gms | German Medical Science

Objective: The intraoperative use of three-dimensional fluoroscopy considerably improves the information available after pedicle screw placement. We report our experience with the Iso-C3D fluoroscopic unit with special reference to pedicle screw placement.

Methods: Within an eight-month period, we collected the data of 40 patients in whom pedicle screw placement was performed for different reasons. Intraoperative three-dimensional fluoroscopy with the mobile Siremobil Iso-C3D C-arm was undertaken to assess the pedicle screw position in thoracic, lumbar and sacral spine surgery. Scanning of the region of interest was done after all screws were implanted in each patient. The Iso-C3D acquires 100 flouroscopic images during a 190° C-arm orbital rotation. The focussed region calculates an image data cube with a length of 119 mm, for the computerized reconstruction. From these data, multislice images (multiplanar reconstruction) with axial, coronal and sagittal slice orientation can be obtained. After the operation conventional CTs were done and compared with the intraoperative images.

Results: In all patients, a total of185 pedicle screws were placed (thoracic: 56; lumbar: 123; sacral: 6). During operation three-dimensional fluoroscopic scanning was done 45 times (navigational procedures: 2; multisegmental scans in one patient: 2; second control scan after screw correction: 1). Altogether 17 pedicle screws were found to be misplaced in all patients (thoracic: 9; lumbar: 8). These screws were repositioned. After surgery no neurological deficits were observed in these patients. Conventional CT-scans were obtained in 27 patients (127 screws) postoperatively. 11 corrected pedicle screws were found to be in a right position. Altogether, 115 unchanged pedicle screws were compared. CT-scans demonstrated 5/115 (4.3%) incorrectly placed pedicle screws compared to intraoperative 3D images (false positive results). However, surgical revision was only necessary in one patient. In another patient, one screw was suspected to be slightly incorrect in the 3D intraoperative imaging, but the postoperative CT-scan showed a correct position (false negative result).

Conclusions: The intraoperative three-dimensional imaging technique provides a real-time three-dimensional imaging for bony structures and surgical implants. The image quality concerning implanted pedicle screws was adequate but inferior to a CT-scan. The false positive results with 3D fluoroscopy may be attributed to the surrounding metallic artefacts of the screws in relation to the size of the pedicle.