Clinical application of 3D-printed drill guiding template in pedicle screw insertion in subaxial cervical spine

English Keywords:Subaxial cervical spine  Pedicle screw  Drill guiding template  3D printed

English Abstract:

  【Abstract】 Objectives: To explore the safety and accuracy of subaxial cervical pedicle screw(CPS) insertion assisted with optimized 3D-printed drill guiding template(DGT). Methods: A retrospective study was conducted to analyze the clinical data of 42 patients aged 32-74 years (50.1±9.8 years) who underwent posterior cervical pedicle screw internal fixation between August 2016 and October 2022. The patients were followed up for 13-25 months(19.6±3.2 months). They were divided into two groups of guiding template group(n=22) and free-hand group(n=20) according to the method of pedicle screw insertion. In the guiding template group, the subaxial CPSs insertions were assisted with 3D-printed DGT, designed individually for each patient based on the design scheme of an optimized pedicle drill guiding template, and the patients consisted of 12 males and 10 females, among which 6 patients were with cervical spine injury or spinal cord injury, 9 were with ossification of posterior longitudinal ligament(OPLL), 5 were with intraspinal tumor, and 2 were with cervical spondylotic myelopathy. In the free-hand group, the subaxial CPSs were inserted with free hand according to the cervical parameters such as pedicle angle and diameter on the CT images measured before operation, and the patients consisted of 10 males and 10 females, among which 4 patients were with cervical spine injury or spinal cord injury, 10 with OPLL, 5 with intraspinal tumor, and 1 with cervical spondylotic myelopathy. There were no significant differences in sex, age, disease, and preoperative visual analogue scale(VAS) score and Japanese Orthopaedic Association(JOA) score between the two groups(P>0.05). The operative time, intraoperative blood loss, and postoperative 12 months of VAS and JOA scores were recorded and compared．CT scan was performed at 1 week after operation on cervical spine, and the accuracy of pedicle screw placement was evaluated in accordance with Kaneyama′s evaluation method: Grade 0, screw was contained in the pedicle; Grade 1, screw penetrated pedicle<50% of the screw diameter; Grade 2, screw penetrated pedicle>50% of the screw diameter; Grade 3, screw completely penetrated the pedicle. Grades 0 and 1 were considered accurate placement, and grades 2 and 3 were considered misplacement. The perioperative complications were recorded for each patient in the two groups. Results: The operative time, intra-operative blood loss in guiding template group(102.2±16.1min, 89.3±17.7mL) were statistically less than those in free-hand group(142.8±20.9min, 133.3±34.0mL)(P<0.01). A total of 216 CPSs were placed: 118 in the guiding template group, including 90 screws of grade 0, 22 screws of grade 1, 5 screws of grade 2, 1 screw of grade 3, with an accuracy rate of 94.9%(112/118); And 98 in the free-hand group, including 48 screws of grade 0, 36 screws of grade 1, 10 screws of grade 2, and 4 screws of grade 3, with an accuracy rate of 85.7%(84/98). The accuracy rate of pedicle screw insertion was significant higher in the guiding template group than that in the free-hand group(P<0.05). No major neurovascular complications nor internal fixation loosening or breakages were observed in two groups of patients. At 12 months after operation, the VAS score in both groups was statistically less than that before operation(P<0.01), and the JOA score in both groups was statistically more than that before operation(P<0.01), and there were no significant differences in VAS score and JOA score between groups, respectively(P>0.05). Conclusions: The optimized design scheme of 3D-printed DGT is helpful in improving the accuracy and safety of subaxial CPS insertion.