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For nearly two decades, Andrew Pearle, M.D., has been working on what many now see as the future of orthopedic surgical planning. Dr. Pearle, Chief Emeritus of the Sports Medicine Institute at the Hospital for Special Surgery (HSS), has long been at the forefront of computer-assisted and robotic procedures. Today, his focus has shifted to a powerful evolution of digital twin technology.​
Through a combination of advanced imaging, physics-based modeling and artificial intelligence (AI), his team is creating personalized virtual replicas of patients’ knees that can simulate real-world biomechanics before a scalpel touches skin. The goal is one that orthopedics has been chasing through many avenues: moving beyond one-size-fits-all surgical planning toward truly personalized care.
Backed by a recent $10 million gift from Lauren and Robert Steers, HSS is working to bring the digital twin technology out of the lab and into everyday clinical practice. In doing so, Dr. Pearle believes orthopedic care can become more predictive and precise, and ultimately more effective for both surgeons and patients.
Surgeons have been technically using early versions of digital twins for years through CT-based planning, robotics and navigation. However, the orthopedic industry has not yet fully embraced the potential of the technology beyond static imaging.
The evolution of digital twins in orthopedics opens the door to running predictive simulations instead of one-off pre-op plans, therefore expanding from implant positioning to risk prediction and outcome forecasting.​
The new definition of “digital twin” is a maturation of the traditional technology that OEMs and surgeons already know and rely on — robotics, imaging and AI — converging into a unified planning system. That’s where things start to get really exciting.
Dr. Pearle and his team have been working on a physics-based computational model of the knee for the past decade. They use MRI scans to create 3D models of patients’ knees that include bone, cartilage and menisci. Creating a model with that much data used to take weeks, but now with AI, it takes minutes.​
Because a patient’s MRI data is fed into the system, the model can simulate specific stresses, such as a pivot shift loading maneuver, and show how a patient’s knee reacts when subjected to that stress. Simulating real biomechanical behavior allows surgeons to see how each individual knee responds.​
“We’ve discovered that knees behave quite differently in the pivot shift exam, even among intact knees,” Dr. Pearle said.
Using digital twin technology and AI to run modeling gives orthopedic surgeons insight into which patients might be more susceptible to ACL injury. It also arms surgeons with more robust planning tools for surgical procedures tailored to each patient’s anatomy.​
“Digital twins inform us as to how we might use this type of data going forward,” Dr. Pearle said. “Orthopedics is all about decision-making. What surgery should I do? What treatment? Is the patient a surgical candidate or a physical therapy candidate? We could receive much more personalized information on our patients.” ​
Beyond the physics-based computational model, Dr. Pearle’s team has been developing additional data to input into a digital twin, including patient gender, the type of sports an athlete plays and neuromuscular control information.​
“The more data that you put into the twin, the more compelling the insights, and that’s what we’re focused on moving forward,” Dr. Pearle said. “All of this data could be amalgamated into a digital twin, perhaps rather than a medical record. Surgeons could run personalized simulations to further refine treatment plans.”
The next step for HSS is to use the funding they received to focus on the clinical implementation of the physics-based computational model. The hope is that within four years, every patient who comes to HSS with a relevant clinical problem will receive a digital twin of their knee.​
From its inception, the platform that Dr. Pearle’s team has been working on was designed to be modular. Inputs like motion analysis, strength data and demographics are critical, and other joints — including shoulder, hip and ankle, as well as spine — are the initial modules that HSS is considering.​
“We want the digital twin platform to eventually be flexible and modular,” Dr. Pearle said. “We can do that at HSS because we’ve got the in-house resources, clinical volume and financial support to make it happen.”
The main objective is to put the platform into everyday clinical practice. Right now, the digital twin model is used on a case-by-case basis in the HSS lab for complex ACL cases.
For example, when surgeons are trying to decide whether to perform a lateral extraarticular tenodesis or an osteotomy to treat a complicated injury, they segment the patient’s MRI scan into a 3D dataset and then run the physics-based computational model on it. Currently, this takes a couple of weeks and is too tedious to do for more than one patient every month.
“We want to complete the process within an hour, so we have the information to inform as many decisions as efficiently as possible,” Dr. Pearle said. “That’s where we’re headed with the digital twin platform. We want to implement it clinically in a real way.”
Though clinical implementation isn’t imminent, Dr. Pearle understands where the challenges lie and what needs to be done to succeed. Data validation and the use of information in clinical decision-making are at the top of the list. For the simulation to be accurate, the data must be correct.​
“We’re at the nascency of this,” Dr. Pearle said. “Integrating the technology into real-world practice is going to take a lot of time, good research and intentional thought.”
Beyond helping surgeons determine which knees are appropriate for conservative treatments or complex ACL reconstruction, or which augmentations of ACL procedures would work best for a particular patient, the digital twin platform can help build a stronger, more trusting relationship between doctor and patient.
Surgeons can show patients exactly what is happening inside their knee and why they are recommending a certain treatment plan. Patients can also have a bit more autonomy as well when it comes to injury prevention or improved recoveries.
​“It’s all about personalizing medicine and predicting outcomes,” Dr. Pearle said. “Digital twin technology can help prevent injuries and optimize a healthy lifestyle for people that maximizes their activity levels while protecting their joints. There’s an unmet need for that, and digital twin platforms can meet it.”
