Anterior Reconstruction with the Dual-Rod Systems in Total 63 Patients with Idiopathic Thoracolumbar Scoliosis - Results of the Minimum Four Years Follow-Up**

• (d - DePuy Japan)

Purpose: This study was designed to survey the relatively long-term results of the patients with idiopathic thoracolumbar scoliosis, which was treated with the anterior dual rod systems.

Materials and Methods: The anterior reconstruction with the dual-rod system of idiopathic thoracolumbar scoliosis was started at first in 1988 in our hospital. The system used between 1988 and 1990 was the threaded-rod and nut system. In this study, the first group of 26 patients was treated with Kaneda side-opened screw /dual-rod system: (not approved by FDA) between 1990 and 1995. And the second group of 37 patients was treated with KASS (the top-opened screw and smooth rod: approved by FDA in 1995) between 1995 and 1998. All of these patients have been followed-up. The average follow-up terms were 8 years and 6 months in the first group, and 5 years and 7 months with minimum 4 years in the second group. The fusion areas did not exceed the major curve in any patients. Shorter fusion was conducted in 8 of 26 patients in the first group and in 19 of 37 in the second group. The extra-pleural and retroperitoneal approach was used in all patients.

Results: There were no pseudarthrosis, no vascular and neurological complications, no instrumentation failures and no infection. As for correction of the frontal curvatures , the upper compensatory curves; 32 (15 to 42)º preoperatively, 17(4 to 32) º at the follow-up and the spontaneous correction rate was 47%. The major curves were 54(47 to 75)º preoperatively, 9º at the follow-up and the correction rate was 83%. The instrumented levels were 43(38-73)º preoperatively, 5(1-12)º at the follow-up, and the correction rate was 90%. Corrections of the sagittal curvatures; the average curves in the instrumented levels were preoperatively 7º of kyphosis and at the follow-up 9º of lordosis. The lower lumbar segments beneath the fusion was 51º of hyperlordosis preoperatively and 34º of normal lordosis at the follow-up. Correction of the trunk shift at the apex was 25mm preoperatively, 4mm at the follow-up and the correction rate was 84%. The lower end vertebra tilt was 36º preoperatively; 1º at the follow-up and the correction rate was 97%. In the shorter fusion group, these were 29º, 5º and 83%. Correction of the apical vertebral rotation measured on CT was 35º preoperatively; 5º at the follow-up and the correction rate was 86%. The average losses of correction at the instrumented levels during follow-up were 1.5º each on the frontal curvatures and on the sagittal curvatures. There was no difference in these data between the first group and the second group.

Discussion and Conclusion: These relative long-term follow-up results shows that the correction of the thoracolumbar scoliosis with the anterior dual-rod systems has been maintained three dimensionally with better correction and solid fusion. Shorter fusion and no invasion to the lumbar muscles have provided supple lumbar spine motion.

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