Anterior Correction of Thoracic Scoliosis With Kaneda Anterior Spinal System

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Abstract
Study Design. Analysis of the clinical results of 20 patients with thoracic scoliosis treated by anterior procedure with Kaneda anterior spinal system. Objectives. To evaluate the efficacy of the anterior surgical correction procedure with a new anterior instrumentation in thoracic scoliosis. Summary of Background Data. Posterior correction and fusion with posterior instrumentation has been a main component of the surgical management of thoracic scoliosis. However, to the best of the authors' knowledge, no clinical results of anterior instrumentation surgery for thoracic scoliosis have been published in the English literature. Methods. Anterior correction and fusion using Kaneda anterior spinal system was performed in 20 patients with thoracic scoliosis (3 patients with King Type II curve, 13 with Type III, and 4 with Type IV). The average follow-up was 3 years, with a range of 2 years, 3 months to 4 years, 1 month. There were 18 patients with idiopathic scoliosis (13 adolescents and 5 adults) and 2 patients with a single thoracic curve caused by other etiologies. All patients had correction of scoliosis by fusion within the major thoracic curve. Radiographic evaluations were performed to analyze frontal, sagittal, and rotational deformities of the spine. Results. The average correction rate of scoliosis was 71%. Above the instrumented levels, the correction rate was 75%. Preoperative kyphosis of the instrumented levels of 7° was corrected to 14° of kyphosis. The trunk shift was improved from 17 mm before surgery to 9 mm at final follow-up evaluation. The average improvement of the tilt-angle in the lower end vertebra of fusion was 81%, and was 83% in the stable vertebra. Apical vertebral rotation showed correction rate of 15% in patients without performing resection of the rib head joints and rod rotation maneuver (n = 6). However, the correction rate was improved to 58% after introduction of the technique discussed (n = 14). The angle of tangential rib deformity (rib hump) showed a correction rate of 50%. There was 1.2° of frontal plane and 1.0° of sagittal plane correction loss within the instrumented area at final follow-up evaluation. At final follow-up, nonunion at the uppermost segment of the fusion range developed in one patient, and decompensation in the lumbar spine was observed in one patient with Type II curve. Conclusions. Anterior correction with Kaneda anterior spinal system provides excellent correction of the frontal curvature and sagittal alignment by fusing within the range of the major curve, without a significant loss of correction and implant failure. Rigid rotational deformity of the thoracic scoliosis is effectively corrected by resection of the rib head joints and rod rotation maneuver. However, too much correction of the thoracic curve should be avoided, to prevent decompensation of the lumbar curve, especially in Type II curves.