• Yong Shen, Zeeshan M Sardar, Matan Malka, Justin Reyes, Prerana Katiyar, Fthimnir Hassan, Jean-Charles Le Huec, Stephane Bourret, Kazuhiro Hasegawa, Hee Kit Wong, Gabriel Liu, Dennis HeyHwee WengHWDepartment of Orthopedic Surgery, National University Hospital (Singapore), Singapore, Singapore., Hend Riahi, Michael Kelly, Joseph M Lombardi, Lawrence G Lenke, and Multi-Ethnic Alignment Normative Study Group.
• Department of Orthopaedic Surgery, Columbia University Irving Medical Center, The Spine Hospital at New York Presbyterian, New York, NY.
• Spine. 2024 Jul 15; 49 (14): 979989979-989.

Study DesignMulti-Ethnic Alignment Normative Study (MEANS) cohort: prospective, cross-sectional, multicenter.ObjectiveTo analyze the distribution of GAP scores in the MEANS cohort and compare the spinal shape via stratification by GAP alignment category, age, and country.Summary Of Background DataThe GAP score has been used to categorize spinal morphology and prognosticate adult spinal deformity surgical outcomes and mechanical complications. We analyzed a large, multiethnic, asymptomatic cohort to assess the distribution of GAP scores.MethodsFour hundred sixty-seven healthy volunteers without spinal disorders were recruited in five countries. Sagittal radiographic parameters were measured via the EOS imaging system. The GAP total and constituent factor scores were calculated for each patient. Kruskal-Wallis rank sum test was performed to compare variables across groups, followed by the post hoc Games-Howell test. Fisher exact test was used to compare categorical variables. The significance level was set to P <0.05.ResultsIn the MEANS cohort, 13.7% (64/467) of volunteers were ≥60 years old, and 86.3% (403/467) were <60 years old. 76.9% (359/467) was proportioned, 19.5% (91/467) was moderately disproportioned, and 3.6% (17/467) was severely disproportioned. There was no significant difference in the frequency of proportioned, moderately, or severely disproportioned GAP between subjects from different countries ( P =0.060). Those with severely disproportioned GAP alignment were on average 14.5 years older ( P =0.016), had 23.1° lower magnitude lumbar lordosis (LL) ( P <0.001), 14.2° higher pelvic tilt ( P <0.001), 13.3° lower sacral slope ( P <0.001), and 24.1° higher pelvic-incidence (PI)-LL mismatch ( P <0.001), 18.2° higher global tilt ( P <0.001) than those with proportioned GAP; thoracic kyphosis and PI were not significantly different ( P >0.05).ConclusionsThe GAP system applies to a large, multiethnic, asymptomatic cohort. Spinal alignment should be considered on a spectrum, as 19.5% of the asymptomatic volunteers were classified as moderately disproportioned and 3.6% severely disproportioned. Radiographic malalignment does not always indicate symptoms or pathology.Level Of Evidence3.Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.

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