Fighting wear and tear

Improving outcomes for patients with hip and knee implants

Every day, John LeFeuvre tries to get in at least 7,000 steps, tracked by his Fitbit.

“I have the competitive nature of a sportsman,’ explains John, a 74-year-old retired special education teacher. “The Fitbit spurs me on.”

John wears a Fitbit as part of a Lawson research study.

The device tracks his activity levels following a hip replacement surgery at London Health Sciences Centre’s (LHSC) University Hospital.

“It was inevitable. I played a fair amount of sports when I was young, everything from football to basketball to hockey. It’s great when you’re young, but you pay for it when you’re older.”

John’s hip replacement was performed using a new surgical technique called a muscle-sparing approach, which holds promise in leading to a faster recovery.

To assess whether activity and function is improved with this technique, a team of Lawson researchers are using technology like Fitbits and wearable sensors. The sensors are custom-programmed to capture data on a patient’s mobility and function. They’re being used with hip replacement patients to assess fall risk.

“We’ve come a long way with artificial joints, but we want to advance even further,” says Dr. Matthew Teeter, Lawson Scientist.

“Our research focuses on developing tools to speed patient recovery, improve function and make implants last longer.”

Harnessing Technology

The different tracking measures being used in various studies are giving researchers and clinicians a clearer picture of the patient’s experience and the success of their implanted device.

“Surgeons need more accurate measures of a patient’s hip or knee function to decide on the best surgical techniques, set targets for recovery and innovate with new ideas,” explains Dr. Teeter, who is also an Assistant Professor at Western University. “Our wearable sensors provide these measures.”

The sensors, programmed in-house by PhD candidate Riley Bloomfield, capture a total of 55 measurements from the upper and lower leg, including multiple angles, velocities and speeds. Through artificial intelligence (AI), the research team is harnessing the complex sets of data to predict patient outcomes.

The sensors are worn by patients below and above each knee as they perform a timed-up-and-go (TUG) test – a routine clinical test that involves getting up from a chair, walking three metres, returning and sitting back down. The faster a patient completes the test, the better their function.

Wearable sensors take the TUG test to a whole new level. The sensors provide a vast amount of data that is transmitted to a mobile app.

“While the original TUG test gives us a prediction of function, it doesn’t measure complexities. It doesn’t tell us whether the patient’s knee is stiff or how it’s bending for example,” says Dr. Brent Lanting, Orthopaedic Surgeon at LHSC and Associate Scientist at Lawson. “The sensors provide much more information.”

In an initial study, the wearable sensors were used with 68 knee replacement patients to assess function before surgery. The data was put into an AI algorithm which identified two groups of patients.

“We weren’t sure why the machine identified these two groups,” explains Dr. Teeter. “We didn’t tell the computer what to do; we simply asked it to make sense of the data.”

Patients continued to perform the tests at regular follow-up appointments and the difference between the two groups soon became clear. Function did not improve following surgery for the majority of patients in the first group while most in the second group experienced significant improvements.

“These findings are critically important. Using data from wearable sensors, a machine was able to predict which patients would improve and which patients would not,” says Dr. Teeter.

The team hopes this research can help personalize care for different groups of patients, communicate expectations and inform health care funding decisions.

“By predicting how a patient will respond after surgery, we will better understand what each patient needs in terms of surgical techniques, length of hospital stay, pain management and physiotherapy,” says Dr. Lanting.

They hope to collect even more data by combining the sensors with patient-reported outcomes like pain. They will also compare function ability against actual activity levels from the Fitbits. Specific groups of patients will be further classified with AI, studying whether recovery differs by implant choice, surgical technique or patient factors like age, sex and BMI.

Retrieving the implant

The team is also working to improve implant design to reduce the need for revision surgeries.

Revision surgeries involve replacing an implant when it wears down or fails due to age, material defects or infection.

“Implants are lasting longer, but people are also living longer and many patients are younger at the time of surgery,” says Dr. Teeter. “With higher rates of obesity and more patients wanting to remain highly active, implant failures remain an issue.”

Dr. Teeter studies recovered implants at Lawson’s Implant Retrieval Laboratory located at LHSC’s University Hospital. The facility is one of only two in Canada and houses more than 4,000 recovered hip and knee implants.

Each implant is examined in an attempt to understand why it failed. They construct ‘wear maps’ by scanning each implant with micro-CT imaging and then visually reconstructing it. The map shows where and how badly the implant has worn down. Researchers can look at corrosion, fractures and cracks under the surface.

“Each implant on its own doesn’t tell us much. But when we’re able to look at groups of them, meaningful patterns emerge,” explains Dr. Lanting. “Our goal is to improve implant design by understanding the effects they have on failure mechanisms and patient outcomes.”

“Lawson has a unique collaborative environment,” adds Dr. Teeter. “There are scientists, surgeons, coordinators, assistants and trainees who are all very keen on research. We bring different disciplines together to develop technological innovation that can be applied directly to patient care.”

Together, they are painting a brighter future for people like John, who views this research as vital. “I’m happy to participate. If you can do something to help future patients, I think it’s a citizen’s obligation.”

CROSS COLLABORATION

With expertise in orthopaedic and microbiome research, Lawson Scientists are collaborating to better understand infections in hip and knee implants.

“Implant infection is a long-standing problem that can be devastating and difficult to treat. Oftentimes it’s not clear whether an implant is infected or not,” says Dr. Matthew Teeter. “Loosening is a primary cause of failure and there’s a growing theory that those implants are actually infected.”

He is collaborating with Dr. Jeremy Burton to test this theory. They are conducting DNA analysis on implants as soon as they are removed from patients who need revision surgery. The implants, even those not thought to be infected, will be studied for signs of bacteria. The team will then look at whether certain regions are more prone to infection than others and analyze the damage in Lawson’s Implant Retrieval Laboratory.

The goal is to provide clinicians with more tools to diagnose and treat infections in the future.