TO THE EDITOR: We read with great interest the article by Liu et al.1 (Liu A, Jin Y, Cottrill E, et al. Clinical accuracy and initial experience with augmented reality–assisted pedicle screw placement: the first 205 screws. J Neurosurg Spine. 2022;36[3]:351-357). The authors performed a retrospective study aimed at reporting on the accuracy of pedicle screw placement using augmented reality (AR) assistance with a head-mounted display (HMD) navigation system. Here, we add our contribution, which may help to better understand the use of AR technology.
To begin, we provide some historical context: the virtual retinal display was created in 1991 at the University of Washington’s human interface technology laboratory.2 The objective was to create a virtual display with full color, a broad field of vision, high resolution, high brightness, and a low cost.2 While there is undoubtedly a lot of excitement about AR right now, this technology has been available for decades, and researchers have been working on it for 30–40 years.
Indeed, current emphasis on AR and the framing of pedicle screw placement accuracy can be explained as the common currency and language in terms of verifying a navigation system and establishing a more accurate system for pedicle screw placement since, in fact, it is not about fixing a problem that does not exist, but this is the barrier to entry for developing a completely new navigational system.3,4
Surgeons are familiar with the remote 2D display that is utilized in conventional manual computer navigation or surgical suites.5 However, certain technological disadvantages have been noted, such as line-of-sight interference. It is not a genuine 3D display since it is created using a remote tracking camera that can only observe the patient’s reference frame and the instrument’s tracking.3–6 A second disadvantage is the learning curve. There is concern that individuals learning how to use this kind of technology may be unable to perform freehand instrumentation.3–6 Third are the hazards of diverting the surgeon’s focus away from the patient and his or her failure to pay attention to the patient, as well as many risks associated with minimally invasive surgery tool placements.5
Despite technological developments such as robotics, we continue to see surgeons staring at a distant screen, unable to connect what is happening in the surgical field with what is happening on the remote screen. To summarize, no technology other than HMD is superior for pedicle screw placement.1,7 It does not require the use of a traditional network device interface camera, which is required for accuracy by all other navigation systems. Instead, it depends on the distance between the tracking frame and the instrument being navigated or tracked or on tracking cameras directly mounted on the surgeon’s headset.1,7 These are intelligent, advanced, high-resolution tracking cameras that are able to perform surface-active matching registration of the patients, allowing the surgeon to see active movements and deformity corrections while receiving objective data via artificial intelligence into the HMD.7 Additionally, they may be used to guide osteotomies, decompression, and soft-tissue surgeries. Thus, research on AR assistance with an HMD navigation system is not about pedicle screw placement. Instead, it is about demonstrating the system’s accuracy via pedicle screw placement so that surgeons may experiment with all the available AR options.
HMD represents a natural progression of spinal navigation technology.1,7 It is clinically accurate and precise, intended to minimize inaccuracies during operations that are potentially very technically deleterious to a patient.1,7 It is intuitive and has a relatively low learning curve. Not to compete with robots, but when robotics advances and image-guided robotics data are put on the surgeon’s head, the experience will be quite similar to wearing a headlamp. It is ultimately cost-conscious and a lot cheaper than any of the other options.1
Disclosures
The authors report no conflict of interest.
References
- 1↑
Liu A, Jin Y, Cottrill E, et al. Clinical accuracy and initial experience with augmented reality–assisted pedicle screw placement: the first 205 screws. J Neurosurg Spine. 2022;36(3):351–357.
- 2↑
Viirre E, Pryor H, Nagata S, Furness TA III. The virtual retinal display: a new technology for virtual reality and augmented vision in medicine. Stud Health Technol Inform. 1998;50:252–257.
- 3↑
Kosmopoulos V, Schizas C. Pedicle screw placement accuracy: a meta-analysis. Spine (Phila Pa 1976). 2007;32(3):E111–E120.
- 4↑
Perdomo-Pantoja A, Ishida W, Zygourakis C, 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.
- 5↑
Bourgeois AC, Faulkner AR, Bradley YC, et al. Improved accuracy of minimally invasive transpedicular screw placement in the lumbar spine with 3-dimensional stereotactic image guidance. J Spinal Disord Tech. 2015;28(9):324–329.
- 6↑
Phillips FM, Cheng I, Rampersaud YR, et al. Breaking through the “glass ceiling” of minimally invasive spine surgery. Spine (Phila Pa 1976). 2016;41(Suppl 8):S39–S43.
- 7↑
Frisk H, Lindqvist E, Persson O, et al. Feasibility and accuracy of thoracolumbar pedicle screw placement using an augmented reality head mounted device. Sensors (Basel). 2022;22(2):522.
