD=7.69 vs 5.21, SD=6.40, P=.74); and PI-LL (5.48, SD=10.96 vs 6.49, SD=10.80 P=.76). CONCLUSIONS VBT 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 STATUS This abstract does not discuss or include any applicable devices or drugs. Sagittal 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 less examinations of the sagittal effects of VBT. Sagittal alignment is significantly associated with a patient's quality of life. This underscores the importance of sagittal alignment when correcting the coronal deformity in these patients. We show that VBT for correction of AIS is non-inferior with regards to sagittal alignment compared to PSF. Retrospective review of AIS patient treated by VBT and PSF at a single medical center. Data was collected from our AIS database of VBT and PSF fusion patients. Our outcome measures are sagittal vertical axis (SVA), cervical SVA (cSVA), pelvic tilt (PT), thoracic kyphosis (TK), cervical lordosis (CL), L4-S1 lordosis, L5 slope, T1 pelvic angle (TPA) and pelvic incidence lumbar lordosis mismatch (PI-LL). We propensity matched by age, Risser score and Lenke classification. We compared preoperative and postoperative sagittal parameters measured by Surgimap with statistical significance set at p<0.050. Comparing PSF to VBT there was no statistically significant difference in change between preoperative and postoperative cSVA (-.45, SD=6.85 vs .97, SD=5.59, P=.48); PT (4.12, SD=6.49 vs 3.41, SD=4.50, P=.68); TK (1.65, SD=12.12 vs -1.59, SD=10.49, P=.35); CL (3.62, SD=8.87 vs 9.04, SD=13.82, P=.16); L4-S1 lordosis (3.25, SD=7.78 vs 6.09, SD=10.19 , P=.34); SVA (-14.95, SD=30.92 vs -26.82, SD=35.76, P=.34); L5 slope (-1.36, SD=5.91vs -2.95, SD=5.43, P=.44); TPA (4.42, SD=7.69 vs 5.21, SD=6.40, P=.74); and PI-LL (5.48, SD=10.96 vs 6.49, SD=10.80 P=.76). VBT 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.