Study Design. Multicenter review of prospectively collected data.
Objective. To analyze the natural history of uninstrumented compensatory curves prospectively during a 5-year postoperative period in patients with selectively fused Lenke type 1C and 5C adolescent idiopathic scoliosis.
Summary of Background Data. After a selective fusion for 1C and 5C adolescent idiopathic scoliosis curve types, there is concern that uninstrumented compensatory curves will continue to progress over time. However, to date, there have been no studies using prospectively collected data beyond 2 years to determine the natural history of these uninstrumented compensatory curves.
Methods. Lenke 1C and 5C adolescent idiopathic scoliosis cases, prospectively collected from a multicenter study were analyzed. All patients underwent a selective fusion (1C only thoracic curve fused; 5C only thoracolumbar/lumbar curve fused). Preoperative, first-erect, 1-year, 2-year, and 5-year postoperative coronal, sagittal, and axial (Perdriolle) radiographical outcomes were compared using repeated measures analysis of variance with Bonferroni post hoc comparisons (P < 0.05).
Results. Twenty-four selectively fused Lenke 1C curves and 21 selectively fused Lenke 5C curves were reviewed. Preoperative compensatory curve Cobb angles were 40° ± 6° and 25° ± 9°, respectively. In Lenke 1C curves, the uninstrumented compensatory lumbar curves were corrected by 32% ± 16% at first erect, 44% ± 17% correction at 1 year, 38% ± 15% correction at 2 years, and 39% ± 19% at 5 years. In Lenke 5C curves, the uninstrumented compensatory thoracic curves were corrected by a mean of 37% ± 29% at first erect, 42% ± 29% at 1 year, 37% ± 29% at 2 years, and 30% ± 23% at 5 years. The sagittal and axial measures of the compensatory curves remained stable during the postoperative period.
Conclusion. In Lenke 1C and 5C adolescent idiopathic scoliosis deformity patterns fused selectively, the uninstrumented compensatory curves adjust to match the instrumented primary curve and do not seem to progress between 1 and 5 years postoperatively.