Accurate Placement and Revisions for Cervical Pedicle Screws Placed With or Without Navigation: A Systematic Review and Meta-Analysis

Navigated percutaneous placement of cervical pedicle screws: An anatomical feasibility study

Introduction

Percutaneous cervical pedicle screw placement is challenging due to complex anatomy, and requires navigation support. It is unclear how to ensure navigation accuracy in minimally invasive procedures.

Research question

How accurate is image-guided percutaneous pedicle screw positioning after referencing with only one clamp for the complete subaxial cervical spine?

Materials and methods

In six cadavers, all subaxial cervical pedicles were fitted with screws using a standardized procedure. Briefly, a reference clamp was placed via a small skin incision on spinous process C7. The procedure started from C3 and progressed towards C7, without additional imaging, using one registration for all vertebrae. Screws were placed using a navigated screwdriver. Cone-beam CT was performed at three time-points. Screw position was directly intraoperatively evaluated by the surgeons using a modified classification-from Grade 1 (perfect placement) to Grade 5 (highly inaccurate)-and these data were re-evaluated by two independent radiologists.

Results

In six human specimens, 10 guidewires each were placed bilaterally in C3-C7. One screw (1.7%) was intraoperatively classified as Grade 3, but as Grade 4 in the second assessment. All other screws were classified as Grades 1-2 (89.8%) or 3 (8.5%). Screw placement accuracy was not significantly impacted by distance to the clamp or side selection.

Discussion

In percutaneously navigated screw placement with intraoperative imaging, safe screw placement was possible with a reference clamp on C7. Clinical application of this technique has been limited to individual cases. We also propose a new classification for improving screw accuracy and clinical consequences.

Design, fabrication, and evaluation of single- and multi-level 3D-printed non-covering cervical spinal fusion surgery templates

Background

Cervical spinal fusion surgeries require accurate placement of the pedicle screws. Any misplacement/misalignment of these screws may lead to injuries to the spinal cord, arteries and other organs. Template guides have emerged as accurate and cost-effective tools for the safe and rapid insertions of pedicle screws.

Questions/Purposes

Novel patient-specific single- and multi-level non-covering templates for cervical pedicle screw insertions were designed, 3D-printed, and evaluated.

Methods

CT scans of two patients were acquired to reconstruct their 3D spine model. Two sets of single-level (C3-C7) and multi-level (C4-C6) templates were designed and 3D-printed. Pedicle screws were inserted into the 3D-printed vertebrae by free-hand and guided techniques. For single-level templates, a total of 40 screws (2 patients × 5 vertebrae × 2 methods × 2 screws) and for multi-level templates 24 screws (2 patients × 3 vertebrae × 2 methods × 2 screws) were inserted by an experienced surgeon. Postoperative CT images were acquired to measure the errors of the entry point, 3D angle, as well as axial and sagittal plane angles of the inserted screws as compared to the initial pre-surgery designs. Accuracy of free-hand and guided screw insertions, as well as those of the single- and multi-level guides, were also compared using paired t-tests.

Results

Despite the minimal removal of soft tissues, the 3D-printed templates had acceptable stability on the vertebrae during drillings and their utilization led to statistically significant reductions in all error variables. The mean error of entry point decreased from 3.02 mm (free-hand) to 0.29 mm (guided) using the single-level templates and from 5.7 mm to 0.76 mm using the multi-level templates. The percentage reduction in mean of other error variables for, respectively, single- and multi-level templates were as follows: axial plane angle: 72% and 87%, sagittal plane angle: 56% and 78%, and 3D angle: 67% and 83%. The error variables for the multi-level templates generally exceeded those of the single-level templates. The use of single- and multi-level templates also considerably reduced the duration of pedicle screw placements.

Conclusion

The novel single- and multi-level non-covering templates are valuable tools for the accurate placement of cervical pedicle screws.

Accuracy and clinical characteristics of robot-assisted cervical spine surgery: a systematic review and meta-analysis

PURPOSE

To evaluate the accuracy and feasibility of robot-assisted cervical screw placement and factors that may affect the accuracy.

METHODS

A comprehensive search was made on PubMed, Embase, Cochrane Library, Web of Science, CNKI, and Wanfang Med for the selection of potential eligible literature. The outcomes were evaluated in terms of the relative risk (RR) or standardized mean difference (MD) and corresponding 95% confidence interval (CI). Subgroup analyses of the accuracy of screw placement at different cervical segments and with different screw placement approaches were performed. A comparison was made between robotic navigation and conventional freehand cervical screw placement.

RESULTS

Six comparative cohort studies and five case series studies with 337 patients and 1342 cervical screws were included in this study. The perfect accuracy was 86% (95% CI, 82-89%) and the clinically acceptable rate was 98% (95% CI, 95-99%) in robot-assisted cervical screw placement. The perfect accuracy of robot-assisted C1 lateral mass screw placement was the highest (96%), followed by C6-7 pedicle screw placement (93%) and C2 pedicle screw placement (86%), and the lowest was C3-5 pedicle screw placement (75%). The open approach had a higher perfect accuracy than the percutaneous/intermuscular approach (91% vs 83%). Compared with conventional freehand cervical screw placement, robot-assisted cervical screw placement had a higher accuracy, a lower incidence of perioperative complications, and less intraoperative blood loss.

CONCLUSION

With good collaboration between the operator and the robot, robot-assisted cervical screw placement is accurate and feasible. Robot-assisted cervical screw placement has a promising prospect.