Accuracy of fiducial-based augmented reality in auricular reconstruction

Reconstruction with autologous costal cartilage remains the gold standard surgical treatment for total or partial ear reconstruction. The different auricular subunits are sculpted from costal cartilage and assembled. The assembly requires a particular skillset and training, including a thorough three-dimensional (3D) understanding of auricular anatomy. The correct positioning of the ear framework can be particularly difficult in patients with hemifacial microsomia because of facial asymmetry. We developed a digital workflow that can help the surgeon in the correct positioning of the framework via per-operative Augmented Reality (AR) and without the use of a pre-operative CT scan.

The digital workflow is illustrated for two patients who underwent surgery in 2023. All patients underwent total ear reconstruction for microtia. A high-resolution digital impression was obtained from the contralateral ear using a unique scanning protocol. A Trios 3 Wireless intraoral scanner (3Shape A/S, Denmark) was used for this purpose. The remaining gaps in the STL file were closed, and the surfaces were smoothed using Meshmixer (Autodesk,US). The digital ear was mirrored and imported together with the STL model of the patients face (Vectra®, Canfield, US) in Mimics Innovation Suite (Materialise, Belgium). The digital ear was correctly positioned, and a surgical guide, including AR fiducials, was printed for peroperative use with a Magic Leap 2 (Florida, US). The digital workflow was validated using three dummy skulls.

The accuracy for all measurements was within the limits of the requested margin of error for autologous ear reconstruction.

The use of AR in Autologous Auricular Reconstruction was validated and appears to be feasible, precise, and useful. Challenging cases with complex facial asymmetry, such as hemifacial microsomia, will particularly benefit from this new development.