The use of assistive technology for placement of pedicle screws has had a tremendous impact on the practice of spine surgery. Computer navigation and robot-assisted navigation are becoming increasingly widespread. The utility of such assistive technology has been well documented. These technologies result in improved accuracy of pedicle screw placement compared to freehand techniques, and therefore lead to fewer complications related to screw placement and less return to the operating room (OR) for malposition.1–12 With the benefit of assistive navigation clear, there has been a host of competing technologies developed and marketed to surgeons and hospital systems (Table 1). Although the nuances among the systems vary, the goal is the same: improved accuracy in placement of pedicle screws and other surgical tasks that fall under the generic heading of intraoperative navigation. The adoption of a particular platform, up to this point, has been mostly dependent on the preferences of a certain group of surgeons, a department, or a hospital system. There does not appear yet to be a clear advantage for any particular system in terms of patient outcomes or workflow. Differences exist with regard the surgical workflow, the need for an intraoperative CT scan, the process for registration, the compatibility with different surgical instruments and vendors, and other factors. Although the accuracy of all these technologies is quite excellent, the focus for further innovation seems to be improvement in the surgical workflow and the surgeon’s experience. Important work is being done in creating a registration process that is more automated, less intrusive, and less time-consuming. Gradual degradation of performance would be an improvement over the acute failure most systems now suffer from. As more and more surgical instruments are trackable, intraoperative navigation becomes ubiquitous and an expectation of the OR environment. Improvements in these areas are underway and will lead to further adoption, prevalence, and the immersion of the surgeon into a heretofore unknown operative experience.
Technologies for spinal navigation
| Product | Vendor |
|---|---|
| StealthStation | Medtronic |
| Intraop spinal navigation | Brainlab |
| Machine-vision image-guided surgery system | 7D Surgical |
| Stryker NAV3i | Stryker |
| Ziehm Vision (FD) Vario 3D | Ziehm |
| Mazor X Stealth robot | Medtronic |
| ExcelsiusGPS robot | Globus |
| ROSA ONE Spine robot | Zimmer Biomet |
| TIANJI robot | Tinavi |
| xvision AR system | Augmedics |
| Arcadis Orbic 3D | Siemens |
| Pulse navigation | NuVasive |
Liu et al. present results from placement of 205 pedicle screws in 28 patients performed using novel augmented reality (AR) assistance.13 Surgeons are fitted with an AR headset that allows for direct image projection onto the operative field and computer-navigated placement of pedicle screws. The authors found that, following independent neuroradiology review of postoperative CT scans, the screw accuracy rate was 98%, based on grade A or B Gertzbein-Robbins14 scores. The use of AR in the area of spinal instrumentation is a novel development and the authors should be commended for pioneering this new technology. The accuracy results presented, although subject to the limitations they describe well, compare favorably to other intraoperative navigation technologies currently available.15–21 Some of the potential benefits of AR-assisted technology would be the ability to simultaneously visualize the actual operative field while benefitting from computer navigation. This would help alleviate challenges associated with line-of-sight interruptions and attention shift, as the authors describe. The current version of this device does not allow for loupe magnification or a head-mounted light source, which would impede surgical workflow in certain situations but will soon be overcome. As the authors describe, screw entry points were identified based on anatomical landmarks while wearing loupes, prior to use of AR assistance for screw placement. Like other computer navigation platforms, this technology requires acquisition of an intraoperative CT scan, which may alter existing surgical workflow and increase OR time. Additionally, there remains the possibility of dislodgment of a reference array, which must be detected and addressed. Whereas the functionality of the AR technology in its current state essentially replicates the functionality of other current navigation systems, future iterations may prove valuable as the technology continues to evolve.
The future of spinal navigation will undoubtedly grow with the continued innovation of computer navigation, robotics, and AR technologies. The improved accuracy attained using these devices compared to freehand techniques is widely supported in the literature. Despite this, adoption of computer-assisted navigation has yet to become completely ubiquitous, with some estimates suggesting that only 15%–20% of eligible surgical cases use this technology. The cost-benefit analysis of these technologies has not been uniformly viewed with enthusiasm. Potential barriers to universal implementation include cost, learning curve, workflow disruption, and compatibility issues with existing vendors and implants.22
The continued expansion of this technology is likely to be dependent on a number of factors independent of pedicle screw placement accuracy. Of these, perhaps the most limiting is the startup and maintenance costs. The capital required to purchase these technologies may be restrictive for some hospital systems, as well as for independent surgical centers or in international settings. The need for personnel to run the equipment for each surgical case adds to the cost. Other needed innovations include improvement in the surgical workflow. Technologies that are cumbersome and increase overall operating time are less likely to be viewed favorably. Additionally, problems with line-of-sight interruptions and attention shift are common occurrences with most of these technologies, and strategies to avoid or minimize these disruptions to surgical workflow may increase utilization. Other considerations include the radiation exposure associated with any assistive technology. Whereas computer navigation and less reliance on intraoperative fluoroscopy have reduced radiation exposure for the surgeon, the use of intraoperative CT is likely to increase patient radiation exposure.23–26 Future innovations minimizing radiation exposure to the patient and OR staff while still achieving the needed registration would be valuable. Expanding the indications for navigation beyond pedicle screw placement may also be advantageous. For example, navigation of interbody device placement and navigated drilling are finding a receptive audience. The ability to coregister with MR images, which intracranial software does routinely, is not commonly available in spine applications and would better allow for use of navigation when dealing with soft-tissue pathologies such as discs or tumors.
The advent of 3D intraoperative navigation technology has changed the practice of spine surgery. Spinal navigation offers clear benefits to patients, with resulting surgeries that are faster and more accurate. New advancements in this domain, of which AR is one, will continue to push the field forward. The question remains which of these incremental improvements will lead to a radical transformation in the treatments that spine surgeons are able to offer their patients.
References
- 1
Perdomo-Pantoja A, Ishida W, Zygourakis C, Holmes C, Iyer RR, et al. Accuracy of current techniques for placement of pedicle screws in the spine: a comprehensive systematic review and meta-analysis of 51,161 screws. World Neurosurg. 2019;126:664–678.e3.
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Molliqaj G, Schatlo B, Alaid A, Solomiichuk V, Rohde V, et al. Accuracy of robot-guided versus freehand fluoroscopy-assisted pedicle screw insertion in thoracolumbar spinal surgery. Neurosurg Focus. 2017;42(5):E14.
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- 13↑
Liu A, Jin Y, Cottrill E, Khan M, Westbroek E, et al. Clinical accuracy and initial experience with augmented reality–assisted pedicle screw placement: the first 205 screws. J Neurosurg Spine. Published online October 8, 2021. doi:10.3171/2021.2.SPINE202097
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