To explore the accuracy and clinical efficacy of advanced 3D printing navigation templates in assisting placement of atlantoaxial pedicle screw.

A retrospective analysis was carried out on 49 cases of patients with atlanto-axial vertebral fractures and dislocations between June 2013 and June 2016, and all of them were given posterior incision, reduction and internal fixation of atlantoaxial pedicle screw. The patients were divided into advanced 3D printing navigation template group (14 cases), early 3D printing navigation template group (16 cases), and routine pedicle screw placement group (19 cases). Atlantoaxial CT data of patients in advanced 3D printing navigation template group and early 3D printing navigation template group were input into Mimics 17.0, then advanced 3D printing navigation template group and early 3D printing navigation which were used in clinic surgery were designed and printed. The relationship between positions of pedicle screw with the pedicle and bone cortex in plain CT image was observed after operation. The quality of the screw position was assessed and the accuracy of three kinds of screwing methods was compared. The accuracy of the screwing angle was assessed by comparing with the differences between the preoperative designed channel inclination angle and postoperative actual screwing angle. Three groups were compared for differences between operation time, intraoperative blood loss, and scores of cervical nerve scale and visual analogue scale (VAS) of neck and shoulder pain by Japanese Orthopaedic Association (JOA).

All 49 cases of patients successfully completed the surgery. Patients of the routine pedicle screw placement group, early 3D group and advanced 3D group correspond operation time for 141.2±20.7 min, 112.5±12.1 min and 103.1±10.4 min, intraoperative blood loss for 314.0±81.4 ml, 243.6±71.2 ml and 181.0+59.1 ml; total accuracy of screwing for 75.0%(54/72), 93.75%(60/64) and 96.43%(54/56). There were statistically significant differences among the routine group, 3D group and advanced 3D group in the mentioned programs. There were no statistical differences between advanced 3D group and 3D group in the inclination angle and head tilt angle with the pre-designed values, while there was statistically significant difference between the routine group and the pre-designed value. The accuracy of the inclination angle and head tilt angle screwing angle were obviously superior in the advanced 3D group and early 3D group to that of the routine group. There were statistically significant differences between preoperative with postoperative VAS scores and JOA scores in the same group, while there were no statistically significant differences among groups in JOA. But there was statistically significant difference between the routine group and the advanced 3D in VAS, and there was no statistically significant difference between the routine pedicle screw placement group and the early 3D in VAS. All three groups of patients had bony fusion of atlanto-axial vertebral body, without loosening, dislocation and fracture of the internal fixators.

Advanced 3D printing templates in assisting the surgical treatment for atlantoaxial fracture and dislocation can improve the accuracy of pedicle screwing and safety of the surgery, reduce the surgery risk, and obtain satisfied clinical curative effects.

Cervical atlas; Axis; Spinal fusion; Bone screws; Surgery, computer-assisted