How “real” is mixed reality navigation and visualization for knee joint reconstruction surgery? At the recently concluded International Society for Technology in Arthroplasty’s 35th Annual Congress on August 31, 2024, two studies were presented that represent mid-course data points for one of the systems currently making its way into orthopedic operating rooms.
The system, brand named STELLAR and developed by Miami-based Polaris, Inc., was bench tested by a Columbia University team for conformance to ASTM standards and then tested by the same team on a cadaveric knee arthroplasty model.
What Is Mixed Reality?
Mixed reality refers to an immersive computer-generated environment in which elements of the physical and virtual world are blended together. Sales of mixed reality gaming, educational and industrial products cleared $3 billion in 2023 and six of the best-selling systems were:
- Microsoft HoloLens 2
- Magic Leap 2
- Meta Quest Pro
- Lenovo Think Reality VRX
- Apple Vision Pro
- Sony PSVR 2
Is there a use-case for mixed reality headsets and software in large joint reconstruction?
Columbia’s two tests suggest there is and that, as a strategy to improve knee arthroplasty accuracy and efficiency, these tools show promise.
The ASTM Test
Using the latest American Society for Testing and Materials (ASTM) standards for surgical navigation and robotic assist systems, the Columbia University research team put Polaris’s STELLAR mixed reality surgical system to the test.
Polaris’s STELLAR system is an open-platform, imageless system with a small footprint (important in the OR), minimal toolkit, and which overlays data holographically onto the surgical scene. “Mixed Reality” in other words.
The team measured the platform’s ability to accurately locate points and planes on tracked tools across the tracking movements, including rotational and positional extremes. Their testing extended the ASTM standard to include additional rotation tests and an evaluation procedure for planar accuracy metrics.
The team found that STELLAR achieved ASTM standard accuracy and reliability levels. Tracking errors were sub-millimeter and sub-degree.
The Cadaveric Test
The Columbia team then evaluated the accuracy of the STELLAR platform in a cadaveric simulated use study with four pelvis-to-toe cadaveric specimens where the left and right knees in each specimen were operated on.
The team collected depth and angular error data for proximal tibial, distal femoral, and posterior femoral resections in eight cadaveric knees. They then compared platform-navigated resection metrics to caliper measured resection depths and post-operative CT measured angles. Finally, the team compared ground truth measurements to the surgeon accepted metrics displayed by the platform before resection.
Again, the team found that the STELLAR met accuracy and reliability standards by achieving sub-millimeter and sub-degree average errors.
Conclusions
John Cooper, M.D., associate professor of orthopedic surgery at Columbia University Irving Medical Center, said, “These findings demonstrate that the STELLAR mixed reality surgical platform achieves sub-millimeter and sub-degree tracking errors, providing balancing and resection accuracy comparable to modern robotic-assisted systems.”
“The system does not need preoperative imaging and requires just 14 intraoperative landmarks, is open-platform and agnostic to knee implant system, overlays meaningful clinical data holographically onto the surgical field, and requires minimal instrumentation, allowing it to maintain a reduced footprint while delivering a comprehensive set of metrics.”
“The new data presented by our research partners is a testament to the precision and reliability of our technology,” said Paul Mikus, CEO of Polaris, manufacturer of the STELLAR system.
“Achieving sub-millimeter and sub-degree accuracy in both cadaveric simulations and ASTM-standard testing demonstrates our platform can match the precision of robotic systems while offering significant advantages in simplicity and usability for TKA [total knee arthroplasty] procedures. We believe our technology represents a significant advancement in surgical guidance, providing surgeons with the tools to enhance surgical precision, patient recovery, and reduce the complexity of TKA procedures.”
OTW asked Dr. Cooper to explain further the way in which spatial computing improves operating precision for doctors and patients. “Accurate identification of a patient’s bony anatomy, range of motion, knee alignment, and soft tissue laxity gives surgeons access to the data to plan and execute a patient-specific surgical plan to optimally restore knee function,” explained Dr. Cooper.
“Technology such as STELLAR Knee allows this data to be gathered in real-time, processed, and allowed to make a personalized surgical plan intraoperatively at the touch of the surgeon’s fingers. Emerging research suggests that these patient-specific plans that can be done with modern technology can lead to better patient outcomes.”
“The STELLAR Knee platform is precise within 2mm and 2 degrees of the surgical target (most of the time within 1mm and 1 degree). This is the gold standard for orthopedic navigation technology and is as good or better than other platforms on the market.”
“The calipers precisely measure the amount of bone resected and provide the gold standard reference for the navigated surgical plan. This is the best way to verify that the surgeon has removed the exact amount of bone that they planned and ensures the implant will sit in the desired position in the patient’s knee.”
“For surgeons, the STELLAR Knee simplifies procedures by providing the precision benefits of robotics without the complexity, footprint and cost of a robot,” Paul Mikus told OTW. “We are providing the information that drives robots directly to the surgeon.”
