Corrosion, Wear Examined in Retrieved Knee, Hip Implants

Researchers at Western University and the London Health Sciences Centre Research Institute (LHSCRI) found that “tribocorrosion”—the simultaneous action of mechanical wear and chemical reactions—is the primary cause of degradation in hip and knee implants, according to a study published in npj Materials Degradation.

The research team examined more than 240 retrieved hip and knee implant components to identify why these devices degrade inside the human body. Using optical microscopy, scanning electron microscopy, and spectroscopy, researchers assigned damage scores to quantify surface corrosion patterns.

Western University chemistry professor Yolanda Hedberg stated that having an implant changes body chemistry, even in patients who experience no pain or obvious symptoms.

How do hip and knee implants degrade over time?

Most modern implants use passive metals like titanium, which form a thin, protective oxide layer to block biological fluids from reaching the metal. However, movement within the joint repeatedly disrupts this barrier.

According to Hedberg, mechanical wear destroys this surface oxide in milliseconds during a single step. This triggers a chemical response before the oxide layer reforms, creating a continuous cycle of damage and repair at a microscopic scale.

Proteins from surrounding fluids also coat the implant surface immediately after surgery. Hedberg described these proteins as the “language of the body,” noting they can either promote bone integration or lead to bacterial colonization and inflammatory responses.

What patient factors influence implant wear?

The study found that implant degradation varies significantly based on individual patient biology and clinical history. Higher damage scores were associated with increased body mass index (BMI), higher body weight, and longer surgical implantation times.

Clinical conditions also played a role. Infection present prior to or during surgery correlated with higher damage scores at the trunnion—the connection point between the metal stem and the artificial ball in hip implants.

Conversely, the researchers found that cemented hip implants and patients with inflammatory arthritis correlated with lower damage scores.

Why does retrieval science matter for future implants?

Saman Nikpour, a postdoctoral associate at Western, noted that the human body is one of the most complex environments a material can encounter. He compared the wear seen in retrieved implants to degradation in industrial systems, though the body adds the complexity of inflammatory responses and changing chemistry.

Because laboratory testing cannot reproduce the full range of immune responses and mechanical forces found in a diverse patient population, retrieved implants provide a “living record” of material behavior.

Matthew Teeter, director of Western’s Bone and Joint Institute, said this collaboration allows researchers to look at the mechanisms of failure rather than just the consequences.

What may happen next?

The datasets connecting clinical histories with surface damage could be used by manufacturers to build more durable devices. Surgeons may also use these insights to make more specific material choices based on a patient’s BMI or existing medical conditions.

Further analysis of retrieved implants from international networks in the United States, Australia, and Slovenia may provide a broader understanding of how different materials react across global populations.

Frequently Asked Questions

What is tribocorrosion?
According to the study, tribocorrosion is mechanically assisted corrosion that occurs when movement and chemistry act on the same surface simultaneously, accelerating damage.

Do all hip and knee implants fail?
No. The research states that modern implants exceed expectations and provide significantly improved life quality and long service times for the vast majority of patients.

Which patient factors increase the risk of implant damage?
Higher body weight, increased BMI, longer implantation times, and infections at the time of surgery are associated with higher damage scores.

Do you believe personalized medical implants based on body chemistry could significantly extend the lifespan of joint replacements?