Predictors of flatback deformity during brace treatment for adolescent idiopathic scoliosis: influence of spinopelvic parameters

Abstract

Introduction: The effect of bracing on the sagittal spinopelvic alignment in adolescent idiopathic scoliosis is unknown. The objective of this study was to determine the influence of pelvic parameters on tendency of patients with adolescent idiopathic scoliosis to develop sagittal alignment changes after brace treatment and its effect on quality of life (QoL) outcomes. Methods: In total, 265 subjects under Boston bracing were recruited between December 2008 and 2013. Posteroanterior and lateral radiographs were obtained before and after completion of bracing with 2-year post-brace follow-up. Multiple regression analyses utilising various parameters of coronal and sagittal parameters to determine sagittal parameter changes was performed and the refined Scoliosis Research Society 22-item questionnaire (SRS-22r) studied QoL changes. Odds ratios (ORs) were generated. Results: Reduced T5-12 kyphosis (mean -4.3° [standard deviation (SD)=8.2]; p<0.001), maximum thoracic kyphosis (mean -4.3° [SD=9.3]; p<0.001), and lumbar lordosis (mean -5.6° [SD=12.0]; p<0.001) were observed after bracing treatment. Increasing pre-brace maximum kyphosis (OR=1.133) and lumbar lordosis (OR=0.92) was associated with post-bracing hypokyphotic change. Pre-brace sagittal vertical axis (OR=0.975), pre-brace sacral slope (OR=1.127), pre-brace pelvic tilt (OR=0.940), and change in maximum thoracic kyphosis (OR=0.878) were predictors for lumbar hyperlordotic changes. These sagittal parameter changes did not lead to worsened SRS-22r scores. Conclusion: Brace treatment leads to flatback deformity with thoracic hypokyphosis and lumbar hypolordosis. Changes in the thoracic spine are associated with similar changes in the lumbar spine. Increased sacral slope, reduced pelvic tilt and pelvic incidence are associated with reduced lordosis in the lumbar spine after bracing, without worsening of QoL.