Spine - 2026-09-21 - Journal Article
Sagittal Alignment in Adolescent Idiopathic Scoliosis with Major Thoracic Curvesss: Pelvic Incidence and Its Influences on Lumbar Lordosis and Thoracic Kyphosis.
Chandirasegaran S, Ong JS, Ong YY, Lee SY, Chiu CK, Chan CYW, Kwan MK
Topics
Key Takeaway
In 506 AIS patients with major thoracic curves, PI correlates with proximal lumbar lordosis (r=0.470) but not distal lumbar lordosis (r=0.007), meaning PI-driven LL variation is entirely a proximal lumbar phenomenon.
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Summary
This retrospective study analyzed preoperative sagittal radiographic parameters in 506 AIS patients (Lenke types 1–4) to determine how PI influences segmental distribution of LL and TK. PI correlated moderately with total LL (r=0.395) but this was driven entirely by PLL (r=0.470); DLL was invariant across low, average, and high PI groups (34.6° vs 34.1° vs 35.2°, P=0.507). Higher PI was associated with reduced TK, primarily through decreased distal TK (r=-0.276), suggesting PI shapes both the lumbar and thoracic sagittal profile in opposing directions.
Key Limitation
No postoperative radiographic or PROM data are included, so whether PI-stratified rod contouring actually improves achieved sagittal alignment or clinical outcomes is entirely undemonstrated.
Original Abstract
STUDY DESIGN
Retrospective study.
OBJECTIVES
To analyse the correlations between pelvic incidence (PI), segmental lumbar lordosis (LL), and segmental thoracic kyphosis (TK) in AIS patients with major thoracic curves. To evaluate the influence of PI, stratified into low, average and high PI groups, on segmental LL and spinopelvic alignment in AIS patients.
SUMMARY OF BACKGROUND DATA
PI is a key anatomic determinant of sagittal spinal alignment. While the relationship between PI and LL is well established, its influence on the distribution of proximal lumbar lordosis (PLL) versus distal lumbar lordosis (DLL) and its relationship with segmental TK in AIS patients remains poorly defined.
METHODS
This retrospective study included 506 patients with AIS (Lenke types 1-4). Preoperative sagittal radiographic parameters measured were LL, PLL, DLL, TK, and PI. Patients were stratified into low PI (<45°), average PI (45-60°), and high (>60°) PI groups.
RESULTS
PI demonstrated a moderate positive correlation with LL (r=0.395, P<0.001), primarily attributable to PLL (r=0.470, P<0.001), but not DLL (r=0.007, P=0.869). PI showed a weak negative correlation with TK (r=-0.199, P<0.001), predominantly due to DTK (r=-0.276, P<0.001). Higher PI groups had a significantly higher LL (low PI: 51.4±10.7°; average PI: 57.4±10.9°; high PI: 63.4±10.8°) (P<0.001), driven by a corresponding increase in PLL (16.8±8.4° vs. 23.3±9.3° vs. 28.2±8.3° (P<0.001). In contrast, DLL were comparable between PI groups (P=0.507).
CONCLUSION
PI significantly influences PLL, but not DLL in AIS patients with major thoracic curves. Although DLL constitutes the majority of LL, it remains relatively constant across varying PI. Increasing PI is associated with reduced TK, primarily driven by a decrease in DTK. These findings highlight the importance of individual PI in planning sagittal rod contouring, as patients with higher PI may require greater proximal lumbar contouring to achieve their native sagittal profile.