Accuracy and Reproducibility of Linear and Angular Measurements in Virtual Reality: a Validation Study.

The purpose of this experimental study is to validate linear and angular measurements acquired in a virtual reality (VR) environment via a comparison with the physical measurements. The hypotheses tested are as follows: VR linear and angular measurements (1) are equivalent to the corresponding physical measurements and (2) achieve a high degree of reproducibility. Both virtual and physical measurements were performed by two raters in four different sessions. A total of 40 linear and 15 angular measurements were acquired from three physical objects (an L-block, a hand model, and a dry skull) via the use of fiducial markers on selected locations. After both intra- and inter-rater reliability were evaluated using inter-class coefficient (ICC), equivalence between virtual and physical measurements was analyzed via paired t test and Bland-Altman plots. The accuracy of the virtual measurements was further estimated using two one-sided tests (TOST) procedure. The reproducibility of virtual measurements was evaluated via ICC as well as the repeatability coefficient. Virtual reality measurements were equivalent to physical measurements as evidenced by a paired t test with p values of 0.413 for linear and 0.533 for angular measurements and Bland-Altman plots in all three objects. The accuracy of virtual measurements was estimated to be 0.5 mm for linear and 0.7° for angular measurements, respectively. Reproducibility in VR measurements was high as evidenced by ICC of 1.00 for linear and 0.99 for angular measurements, respectively. Both linear and angular measurements in the VR environment are equivalent to the physical measurements with high accuracy and reproducibility.