The influence of contoured distraction rods on thoracic sagittal curves

The influence of sagittally contoured rods on thoracic sagittal curves was studied in 19 patients who underwent fusion and instrumentation for right thoracic idiopathic scoliosis. Group I included 13 patients who underwent fusions with contoured rods and no releases. Group II included six patients who had anterior or posterior spinal release procedures in addition to contoured rods and fusion. Harrington distraction rods were contoured to either increase, decrease, or maintain preoperative thoracic kyphosis. The number of kyphotic curves that changed in the intended direction, the degree of change, the relationship of the rod contour to the patient's postoperative kyphosis, and the postoperative rod contour were compared. Thirty-eight percent of the curves in group I underwent change in the unintended direction while 62% of group I curves and 100% of group II curves changed in the intended direction. The curves that demonstrated intended change exhibited variability in the relationship of the postoperative kyphosis to the rod contour. In no case did the postoperative rod kyphosis exceed the measured intraoperative rod kyphosis.