- A new artificial cartilage holds up to cartilage through at least 100,000 cycles.
- Doctors can replace joints, but cartilage remains both elusive and highly sought-after.
- This material is a woven combination of three polymer hydrogels.
Scientists from Duke University have developed a new synthetic cartilage they say can feasibly work even in the human knee. The revolutionary hydrogel could eliminate the need for hundreds of thousands of knee replacements each year, along with many thousands of other joint replacements.
The new cartilage analog is made of three hydrogels—polymers boosted with absorbed water—with different structures, and these are “woven” together to make a multidirectionally flexible and redundant cushioning structure. It’s like a basket wrapped in flexible netting.
When the material is stretched, Science Alert reports, the third polymer is the one that keeps the whole thing intact. Meanwhile, the first two polymers, which are negatively charged, “repel each other and stick to water, so the original shape can be restored.
“The hydrogel has the same aggregate modulus and permeability as cartilage, resulting in the same time‐dependent deformation under confined compression. The hydrogel is not cytotoxic, has a coefficient of friction 45 percent lower than cartilage, and is 4.4 times more wear‐resistant than a PVA hydrogel.”
In extremely long tests, the hydrogel microbasket structure performed as well as cartilage.
Why is artificial cartilage so in demand and so elusive? For starters, knee replacement is a serious surgery. It’s invasive and painful, with recovery that involves steady physical therapy starting almost the same day to avoid loss of mobility in the joint. Even so, like a hip or even a root canal, the new joints have a lifetime of only up to about 20 years before they must be replaced again.
That’s not bad science or medical malfeasance—it’s just a testament to how load-bearing, dynamic, and mechanically excellent a functional knee joint is. There are medical reasons other than cartilage that people must undergo knee replacements, but cartilage is often the missing link.
Scientists can replace tough and sturdy bone with other things. They can work on the mechanical design of the joint. Cartilage, however, is special. It’s extremely tough, but stays flexible and load-cushioning for, ideally, our whole lives. Imagine a car that ran for 80 years on one engine that had the same 5 quarts of oil that entire time.
The big news? This is “the first hydrogel with the strength and modulus of cartilage in both tension and compression, and the first to exhibit cartilage-equivalent tensile fatigue strength at 100,000 cycles,” the researchers explain.
If one step represents a knee cycle, 100,000 cycles is the equivalent of about 57 miles for someone taking three-foot steps. And since this is just the first hydrogel to pass that milestone, that’s not necessarily the ceiling.