Varjo XR-3 vs HoloLens 2 for Maxillofacial Surgery: A Preliminary Comparative Assessment

The primary procedures performed in maxillofacial surgery are osteotomy and repositioning. Surgeons usually exploit 3D printed guides and splints which entail considerable production time and high costs. To address these issues, innovative technologies such as mixed reality (MR) are emerging, but accuracy must still be assessed. Head-mounted displays (HMDs) are categorised into two main types: optical and video see-through. Recognisable comparisons between HoloLoens 2 (optical see-through) and Varjo XR3 (video see-through) are still not available in the scientific literature. This paper compares the accuracy of simulating maxillofacial surgery through these two different headsets. For the evaluation, a 3D model of a skull was 3D printed using Color Material Jetting 3D printing technology. Six people tested the MR application by i) tracing lines and holes with a pen following the holograms displayed on the phantom’s anatomy for osteotomies, ii) moving the maxillary fragmented bone according to the projected hologram for repositioning. Times were recorded during the trial. The tested geometries were then 3D scanned to reconstruct the traced cutting lines and holes, and quantitative results were extracted in CloudCompare by comparing the drawn and nominal lines. For the repositioning, deviations have been computed to calculate the mean deviation from the planned displacement. The accuracy of the two HMDs resulted similar for the osteotomy, while Varjo XR3 proved to be preferable for the repositioning.