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Objective This study aimed to evaluate the accuracy of screw placement and clinical outcomes in patients undergoing occipitocervical fusion. Methods Patients who underwent occipitocervical fusion with O-arm–based navigation were retrospectively reviewed between January 2015 and December 2017. The patients' characteristics, clinical and radiographic outcomes, and surgical complications were recorded and analyzed. Cervical screw insertion accuracy was evaluated using the Richter scale. Results Thirty consecutive patients (11 male and 19 female) with an average treatment age of 40.03 ± 15.19 years were studied. The most common cause was atlantoaxial instability combined with Chiari malformation (63.33%). Weakness (76.67%) and paresthesia (70.00%) were the most common symptoms. Eighty-six occipital and 139 cervical screws were placed using an O-arm–assisted navigation system. In total, 130 (93.53%) cervical screws were graded as group A and 9 (6.47%) as group B. The optimal accuracy rate was 88.41% (61 of 69 screws) in the first 15 patients and 98.57% (69 of 70 screws) in the subsequent 15 patients. The mean follow-up time was 7.50 ± 5.70 months. The mean Japanese Orthopedic Association scores were 13.30 ± 2.41 preoperatively and 15.30 ± 1.60 at final follow-up ( P < 0.001), and the mean recovery rate in the Japanese Orthopedic Association score was 53.26 ± 33.82%. Clinical improvement was seen in 25 patients (83.33%), whereas no change was observed in 5 patients (16.67%). The overall complication rate was 6.67% (2/30), with 1 intraoperative vertebral artery injury and 1 postoperative screw loosening. Conclusion Occipitocervical fusion with O-arm–based navigation is effective and safe for treating instability of the craniovertebral junction. Intraoperative navigation can help surgeons insert screws accurately. [ABSTRACT FROM AUTHOR]

Objective We sought to study the application of precise intraoperative localization of small intramedullary spinal cord tumors. Methods From November 2015 to August 2017, 5 patients with small intramedullary spinal cord tumors were arranged in this group. By using the O-arm image system, we acquired the intraoperative computed tomography images of all patients and sent them to the Stealth navigation system. Medtronic Synergy Cranial software was used to complete the image fusion with preoperative magnetic resonance images, and the fused images were used to localize the intramedullary spinal cord tumors by the navigation system. The navigation errors were evaluated by measuring the maximum distance between the end of the tumor in sagittal magnetic resonance imaging and its real position. Results Five patients accomplished the multimodal image fusion, and we successfully completed the image-guided surgeries. The mean diameter of tumors was 12.2 ± 3.1 mm in sagittal magnetic resonance imaging, and the mean incision length was 12.7 ± 3.3 mm. The time of image processing was between 13 minutes and 17 minutes, and the mean value was 15 ± 1.6 minutes. The navigation error was between 0.9 mm and 1.5 mm, and the mean value was 1.2 ± 0.2 mm. Conclusions The application of the multimodal image fusion combined with intraoperative O-arm image navigation system can be used to localize small intramedullary tumors. Highlights • By using the O-arm and Stealth navigation system, we completed the image fusion with preoperative MRI. • The fused images were used to localize the intramedullary spinal cord tumors aided by the navigation system. • Application of the multimodal image fusion combined with intraoperative O-arm image navigation system was completed. • Our results confirmed this technique's clinical feasibility and value. [ABSTRACT FROM AUTHOR]