The Chiba Spinal System was developed for three-dimensional correction of scoliosis. The system consists of a 7-mm diameter smooth solid rod, closed and open hooks, and specially designed conical sleeves. The rod does not have ratchets or threads, thus minimizing stress concentrations. The closed and open hooks are attached to the rod using the conical sleeves. The sleeves have longitudinal slits permitting compression during insertion. The outrigger system with a torque wrench is used to correct the deformity in the frontal plane. When correcting lordosis with vertebral rotation, a sagittal correction device may be used. Fifty-two patients with idiopathic scoliosis were operated on with this system from 1986 through 1989. The average correction of the scoliosis was 58percnt;. For the 21 patients with thoracic lordosis less than 0deg;, the mean preoperative lordosis was minus;8deg;, which was corrected to plus;7deg;. The mean correction of the vertebral rotation was 24percnt;. Two patients complained of paresthesia of the thoracic region after operation, but this disappeared within 2 weeks. In 32 patients with more than 2 years' follow-up, the mean loss of correction was 3deg;. One case with instrumentation failure was noted.
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