Analyzing Augmented Reality (AR) Use in Spinal Surgery

Virtual reality (VR) is quickly establishing itself as a prominent force in the medical field. The VR market in healthcare is expected to grow to $3.8 billion by 2020, as per a Global Industry Analysts report. Another report by Grand View Research predicts this market to grow to a staggering $5.1 billion by 2025. This technology holds promise in revolutionizing the healthcare industry, with applications ranging from training medical professionals to providing precise assistance in the operating room.

The latter can be achieved by projecting a hologram of the surgical plan above the patient that is visible through goggles worn by the surgeon. In this approach known as augmented reality (AR), the surgeon can see both the physical patient and the virtual animation simultaneously. A study published on Oct. 25th, 2019, in The Spine Journal evaluated the use of this AR holographic navigation in spine surgery.

Background of the AR Surgery Study

The purpose of this study was to evaluate the surgical accuracy of holographic pedicle screw navigation using a 3D intraoperative fluoroscopy headset. Pedicle screws are often used in spinal fusion surgery to add strength and support. They are placed above and below the fused vertebrae and a rod is used to connect the screws to prevent excess motion and allow the bone graft to heal properly.

This experiment was a cadaver study that compared the accuracy of surgical navigation using the AR system to that of a traditional pose-tracking system. Three lumbar cadaver spines were placed in a non-transparent gel, with the only visible aspects of the spine being those that are commonly seen in the operating room. Preoperative planning was incorporated through

3D fluoroscopy and fiducial markers that were attached to the vertebrae of the lumbar spine. Real-time navigation was enabled via trackable, custom-made drill sleeve guides.

A total of 20 Kirschener-wires (K-wires) were navigated into the lumbar pedicles using the AR navigation, and 10 K-wires using the traditional state-of-the-art pose-tracking system. K-wires are surgical wires used to hold bone in place after an operation.

Results of the Cadaver Experiment

3D models of the spinal anatomy were created using post-experimental computed tomography (CT) scans. These models were used to assess the accuracies of each approach to the surgery. The researchers found no significant difference in the accuracies measured between AR-navigated drillings and the traditional pose-tracking system approach.

The mean translational errors between entry points (3D vector distance; p = 0.85) were 3.4 ± 1.6 mm compared to 3.2 ± 2.0 mm for each approach, respectively. In addition, the mean angular errors between trajectories (3D angle; p = 0.30) were found to be 4.3 ± 2.3° and 3.5 ± 1.4°, respectively.

The researchers concluded that holographic surgical navigation by way of a head-mounted device yields a similar accuracy to that of the high-end pose-tracking systems, which are perceived as the gold standard for the operation.

“These promising results could result in a new way of surgical navigation with minimal infrastructural requirements but now have to be confirmed in clinical studies,” the authors concluded.