Darren R. Lebl, MD, MBA

Since the rise of pedicle screw instrumentation for stabilization of the spine in the 1990s, the status quo has consisted of surgeons inserting the implants “freehand.” The technique has historically involved direct surgical exposure of spinal landmarks and insertion of screws by surgeons who were trained expert craftsmen through experience with direct visualization of the spinal anatomy in the surgeon’s “mind’s eye.”

In recent years, surgical navigation has provided a valuable supplement by providing an intraoperative “map” or visualization of the patient’s anatomy for guidance of implant placement. This GPS-type concept is familiar to anyone who has driven a car using a navigation system or used a smart phone to determine one’s location. Similarly, surgeons can use infrared cameras placed in the OR to visualize LEDs or optical markers placed on their surgical instruments. After obtaining an intraoperative “reference scan,” the position of the surgeon’s instruments relative to the patient’s spinal anatomy can be visualized. This concept underlies surgical navigation systems, which are booming in popularity. The value added by augmented reality consists of providing the surgeon with a headset such that the navigation images showing instrument and implant position inside the patient’s body are overlayed onto the surgeon’s visual field such that the surgeon need not look away at a separate monitor or screen.

Maximilian Schwendner, MD, and colleagues reported a modification of this known technology in which the infrared cameras are attached to the surgical instruments and the reference array rather than a separate free-standing tower in the OR. Augmented reality goggles were used to present the 3D imaging and surgical plan onto the operative field to place 180 screws in 20 patients. The authors had to replace three (1.7%) of the screws and the accuracy was 90.5% as desired (Gertzbein-Robbins scale grade A), which is similar to several other studies of screw placement both freehand and with navigation. That leaves 9.5% of screws that had Gertzbein-Robbins scale grades B, C , D and E (2 mm to more than 6 mm of deviation of the implant position from the planned position), which represents an opportunity for improvement.

Several studies have demonstrated value of augmented reality, navigation and robotic systems to improve accuracy and reduce radiation exposure relative to freehand screw placement. The novelty of the current study consists predominantly of a more compact and streamlined setup. As these technologies improve, these types of innovations that lower the physical footprint of the navigation system and increase its portability will improve the broader adoption of these techniques at ASCs and provide lower-cost options for hospitals worldwide.

Reference:

Avrumova F, et al. J Spine Surg. 2021;doi:10.21037/jss-20-687.