title: Patient-specific polyetheretherketone facial implants in a computer-aided planning workflow.
abstract: OBJECTIVE
  In the present study, we report an innovative workflow using polyetheretherketone (PEEK) patient-specific implants for esthetic corrections in the facial region through onlay grafting. The planning includes implant design according to virtual osteotomy and generation of a subtraction volume. The implant design was refined by stepwise changing the implant geometry according to soft tissue simulations.
  
  
  METHODS
  One patient was scanned using computed tomography. PEEK implants were interactively designed and manufactured using rapid prototyping techniques. Positioning intraoperatively was assisted by computer-aided navigation. Two months after surgery, a 3-dimensional surface model of the patient's face was generated using photogrammetry. Finally, the Hausdorff distance calculation was used to quantify the overall error, encompassing the failures in soft tissue simulation and implantation.
  
  
  RESULTS
  The implant positioning process during surgery was satisfactory. The simulated soft tissue surface and the photogrammetry scan of the patient showed a high correspondence, especially where the skin covered the implants. The mean total error (Hausdorff distance) was 0.81 ± 1.00 mm (median 0.48, interquartile range 1.11). The spatial deviation remained less than 0.7 mm for the vast majority of points.
  
  
  CONCLUSIONS
  The proposed workflow provides a complete computer-aided design, computer-aided manufacturing, and computer-aided surgery chain for implant design, allowing for soft tissue simulation, fabrication of patient-specific implants, and image-guided surgery to position the implants. Much of the surgical complexity resulting from osteotomies of the zygoma, chin, or mandibular angle might be transferred into the planning phase of patient-specific implants.
authors.affiliation: PhD Student, Facial Esthetics Engineering Group, University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University of Vienna, Vienna, Austria.
authors.forename: Godoberto
authors.initials: G
authors.lastname: Guevara-Rojas
authors.affiliation: Assistant Professor, Center of Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria. Electronic address: michael.figl@meduniwien.ac.at.
authors.forename: Michael
authors.initials: M
authors.lastname: Figl
authors.affiliation: Associate Professor, Head of Facial Esthetics Engineering Group, University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University of Vienna, Vienna, Austria.
authors.forename: Kurt
authors.initials: K
authors.lastname: Schicho
authors.affiliation: Assistant Professor, Facial Esthetics Engineering Group, University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University of Vienna, Vienna, Austria.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Seemann
authors.affiliation: Assistant Professor, Center of Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria.
authors.forename: Hannes
authors.initials: H
authors.lastname: Traxler
authors.affiliation: Teaching Assistant, Center of Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria.
authors.forename: Apostolos
authors.initials: A
authors.lastname: Vacariu
authors.affiliation: Professor, Otto Friedrich Universität Bamberg, Bamberg, Germany.
authors.forename: Claus-Christian
authors.initials: CC
authors.lastname: Carbon
authors.affiliation: Professor Emeritus, Facial Esthetics Engineering Group, University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University of Vienna, Vienna, Austria.
authors.forename: Rolf
authors.initials: R
authors.lastname: Ewers
authors.affiliation: Head of the Department of Cranio-Maxillofacial and Oral Surgery, St. Pölten, Austria.
authors.forename: Franz
authors.initials: F
authors.lastname: Watzinger
mesh_terms: D000328:Adult; D001577:Benzophenones; D001672:Biocompatible Materials; D017076:Computer-Aided Design; D005145:Face / Q000033:anatomy & histology; D005147:Facial Bones / Q000601:surgery*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007659:Ketones; D008953:Models, Anatomic; D010027:Osteotomy / Q000379:methods; D010347:Patient Care Planning; D010780:Photogrammetry / Q000379:methods; D011092:Polyethylene Glycols; D011108:Polymers; D019736:Prostheses and Implants; D011474:Prosthesis Design; D025321:Surgery, Computer-Assisted / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods; D014584:User-Computer Interface; D015050:Zygoma / Q000002:abnormalities / Q000601:surgery
chemical_list: D001577:Benzophenones; D001672:Biocompatible Materials; D007659:Ketones; D011108:Polymers; C063834:polyetheretherketone; D011092:Polyethylene Glycols