Automated true vertical line determination for orthognathic surgery virtual planning using smartphone photography and open-source applications

This technical note describes a novel method for recording the natural head position (NHP) for virtual surgical planning (VSP) in orthognathic surgery using a smartphone and open-source software. The authors utilize the OpenCamera application on standard smartphones to capture clinical photographs. This app embeds critical device orientation data, including roll, pitch, and yaw from the built-in accelerometer, directly into the image metadata. These photographs are then imported into a custom module (MaxiSlicer) developed for the open-source 3DSlicer platform. The module automatically reads the orientation data to calculate and incorporate the true vertical line into the image, subsequently aligning the photograph to this digital reference. This approach eliminates the need for physical references such as plumb lines or laser levels, reducing operational variables and potential human error. The integration of smartphone sensor data with digital planning tools offers a practical, accessible, and low-cost solution for achieving accurate and reproducible NHP registration in VSP workflows.