External Validation of the Global Alignment and Proportion Score as Prognostic Tool for Corrective Surgery in Adult Spinal Deformity: A Systematic Review and Meta-Analysis

Julian L Gendreau; Andrew Nguyen; Nolan J Brown; Zach Pennington; Alexander M Lopez; Neal Patel; Sachiv Chakravarti; Cathleen Kuo; Gaston Camino-Willhuber; Stephen Albano; Joseph A Osorio; Michael Y Oh; Martin H Pham

doi:10.1016/j.wneu.2023.06.109

External Validation of the Global Alignment and Proportion Score as Prognostic Tool for Corrective Surgery in Adult Spinal Deformity: A Systematic Review and Meta-Analysis

World Neurosurg. 2023 Jun 30:S1878-8750(23)00893-8. doi: 10.1016/j.wneu.2023.06.109. Online ahead of print.

Authors

Affiliations

¹ Department of Biomedical Engineering, Johns Hopkins Whiting School of Engineering, Baltimore, Maryland, USA.
² College of Medicine, University of Florida, Gainesville, Florida, USA.
³ Department of Neurosurgery, University of California Irvine, Orange, California, USA. Electronic address: nolanb@hs.uci.edu.
⁴ Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, USA.
⁵ Department of Neurosurgery, University of California Irvine, Orange, California, USA.
⁶ School of Medicine, Mercer University, Savannah, Georgia, USA; Department of Neurosurgery, University of California San Diego, La Jolla, California, USA.
⁷ Department of Neurosurgery, University of California San Diego, La Jolla, California, USA.

PMID: 37393993
DOI: 10.1016/j.wneu.2023.06.109

Abstract

Background: Since its proposal, the Global Alignment and Proportion (GAP) score has been the topic of several external validation studies, which have yielded conflicting results. Given the lack of consensus regarding this prognostic tool, the authors aim to assess the accuracy of GAP scores for predicting mechanical complications following adult spinal deformity correction surgery.

Methods: A systematic search was performed using PubMed, Embase, and Cochrane Library for the purpose of identifying all studies evaluating the GAP score as a predictive tool for mechanical complications. GAP scores were pooled using a random-effects model to compare patients reporting mechanical complications after surgery versus those reporting no complications. Where receiver operator curves were provided, the area under the curve (AUC) was pooled.

Results: A total of 15 studies featuring 2092 patients were selected for inclusion. Qualitative analysis using Newcastle-Ottawa criteria revealed moderate quality among all included studies (5.99/9). With respect to sex, the cohort was predominantly female (82%). The pooled mean age among all patients in the cohort was 58.55 years, with a mean follow-up of 33.86 months after surgery. Upon pooled analysis, we found that mechanical complications were associated with higher mean GAP scores, albeit minimal (mean difference = 0.571 [ 95% confidence interval: 0.163-0.979]; P = 0.006, n = 864). Additionally, age (P = 0.136, n = 202), fusion levels (P = 0.207, n = 358), and body mass index (P = 0.616, n = 350) were unassociated with mechanical complications. Pooled AUC revealed poor discrimination overall (AUC = 0.69; n = 1206).

Conclusions: GAP scores may have a minimal-to-moderate predictive capability for mechanical complications associated with adult spinal deformity correction.

Keywords: Deformity; Fusion; Global alignment and proportion score; Mechanical failure; Pedicle subtraction osteotomy; Realignment; Scoliosis; Spine.