MIAMI, Fla. -

Johnny Pierce used to be in excruciating pain just by simply walking.  An injury a year ago resulted in an ankle fusion, which left him unable to flex his foot.

Fortunately, the Food and Drug Administration recently approved a new ankle replacement device that helps patients regain their range of motion.

"I think for the severe ankle, in my mind, this is probably the best so far," said Foot and Ankle Specialist Dr. Michael Cohen.

What makes it so great is the ability to customize the implant to the patient's anatomy. It starts out with a CT scan to see what the patients ankle actually looks like.

"Every arthritic ankle is different and they all have spurs in different places just like a fingerprint," Cohen explained.

From the image, a plastic mold is made for the surgeon to use to form a perfect fit during the procedure.

"Whereas if we did it by eyesight, we kind of guesstimate where the foot should be. This gets it exactly right," added Cohen.

In the end, patients regain the flexibility they need to do every day activities with ease.

"It feels normal, like you know, when I felt like when I was young," said Pierce. "I got no problems I can do anything I want to."

The ankle replacement procedure is not recommended for diabetics or for people who weigh over 250 pounds because the implant may wear out prematurely. The replacements can last 15 years, depending on the patients activity level, weight and coexisting medical problems - such as bone density.