• Peter G Passias, Lara Passfall, Tyler K Williamson, Andrew J Schoenfeld, Stephane Owusu-Sarpong, Ekamjeet Dhillon, Oscar Krol, Nicholas A Kummer, Peter Tretiakov, Bailey Imbo, Rachel Joujon-Roche, Kevin Moattari, Jordan Lebovic, Shaleen Vira, Bassel Diebo, Justin S Smith, Paul Park, Praveen Mummaneni, Saman Shabani, Dean Chou, Renaud Lafage, and Virginie Lafage.
• Division of Spinal Surgery, Departments of Orthopaedic and Neurosurgery, New York University Langone Medical Center, New York Spine Institute, New York, New York.
• Spine. 2022 Jul 15; 47 (14): 9951002995-1002.

Summary Of Background DataThe impact of not achieving ideal realignment in the global alignment and proportion (GAP) score in adult spinal deformity (ASD) correction on clinical outcomes is understudied at present.ObjectiveTo identify the clinical impact of failing to achieve GAP proportionality in ASD surgery.Study DesignRetrospective cohort.MethodsOperative ASD patients with fusion to S1/pelvis and with pre-(BL) and 2-year (2Y) data were included. Patients were assessed for matching their 6-week (6W) age-adjusted alignment goals. 1 Patients were stratified by age-adjusted match at 6W postoperatively (Matched) and 6W GAP proportionality (proportioned: GAP-P; moderately disproportioned: GAP-MD; severely disproportioned: GAP-SD). Groups were assessed for differences in demographics, surgical factors, radiographic parameters, and complications occurring by 2Y. Multivariable logistic regression was used to assess independent effects of not achieving GAP proportionality on postoperative outcomes for Matched and Unmatched patients.ResultsIncluded: One hundred twenty three ASD patients. At baseline, 39.8% were GAP-SD, and 12.2% GAP-SD at 6W. Of 123 patients, 51.2% (n =63) had more than or equal to one match at 6W. GAP-SD rates did not differ by being Matched or Unmatched ( P = 0.945). GAP-SD/Unmatched patients had higher rates of reoperation, implant failure, and PJF by 2Y postop (all P <0.05). Regressions controlling for age at BL, levels fused, and CCI, revealed 6W GAP-SD/Unmatched patients had higher odds of reoperation (OR: 54 [3.2-899.9]; P =0.005), implant failure (OR: 6.9 [1.1-46.1]; P =0.045), and PJF (OR: 30.1 [1.4-662.6]; P =0.031). Compared to GAP-P or GAP-MD patients, GAP-SD/ Matched patients did not have higher rates of reoperation, implant failure, or junctional failure (all P >0.05). The regression results for both Matched and Unmatched cohorts were consistent when proportionality was substituted by the continuous GAP score.ConclusionIn ASD patients who meet age-adjusted realignment goals, GAP proportionality does not significantly alter complication rates. However, GAP proportionality remains an important consideration in patients with sub-optimal age- adjusted alignment. In these cases, severe global disproportion is associated with higher rates of reoperation, implant failure, rod fracture, and junctional failure.Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.

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