title: Using Free Navigation Reference Points and Prefabricated Bone Plates for Zygoma Fracture Model Surgeries.
abstract: Surgical navigation systems have been an important tool in maxillofacial surgery, helping surgeons create a presurgical plan, locate lesions, and provide guidance. For secondary facial bone reductions, a good presurgical plan and proper execution are the key to success. Previous studies used predetermined markers and screw holes as navigation references; however, unexpected situations may occur, making the predetermined surgical plan unreliable. Instead of determining positions preoperatively, this study proposes a method that surgeons can use intraoperatively to choose surface markers in a more flexible manner. Eight zygomatic fractures were created in four skull models, and preoperative computed tomography (CT) image data were imported into a self-developed navigation program for presurgical planning. This program also calculates the ideal positions of navigation references points for screw holes. During reduction surgery, markers on fractured bone are selected, registered, and calculated as free navigation reference points (FNRPs). The surface markers and FNRPs are used to monitor the position of the dislocated bone. Titanium bone plates were prefabricated on stereolithography models for osteosynthesis. Two reductions with only FNRPs, as well as six reductions with FNRPs and prefabricated bone plates, were successfully performed. Postoperative CT data were obtained, and surgical errors in the six-reduction group were evaluated. The average deviation from the screw hole drilling positions was 0.92 ± 0.38 mm. The average deviation included displacement and rotation of the zygomas. The mean displacement was 0.83 ± 0.38 mm, and the average rotations around the x, y, and z axes were 0.66 ± 0.59°, 0.77 ± 0.54°, and 0.79 ± 0.42°, respectively. The results show that combining presurgical planning and the developed navigation program to generate FNRPs for assisting in secondary zygoma reduction is an accurate and practical method. Further study is necessary to prove its clinical value.
authors.affiliation: Division of Plastic and Reconstructive Surgery, Department of Surgery, Taipei Veterans General Hospital, Taipei, 11217 Taiwan ; Department of Mechanical Engineering, National Central University, 300 Jhongda Road, Jhongli District, Taoyuan, 32001 Taiwan ; School of Medicine, National Yang-Ming University, Taipei, 11221 Taiwan.
authors.forename: Tien-Hsiang
authors.initials: TH
authors.lastname: Wang
authors.affiliation: Division of Plastic and Reconstructive Surgery, Department of Surgery, Taipei Veterans General Hospital, Taipei, 11217 Taiwan ; School of Medicine, National Yang-Ming University, Taipei, 11221 Taiwan.
authors.forename: Hsu
authors.initials: H
authors.lastname: Ma
authors.affiliation: Department of Mechanical Engineering, National Central University, 300 Jhongda Road, Jhongli District, Taoyuan, 32001 Taiwan.
authors.forename: Ching-Shiow
authors.initials: CS
authors.lastname: Tseng
authors.affiliation: Department of Radiology, Taipei Veterans General Hospital, Taipei, 11217 Taiwan ; School of Medicine, National Yang-Ming University, Taipei, 11221 Taiwan.
authors.forename: Yi-Hong
authors.initials: YH
authors.lastname: Chou
authors.affiliation: Department of Mechanical Engineering, National Central University, 300 Jhongda Road, Jhongli District, Taoyuan, 32001 Taiwan.
authors.forename: Kun-Lin
authors.initials: KL
authors.lastname: Cai
keywords: Computer-assisted surgery; Fracture fixation; Image processing; Navigation; Registration; Surgical planning; Virtual reality