gms | German Medical Science

Introduction: Transpedicular screws in dorsal instrumented procedures is still the “gold standard” for every fusion- or fracture-procedure. The correct pedicular screw placement is a mandatory step in every instrumented spine procedure to achieve fusion, prevent neurological injury or to support appropriate healing. To secure the correct placement of inserted screws intraoperative fluoroscopy is the standard today. But the one-dimensional view could never secure a correct placement.

This study was to determine the possible benefits and accuracy of intraoperative 3D-scans during thoraco-lumbar cannulated transpedicular fusion procedures.

Material and methods: 739 screws in 147 procedures were reviewed. 3D-scans were performed by a Siemens IsoC Orbic 3D. A minimum of 1 scan was performed during surgery with k-wires positioned for transpedicular screw fixation. If misplacement of the k-wire was detected, the wire was replaced and confirmed by an optional additional scan. A postoperative CT scan was performed on a routine base. Intraoperative radiation exposure, numbers of scans, revisions of k-wires and OR-time was recorded. Placements of k-wires were analyzed by modified “Rongming Xu” criteria.

Results: Minimum of 1 scan and max of 4 scans were performed. Intraoperative k-wire scan correlate exactly with postoperative CT scan. Our revision rate was reduced to 1.48%. Only 6 patients (11 screws) had revision surgery due misplaced screws. Within these cases 3 patients (6 screws) were analyzed in a poor transpedicular position retrospectively in reviewed 3D-scan. In 13% 58 patients, the placed k-wire was revised after performed 3D-scan. Postoperative CT scan showed excellent placement in 83%. Intraoperative radiation exposure could be decreased by 50% during learning curve and is lower compared to standard fluoroscopy procedures in existing literature.

Conclusion: Intraoperative 3D-scans of transpedicular k-wires are a helpful, precise and safe tool during cannulated transpedicular fusion procedures, especially in departments were additional navigation is not available. Scans of implanted screws were seen to be not applicable for detection of misplacement due to high artifacts. A learning curve was detected with reduction of intraoperative radiation exposure and with increased recognition of misplaced k-wires. Placement of k-wires could predict to final screw position. Our revision rate was decreased to 1.48%. With the knowledge of some pitfalls we could perform cannulated k-wire procedures safer, and with less radiation exposure for the patients and the surgeon.