This study showed that utilizing all the features of a hybrid operating room can improve the accuracy of pedicle screw placement for fractures on all thoracolumbar levels from T1 to L5. Compared to the systematic review of Perdomo-Pantoja et al. that reported an accuracy rate of 95.5% with CT-navigation and 91.5% in fluoroscopy assisted technique, we achieved a considerably lower screw perforation rate. Using the described algorithm in Fig.
2, perforation of more than 2 mm only occurred in 0.9% of the cases. This is one of the lowest evaluated rates of perforation compared to literature [
6,
9]. After navigated or non-navigated
K-Wire placement, a 3D-Scan was performed and misplaced
K-Wires were corrected. This was necessary in 19.3% of the cases and significantly more often in navigated procedures. The replacement in these cases prevented perforation rates like seen in comparable studies. The higher rate on perforation in navigated procedures as well as the higher rate of replaced
K-wire might be explained by smaller pedicles and more complex trajectories. Even with 3D navigation there is always a small percentage of misplacement. Compared to the study of Tjasic et al., who also used 3D-navigation, our study had more minor breaches [
10]. While Tjasic et al. reported 1.6% perforation over 4 mm, only perforation under 4 mm were evaluated in this study which also can be explained by the K-wire correction. Liu et al. compared pedicle screw placement for fractures in the thoracic spine either using fluoroscopy or 3D-Scan via O-arm to control
K-wire position. A significantly higher rate of satisfactory positioned pedicle screws (grade 0 and I) was observed in the O-arm control group [
11]. The rate of perforations with less than 2 mm was with 96.6% comparable to the 98.3% in our study underlining the importance of a
K-wire control after fluoroscopy guided pedicle screw placement. Perforation over 4 mm could be prevented in both studies. The slightly higher accuracy in our study might be explained by the use of 3D-navigation in complex cases with insufficient imaging. Comparable results for perforations less than 2 mm were seen by Shin et al. with 97.1% in the navigated group using O-arm navigation and 94.1% in the non-navigated group [
12]. Still in both groups 1 vs 4 pedicle screws with perforations over 4 mm were found. Due to the K-wire correction after placement in both groups we could achieve a slightly higher accuracy and prevent perforation over 4 mm. In 16.9% of the cases 3D-navigation was used mainly in the thoracic spine because of insufficient fluoroscopy. In our study, navigated procedures showed 81.2% of the screws completely inside the pedicle and 15.3% showed perforation less than 2 mm. In comparison, Scarone et al. showed a higher rate of accuracy for O-arm and iCT-Airo navigated pedicle screw placement with 92.1% [
13]. The rate of pedicle screws completely inside the pedicle also was higher in the study of Shin et al. with 93.3% and in the study of Tjasic et al. with 92.8% for 3D-C-Arm navigated and 98.9% for O-Arm navigated [
12,
14]. The higher rates might be explained by the selection bias of our study that was not concepted as a comparison between navigated and non-navigated cases. Therefore the majority of navigated case were thoracic cases from T1-T10 with often poor imaging quality and small pedicle diameters, while Scarone et al. and Tajsic et al. placed more navigated screws in the lumbar spine [
13,
14].
Main disadvantages of a hybrid operating room are extensive costs for the initial outlay of about 1.2 million dollars and the anticipated high radiation dose. While the costs for the initial outlay are high the operating time might be lower due to better imaging quality and through direct control of the C-Arm by the surgeon. Bronsard et al. reported an operating time of 83.5 min for mainly lumbar fractures with 4 percutaneously implanted screws using only fluoroscopy [
15]. In comparison, mean operating time in the present study for 4 lumbar screws was 56 min. For fluoroscopic thoracic pedicle screw placement mean time was 99 min which is considerably faster than the study of Liu et al. with an average of 195 min. Navigated surgery showed significantly longer operating time which is in line with literature [
9,
16]. Shin et al. demonstrated placing the screws with help of navigation is comparable time consuming than under fluoroscopic control but uses much more time for preparation [
12]what might explain the longer operating time. Compared to O-Arm navigation with about 200 min operating time in different studies [
9,
13] the operating time with 3D-C-Arm with navigation in this study was noticeable shorter with a mean time of 135 min. Also, with a comparable technique Tjasic et al. needed about 200 min. As described by Ryang et al. navigated procedures come with a steep learning curve and constant improvement for in radiation and operating time [
17]. The authors are using 3D navigation since 2015 for pelvic and spinal surgeries and accumulated a lot of experience and cases what might explain the faster operating times.
As expected, thoracic cases needed more radiation dosage than thoracolumbar and lumbar cases. Furthermore, navigated cases used more radiation than non-navigated cases. Schuetze et al. showed that navigation reduces the radiation exposure for the operating personnel because it can leave the room during 3D-Scans [
18,
19]. Furthermore, with the help of the ALARA principles radiation can be further reduced. The study of Bronsard et al. and Tajsic et al. had an effective dose of about 1.5 mSv only using fluoroscopy [
14,
15]. Mean dosage for non-navigated cases was 11.6 mSv considerably higher but can be explained by the control 3D-Scan to verify
K-Wire position. Furthermore, the 3D-Scan was even repeated if a
K-Wire needed revision. Compared to the mentioned studies the accuracy of the pedicle screws was as mentioned above higher which in our opinion justifies the higher radiation dosage. For navigated procedures we measure a mean radiation dosage of 20.3 mSv. This is in line with a comparable study using iCT-Airo and O-Arm navigation [
13].