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Yale team implants new prosthetic ankle

Yale Medicine Magazine, 2008 - Spring


A tailor-made prosthetic joint restores function while reducing side effects and amputation risk.

The ankle’s position in the hierarchy of artificial joints corresponds roughly to its location at the bottom of the human body; however, a new Yale team—armed with prostheses that better mimic the ankle’s structure—aims to raise its stature.

The development of a prosthetic hip in the early 1960s set the modern standard for arthroplasty, followed by advances in other manmade joints. “We know a ton about the knee. We know a ton about the hip,” said John S. Reach Jr., M.D., assistant professor of orthopaedics and the new director of the reconstituted Yale Foot and Ankle Service. “The foot, in medicine, hasn’t been looked at much at all. It just hasn’t gotten enough respect. The hand is sexier. A hip is easy to put in; it’s a ball and socket,” Reach said. “An ankle is pretty complex. It’s small. It’s fussy.”

Prosthetic ankles have “lagged behind, but not for lack of trying,” Reach said. They have come a long way from 19th-century efforts to fashion a ball and stem from elephant tusks. The first modern synthetic ankle, developed in the 1970s, was “a basic hinge,” but doctors learned quickly that the human body isn’t that simple. The latest generation of prosthetic ankles more closely follows the joint’s anatomy. “Now they look more like what God gave you,” Reach said.

The components of the new implant could easily be mistaken for parts that hold a dishwasher together. The implant—made of titanium, chromium and plastic—replaces the top of the talus and base of the tibia. Because the prosthesis is modular, each part is tailored to the patient. In November, Reach performed Connecticut’s first total ankle replacement with the new device, called the Inbone, on a 38-yearold man whose life was upended in a bizarre auto accident one Sunday in 1994.

The patient, Damian Diaz, who lives in the Fair Haven neighborhood in New Haven, lost an eye, a shoulder and his lower left leg in the crash when the wheel came off the axle and burst through the floorboard. He had had 30 surgeries, and though he felt lucky to be alive, the pain in his right ankle limited his walking to no more than a few steps at a time. “My bone was disappearing,” Diaz said. “I could not live with the hurt every day.”

Diaz was a good candidate for total ankle replacement. Trauma patients often develop severe arthritis in the ankle, and though it’s less common than hip or knee arthritis, Reach expects the incidence of post-traumatic arthritis to rise—partly because advances in medicine and safety enable younger people to survive these traumas. Airbags protect the upper body, but “people are left with horribly mangled feet,” he said. “When you have pain in the joints, it’s bad. It’s bone against bone.”

The first lines of treatment for ankle arthritis are painkillers and braces. Another established option is fusing the ankle bones, but that can leave patients with a permanent limp. It can also lead to further arthritis and, perhaps, amputation. A recent review of the literature found that 1 percent of patients who had a total ankle replacement needed an amputation, compared to 5 percent of the fusion patients. Reach expects 85 percent of the new prosthetic ankles to last at least eight years.

Diaz said that so far he’s happy with the prosthetic ankle. “I’m waiting to get used to it, but I’m walking,” he said. “It doesn’t hurt anymore.”