Accuracy of Thoracic Vertebral Screw Insertion in Adolescent Idiopathic Scoliosis

Abstract

A cross-sectional study with axial computed tomography (CT) to compare the accuracy of vertebral screw insertion in the thoracic spine for adolescent idiopathic scoliosis (AIS) between the thoracoscopic and the mini-open thoracotomy approach. To evaluate the safety of vertebral screw placement in anterior instrumentation for thoracic AIS. Thoracoscopic anterior instrumentation has been used with good results for AIS. It is technically demanding especially for the insertion of vertebral screws. The important issue of whether the screws inserted thoracoscopically is as accurate and safe as those inserted through thoracotomy approach has not been well studied. Thirty-one patients with thoracic AIS receiving thoracoscopic or mini-open thoracotomy anterior instrumentation were included in this study. They were divided into Group A and B, respectively. Postoperative sequential CT scanning on the thoracic vertebral screws was carried out. The relative position between screws and the spinal canal, the aorta, and the bicortical purchase were analyzed with CT images. The percentage of screws in good position was defined and further analyzed. Seventy-three and 162 thoracic vertebral screws were inserted in 10 patients in Group A and 21 patients in Group B, respectively. Eighty-nine percent of screw tips in Group A and 80.2% in Group B were distant from the aorta, 89.0% and 87.0% of screws achieved bicortical purchase in Group A and B, respectively. No significant difference was found in all thoracic levels including the upper thoracic, periapical, or lower thoracic vertebrae. Seventy-four percent and 66.7% of screws were in good positions in Group A and B, respectively and there was no statistically significant difference between the 2 groups. The vertebral screws inserted through thoracoscopic approach were as accurate as those inserted through a mini-open thoracotomy approach. The accuracy could be enhanced by using screws with smaller increments, with special attention to the possible migration of aorta with anterior spinal instrumentation.