Paper #39: Thoracic Volume Modeling of Growing Spine Interventions in Early-Onset Scoliosis

Abstract

objective measure of parasol rib deformity from spine X-rays; 2) compare efficacy of rib-based instrumentation (RBI) versus spine-based instrumentation (SBI) to improve parasol rib deformity and pulmonary function. Methods: A retrospective review of 2 multicenter databases was conducted to identify patients with hypotonic neuromuscular scoliosis treated by growth-friendly RBI or SBI with greater than 1 year follow-up. Preoperative and final spine X-rays were assessed for parasol rib collapse, as well as measures of spine asymmetry (Cobb and kyphosis) and thoracic deformity (RVA at apex scoliosis, thoracic, and hemithoracic widths at T6 and T12, maximum thoracic width, and pelvic inlet width). Multivariable analysis was performed on combinations of these measurements to identify the best descriptor of parasol rib deformity. Using this measurement, the ability of RBI versus SBI to correct and/or prevent parasol rib deformity was then compared. Assisted ventilation rating (AVR) before surgery and at final follow-up was also compared between the 2 groups. Results: A total of 23 patients treated with RBI (average age, 6.7 years; average follow-up, 3.3 years) were compared with 22 patients treated with SBI (average age, 7.7 years; average follow-up, 2.9 years). The equation Parasol Score 5 (T6 width convex hemithorax / T6 width concave hemithorax) Â (T6 thoracic width / T12 thoracic width) was the most accurate descriptor rib collapse (area under the curve 5 0.927 with receiver operating characteristic analysis). The parasol score was correlated with AVR. It did not significantly change over time for patients treated with SBI but it had a tendency to worsen for patients treated with RBI. The AVR did not change significantly in either group from before surgery to final follow-up. Cobb angle and kyphosis angle were better corrected using SBI. Conclusions: In children with hypotonic neuromuscular scoliosis, parasol rib deformity, measured by Parasol Score 5 (T6 width convex hemithorax / T6 width concave hemithorax) Â (T6 thoracic width / T12 thoracic width), did not improve after treatment with RBI or SBI. The AVR did not change significantly in either group.Introduction: Early-onset scoliosis commonly results in decreased thoracic volume and can cause severely compromised cardiopulmonary function. Yet little research has evaluated the effect of early-onset scoliosis treatments on thoracic volume. Thoracic volume may be estimated using computed tomographic (CT) scans or surrogate measures such as T1eS1 height, but neither is optimal because of safety concerns from recurrent radiation exposure from CT scans and limited accuracy of surrogates. The authors have developed a novel methodology to obtain patient-specific thoracic volumes from conventional orthogonal radiographs using opensource 3-dimensional (3D) graphics and animation software (Blender 2.71). The software allows manipulation of rib and vertebral elements to fit radiographs in coronal and sagittal planes, creating 3D thorax models. A validation study has demonst...