title: [A cadaveric study on establishing an individualized navigation template for the placement of occipital condyle screws using a three-dimensional printing technique].
abstract: OBJECTIVE
  To investigate the feasibility of establishing an individualized navigation template for occipital condyle screws insertion using a fused deposition modeling based three-dimensional printing forming technique, and to evaluate the accuracy and safety of template-assisted condyle screw insertion.
  
  
  METHODS
  Thirty adult occipitocervical specimens were selected to take a CT-scan. After original Dicom data imported into the Mimics software, the craniocervical junction models were created, which were used to evaluate anatomic structures and define the screw-related parameters. Design and generate the cavity models of the occipital condyle based on a three-dimensional printing forming technique. After using a free-hand procedure to create a navigation template with a well-established screw path, finish bilateral condyle screws insertion assisted by the navigation template. Anatomy study and CT-scan were taken postoperatively to access the position of the screws.
  
  
  RESULTS
  Sixty condyle screws were implanted assisted by 30 individualized navigation templates with an average time cost of (91.4 ± 8.2) s. The axial medial angle, sagittal cranial angle and distance between the entry point to atlantooccipital joint surface were (33.2 ± 6.4)°, (8.9 ± 3.4)°, (3.9 ± 0.9) mm, respectively. The variations due to different sex and sides resulted in a statistically insignificant difference of the parameters. Anatomy study and CT-scan indicated no intrusion of the vertebral artery, hypoglossal canal, condyle emissary vein canal or atlantooccipital joint. Fifty-nine condyle screws were completely contained within the condyle, while only 1 screw perforated lateral condyle wall.
  
  
  CONCLUSIONS
  Using the Mimics software for establishing the occipital condyle and related cavity model based on CT-scan images proves to be a feasible and precise method.Occipital condyle screws insertion assisted by a three-dimensional printing model is highly accurate and simple, which could be a new alternative to conventional technique.
authors.affiliation: Department of Orthopedics, Changhai Hospital, Second Military Medical University, Shanghai 200433, China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Huang
authors.forename: Fengning
authors.initials: F
authors.lastname: Li
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.forename: Kun
authors.initials: K
authors.lastname: Wang
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Yang
authors.forename: Ruishan
authors.initials: R
authors.lastname: Dang
authors.forename: Jiacan
authors.initials: J
authors.lastname: Su
authors.affiliation: Email: shenhxgk@126.com.
authors.forename: Hongxing
authors.initials: H
authors.lastname: Shen
authors.forename: Ming
authors.initials: M
authors.lastname: Li
mesh_terms: D000328:Adult; D000368:Aged; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000601:surgery*; D066330:Printing, Three-Dimensional; D025321:Surgery, Computer-Assisted