Health Watch: Building a Better Ankle Implant
Once considered a risky practice, total ankle replacement surgeries are now becoming more common. Surgeons report dramatic pain relief among recipients while new technology spurs wider competition among manufacturers trying to develop better implants.
Although some are more cautious than others, central Ohio orthopedic surgeons say success rates are encouraging. Nearly 90 percent of total ankle replacements can now last 10 years, according to some studies. A decade ago, the results were not nearly as good, says Dr. Robert Gorsline, of Orthopedic One, who also practices at the Mount Carmel West trauma center.
“Today, we're seeing improved implant design, materials and—the most important thing—the instrumentation,” says Dr. Gregory Berlet, who performs hundreds of ankle replacement surgeries a year.
Artificial ankles lagged behind knee and hip replacements, even though they initially came on the market about the same time. About 50 years ago, ankle replacements led to complications, early joint failure and renewed pain, and orthopedists mostly decided to fuse debilitated and pain-ridden ankles together. Ankle fusion still occurs frequently, and the surgery provides enough stability for construction workers, as well as other people who need durability over flexibility.
“Today, for the most part, the orthopedic community is excited that the newer designs seem to be working well, certainly better than the first and second generation,” says Dr. Adam Groth, a foot and ankle specialist at the OSU Wexner Medical Center. “There are still patients for various reasons—whether because of deformity, their medical status or metabolic bone conditions—who are not candidates for replacement. Each surgeon is approaching it with caution but with more enthusiasm.”
Chronic pain justifies ankle replacement. Deep within the joint during motion of the ankle, the pain is often accompanied by end-stage, bone-on-bone arthritis, which is more often caused by repetitive injury than the aging process.
As a result, ankle replacement candidates are “a different demographic,” says Berlet, with Orthopedic Foot and Ankle Center in Westerville. While knee or hip replacement occurs more frequently between ages 70-80, ankle surgeries tend to occur earlier, making it more difficult for a device to last the rest of a patient's life. “For joint replacement on a 55-year-old, the bar is higher,” Berlet says. “That person's going to be active and is likely to outlive the implant.”
All three specialists contacted for this story agree pain relief is remarkable for patients. “Most patients are off pain meds within two days,” says Berlet, a design surgeon for a manufacturer of the devices, as well as a team orthopedist for the Columbus Blue Jackets and OSU athletics. “In some ways it's like a cavity and filling. You've covered up the nerve endings where the cartilage has worn off and exposed nerve endings.”
Groth calls the pain relief “a little more dramatic in [ankle] replacement,” but he adds that ankle fusion—the preferred option until recently—can relieve arthritic pain, too.
In total ankle replacement, the natural joint and cartilage is replaced by a chromium/titanium alloy that grows into the surface of both the talus and the tibia. A polyethylene surface coats the metals to relieve friction and allow the foot to move up and down. The joints come in standard sizes but still can cost $2,500 to $8,000, with five-figure hospital and doctor fees almost guaranteed to sap a year's insurance deductible in one procedure, which can run $20,000 to $40,000 without insurance.
While Berlet is a self-described “early adopter” in ankle replacement, the surgery remains rare in central Ohio. “A very busy foot and ankle specialist probably does 15 [total ankle replacements] a year, so not nearly as common as some partners who do 500 of those cases a year in hips and knees,” says Gorsline.
Still, the number of ankle replacements has doubled in recent years nationwide to around 5,000 per year, while more than 700,000 knee and hip replacements are performed annually in the United States.
So why has it taken so long for the humble ankle to get medical attention? Gorsline outlined previous problems, suggesting some are still with us: a lack of sophisticated metallurgy to bind bone and metal; forces acting on the ankle are just as strong as those acting on the knee and with less surface to absorb or manage them; and an unstable ligament—or a poorly aligned replacement joint—that often leads to poorly balanced ankle joints and early failure. “With the ankle, there is so much force in so many directions and all loaded on a small surface area, so you need the alignment just right,” Groth says.
Increased demand, better technology, more market competition and higher levels of patient satisfaction are driving the acceptance of the new ankle joints, the three physicians agree. “New designs are refining the instrumentation so we can get the alignment correct and have a successful outcome,” Groth says, even though the procedure remains difficult for any non-specialist.
“Some of the trend is driven by industry,” Gorsline says. “They would like to sell expensive equipment. If a company can come out with an implant that captures the marketplace, they'll want to do that, so a lot more companies are coming out with an implant.”
The prognosis for patients may be just as optimistic as for ankle manufacturers hoping for product growth. Aside from walking pain-free after ankle replacement, patients can also pursue a fairly wide variety of low-impact fitness activities, such as hiking, walking, swimming, golfing and even skiing for some, says Groth. Jumping, basketball and long-distance running are out, and hockey will stress the joint even with the best skates.
“What we're trying to achieve is to flatten the learning curve and make the technology available more widely,” Berlet says. He hopes the instrumentation for total ankle replacement will become easier to use for a wider range of orthopedic surgeons. Meanwhile, he's still looking for the next disruptive breakthrough in technology for the foot and ankle. “I want to be at the leading edge, pioneering the new developments,” he says.
Mike Mahoney is a freelance writer.