November 19, 1999

New prosthesis a big step forward in treating recurring ankle pain

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During a recent follow-up examination, Dr. Kenneth Johnson checked the flexibility of patient Juanita Davis’ “new” ankle, which was replaced with a prosthesis like the one pictured below. (photos by Dana Johnson)

New prosthesis a big step forward in treating recurring ankle pain

A new orthopaedic procedure at Vanderbilt University Medical Center is giving hope to those with persistant ankle problems.

The procedure, total ankle arthroplasty, involves replacing the ankle joint and is a major breakthrough for certain patients with problem ankles, said Dr. Kenneth D. Johnson, professor of Orthopaedics and Rehabilitation. Johnson is the first doctor in the area to perform the surgery.

"I think it is a big step forward," Johnson said. "It takes away people's pain, allows a give-point in their ankle and takes the stress off their hind foot. It provides our patients with a significant option when dealing with really complicated hind-foot and ankle problems. I find that it works very well for these patients."

The procedure involves replacing the ankle joint with a small device composed of two different kinds of metal, cast chrome cobalt and shiny titanium. A plastic polyethylene liner provides a base for the movable joint section. The exterior is porous, which allows the bone to grow into the prosthesis, further stabilizing the new joint.

The prosthesis fits in the tibia and fibula, Johnson said. Carefully aligning the ankle area, doctors shave out a square area of bone to put in the prosthesis.

"Just before we finish the procedure, we take the two bones in the lower leg and fuse them, which squeezes these two bones together to grip the prosthesis firmly to prevent it from loosening up," Johnson said.

This new artificial ankle joint is especially noteworthy, Johnson said, because artificial ankles in years past were unsuccessful.

"I think we would have to say that they were a dismal failure. They worked only minimally and they only worked for people with rheumatoid arthritis or very limited physical capacity," Johnson said.

"They were a very poor option for post-traumatic arthritis, which is much more common since people often develop problems after they break their ankle."

Johnson said ankle arthrodesis (fusing the anklebones) is still a very viable alternative for some patients, but he likes the new arthroplasty procedure for several reasons.

"This procedure does not use cement, which has always been a weak link in joint replacements. If cement chips or cracks or breaks, the whole system is loose.

"This fuses the two bones together, which creates a broader platform to place the prosthesis in. And by squeezing these two bones together, after you have put the prosthesis in, you can actually grip it and sort of squeeze it together, so it is harder for it to get loose. You can also expect bone to grow into the prosthesis better, which obviously is a better fixation."

Johnson said research shows that this artificial ankle will also last longer than those in the past, for as long as 10-14 years.

He advises patients that the artificial ankle will not give them full flexibility, but the special joint does allow a small side-to-side rocking motion, in addition to a normal up-and-down ankle motion.

"There is no way that you can expect this ankle arthroplasty to give you the kind of motion you would get in a normal ankle," Johnson said.

"At best, a really good outcome which is approximately 50 percent of normal ankle motion, but that is certainly tolerable for most people.

"We put most artificial joints in people so that they can walk normally. We expect them to use it in normal day-to-day activities and to have no pain when they walk."

Forty-four year-old Juanita Davis had her artificial ankle implanted about a month ago. Her own ankle was mangled in a car accident 27 years ago and was subsequently repaired with surgery. But she said in recent years, she was feeling more and more pain.

"It just got to where it hurt so bad and stayed swollen that I knew I had to try and find something to relieve the pain and be more mobile," Davis said. "It was limiting me a lot. I even walked with a limp."

Davis is still on crutches and in a wheelchair, but she can already tell a difference. She said the pain is gone.

Johnson said recovery time for Davis will be from three months to more than a year, depending on how physical therapy goes.

Davis is already planning her first pain-free walks.

"I am looking forward to walking normally and playing with my grandchildren. And I am anxious to finally be able to swim without pain," she said.