Clinical application of 3D-printed navigation template in posterior atlantoaxial pedicle screw fixation

Abstract

Objective To discuss the feasibility and clinical efficacy of 3D-printing navigation template for posterior atlantoaxial pedicle screw fixation for the treatment of atlantoaxial fracture and dislocation. Methods From January 2015 to June 2017, 11 patients receiving posterior internal fixation with atlantoaxial pedicle screw placement assisted by the 3D-printed navigation template at Affiliated Shimen Hospital of Changsha Medical University were recruited, and their clinical data were reviewed. There were 9 males and 2 females, who were aged from 52 to 60 years old. Four cases had fracture of atlas, with 2 cases in the anterior arch and 2 cases in both anterior and posterior arches. Five cases had atlantoaxial fracture, with 4 cases of type ⅡC odontoid process fracture and 1 case of Hangman's fracture. Two cases had dislocation of the atlantoaxial joint. Dicom images from preoperative cervical CT scan were imported into the reverse engineering software. Segmentation and reconstruction of the target vertebral body were performed. Mask expansion was conducted for the surface morphology of the posterior structure of the target vertebral body. Boolean operation was implemented to obtain the navigation template. Polylactic acid(PLA) and photosensitive resin were used for 3D-printing and rapid prototyping of atlantoaxial fracture and dislocation model and navigation template model, respectively. The surgery was first simulated using the 3D-printed PLA of atlantoaxial fracture and dislocation model, so as to conform the accuracy of navigation template design. The photosensitive resin was disinfected with ethylene oxide and encapsulated prior to use. A conventional posterior cervical approach was adopted. The surface morphology of the posterior vertebra was fully exposed during operation and the atlantoaxial pedicle screw was placed with the assistance of 3D-printed navigation template according to preoperative simulation. The surgical time, intraoperative blood loss and incidence of complications were recorded. The position relationship of the pedicle screw and pedicle of vertebral arch was determined by CT scan at 6 months after surgery. The quality of pedicle screw placement was assessed by using Kawaguchi's method. The neck and shoulder pain were assessed by using the VAS score at 1 year after surgery. The function of the cervical nerve was assessed by JOA score. Results The operation was successfully performed for all 11 patients. The average surgical time was (130.55±18.83) min, and the average intraoperative blood loss was (266.36±72.43) mL. A total of 44 pedicle screws were placed in 11 patients. Using Kawaguchi's grading system, 93.18%(41/44) of pedicle screw were of grade 0, 4.55%(2/44) of pedicle screw were of grade 1 and 2.27%(1/44) of pedicle screw were of grade 2. All patients were followed up for an average of 17.18 months (12 to 26 months). No postoperative complications, such as incision infection and cerebrospinal fluid leak, occurred during the follow-up. The average VAS score at 1 year after surgery (1.00±0.77) was significantly improved as compared with that before surgery (7.91±1.04). The average JOA score characterizing the function of cervical nerve at 1 year after surgery (13.45±1.69) was also significantly improved as compared with that before surgery (8.18±1.17), there were statistical differences (t=3.020 and 14.685, all P values<0.05). Conclusions Posterior atlantoaxial pedicle screw fixation with the assistance of 3D-printed navigation template for the treatment of atlantoaxial fracture and dislocation can reduce the difficulty of pedicle screw placement while improve the accuracy of such placement. It is a safe and effective method and which can achieve a good short-term efficacy. This technology is worthy of popularization. Key words: Cervical atlas; Atlas; Spinal fractures; Fracture fixation; Three-dimensional printing