The Effect of Dual Growing Rod Instrumentation on the Apical Vertebral Rotation in Early-onset Idiopathic Scoliosis

Background and Aim: Treating progressive early-onset idiopathic scoliosis is challenging. Surgical treatment is indicated in patients whose curves progress despite nonsurgical treatment. Dual growing rod (DGR) technique allows control of the curve while permitting continued spine growth and pulmonary development. Correction in coronal and sagittal planes with this technique has demonstrated both clinically and radiologically in previous studies. It is shown that apical vertebra rotation (AVR) increases with single-rod instrumentation technique. The effect of DGR technique on AVR has not been investigated, yet. The aim of our study was to assess the impact of DGR instrumentation technique on the apical AVR. Methods: The study included 12 patients with early-onset idiopathic scoliosis treated with DGR technique. Mean follow-up was 74 months. Vertebral rotation angle in the apex of the curve in preindex surgery was measured with Perdriolle and Stokes' method. As pedicle shadows were masked by rods post-operatively, vertebral rotation angle of same levels in final computed tomography scans was measured using Aaro and Dahlborn's method. Standing anterior-posterior and lateral x-rays were measured for assesing Cobb angle, thoracic kyphosis, lumbar lordosis in coronal and sagittal planes preoperatively, postoperatively, and at the time of final follow-up. Results: Mean age at the time of growing rod instrumentation was 69 (36 to 108) months. Mean follow-up was 77 (57 to 91) months. The mean preoperative AVR angle was 27 (18 to 38) degrees and decreased to 18 (4 to 35) degrees at the time of final follow-up. The difference between preoperative and final follow-up AVR was found to be significant (P = 0.003). Preoperative mean Cobb angles were found to be 63.8 (40 to 98) degrees, 25 (10 to 46) degrees (60%) (P < 0.001) after index surgery and at the time of final follow-up 20 (7 to 42) degrees (66%) (P < 0.001). The mean thoracic kyphosis and lumbar lordosis angles were found to be 46 (20 to 90) and 34 (16 to 80) degrees at preoperative stage; 25 (12 to 50) and 22 (8 to 35) degrees at immediate postoperative stage; and 38 (16 to 83) and 37 (16 to 60) degrees at the time of final follow-up. Conclusions: This study proves that the DGR technique has no negative effect on transverse plane deformities. When compared with preoperative values, correction of the AVR during the treatment period suggests that DGR is effective in controlling the coronal and sagittal planes along with transverse plane deformities. Further studies are needed to prove that DGR treatment definitely prevents progression of AVR.