Are We Missing the Mark? Evaluating Sagittal Deformity in AIS Below Surgical Cutoffs
Location
LSUHSC-NO Center for Advanced Learning and Simulation
Document Type
Presentation
Start Date
21-6-2025 10:20 AM
End Date
21-6-2025 11:15 AM
Publication Date
June 2025
Description
Introduction: Adolescent idiopathic scoliosis (AIS) is traditionally managed based on the degree of coronal curvature, with surgical intervention typically reserved for Cobb angles >50º. However, adult spine literature identifies sagittal malalignment—including SVA, PI-LL mismatch, and T1-pelvic angle—as key predictors of long-term morbidity. This study evaluates the sagittal alignment of nonoperative AIS patients with moderate coronal curves and questions whether coronal-based thresholds may overlook high-risk alignment profiles.
Methods: We conducted a retrospective review of AIS patients treated between 2016 and 2022. Inclusion criteria were reaching skeletal maturity without surgical intervention and major coronal curve between 30º and 50º. Radiographic parameters included traditional sagittal metrics (SVA, PILL mismatch, thoracic kyphosis, pelvic tilt, cervical lordosis, T1-pelvic angle), as well as emerging alignment measures: C2 pelvic angle (C2PA), T4 pelvic angle (T4PA), L1 pelvic angle (L1PA), and C2 slope. Thresholds for concerning alignment included: SVA >5 cm, PI-LL mismatch >10º, T1-pelvic angle >14º, pelvic tilt >25º, thoracic kyphosis <20º, and cervical lordosis <20º.
Results: Sixty-seven patients were included (mean Cobb angle: 38.2º). Among these, 32.84% had a PI-LL mismatch >10º, 10.45% had T1-pelvic angle >14º, and 4.48% had an SVA >5 cm. Additional findings included thoracic hypokyphosis (<20º) in 4.48% and pelvic tilt >25º in 4.48%. Roussouly classification revealed 10.45% type 1, 7.46% type 2, 56.72% type 3, and 25.37% type 4.
Discussion: Despite not meeting traditional surgical criteria, a substantial proportion of nonoperative AIS patients demonstrated sagittal misalignments associated with long-term spinal degeneration in adults. These findings challenge the reliance on coronal Cobb angles alone in determining surgical candidacy and suggest that early intervention may be warranted in select patients based on sagittal profile.
Significance/Clinical relevance: Sagittal malalignment is present in a meaningful subset of nonoperative AIS patients. As spine surgery trends toward precision alignment and long-term quality of life outcomes, incorporating sagittal criteria into surgical decision-making may better identify at-risk patients and optimize long-term spine health.
Recommended Citation
Piedy, Erik, "Are We Missing the Mark? Evaluating Sagittal Deformity in AIS Below Surgical Cutoffs" (2025). Dept. of Orthopaedics: Robert D. D’Ambrosia Lectureship & Research Day. 3.
https://digitalscholar.lsuhsc.edu/ortho_rd/2025/presentation2/3
Are We Missing the Mark? Evaluating Sagittal Deformity in AIS Below Surgical Cutoffs
LSUHSC-NO Center for Advanced Learning and Simulation
Introduction: Adolescent idiopathic scoliosis (AIS) is traditionally managed based on the degree of coronal curvature, with surgical intervention typically reserved for Cobb angles >50º. However, adult spine literature identifies sagittal malalignment—including SVA, PI-LL mismatch, and T1-pelvic angle—as key predictors of long-term morbidity. This study evaluates the sagittal alignment of nonoperative AIS patients with moderate coronal curves and questions whether coronal-based thresholds may overlook high-risk alignment profiles.
Methods: We conducted a retrospective review of AIS patients treated between 2016 and 2022. Inclusion criteria were reaching skeletal maturity without surgical intervention and major coronal curve between 30º and 50º. Radiographic parameters included traditional sagittal metrics (SVA, PILL mismatch, thoracic kyphosis, pelvic tilt, cervical lordosis, T1-pelvic angle), as well as emerging alignment measures: C2 pelvic angle (C2PA), T4 pelvic angle (T4PA), L1 pelvic angle (L1PA), and C2 slope. Thresholds for concerning alignment included: SVA >5 cm, PI-LL mismatch >10º, T1-pelvic angle >14º, pelvic tilt >25º, thoracic kyphosis <20º, and cervical lordosis <20º.
Results: Sixty-seven patients were included (mean Cobb angle: 38.2º). Among these, 32.84% had a PI-LL mismatch >10º, 10.45% had T1-pelvic angle >14º, and 4.48% had an SVA >5 cm. Additional findings included thoracic hypokyphosis (<20º) in 4.48% and pelvic tilt >25º in 4.48%. Roussouly classification revealed 10.45% type 1, 7.46% type 2, 56.72% type 3, and 25.37% type 4.
Discussion: Despite not meeting traditional surgical criteria, a substantial proportion of nonoperative AIS patients demonstrated sagittal misalignments associated with long-term spinal degeneration in adults. These findings challenge the reliance on coronal Cobb angles alone in determining surgical candidacy and suggest that early intervention may be warranted in select patients based on sagittal profile.
Significance/Clinical relevance: Sagittal malalignment is present in a meaningful subset of nonoperative AIS patients. As spine surgery trends toward precision alignment and long-term quality of life outcomes, incorporating sagittal criteria into surgical decision-making may better identify at-risk patients and optimize long-term spine health.
Comments
Student and Fellow Presentation