Adolescent Idiopathic Scoliosis Treated with Simultaneous Translation on Two Rods (ST2R) Involving Preoperative, Postoperative, and Follow-Up Evaluation by EOS 3D Imaging: A Case Series

Objective: To evaluate preoperative, postoperative, and follow-up of spinal and pelvic parameters using EOS 3D imaging in adolescent idiopathic scoliosis (AIS) patients who underwent simultaneous translation on two rods (ST2R) technique for corrective posterior spinal surgery. Methods: Five patients had surgical correction of Lenke type 1 or 2 AIS using the ST2R technique. The preoperative average Cobb angle was 72.4° ± 19.4. Low-dose standing biplanar radiographs were obtained to evaluate several spinal and pelvic parameters preoperatively (five patients), immediately postoperatively (four patients), and at follow-up (four patients). Three-dimensional reconstructions were performed (a total of 13 reconstructions). Results: The mean number of levels fused was 11.2° ± 2.0. The number of pedicle screws used for constructs averaged 19.2° ± 3.06 (1.75 density screw per vertebra). The Cobb angle values were significantly changed by the operation (75° ± 21 to 28° ± 7, p = 0.009), but no other parameters were altered. The maximal apical axial change at the junctional region was 32.8° (absolute value), and the minimal apical axial change at the apical region was 4.8° (absolute value). The intervertebral rotation difference in the axial plane was larger near the apical region (T8-T9), from 2.1° ± 2.7 to -14° ± 6.9, and smaller near the junctional region (T12-L1), from -2.6° ± 2.9 to -1.1° ± 8.4. Conclusion: This case series suggests that corrective posterior spinal surgery for AIS using ST2R can achieve both 3D correction of the spine and additional intervertebral axial rotation, with minimal deterioration during follow-up. Preoperative, postoperative, and follow-up evaluation can be accurately evaluated with EOS low-dose 3D imaging.