Abstract
Introduction
Pedicular screw has become the most popular device in spine surgeries, especially in the treatment of adolescent idiopathic scoliosis (AIS). They lead to better curve correction in coronal, sagittal, and rotational planes, shorter constructions, and better pulmonary function compared with other devices. Despite those advantages, this technique is potentially dangerous. Intraoperative neuromonitoring is frequently used to detect the misplacement of screw and reverse possible neurological complications. The aim of this study is to analyze the relation between electromyographic records of the inserted screws and their position by postoperative CT scan.
Materials and Methods
This is an observational prospective study which includes 16 patients undergoing AIS surgical correction between March and December 2013 at one institution. All procedures were monitored with electromyography (EMG) of the inserted screws and the stimulation threshold of each screw was recorded. Those values were compared with the position of the screws, based on the postoperative CT scan, according to the classification proposed by Abul-Kasim et al.
Results
Included were 16 patients with 281 pedicles instrumented (17.5 per patient). No patient presented with any neurological deficit or complaints after surgery. In the axial plane, 195 screws were ideally inserted in the pedicles (69.4%) and in the sagittal plane, 226 screws were ideally inserted in the pedicles (80.4%). Considering both the axial and sagittal planes, 166 (59.1%) did not breach any pedicular cortical wall. No statistical correlation was observed between EMG threshold and screw position in the axial CT-scan position, as in the medial or lateral misplacement (p = 0.425), but statistical significant correlation was observed between EMG threshold and screw position in the sagittal CT-scan position, with smaller results when the screws were misplaced inferiorly, closer to the foraminal roots (p = 0.017).
Conclusion
Pedicular screws were safe in this AIS surgery series, even with misplaced position. EMG monitoring has shown to be efficient in identifying misplacement of pedicle screws in the sagittal plane (inferior foraminal perforation) but not so much in identifying the axial plane misplacement (lateral or medial).