Quantifying the Impact of Spinal Shape: Incorporating Roussouly Criteria into Novel Alignment Schemata Increases Probability of Optimal Radiographic Alignment in Adult Spinal Deformity Surgery

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
EB

Emmanuel Budis

United States
BD

Bassel Diebo, MD

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

Pawel Jankowski

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
AS

Andrew J. Schoenfeld, MD, MSc

Associate Professor
Brigham and Women's Hospital, Department of Orthopaedic Surgery
Boston, Massachusetts, 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

View E-Poster

Disclosure(s):

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

Background: Harmonizing the various ideal parameters defined in adult spinal deformity (ASD) surgery has recently come into prominence. GAP scoring, was itself superseded by the SAAS system, which incorporated GAP and age-adjusted parameters to predict associations with proximal junctional kyphosis and post-operative outcomes. However, the incorporation of Roussouly typing into such schema has not been fully explored, and may be necessary in order to prevent post-operative complications and improve patients’ quality of life.

Purpose: To quantify spinal shape as defined by the Roussouly classification, in conjunction with existing Global Alignment and Proportion (GAP) parameters and the novel Sagittal Age-Adjusted Score (SAAS), to identify unique schema associated with optimal post-operative outcomes.

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-years (2Y) were isolated. Patients were grouped by “theoretical” Roussouly type (Type I: PI < 45°, LL apex below L4; Type II: PI < 45°, LL apex above L4, L4-L5 space; Type III: 45°< PI < 60°; Type IV: PI>60°) at baseline. Crosstabulation and univariate analysis determined distribution of BL GAP and sagittal age-adjusted score (SAAS) parameters within each group. Logistic predictive modeling and with achieving optimal outcomes, defined as ≥2 of the following: 1) no PJK or PJF by 2Y, 2) no major surgical 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 GAP and SAAS scores associated with matching target Roussouly typing by 6W.

Results: 244 ASD patients were included (61.38±13.66 years, 77% female, 27.90±5.89kg/m2, mean CCI: 1.85±1.73). At BL theoretical Roussouly classification, 51.4% of patients were classified as Type II, 34.2% were classified as Type III, 14.4% were classified as Type IV, and none were classified as Type I. GAP proportionality at BL was significantly different between groups, with increasing Roussouly classification significantly associated with increasing probability of categorization as GAP-Severely Disproportioned (p <.001). BL SAAS scores also differed by theoretical Roussouly types (p <.001), with Bonferroni-adjustment demonstrating significantly lower scores between Type II vs Type III or Type IV patients (both p<.001). CIT analysis revealed that for Type II, 6W GAP scores < 1 (p=.005) and 6W SAAS >0 (p <.001) were predictive of meeting optimal outcome. For Type III, 6W GAP scores ≤2 (p=.031) and 6W SAAS >3 (p <.001) were predictive of meeting optimal outcome. For Type IV, 6W GAP scores ≤4 (p <.001) were also predictive of meeting optimal outcome.

Conclusions: Unification of the various alignment schema within adult spinal deformity (ASD) surgery continues to be a challenging issue, yet incorporation of pelvic-incidence based on Roussouly classification remains understudied. Our study demonstrates that adaptation of GAP and SAAS goals in alignment of patients’ spinal morphology may increase probability of achieving optimal outcomes post-operatively. In addition with the lower Roussouly types (Type I, II) associated with a greater need for adhering to stricter alignment by the GAP and SAAS parameters to achieve optimal outcomes and maintain spinal morphology.