C-OnSite^sup ^ for intraoperative 3D control of pedicular screw positions

Two-dimensional image guidance and navigation can help to reduce the number of misplaced pedicle screws, but do not completely prevent misplacement. This experimental, retrospective, non-inferiority study was designed to evaluate and compare the efficacy of a novel 3D imaging technique versus conventional postoperative CT-scan, for intra-operative determination of pedicle screw position accuracy. The capacity of C-OnSite to intraoperatively assess screw placement was evaluated in 28 clinical cases and 23 deliberately misplaced screws in a cadaver model, and compared to placement accuracy determined by standard CT. The position of each implant, as viewed by both modalities, was graded by three neurosurgeons, one orthopaedic-surgeon and one radiologist. The intermodal variance determined the difference between CT- and C-OnSite results for each observer, while the inter-observer variance measured the difference between ratings of the same modality by different observers. C-OnSite successfully assessed 120/138 screws (25/28 cases). Mean procedural fluoroscopy time was 132±51s, and 40±16s per C-OnSite scan. The average inter-modality variance was ,15 % with mismatches >1° between C-OnSite and the gold-standard imaging technique in only 2 % of the comparisons. Average inter-observer variances were about similar (12 % for CT and 18 % for C-OnSite), with deviations of >1° reaching 1 % for CT and 3 % for C-OnSite. Individual variances between experienced only observers differed even less. C-OnSite is a feasible, reliable and intuitive means of intraoperatively visualizing pedicle screw positions and might render the majority of postoperative CTs superfluous. C-OnSite might help avoid re-operations for screw re-positioning.[PUBLICATION ABSTRACT]