Implant lets patients put the best foot forward

All of us seem to know someone who has had a hip replacement or knee replacement (if not two). But the ankle’s position in the hierarchy of artificial joints corresponds roughly to its location at the bottom of the body. Now a School of Medicine team—armed with prostheses that better mimic the ankle’s structure—aims to raise the stature of this crucial joint.

The development of a prosthetic hip in the early 1960s set the modern standard for joint replacement, followed by advances in other manmade joints. “We know a ton about the knee. We know a ton about the hip,” says John S. Reach Jr., M.D., assistant professor of orthopaedics and the director of the newly 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. A hip is easy to put in; it’s a ball and socket. An ankle is pretty complex. It’s small. It’s fussy.”

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

The new implant—made of titanium, chromium and plastic—replaces the top of the ankle bone and the base of the shin bone. Because it’s modular, each part can be tailored to the patient. In November, Reach performed Connecticut’s first total ankle replacement with the new device, called the Inbone, on a 38-year-old 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 of New Haven lost an eye, a shoulder, and his lower left leg in the crash, when a wheel came off an axle and burst through the floorboard. He 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. “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 ankle arthritis, and though it’s less common than hip or knee arthritis, Reach expects the incidence of posttraumatic arthritis to rise—partly because medicine and safety advances enable younger people to survive trauma like that Diaz endured. Car airbags protect the upper body, but “people are left with horribly mangled feet,” he says. “When you have pain in the joints, it’s bad. It’s bone against bone.”

The first lines of treatment are painkillers and braces. Another established option is fusing the ankle bones, but that can leave patients with a permanent limp and lead to further arthritis and, perhaps, amputation.

However, 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 suspects that 85 percent of the new prosthetic ankles will last at least eight years, and Diaz says that he’s happy so far. “I’m waiting to get used to it, but I’m walking,” he says. “It doesn’t hurt any more.”