Lightning Podiums: Adult Spinal Deformity - Room 801A

Presented by: P. Passias

Author(s):

S. Horn(1), N. Frangella(1), G. Poorman(1), D. Vasquez-Montes(1), B. Diebo(2), C. Bortz(1), F. Segreto(1), L. Steinmetz(1), N. Stekas(1), J. Moon(1), P. Zhou(1), S. Vira(1), A. Sure(1), M. Siow(1), J. Tishelman(1), B. Beaubrun(1), W. Bronson(1), C. Wang(1), T. Errico(1), V. Lafage(3), A. Buckland(1), P. Passias(1)

(1) New York University Langone Orthopedic Hospital, Division of Spinal Surgery, New York, NY, United States
(2) SUNY Downstate Medical Center, Department of Orthopaedic Surgery, Brooklyn, NY, United States
(3) Hospital for Special Surgery, Department of Orthopaedic Surgery, New York, NY, United States

Abstract

Introduction: Prior studies have built a foundation for understanding the mechanisms of compensation in adult spinal deformity patients using full-body stereographic assessments. However, our knowledge of the effects of age-adjusted alignment targets on this compensation, broken down by age groups, has yet to be fully studied. The aim of this study is to assess lower limb compensatory mechanisms used on patients who failed to meet targets for age-adjusted alignment goals.

Methods: Single-center retrospective review. Inclusion: pts ≥ 18 yrs with full body stereographic x-rays (baseline and 1Y) meeting ASD criteria (SVA>5cm, PI-LL>10°, or PT>20°). Patients were stratified into age cohorts: < 40y, 40-65y, ³65y. Correction groups were created comparing actual alignment (ACTUAL) with age-adjusted ideal values (IDEAL) for sagittal vertical axis (SVA), T1 pelvic angle (TPA), pelvic tilt (PT), and spino-pelvic mismatch (PI-LL) based on published formulas. The differences between ACTUAL and IDEAL alignment (OFFSET) was determined. Patients who matched ('match') ±10 years threshold for age-adjusted targets were compared to unmatched cases ('under-corrected' or 'over-corrected'). Lower limb compensation: pelvic shift (PS), hip extension (SFA), knee flexion (KA), ankle flexion (AA), and global sagittal angle (GSA). Spinal alignment and compensatory mechanisms were compared across correction groups using ANOVA and paired t-tests for all age categories.

Results: 116 ASD patients (66.4% female ) improved in SVA (71 to 41 mm ), TPA (27 to 22°), PT (26 to 25°), and PI-LL (19 to 11°) at 1Y (all p< 0.001). Optimal alignment was achieved for SVA in 30% of patients, 28% for TPA, 25% for PT and 19% for PI-LL. Nearly all lower body compensations increased gradually with age in individuals matching ideal pelvic tilt at 1 year. Knee flexion, ankle flexion and global sagittal alignment angle increased anteriorly with age in the match cohorts of SVA and TPA. Under-correction of PI-LL and PT was associated with statistically higher hip extension in individuals 40+, while only the oldest age group presented this trend for TPA.

Conclusions: Optimal alignment was achieved in 30% of patients for SVA, 28% for TPA, 25% of PT, and 19% for PI-LL. Significant increases in various compensations were associated with age progression in individuals matched for calculated radiographic ideals. Thus, optimal alignment following surgery requires increased adjustments by the aged ASD population. More research is needed to accurately link acceptable ranges of lower-body compensations to age, leading to the minimization of discomfort and the highest quality of life following surgical correction of ASD.