Evaluating the Reliability of Three-dimensional Models Constructed Photogrammetry Software 3DF Zephyr by Measuring Joint Angles of Fingers: A Comparison to a Conventional Goniometer

Objectives: Photogrammetry is a method of producing three-dimensional (3D) data from multiple photographs and videos. The purpose of this study was to evaluate the reliability of 3D hand models constructed using photogrammetry.Methods: The angles of the distal (DIP) and proximal (PIP) interphalangeal joints of the author's index finger were measured using a protractor goniometer. Five different blocks were used to stabilize the angles of the fingers. We collected 50 photographs and one video. Digital 3D models of the hand were constructed using 3DF Zephyr photogrammetry software. The angles of the DIP and PIP joints of the model were measured in virtual space. The angles obtained via the two methods were subjected to correlation analysis.Results: Eighty values (40 joints of 20 fingers; goniometer/3D model) were obtained. The maximum value obtained was 84° and the minimum was 33°. The average time required to take the original photographs of the model was 3 minutes, and that for the videos was 51 seconds. The average time required to construct a 3D image was 12 minutes. The greatest difference between the methods was 9° and the mean difference was 0.2°. The intraclass correlation coefficient (2,1) was 0.971.Conclusions: A high level of agreement was found between these angles. A 3D hand model constructed using photogrammetry is reproducible.