# Augmented Reality: Mapping Methods and Tools for Enhancing the Human Role in Healthcare HMI
## 3 Results
### Intraoperative Solution
#### 3.3.2 Spine Surgery
Verification of correct screw insertion was assessed post-operatively with a CT scan and compared with the fluoroscopy technique. While there was no major violation of the fluoroscopic technique, some screws inserted with AR suffered an initial positioning error, while their overall orientation resulted to be parallel to the original trajectory, as expected. [PERSON] et al. [66] presented a Microsoft HoloLens-based navigation method, to capture the intraoperatively reachable surface of vertebrae, and to register and track instruments with live views without imaging acquired during surgery. The developed system allows to perform marker tracking and pose estimation, digitalize intraoperative surfaces for registration purposes, and features designed for surgical navigation. Preoperative planning of 3D screw trajectories was performed by acquiring computed tomography (CT) images from cadavers. The orthopedic procedure was performed on phantoms by a surgeon and checked postoperatively with CT acquisition, demonstrating that combining HoloLens with the proposed navigation method can lead to precise lumbar pedicle screw insertion. [PERSON] et al. [69] also attempted to compare AR-assisted insertion of pedicle screw with conventional methods. Accuracy was assessed by acquiring a CT following the insertion of 120 pedicle screws in five male cadaveric torsos. The AR system proved to have excellent usability, and the screw placement accuracy was not inferior to the accuracy reported for manual computer-guided pedicle insertion. In contrast, when evaluated using the Gertzbein-Robbins grading system, the accuracy results obtained with the AR system improved the results achieved with FH insertion. In their study, [PERSON] et al. [51] evaluated if a new AR-supported technique, using a cutting-edge AR headset, could improve pedicle screw insertion accuracy compared to the standard FH technique in both a group of experienced and a group of novice surgeons. Through manual alignment, the virtual information displayed by the AR headset can be overlaid on the anatomy in the real world. As hypothesized, in a laboratory setting, the optimized visualization improved the pilot holes accuracy for the pedicle screws and reduced the effect of the surgeon's experience. For novice surgeons, the group trained with AR showed a strong decrease in primary and secondary perforation of the screws, and greater accuracy of the craniocaudal tilt angle and a mediolateral convergence compared to the group trained with the traditional FH technique, while no difference was observed for experienced surgeons. Other studies, instead, proved considerably greater accuracy in the placement of pedicle screws using different ARSN systems that provide 3D data to the surgeon than the FH methodology. The same system was evaluated in a subsequent study on its feasibility in a clinical environment [28]. Surgeons received an introduction to Microsoft HoloLens functionality, then a training phase preceded the testing phase during which they were asked to wear the HoloLens during surgery. For each operation, commercial software generated a 3D triangular surface model of the patients' readily available CT data. The results showed that the image quality of the head-mountedAR device was generally considered adequate, although some ergonomic and technical weaknesses were noted, such as inaccurate interaction with gestures and voice commands. The same group [29] developed an AR-guided navigation device for the insertion of the Sacral Alar Iliac (SAI) screw, in which the 3D model, including optimized and previously planned screw trajectories, was loaded onto an AR-HMD (Microsoft HoloLens). Their new proposal involves the use of an AruCo fiducial marker to track, register, and overlay the holographic image onto the pelvic model, theoretically avoiding the need for large and expensive infrastructure within the operating room.