[Correction of stiff thoracic idiopathic adult scoliosis. Prediction from the traction radiograph]. / Réduction des scolioses idiopathiques raides de l'adulte.

ABSTRACT

PURPOSE OF THE STUDY The aim of this study was to determine the predictive value of the traction radiograph in adults with stiff curve (preoperative Cobb angle>60 degrees and reduction of less than 35% with traction) thoracic scoliosis. We wanted to compare this predictive value with that observed in reducible scoliosis. MATERIAL AND METHODS: A traction radiograph was obtained using a standard protocol with dynamometric control of the force applied. Patients with stiff scoliosis had 47 thoracic curves and 11 thoracolumbar curves (with primary anterior release for ten thoracic curves and eight thoracolumbar curves) and patients with reducible scoliosis had 56 thoracic curves. Cortre-Dubousset instrumentation was used for treatment in all patients. RESULTS: The postoperative Cobb angle for the stiff curves (without anterior release) was strongly correlated with the preoperative angle with traction (r=0.91; p<0.0001). The correlation between the postoperative Cobb angle and the preoperative Cobb angle without traction was less pronounced (r=0.86; p<0.0001). The traction radiographs were less predictive of the Cobb angle correction than the postoperative Cobb angle. The difference was 17.5+/-7 degrees , which corresponds to a supplementary gain in reduction after surgery. For the thoracic curves alone, the differences between the traction Cobb angle and the postoperative Cobb angle was 14.5 degrees for stiff curves and 6.5 degrees for reducible curves. Furthermore, the correlation between the Cobb angle with traction and the postoperative Cobb angle was stronger for stiff curve thoracic scoliosis (r=0.90) than reducible thoracic scoliosis (r=0.78). DISCUSSION AND CONCLUSION: The standard traction radiographs were highly predictive of postoperative reduction of stiff thoracic and thoracolumbar curves treated by segmental instrumentation. The postoperative result can thus be estimated with a margin of error of +/-7 degrees . For the stiff curves, the postoperative Cobb angle was 17.5 degrees on average less than predicted on the traction radiograph (on average 20% supplementary gain in reduction). This angle gain, which was greater for stiff than reducible curves, corresponds to the determining effect of release occurring with stiff curves. Finally, because of the stronger correlation between the traction Cobb angle and the postoperative Cobb angle for stiff curves, the predictive value of the traction radiograph is greater for stiff curves than for reducible curves. In conclusion, one of the contributions of the traction radiograph, which results from the predictability of the postoperative angle with a small margin of error, is to enable adequate prediction of the postoperative outcome for a given patient or a specific sub-group of patients, e.g. with or without anterior release.