Certain implanted medical devices, like pacemakers, have sensors that allow data transmission between patients and doctors. But orthopedic implants typically haven't had these features — until the arrival of  Zimmer Biomet's "smart knee," Peter Loftus reports for the Wall Street Journal.

A knee replacement that can talk to your doctor

Zimmer's smart knee, developed alongside  Canary Medical, contains a sensor device with electronics, accelerometers, and gyroscopes to track the movement of the knee, all powered by a battery that can last at least 10 years.

The sensors in the knee transmit data on walking speed, stride length, and more via radio waves to a home-base station that's roughly the size of a small notebook, Loftus reports. That box can then be connected to a computer. The data is automatically sent to physicians through an online dashboard, and can be sent to patients through a phone app.

Canary Medical CEO Bill Hunter said more research could glean more potential clinical benefits from the smart knee. For example, data from the knee could tell the physician the patient is unable to bend or extend their knee as far as they'd expect, so the doctor could order a more aggressive physical therapy regimen in order to avoid a buildup of scar tissue that could require more expensive future interventions.

Canary is also working on ways to utilize machine learning to analyze data and find signs of trouble, Hunter said. "We can start to give the physicians some sort of early-warning system as to whether or not there's a problem."

What the future could hold

Typically, doctors monitor patients' progress following an orthopedic implant through in-person checkups, patient self-reporting, and imaging procedures, if necessary. Useful information can often be missed with these methods, like if a patient is taking fewer steps each day than they're supposed to, Loftus reports. Patients could also report inaccurate information to their physician.

"We've never had the ability to objectively know how a patient's truly doing after their surgery," said Yair Kissin, an orthopedic surgeon and sports medicine specialist at  Hackensack University Medical Center.

But now, doctors and medical device engineers say it's likely sensors will be added to artificial hips, shoulders, and spinal implants, Loftus reports. These sensors could even be applied to other devices not related to orthopedics, like tracking whether a brain aneurysm is about to burst or whether hearing aids or vision devices need to be adjusted.

"Using sensors to get data from a patient, you can have thousands of data points to analyze and figure out exactly what's going on with a patient," said Edward Harvey, a trauma surgeon and professor of medicine at  McGill University.

For its part, Canary is working on different versions of their sensor device that could be applied to artificial hips and shoulder implants, Hunter said.

Meanwhile,  Johnson & Johnson is developing a version of its surgical trauma plates — which are used to stabilize bone fractures while they're healing — that will be equipped with sensors and could potentially tell a surgeon whether a fracture site is healing, according to a company spokesperson.

"Most every major medical device should provide some sort of feedback to the clinician," Hunter said. "Ten years from now, we'll think it's crazy that major medical devices didn't provide any type of feedback to the doctor." (Loftus, Wall Street Journal, 4/11)