Ankle Replacement -De Puy Mobility
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Ankle replacement has been available as an intervention for ankle arthritis since the 1970s. The initial implants were engineered on the assumption that the human ankle joint functioned as a true hinge . They were therefore designed only to allow uniplanar movement (plantar and dorsiflexion) and comprised just 2 components which were mechanically linked. The ankle joints they were implanted into however also functioned with a degree of rotation which had to occur at the weakest point in the “mechanism”. Given the robustness of the implanted ankle hinges this transpired to be the implant/joint interface which therefore led invariably to early implant failure.
The “eureka” moment in ankle replacement came with the introduction of 3 component replacements in which the Tibial and Talar components were linked by a UHMW polyethylene meniscus which allowed an element of rotation to occur within the joint itself as well as providing adequate component stability.
These initial replacements whose results still define what longevity an ankle replacement should attain are the STAR , Beuchal-Pappas and Salto implants. In general their 10 year survivorships are lower than reported for hip and knee replacements but are still in the mid to high 80 percents.
In general terms an ankle replacement will not be recommended for younger and higher demand patients due to concerns of accelerated wear of the implant .
Author: Mark Herron FRCS
Institution: The Wellington Hospital , London ,UK.