Antagonistic role of vertebral translation against vertebral rotation in the spontaneous post-operative modulation of the anterior chest wall contour in thoracic idiopathic scoliosis.
Study Design. A computed tomography (CT) study.Objective. To identify the best scoliotic deformity components that show impact upon the spontaneous post-operative modulation of the deformed anterior chest wall contour in right-convex thoracic adolescent idiopathic scoliosis (AIS).Summary of Background Data. Spontaneous post-operative aggravation of the anterior concave costal projection was a common occurrence in AIS, yet the risk factors that effectively bridged the gap between what the surgeons did in the interior and how the rib cages reacted on the exterior were still open to debate.Methods. Pre and post-operative CT scans of 77 right thoracic AIS patients were retrieved and analyzed. According to the post-operative variation of anterior chest wall angle (CWA), the patients were divided into two groups with either aggravated or improved CWA. Multiple scoliotic deformity parameters and their surgical correction rates were evaluated, correlated and then compared between the two groups. Moreover, patients with apex located at T9 were isolated and evaluated independently. A logistic regression analysis was used to figure out the independent predictors of the spontaneous post-operative modulation of the anterior chest wall contour.Results. The surgical correction rate of Cobb angle (supine), the RAsag angle, the RAml angle, the MLdev angle, the posterior hemithorax ratio (PHR), the vertebral translation (VT) and the thoracic rotation (TR) averaged 64.6%, 19.5%, 30.8%, 39.2%, 15.0%, 41.2% and 28.7%, respectively. Ratio of aggravated anterior chest wall contour was the highest at the T7 apex group(84.6%) as compared with T8 apex group(47.1%), T9 apex group(19.5%) and T10 apex group(0.0%). The pre-operative CWA was significantly lower in the aggravated CWA group when compared with the improved group (2.1±1.8° vs. 6.6±2.4°, p<0.001). Besides, in the aggravated CWA group, significantly greater surgical correction of VT and lesser correction of RAsag angle were demonstrated when compared with the improved CWA group (VT: 53.0% vs. 34.8%, p = 0.001; RAsag: 2.5% vs. 28.7%, p = 0.000). In the T9 subgroup, remarkably different correction rate of VT and RAsag were similarly observed (VT: 54.9% vs. 35.3%, p = 0.046; RAsag: 4.9% vs. 23.5%, p = 0.034). In terms of other deformity parameters, no significantly different correction rate was consistently detected. In the logistic regression analysis, apex location, CWA and correction rate of RAsag were demonstrated to be independent factors predictive of the alteration of chest wall contour.Conclusion. In addition to the smaller preoperative CWA and higher apex location, lesser correction of vertebral rotation, if accompanied by great surgical correction of apical vertebral translation, could also largely result in a poor post-operative anterior chest wall contour.