Cotrel-Dubousset instrumentation in idiopathic scoliosis

Although well accepted in the patient undergoing Harrington instrumentation, the validity of King's criteria in patients undergoing correction of idiopathic scoliosis using the Cotrel-Dubousset system has been questioned. The cases of 64 patients with Type II (N = 40) and Type III (N = 24) idiopathic scoliosis treated with Cotrel-Dubousset instrumentation were reviewed. The average curve correction for Type II spinal curvature was 69.4% after surgery and 57.8% at follow-up examination. Decompensation was evident in 40% of the curves that were fused beyond the stable vertebra. However, the patients were only aware of their trunk decompensation if it was larger than 10 mm, and this was found in 35% of the patients. Decompensation occurred in 60% of those that were fused short of or to the stable vertebra. Only 42% of this group were aware of their decompensation. Decompensation was measured to the left of the spine in all patients. The difference between the subgroups based on the choice of distal fusion levels was not statistically significant (P greater than 0.05). The average curve correction for Type III scoliosis was 62.9% after surgery and 54.6% at the time of follow-up examination. There was no correlation between caudal fusion levels and the incidence of decompensation with Type III curves. It was concluded that there was no statistically significant relationship between choice of distal fusion level and the amount of decompensation, thereby indicating that the use of King's criteria for the selection of fusion levels in patients undergoing correction of idiopathic scoliosis using the Cotrel-Dubousset instrumentation may not be useful.