| Objectives. In this study, an intraoperative computed tomography (iCT) using a mobile scanner with integrated neuronavigation system (NNS) was applied for individualized treatment for congenital craniovertebral junction malformation (CVJM). The aim of this article is to demonstrate our concept and workflow of intraoperative CT integrated with NNS in microsurgery, to prove its efficiency and to explore the clinical application of iCT with integrated NNS for individualized treatment of congenital CVJM.Summary of background. The pathological changes of CVJM include congenital, developmental and acquired abnormalities. Congenital oseous deformities were mainly observed in Chinese and the syndrome with variety of pathological changes include platybasia, basilar invagination, atlantooccipital fusion, atlantoaxial dislocation, and other malformations such as cerebellar tonsillar herniation as well as syringomyelia.The primary aims of treatment are relief of compression at the cervicomedullary junction, arrangement the disrupted atlantoaxial complex and stabilization and the commonly used surgical strategies include anterior decompression and posterior stabilization. During the anterior decompressive procedures, congenital anomalies of form and segmentation, as well as rotational deformity, may distort the usual anatomical landmarks and may mislead the surgeon during the procedure. Besides, in some cases, the depth and narrowness of the operating field may also hinder sufficient exposure of the pathological lesion and restrict the extent of resection, especially in cases of the odontoid drifting away from the midline. During the posterior stabilization, because of the complex changes in geometry and bony structure in craniovertebral junction malformation, some patients have vertebral artery anomalies in CVJ and abnormal development of bony structures. Screw fixation procedures are obviously complex and dangerous for such patients. The traditional neuronavigation technology is based on preoperative image data and can not meet the real-time navigation. However the rapid advances in intraoperative imaging system, the emergence of iCT iMRI etc, have improved the quality of surgical interventions. The benefit of intraoperative imaging system in neurosurgery is clearly its ability to provide intraoperative updates for neuronavigation at any time during surgery. It helps to not only eliminate, or at least to minimize, the problem of discrepancy between the preoperative CT scans and true surgical anatomical relationships but also keep the navigative image consistent with the patient's anatomy ongoing surgery. Meantime, because iCT can provide high image-quality of bony structure compared to other imaging system, many neurosurgeons have gradually applied intraoperative CT in spinal surgery and skull base.Methods. A sliding gantry 40-slice CT scanner was installed in a preexisting operating room. the head was fixed at the end of the operating table using a radiolucent head clamp (Trumpf, Germany) and a radiolucent reference clamp for the NNS was attached. The intraoperatively acquired CT image data could be transferred immediately to the navigation system, and registered immediately and fully automatically. We present 42 cases that outline our experience with intraoperative CT scanning for navigated procedures from March 2009 to March 2010, among whom,22 were male, and 20 were female. The ages of these patients were 13-58 years (mean:32.5 years). If necessary, iCT can offer images used for updating the navigation system any time during surgery and allow the surgeon an intraoperative assessment of operation effect and complication.Results. iCT integrated with NNS was successfully used for anterior decompression and posterior stabilization in 42 patients. Anerior decompressive procedure was performed in 19cases:Among them,17 patients were underwent transoral odontoidectomy. With the extra help of iCT integrated with NNS, odontoidectomy via posterior midline approach, as well as transoral lateral mass resection was firstly performed for treating complex CVJM. Of the 19 cases, assessment of iCT scans obtained in 4 indicated further bone removal was required. The results revealed that the goal of osseous resection had been met. Neuronavigation was found to correlate well with the intra-operative findings and the recalibration was uneventful in all cases and had an accuracy of 1.6mm (1.6: 1.2-2.0); Screw and rod fixation procedures were performed in 23 cases:Seven patients underwent C1 lateral mass and C2 pedicle screw fixation. C1-C2 transarticular screw fixation were performed in six patients. Ten patients were treated with individualized occipitocervical fixation surgery. The results manifested that there were no vascular or neural complications but pedicle perforation were detected in two patients and corrected intraopertively. NNS was found to correlate well with the intra-operative findings and the recalibration was uneventful in all cases with an accuracy of 1.8 mm (1.8:0.6-2.2). All patients were clinically evaluated by Nurick grade criteria9 and concerning neurologic deficits 3-month after surgery.36 (85.7%) patients improved at least 1 Nurick grade, whereas the grade did not change in 6 (14.3%) patients.Conclusions. The image quality of iCT and navigation precision completely satisfied the treatment for CVJM. If necessary, iCT can offer images used for updating the navigation system any time during surgery, provided real-time navigation, greatly improved the success rate of surgical procedure, and effectively reduced the intraoperative complications. Meanwhile the combination of an iCT scanner with a neuronavigation system not only permits the intraoperative control of the position and depth of screws placement, verification of the extent of decompression, detection of complications, but also the reduction patient reoperation of possibilities and operation injury. Therefore, incorporation of iCT seems to be useful in spinal navigation procedures, especially in cases with complex CVJM.
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