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Artificial Ankle Takes Giant Step Forward
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Page: << Prev | 1 | 2 Replacements already exist for hips, knees, elbows, shoulders and some finger joints, but ankles have been a particular challenge.
"The ankle is unique for several reasons," Mann said. "It has more stress across it than other joints. The hip and the knee have about two-and-a-half times the body weight across the joints when the person is walking. The ankle has four times the body weight so it's almost twice as much stress coming across an area only about two inches square. Plus it's not covered by a lot of tissue. It sort of sticks out there in the breeze, whereas the hips you can bury and the knees you can bury to a certain extent."
"The upper extremities are not weight-bearing," Baumhauer added. "The knee surface is a lot larger. The ankle is much smaller. It's like a little Rubik's cube."
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The STAR ankle, which costs $9,850 for the device alone, is basically a flat piece of metal extending across the end of the tibia bone and held in place by two "barrels" drilled into the bone. Metal bearings move across a piece of high-density polyethylene placed between the two pieces of metal.
The average age of candidates for ankle replacement is 62, Mann said. Half are needed because of some kind of trauma, such as a break or chronic ankle sprain, and half because of arthritis, including rheumatoid arthritis. Roughly 10,000 a year are done worldwide, he said.
"This may well be an important moment in orthopedics, similar to those we've seen in hip, knee and spine, when the gold standard transitioned from fusion to arthroplasty," Mann said.
More information
The American Orthopaedic Foot & Ankle Society has more about feet and ankles.
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Copyright © 2009 ScoutNews, LLC. All rights reserved.
Last updated 6/18/2009
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SOURCES: Roger Mann, M.D., orthopedic surgeon and co-editor, Surgery of the Foot & Ankle, Oakland, Calif.; Judith Baumhauer, M.D., associate chairwoman, academic affairs, Department of Orthopedics, University of Rochester Medical Center, Rochester, N.Y.
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