Does the combined ventral derotation system (VDS) followed by Harrington instrumentation improve the vital capacity in patients with idiopathic double major curve pattern scoliosis? An analysis of 33 cases and review of the literature.

A young, homogenous population of 33 patients with idiopathic scoliosis of double major curve pattern (DMC), a mean thoracic curve of 70.6 degrees (standard deviation [SD] = 20.6), and a mean lumbar curve of 72.9 degrees (SD = 15), had a measurement of the vital capacity (VC) at rest before and at a minimum of one year after combined ventral derotation system (VDS). This was followed by Harrington instrumentation and fusion to evaluate the effect of scoliosis, kyphosis, and their surgical correction on VC at rest. A regression analysis showed that the VC was significantly lowered before operation to 69.6% of predicted value, whereas individuals with thoracic curvatures greater than 70 degrees had a lower VC. The surgical correction of the thoracic curve of 50.8% and the lumbar curve of 68.4% was permanent in the follow-up evaluation, and the functional improvement in postoperative VC was 4.36%, statistically not very significant. The time between the two evaluations did have a significant statistical correlation with the observed improvement of the VC. The longer the interval between the two evaluations, the better the improvement of the VC. The age of the patient at the time of the first (VDS) operation influences the changes of the observed VC, significantly favoring the younger patients. The number of the functional vertebral segments included by the spinal instrumentation and fusion does not improve the VC.(ABSTRACT TRUNCATED AT 250 WORDS)