An individualized navigation template based on the three-dimensional printing technique: application to the occipital condyle screw insertion

English Keywords:Three-dimensional printing  Occipital condyle screw  Navigation templates  Fused deposition modeling  Polylactic acid

English Abstract:

  【Abstract】 Objectives: To investigate the feasibility of establishing an individualized navigation template for occipital condyle screws insertion by using the three-dimensional printing technique, and to evaluate the accuracy and safety of template-assisted condyle screw insertion. Methods: Twenty adult occipitocervical specimens were selected to take a CT-scan. After importing original Dicom data into the Mimics software, 3D-models of the craniocervical junction were created, which were used to evaluate anatomic structures related to condyle screws and define the parameters of screw placement. The screw path was determined through the guidance of canal and the cavity model of occipital bone structure, which were assembled together to generate the navigation template with a well-established screw path based on the three-dimensional printing forming technique. Anatomy study and CT-scan were taken to access the position of the screws after the insertion of bilateral condyle screws on cadaveric specimens and 3D-models. Results: Significant individual variation of the anatomical structure related to the occipital condyle screw was identified. The axial medial angle, sagittal cranial angle and the distance between entry point and atlantooccipital joint were 30.2°±6.3°, 8.1°±2.6° and 3.69±0.42mm, respectively. Forty condyle screws were implanted assisted by 20 individualized navigation templates with an average time of 60.1±9.3s. Anatomy study and CT-scan showed no intrusion of the vertebral artery, hypoglossal canal, condylar emissary canal or atlantooccipital joint. All screws were completely contained within the condyle. Conclusions: The study proves the feasibility of using the Mimics software for establishing 3D-models of the occipital condyle and related anatomy structures. The individualized navigation template, designed and generated by the three-dimensional printing technique based on established screw path parameters, is proved to be a feasible, precise and low-cost method, which can be a new alternative to conventional technique for screw placement.