Accuracy of Patient-Specific 3D-Printed Drill Guides for Pedicle and Lateral Mass Screw Insertion

Abstract

Study Design. Single-center retrospective case series. Objective. The purpose of this study was to assess the safety and accuracy of three-dimensional (3D)-printed individualized drill guides for pedicle and lateral mass screw insertion in the cervical and upper-thoracic region, by comparing the preoperative 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 postoperative 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

A Comparison of Drill Guiding and Screw Guiding 3D-Printing Techniques for Intra- and Extrapedicular Screw Insertion

“…The improvement for lumbar region might be best explained by the lumbar screw thickness and associated wider thread, allowing the screws to easily deviate from pilot trajectory, which seems to be prevented by the actively screw steering mechanism of modular guides. The entry point deviations of regular drill guides in the lumbar region diverge considerably from our earlier study 20 . Though previous results were limited to the upper-thoracic spine, this may be related to the interspinous ligament sparing design that was specifically used in the current study.…”

“…The entry point deviations of regular drill guides in the lumbar region diverge considerably from our earlier study. 20 Though previous results were limited to the upper-thoracic spine, this may be related to the interspinous ligament sparing design that was specifically used in the current study. The current study design does not allow us to directly examine the possible negative accuracy effect of the ligament sparing design, but examining this issue should be the focus of future research.…”

“…In fact, our 3D accuracy studies into patient-specific guides revealed a mean screw deviation of 1.40 mm and 6.78 for the entry point and angular deviation, while drilling of the pilot hole itself has shown lower deviations of respectively 0.76 mm and 3.2. 19,20 These results indicate potential improvement, just by improved alignment of screws with 3D-guided pilot holes. To achieve improved alignment, some authors advocated to also guide the actual screw after drill bit guidance, by using an additional guide or a removable inlay in a modular designed guide.…”

Vital Role of In-House 3D Lab to Create Unprecedented Solutions for Challenges in Spinal Surgery, Practical Guidelines and Clinical Case Series

“…In both metal and polyamide lay-on drill guides, screw tip deviation can still be >2 mm (Figure 2) [23][24][25][26], which is unacceptable in the axial plane of cervical vertebrae, especially in young and small children [17,18]. To aid surgeons with pedicle screw positioning in adults, patient specific 3D-printed drill guides have been developed by several groups [16,[20][21][22]. These drill guides are based on direct surface contact on the laminae and transverse and spinous processes of one or sequential vertebrae, but this does not always reach the required accuracy for cervical use [23][24][25][26].…”

“…To aid surgeons with pedicle screw positioning in adults, patient specific 3D-printed drill guides have been developed by several groups [ 16 , 20 , 21 , 22 ]. These drill guides are based on direct surface contact on the laminae and transverse and spinous processes of one or sequential vertebrae, but this does not always reach the required accuracy for cervical use [ 23 , 24 , 25 , 26 ].…”