Scientists invent artificial knee cartilage that functions better than the real thing

Researchers at Duke University have created a new gel-based material that can replace cartilage in the knee. This new substitute is stronger and lasts longer than natural cartilage. Knee pain from worn-out cartilage, known as osteoarthritis, affects nearly one in six adults worldwide.

This gel-based substitute could help patients avoid knee replacement surgery and might offer a better treatment option for those with knee pain. Sparta Biomedical is developing and testing the implant in sheep, and human clinical trials started in 2023.

In testing, the hydrogel was found to be 26% stronger than natural cartilage in tension and 66% stronger in compression. The team has solved several design challenges related to creating the implant, such as attaching it to the joint and getting it to stay put, which previous studies have not been able to achieve.

The team’s method of attachment involves cementing and clamping the hydrogel to a titanium base, which is then pressed and anchored into a hole where the damaged cartilage used to be. The hydrogel mimics the smooth, slippery, cushiony nature of real cartilage and offers a more durable and effective treatment option for knee pain sufferers.

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Knee pain is a common affliction for many people, especially as they age. The pain can be caused by a range of factors, including injury, overuse, and conditions such as osteoarthritis. Osteoarthritis affects nearly one in six adults worldwide, totaling 867 million people. It is a progressive condition that wears down the cartilage that cushions the ends of bones and can lead to chronic pain, inflammation, and stiffness.

There are several treatment options available to alleviate knee pain, including over-the-counter pain relievers, physical therapy, and steroid injections. However, for some patients, these treatments are not enough to provide relief, and knee replacement surgery may be required.

Knee replacement surgery involves removing the damaged cartilage and replacing it with an artificial joint made of metal or polyethylene. While this surgery can be successful, it is a major operation that requires months of rehabilitation and can come with risks, such as infection and blood clots.

A new option may soon be available to knee pain sufferers that could provide a less invasive and more effective treatment. Researchers at Duke University have developed a gel-based cartilage substitute that is stronger and more durable than natural cartilage. The team, led by chemistry professor Benjamin Wiley and mechanical engineering and materials science professor Ken Gall, published their findings in the journal Advanced Functional Materials.

The hydrogel is made from thin sheets of cellulose fibers that are infused with a polymer called polyvinyl alcohol. The cellulose fibers act like the collagen fibers in natural cartilage, giving the gel strength when stretched, while the polyvinyl alcohol helps it return to its original shape. The resulting material is a Jello-like substance that is 60% water but is surprisingly strong.

The researchers found that the hydrogel can be pressed and pulled with more force than natural cartilage and is three times more resistant to wear and tear. Natural cartilage can withstand up to 8,500 pounds per inch of tugging and squishing before breaking, while the lab-made version can handle even more. It is 26% stronger than natural cartilage in tension and 66% stronger in compression.

In addition to being stronger, the hydrogel mimics the smooth, slippery, cushiony nature of real cartilage, protecting other joint surfaces from friction as they slide against the implant.

The researchers tested the implant's wear over time by spinning artificial cartilage and natural cartilage against each other a million times, with a pressure similar to what the knee experiences during walking.

Using a high-resolution X-ray scanning technique called micro-computed tomography, the scientists found that the surfaceof the implanted cartilage remained smooth and intact after the million rotations, indicating that it had minimal wear and tear.

The researchers were thrilled with the results of their testing, as it suggested that the implant could potentially last for many years without needing to be replaced. However, they knew that further testing would be necessary to confirm their findings and to ensure that the implant was safe and effective for use in humans.

To this end, the team began planning a series of animal studies to evaluate the implant's long-term safety and effectiveness. They also began exploring potential partnerships with medical device companies to help bring their technology to market and make it available to patients in need.

As news of the breakthrough spread, the research team received numerous accolades and awards for their work. They were even invited to present their findings at international conferences and symposia, where they shared their insights with other researchers and medical professionals.

Despite the recognition they received, the researchers remained focused on their ultimate goal: to develop a safe and effective implant that could help improve the lives of people with knee osteoarthritis. And with each new study and experiment, they came one step closer to achieving that goal.

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