Objective:

To assess agreement between pedicle screw placement evaluated on post-operative computed tomography (CT) and on intra-operative cone beam computed tomography (CBCT) and compare procedure characteristics when using 1^st and 2^nd generation robotic C-arm systems in the hybrid operation room.

Methods:

All patients who received pedicle screws for spinal fusion at our institution between June 2009 and September 2019 and underwent intra-operative CBCT and post-operative CT were included. The CBCT and CT images were reviewed by two surgeons to assess the screw placement using the Gertzbein-Robbins and the Heary classifications. Inter-method agreement of screw placement classifications -as well as inter-rater agreement were assessed using Brennan-Prediger and Gwet’s agreement coefficients. Procedure characteristics using 1^st and a 2^nd generation robotic C-arm systems were compared.

Results:

Fifty-seven patients were treated with 315 pedicle screws at thoracic, lumbar and sacral levels. No screw had to be repositioned. On CBCT, accurate placement was found for 309 (98.1%) screws using the Gertzbein-Robbins classification and 289 (91.7%) using the Heary classification and on CT these were 307 (97.4%) and 293 (93.0%) respectively. Inter-method between CBCT and CT, and inter-rater agreements between the two raters were almost perfect (>0.90) for all assessment. There were no significant differences in mean radiation dose (p=0.83) and fluoroscopy time (p=0.82), but length of surgery using the 2^nd generation system was estimated 107.7 min (95% CI: 31.9 to 183.5min, p=0.006) shorter.

Conclusions:

Intra-operative CBCT provides accurate assessment of pedicle screw placement and enables intra- operative repositioning of misplaced screws.