Automatic virtual reduction of unilateral zygomatic fractures based on ICP algorithm: A preliminary study

Objective: To establish an automatic reduction method for unilateral zygomatic fractures based on Iterative Closes Point (ICP) algorithm. Material and methods: 60 patients with unilateral type B zygomatic fractures were included. After acquiring CT images, zygomatic fragments were segmented using self-developed software MICSys. Mid-Sagittal-Plane (MSP) was manually defined using anatomical skull landmarks. Surface of zygoma on the healthy side was then “mirrored” according to MSP. Referring to mirror image, the fragments were reduced by both automatic and manual methods. In automatic group, fragments were registered onto mirror images by ICP algorithm in MICSys. In manual group, an experienced maxillofacial surgeon translated and rotated fragments until coincided with mirror images. Operating time of each group was recorded. RMSE between reduced fragment and mirror image was calculated to evaluate accuracy. Operating time and accuracy between the two groups were compared using T-test. Results: Virtual bone reduction was conducted for all 60 patients by the two methods. Operating time of automatic group and manual group were 3.06 ± 1.93 s and 65.45 ± 32.19 s, with significant difference (P < 0.0001). RMSE of automatic group and manual group were 1.94 ± 0.59 mm and 2.33 ± 0.57 mm, with significant difference (P < 0.0001). Conclusion: Automatic reduction method based on ICP Algorithm for unilateral zygomatic fractures was initially established and clinically acceptable.