Augmented Reality Applications in Orthopedic Spine Surgery

Abstract and Introduction

Abstract

The application of augmented reality (AR) in surgical settings has primarily been as a navigation tool in the operating room because of its ease of use and minimal effect on surgical procedures. The surgeon can directly face the surgical field while viewing 3D anatomy virtually, thus reducing the need to look at an external display, such as a navigation system. Applications of AR are being explored in spine surgery. The basic principles of AR include data preparation, registration, tracking, and visualization. Current literature provides sufficient preclinical and clinical data evidence for the use of AR technology in spine surgery. AR systems are efficient assistive devices, providing greater accuracy for insertion points, more comfort for surgeons, and reduced operating time. AR technology also has beneficial applications in surgical training, education, and telementorship for spine surgery. However, costs associated with specially designed imaging equipment and physicians' comfort in using this technology continue to remain barriers to its adoption. As this technology evolves to a more widespread use, future applications will be directed by the cost-effectiveness of AR-assisted surgeries.

Introduction

One of the main applications of virtual reality (VR) and augmented reality (AR) systems in the operating room (OR) is as a navigation tool. In standard surgical navigation, the surgeon must divert their attention away from the surgical site to consult a separate navigation screen, where they can verify anatomical landmarks and positions displayed on a 3D model. AR-based navigation would enable the surgeon to view this information without obstructing their field of view or causing distractions. In AR-based navigation, virtual information is overlayed onto the real-world environment, allowing the surgeon to view both simultaneously (Figure 1). AR can improve surgical efficiency and encourage the wider adoption of navigation technologies in spine surgery. AR is easier to use in the OR and does not markedly change the surgical procedure. However, the costs associated with specially designed imaging equipment and physicians' comfort in using this technology continue to remain barriers to its adoption.^[1]

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Figure 1.

Image showing the surgeon's operating view using augmented reality to superimpose medical scans and data in the field of vision above the patient's open surgical site.⁴¹

In this article, we review the current literature regarding the use of AR in spine surgery and various other areas where it is applicable.

Table 1. Summary of Registration Strategies
	Specifications	Advantages	Disadvantages
Marker-based	Detecting an object (marker) placed onto a patient's anatomy as a reference point to align a 3D model onto the operating field	Minimal infrastructural requirements, superior accuracy than established methods, minimal added cost, and time	Markers can become displaced or obscured during surgery, are large and require attachment to the patient's body, necessitate sterilization, and can be expensive
Surface-based	Intraoperative, accessible surfaces are used as markers, using the unique pattern of a bone surface as a marker to align the 3D surgical plan with the actual surgical field	Radiation-free; only requires AR-HMD, a pointing device to navigate, and a marker to sense the exposed bone surface	This registration methods have only been studied on cadavers without any motion compensation
CAMC (camera-augmented mobile C-arm) system	Mobile C-arm with a standard video camera. Intraoperative radiographs are matched with the camera image of the surgical area using a 3D coordinate system shared with an AR headset	Requires a lower radiation dose, augments surgeon's vision of the operation situs. Radiographs can be viewed in real time during the operation	Requires the use of C-arm, high translational error in tracking the C-arm (0.8 mm), only used in procedures, and good for tasks that do not require very high accuracy, such as moving the C-arm or obtaining radiographs from different angles to check tool placement
Marker-less	Using references from the real environment instead of markers to place virtual images onto the operating field	No need for an object-tracking system, skin features such as spots, moles, and pigmentation are used for navigation	Needs advanced technological cameras, sensors, processors, and algorithms

Table 2. Augmented Reality User Interfaces in Spine Surgery
AR-User Interface	Description	Display
Monitor-based AR	C-arm contains embedded video cameras that are directed toward the operating field	OR monitor displays the video feed with AR overlay
HMD-AR	Worn on the surgeon's head as goggles	The AR view is superimposed within the goggles (ie, surgeon's visual field)
Microscope-AR	Projected predefined AR objects in the microscope's view during microsurgery	AR view seen through the microscope's lens
Projector-based AR	Holographic AR overlays are displayed on glass screens placed between the surgeon and the surgical site	AR view displayed on the glass screens