Accuracy Assessment of Using Rapid Prototyping Drill Templates for Atlantoaxial Screw Placement: A Cadaver Study

Accuracy of cervical pedicle screw placement with four different designs of rapid prototyping navigation templates: a human cadaveric study

PURPOSE

Due to the high perforation rate of cervical pedicle screw placement, we have designed four different types of rapid prototyping navigation templates to enhance the accuracy of cervical pedicle screw placement.

METHODS

Fifteen human cadaveric cervical spines from C2 to C7 were randomly divided into five groups, with three specimens in each group. The diameter of pedicle screw used in this study was 3.5 mm. Groups 1-4 were assisted by the two-level template, one-level bilateral template, one-level unilateral template and one-level point-contact template, respectively. Group 5 was without any navigation template. After the surgery, the accuracy of screw placement in the five groups was evaluated using postoperative computed tomographic scans to observe whether the screw breached the pedicle cortex.

RESULTS

A total of 180 pedicle screws were inserted without any accidents. The accuracy rate was 75%, 100%, 100%, 91.7%, and 63.9%, respectively, from Groups 1 to 5. All the template groups were significantly higher than Group 5, though the two-level navigation template group was significantly lower than the other three template groups. The operation time was 4.72 ± 0.28, 4.81 ± 0.29, 5.03 ± 0.35, 8.42 ± 0.36, and 10.05 ± 0.52 min, respectively, from Groups 1 to 5. The no template and point-contact procedures were significantly more time-consuming than the template procedures.

CONCLUSION

This study demonstrated that four different design types of navigation templates achieved a higher accuracy in assisting cervical pedicle screw placement than no template insertion. However, the two-level template's accuracy was the lowest compared to the other three templates. Meanwhile, these templates avoided fluoroscopy during the surgery and decreased the operation time. It is always very challenging to translate cadaveric studies to clinical practice. Hence, the one-level bilateral, unilateral, and point-contact navigation templates designed by us need to be meticulously tested to verify their accuracy and safety.

3D-printed drill guide template, a promising tool to improve pedicle screw placement accuracy in spinal deformity surgery: A systematic review and meta-analysis

PURPOSE

This study aimed to compare the pedicle screw placement accuracy and surgical outcomes between 3D-printed (3DP) drill guide template technique and freehand technique in spinal deformity surgery.

METHODS

A comprehensive systematic literature search of databases (PubMed, Embase, Cochrane Library, and Web of Science) was conducted. The meta-analysis compared the pedicle screw placement accuracy and other important surgical outcomes between the two techniques.

RESULTS

A total of seven studies were included in the meta-analysis, comprising 87 patients with 1384 pedicle screws placed by 3DP drill guide templates and 88 patients with 1392 pedicle screws placed by freehand technique. The meta-analysis results revealed that the 3DP template technique was significantly more accurate than the freehand technique to place pedicle screws and had a higher rate of excellently placed screws (OR 2.22, P < 0.001) and qualifiedly placed screws (OR 3.66, P < 0.001), and a lower rate of poorly placed screws (OR 0.23, P < 0.001). The mean placement time per screw (WMD-1.99, P < 0.05), total screw placement time (WMD-27.86, P < 0.001), and blood loss (WMD-104.58, P < 0.05) were significantly reduced in the 3DP template group compared with the freehand group. Moreover, there was no significant statistical difference between the two techniques in terms of the operation time and correction rate of main bend curve.

CONCLUSIONS

This study demonstrated that the 3DP drill guide template was a promising tool for assisting the pedicle screw placement in spinal deformity surgery and deserved further promotion.

[Assessment of the safety and accuracy of implantation of screws into the C2 vertebra using individual 3D-navigation matrices]

Introduction

Individual 3D-navigation matrices are valuable to increase the safety of screw implantation into the axis.

Objective

To analyze safety and accuracy of screw deployment into the axis using individual 3D-navigation matrices compared to free hand technique.

Material and methods

A retrospective analysis included 23 patients (group 1) who underwent implantation of 44 screws into the axis using the «free hand» technique. The screws were installed along the transpedicular or pars trajectory. A prospective analysis enrolled 17 patients (group 2) who underwent installation of 34 screws using individual navigation matrices. 3D-printing technology was applied for manufacturing these matrices. Implantation results were evaluated considering postoperative CT data and SGT (Screw Guide Template) system.

Results

In the 1st group («free hand»), grade 0 and 1 (no malposition or less than 50% of screw diameter) were recorded for 29 (65.91%) screws, grade 2 - for 13 (29.55%) screws, grade 3 - for 2 (4.45%) screws. Intraoperative injury of the vertebral artery without postoperative neurological deficit occurred in 4 (8.89%) patients. In the 2nd group, 97% of screws were implanted in accordance with grades 1 and 2. Deviation grade 2 was registered in 11 cases (32.35%). Mean deviation was 1.8 ± 1.0 mm. In the 2nd group, 28 (82.35%) out of 34 screws were completely within the bone structures (grade 0), 4 (11.76%) screws perforated pedicles for less than 50% of their diameter (grade 1). There were 2 cases of malposition grade 2 and 3 without vertebral artery injury.

Conclusion

Individual 3D navigation matrix is an effective method for screw installation into the axis. This approach exceeds fluoroscopy-assisted "free hand" technique in terms of safety of implantation.