The clinical impact of global coronal malalignment is underestimated in adult patients with thoracolumbar scoliosis

Study design: Retrospective review of multicenter adult spine deformity (ASD) database. Objectives: A recent publication demonstrated that the laterality of the coronal offset is a key parameter that directly impacts postoperative outcomes. The objective of this study is to analyze the relationship between global coronal malalignment (GCM) and functional outcomes in a North American population of ASD patients with no history of previous surgery. Summary of background data: The clinical impact of GCM in patients with ASD remains controversial. Methods: Primary patients were drawn from a multicenter database of ASD patients and categorized with the Qiu classification: Type A = GCM < 3 cm; Type B = GCM > 3 cm toward the concave side of the curve; and Type C = GCM > 3 cm toward the convex side. In addition to the classic radiographic parameter, the coronal truncal inclination was investigated in regard to the pelvic obliquity. Clinical outcomes, radiographic parameters, and demographics were compared across the three Qiu Types using analysis of variance. The analysis was repeated after propensity matching of the three types by age and sagittal alignment (PI–LL mismatch, pelvic tilt, and sagittal vertical axis). Results: 576 ASD patients (mean age 58.8 years) were included. Type B patients had significantly worse functional scores (Oswestry Disability Index, 36-item Short Form Survey physical component summary, and Scoliosis Research Society-22) and a more severe coronal deformity in terms of maximum Cobb angle, global coronal deformity angle, and coronal malalignment; they were also older (65.4 vs. 58.8 years, p = 0.004) and displayed more severe sagittal malalignment. Similar findings were observed after propensity matching. Conclusions: This study is the first to establish an association between functional outcomes and the severity of the coronal plane deformity in the setting of a specific coronal curve pattern in patients without previous surgery. Coronal malalignment significantly affects the health status of patients when the offset is greater than 3 cm in the direction of curve concavity. Level of evidence: III.