Accuracy of Patient-Specific 3D-Printed Drill Guides for Pedicle and Lateral Mass Screw Insertion: An Analysis of 76 Cervical and Thoracic Screw Trajectories

STUDY DESIGN: Single-center retrospective case series.

OBJECTIVE: The purpose of this study was to assess the safety and accuracy of 3D-printed individualized drill guides for pedicle and lateral mass screw insertion in the cervical and upper-thoracic region, by comparing the pre-operative 3D-surgical plan with the postoperative results.

SUMMARY OF BACKGROUND DATA: Posterior spinal fusion surgery can provide rigid intervertebral fixation but screw misplacement involves a high risk of neurovascular injury. However, modern spine surgeons now have tools such as virtual surgical planning and 3D-printed drill guides to facilitate spinal screw insertion.

METHODS: A total of 15 patients who underwent posterior spinal fusion surgery involving patient-specific 3D-printed drill guides were included in this study. After segmentation of bone and screws, the post-operative models were superimposed onto the preoperative surgical plan. The accuracy of the realized screw trajectories was quantified by measuring the entry point and angular deviation.

RESULTS: The 3D deviation analysis showed that the entry point and angular deviation over all 76 screw trajectories were 1.40 ± 0.81 mm and 6.70 ± 3.77°, respectively. Angular deviation was significantly higher in the sagittal plane than in the axial plane (P = 0.02). All screw positions were classified as 'safe' (100%), showing no neurovascular injury, facet joint violation, or violation of the pedicle wall.

CONCLUSIONS: 3D virtual planning and 3D-printed patient-specific drill guides appear to be safe and accurate for pedicle and lateral mass screw insertion in the cervical and upper-thoracic spine. The quantitative 3D deviation analyses confirmed that screw positions were accurate with respect to the 3D-surgical plan.

LEVEL OF EVIDENCE: 4.