[A cadaveric study on establishing an individualized navigation template for the placement of occipital condyle screws using a three-dimensional printing technique].

Objectives: 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.