June 01, 2021

From aiding in the design and testing of some of the latest robotic technology to conducting research aimed at improving surgical accuracy and patient outcomes, surgeons in the Department of Orthopaedic Surgery at Washington University School of Medicine are leading the way in advocating for robotic-assisted tools to become the global standard of care for partial knee replacements.

Leading the Way

In the latest research in the field, orthopedic surgeons here found that robotic technology dramatically improves patient outcomes for partial knee replacements. The research, published online in The Bone & Joint Journal in March 2021, noted that robotic-assisted surgery improved alignment accuracy five to 10 times better than with manual joint reconstruction procedures. The research comes on the heels of a study published last year by WashU orthopedic surgeons that highlighted the connection between alignment accuracy and revision rates for partial knee replacements.

“It’s a known problem that the risk for revision surgery is high for partial knee replacements, no matter the expertise of the surgeon or the type of implant used,” says knee and hip specialist Robert Barrack, MD, the Charles F. and Joanne Knight Professor of Orthopaedic Surgery. “That’s because we have to account for multiple angles when preparing bone and inserting implants. Even being slightly off of perfect alignment can cause issues down the road, including the need for revision surgery.”       

Globally, partial knee replacement revision surgeries were needed in up to 15% of all cases within 10 years of the initial procedure. Significantly, a WashU study published in the Journal of Bone and Joint Surgery in 2020 found that less than 20% of partial knee replacement procedures reviewed hit all alignment targets. The study here mirrored other studies around the world examining long-term outcomes.

“Alignment accuracy jumps to 92% and higher with robotic-assist technology,” says Ryan Nunley, MD, a WU joint preservation, resurfacing and replacement specialist who has worked to enhance robotic technology for joint replacement procedures.

Robotic surgery

Orthopedic surgeon Ryan Nunley, MD, performs a knee surgery using a Stryker Mako robot at Barnes-Jewish West County Hospital with fellow Lee Sasala, MD.

Surgeons at Washington University School of Medicine have tracked patient outcomes from robotic partial knee replacements for the past three years. None have failed and all were within the tight parameters customized for every patient for successful alignment.

Alignment is fine-tuned by using a pre-operative CT scan of the knee coupled with real-time tracking devices on a patient’s upper and lower leg bones. The robotic system then creates a 3D visual model of the knee highlighting the proper alignment and surgical path in bright green that the surgeon can view real-time on an imaging monitor in the operating room. While robotic total knee replacements also are done, surgeons say partial knee procedures benefit the most. “In those cases, the space to work in is so small and our field of view is not as expansive as with a total knee replacement,” says Nunley. “The robot helps us make our cuts more accurately and our alignment on all planes is so much better.”

Investing in Robotic Technology, Research and Training

Washington University Orthopedics is expanding its robotic program to include three new faculty who are fellowship-robotic trained. Plans are in the works to expand the number of robots available. As more are added, robotic options may expand to other areas, such as the hip, shoulder and spine.

Ongoing research seeks to improve the technology even more and track long-term outcomes. Among the advantages of robotic systems are that they can store data much like the “black boxes” found in airplanes, collecting and storing all surgical information for later review and study. The data includes any angle adjustments made by the surgeon during a procedure.

Robotics is a core training module within the orthopedic residency and fellowship training programs at Washington University. All trainees also receive comprehensive training in non-robotic procedures. Notes Barrack, “There are still cases in which a non-robotic open surgery or arthroscopic procedure must be performed, and our fellows receive extensive training in all types of surgical techniques to make the best decisions for their patients.”

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