Crankshaft phenomenon in congenital scoliosis: a preliminary report.

To determine whether or not the crankshaft phenomenon occurs after spinal fusion in patients with congenital scoliosis, we reviewed 23 curves in 21 patients who were operated on before age 10 years. Operative procedures consisted of various kinds of posterior fusions as well as anterior and posterior hemiepiphyseodeses. Seven of the 23 curves progressed greater than or equal to 10 degrees during the course of follow-up, and six of the seven demonstrated increased rotation and were believed to demonstrate the crankshaft phenomenon. No spines rotated without curve progression. The only statistically predictive factor was length of follow-up. No curve that underwent anterior and posterior hemiepiphyseodeses demonstrated the crankshaft phenomenon. Although the crankshaft phenomenon can occur in young patients operatively treated for congenital scoliosis, apparently it can be prevented by anterior fusion.