Curve progression in Risser stage 0 or 1 patients after posterior spinal fusion for idiopathic scoliosis.

A retrospective review was performed to determine "crankshaft" prevalence in 86 immature patients who underwent posterior spinal fusion for idiopathic scoliosis. Tanner stage, chronologic age, bone age, and epiphyseal status were used as maturity indicators. Overall, 62 (72%) patients progressed < or = 10 degrees, 18 (21%) patients progressed 11-15 degrees, and six (7%) patients progressed > or = 16 degrees in the coronal plane. Tanner I patients with open triradiate cartilage had the highest rate of crankshaft occurrence; nine (75%) of 12 patients progressed >10 degrees (p < 0.05). Fifty-two percent of Tanner I, 26% of Tanner II, 11% of Tanner III, and no Tanner IV patients progressed >10 degrees (p < 0.05). Cobb angle increases of >10 degrees degrees occurred in 54% of patients with open triradiate cartilage (p < 0.05) and in 48% of patients with open capital femoral epiphyses (p < 0.05). Anterior and posterior spinal fusion should be considered in prepubertal (Tanner I) patients with open triradiate cartilage.