Validity of surgeon perception of navigated pedicle screw position: a cadaveric study

Analysis of 5,070 consecutive pedicle screws placed utilizing robotically assisted surgical navigation in 334 patients by experienced pediatric spine deformity surgeons: surgical safety and early perioperative complications in pediatric posterior spinal fusion

PURPOSE

This study evaluates the intraoperative and short-term complications associated with robotically assisted pedicle screw placement in pediatric posterior spinal fusion (PSF) from three surgeons at two different institutions.

METHODS

We retrospectively reviewed 334 pediatric patients who underwent PSF with robotic-assisted navigation at 2 institutions over 3 years (2020-2022). Five thousand seventy robotically placed screws were evaluated. Data collection focused on intraoperative and early postoperative complications with minimum 30-day follow-up. Patients undergoing revision procedures were excluded.

RESULTS

Intraoperative complications included 1 durotomy, 6 patients with neuromonitoring alerts not related to screw placement, and 62 screws (1.2%) with documented pedicle breaches, all of which were revised at time of surgery. By quartile, pedicle breaches statistically declined from first quartile to fourth quartile (1.8% vs. 0.56%, p < 0.05). No breach was associated with neuromonitoring changes or neurological sequelae. No spinal cord or vascular injuries occurred. Seventeen postoperative complications occurred in eleven (3.3%) of patients. There were five (1.5%) patients with unplanned return to the operating room.

CONCLUSION

Robotically assisted pedicle screw placement was safely and reliably performed on pediatric spinal deformity by three surgeons across two centers, demonstrating an acceptable safety profile and low incidence of unplanned return to the operating room.

Optimization of Pedicle Screw Parameters for Enhancing Implant Stability Based on Finite Element Analysis

OBJECTIVE

To improve implant stability parameters, including pedicle screw (PS) outer diameter, thread depth, and pitch, by finite element analysis.

METHODS

Insertion and pullout of the PS were simulated by finite element analysis, and the precision of simulation was evaluated by comparison with mechanical tests. Influences of the parameters on the maximum insertion torque and maximum pullout force were analyzed by computational simulations, including single-factor analysis and orthogonal experiments.

RESULTS

The simulation results agreed with the mechanical test results. The order of parameters influencing insertion torque and pullout force was outer diameter > pitch > thread depth. When the pilot hole diameter is 0.1 mm larger than the inner diameter of the PS, the calculated Pearson correlation coefficient between the maximum insertion torque and maximum pullout force was r = 0.99. The optimized PS had a maximum insertion torque of 485.16 N·mm and a maximum pullout force of 1726.33 N, 23.9% and 9.1% higher, respectively, than the values of standard screws.

CONCLUSIONS

The presently used models are feasible for evaluating the implant stability of PSs. The maximum insertion torque and maximum pullout force of PSs are highly correlated and can be improved by increasing the outer diameter and decreasing pitch. Although with the parameters of the PS, pedicle size and bone mineral density are 2 additional factors to consider for better implant stability.

Reliability of the Planned Pedicle Screw Trajectory versus the Actual Pedicle Screw Trajectory using Intra-operative 3D CT and Image Guidance

BACKGROUND

Technological advances, including navigation, have been made to improve safety and accuracy of pedicle screw fixation. We evaluated the accuracy of the virtual screw placement (Stealth projection) compared to actual screw placement (intra-operative O-Arm) and examined for differences based on the distance from the reference frame.

METHODS

A retrospective evaluation of prospectively collected data was conducted from January 2013 to September 2013. We evaluated thoracic and lumbosacral pedicle screws placed using intraoperative O-arm and Stealth navigation by obtaining virtual screw projections and intraoperative O-arm images after screw placement. The screw trajectory angle to the midsagittal line and superior endplate was compared in the axial and sagittal views, respectively. Percent error and paired t-test statistics were then performed.

RESULTS

Thirty-one patients with 240 pedicle screws were analyzed. The mean angular difference between the virtual and actual image in all screws was 2.17° ± 2.20° on axial images and 2.16° ± 2.24° on sagittal images. There was excellent agreement between actual and virtual pedicle screw trajectories in the axial and sagittal plane with ICC = 0.99 (95%CI: 0.992-0.995) (p<0.001) and ICC= 0.81 (95%CI: 0.759-0.855) (p<0.001) respectively. When comparing thoracic and lumbar screws, there was a significant difference in the sagittal angulation between the two distributions. No statistical differences were found distance from the reference frame.

CONCLUSION

The virtual projection view is clinically accurate compared to the actual placement on intra-operative CT in both the axial and sagittal views. There is slight imprecision (~2°) in the axial and sagittal planes and a minor difference in the sagittal thoracic and lumbar angulation, although these did not affect clinical outcomes. In general, we find that pedicle screw placement using intraoperative cone beam CT and navigation to be accurate and reliable, and as such have made it a routine part of our spine practice. This study was approved by the University of Minnesota IRB (#1303E30544).

Spinal Navigation and Imaging: History, Trends, and Future

The clinical practice of spine navigation has rapidly grown with the development of image-based guidance. In this paper, a brief history of spinal navigation is presented and a review of clinical outcomes for 12,622 pedicle screws placed using the latest technology in the sacral, lumbar and thoracic regions. The clinical evidence demonstrate that intraoperative 3D image guided surgery has a 96.8% success rate. A concluding section detailing existing barriers that limit more widespread adoption and future development efforts is presented.

A prospective multicenter registry on the accuracy of pedicle screw placement in the thoracic, lumbar, and sacral levels with the use of the O-arm imaging system and StealthStation Navigation

STUDY DESIGN

An international, multicenter, prospective, postmarketing clinical registry to record the accuracy of pedicle screw placement, using the O-arm Complete Multidimensional Surgical Imaging System with StealthStation Navigation.

OBJECTIVE

To evaluate the accuracy of pedicle screw placement in common neurosurgical practice and assess the patient's radiation exposure.

SUMMARY OF BACKGROUND DATA

Several imaging techniques have been used to increase accurate pedicle screw placement. The O-arm 3-dimensional (3D) imaging (Medtronic Navigation, Louisville, CO), an intraoperative computed tomographic (CT) scan, combined with an existing navigation system was reported to further increase accuracy of screw placement, especially because an intraoperative 3D scan provides information for screw adjustment before wound closure.

METHODS

Patients already planned for instrumented spinal surgery were operated while using the O-arm as imaging device and the StealthStation Navigation (Medtronic Navigation, Louisville, CO) as navigation tool. At the end of all pedicle screw insertions, the placement was classified according to a validated method. The accuracy of pedicle screw placement based on the intraoperative 3D scan and the surgeon's perception of correct screw placement were assessed as well as the radiation doses the patient received during the entire procedure.

RESULTS

During a 16-month period, a total of 1922 screws in 353 patients were evaluated. In 97.5%, the screws were correctly placed. Only 2.5% of the screws were considered as misplaced, and 1.8% of the screws were revised during the same procedure. When the surgeon perceived the screws to be correctly placed, the CT scan verified his assessment in 98.5% of the cases. The mean radiation dose was comparable with half the dose of a 64 multislice CT scan.

CONCLUSION

The use of the O-arm in combination with a navigation system increases the accuracy of pedicle screw placement. The accuracy of the surgeon's perception and the need to limit the radiation dose for the patient justify an additional CT scan only after careful assessment of the potential additional value.