Identifying Thresholds for Optimal Outcomes in Adult Spinal Deformity Patients with Isolated Pelvic Incidence Minus Lordosis (PI-LL) Mismatch

Thursday, June 1, 2023

8:30 AM – 6:15 PM

Location: Salons 7-8

Co-Author(s)

PT

Peter S. Tretiakov, BS

United States
PD

Pooja R. Dave

Miami, Florida, United States
JM

Jamshaid M. Mir, MD

Research Fellow
NYU Langone Health | NY Spine Institute, United States
OO

Oluwatobi Onafowokan

United Kingdom
SO

Stephane Owusu-Sarpong, MD

Orthopedic Surgery Resident
NYU Langone Health, United States
BD

Bassel Diebo, MD

Spine Surgeon
Brown University
Brooklyn, Rhode Island, United States
RL

Renaud Lafage, MS

Senior Biomedical engineer
Lenox Hill Hospital
new york, New York, United States
TP

Themistocles S. Protopsaltis, MD

Chief, Division of Spine Surgery
NYU Langone Health Department of Orthopedic Surgery
New York, New York, United States

Presenting Author (Person doing the Podium Present(s)

PP

Peter G. Passias, M.D.

Spine Surgeon
NYU Langone Orthopedic Hospital
New York, New York, United States

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Submitter(s)

PP

Peter G. Passias, M.D.

Spine Surgeon
NYU Langone Orthopedic Hospital
New York, New York, United States

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Disclosure(s):

Peter G. Passias, MD: No relevant disclosure to display

Background: The importance of spinopelvic harmony [pelvic incidence (PI) = lumbar lordosis (LL) ±10 degrees] is well established in the literature. However, patients presented with isolated increased PI-LL mismatch in the absence of global deformity, especially in regards to the often associated increase in sagittal vertical axis (SVA), is not well described in literature.

Purpose: To identify thresholds for optimal outcomes in ASD patients with isolated pelvic incidence minus lordosis (PI-LL) mismatch.

Methods: Surgical ASD patients (SVA≥5cm, PT≥25°, or TK ≥60°, >3 levels fused) ≥18 years old with available baseline (BL) radiographic data at baseline (BL) and 2-year (1Y) were isolated in the single-center database. Patients were isolated based upon meeting BL Lafage et al. SAAS TPA and PT metrics. Logistic predictive modeling and with achieving optimal outcomes, defined as ≥2 of the following: 1) no PJK or PJF by 2Y, 2) no major complication or reoperation by 2Y, 3) achieving MCID in ODI or Smith et al. Best Clinical Outcomes (BCO) in ODI. Conditional Inference Tree (CIT) analysis determined PI-LL thresholds for meeting optimal outcomes in patients considered matched in PT and TPA (pure PI-LL deformity).

Results: 355 ASD patients were included (61.38±13.66 years, 77% female, 27.90±5.89kg/m2, mean CCI: 1.85±1.73). At baseline, 27.9% of patients were considered matched per SAAS. By SAAS components, 30.6% of patients were considered matched by PT, 30.1% were considered matched in TPA, and 17.5% were considered matched in PI-LL. Of all patients included, 9.5% were considered to have pure PI-LL mismatch. Logistic regression, accounting for BL age, gender, and levels fused determined radiographic PI-LL and SAAS PI-LL modifiers to be significant predictors of achieving optimal outcomes. Linear regression identified a strong negative correlation between BL PI-LL mismatch and optimal outcomes score count (r2=.88, p<.001). CIT analysis revealed patients with a BL SAAS PI-LL point score of < 1, or mismatch of ≤ 15.44⁰ to be significantly more likely to achieve optimal outcomes by 2Y (p=.03, <.001, respectively).

Conclusions: Increased pelvic incidence minus lumbar lordosis (PI-LL) of 15.44⁰ or greater, or a baseline SAAS PI-LL modifier greater than 1 is strongly associated with decreased likelihood of achieving optimal outcomes post-operatively, even in the absence of SAAS pelvic tilt or TPA mismatch. As such, operative treatment of ASD patients with pure PI-LL deformity may be clinically beneficial.