Maintenance of Thoracic Kyphosis in the 3D Correction of Thoracic Adolescent Idiopathic Scoliosis Using Direct Vertebral Derotation

ObjectivesThrough a review of prospectively collected data, we sought to analyze the outcomes related to 3-dimensional correction of adolescent idiopathic scoliosis (AIS) after posterior spinal fusion (PSF) and instrumentation using an aggressive combination of correction strategies.Background SummaryNew techniques have been used to address sagittal plane deformity while maximizing coronal and axial correction, including Ponte osteotomy, differential rod over-contouring, and direct vertebral rotation with uniplanar screws.MethodsThis is a consecutive single-center series of AIS patients with thoracic curves (Lenke 1 and 2) with 2-year follow-up who underwent PSF and instrumentation with the use of the following correction strategies: segmental uniplanar screws, ultra high-strength 5.5 mm steel rods, aggressive differential rod contouring, periapical Ponte osteotomies, and segmental direct vertebral derotation. Scoliosis Research Society (SRS)-22, radiographic and clinical parameters were evaluated at preoperative and 2-year time points.ResultsTwenty-six patients were included (mean age 13.6 ± 1.5 years). Preoperative thoracic Cobb measured 52 ± 9°, which improved to 17 ± 4° at 2-year follow-up, resulting in 68 ± 9% correction. The average thoracic kyphosis from T5-T12 did not significantly change (21 ± 10° to 22 ± 5° at 2 years); however, in patients with kyphosis less than 20° preoperatively (avg. 13 ± 5°) kyphosis increased significantly at 2-year follow-up (avg. 20 ± 4°, p<.05). Preoperatively, axial rotation was more than 13° in 21 of 26 cases. At 2-year follow-up, axial rotation remained more than 13° in 4 of 26 cases (p<.01). Rib hump prominence was 17 ± 5° preoperatively, which improved significantly to 10 ± 4° at 2-year follow-up (p<.05). Postoperative SRS domain scores significantly improved in pain (4.3 to 4.7), self-image (3.7 to 4.3), and satisfaction (3.3 to 4.6) (p<.05).ConclusionA high degree of coronal correction can be achieved in association with vertebral derotation without sacrificing sagittal plane alignment. High-strength rods aggressively bent to create kyphosis allow both restoration of kyphosis and axial plane derotation in thoracic idiopathic scoliosis.