A Closer Look At Total Ankle Replacement Revision
Following these changes, the implant became widely available to surgeons who completed a company-sponsored surgical skills course at the American Academy of Orthopaedic Surgeons Learning Center in Rosemont, Illinois, starting in 1998.16,19 The Agility Total Ankle Replacement System was the only FDA-cleared ankle replacement readily available in the U.S. until 2007. As a result, the Agility Total Ankle Replacement System was the most widely implanted ankle replacement in the U.S. for over a decade. Complications began to surface that predominantly involved three modes of failure: (1) syndesmosis nonunion and subsequent tibial component malalignment or loosening; (2) talar component subsidence; and (3) aseptic osteolysis.14,16,19-27 The last two modes of failure usually coincide.
As a result, the next changes to the Agility Total Ankle Replacement System occurred in 2002 with alterations to the talar component, making it 18 percent wider, shortening the length of the fin and adding the ability to create a custom-stemmed talar component to replace lost height due to subsidence and cystic changes, and perform concomitant arthrodesis of the subtalar joint.9,14 This was followed in 2003 with the ability to create a custom-stemmed total talar replacement and in 2004 with the use of a plate and screw construct to enhance syndesmosis union.14,28,29 Unfortunately, as of December 8, 2011, any Agility Total Ankle Replacement System custom-stemmed talar component is no longer available for clinical use due to U.S. FDA regulation and the availability of this in the future remains uncertain.30
The final changes occurred in 2007 after surgeons and engineers developed the Agility® LP Total Ankle System, which included three major modifications. The first modification was the development of a broad-based “winged” and 2 mm thicker talar component to reduce the incidence of subsidence with primary implantation, and allow for the ability to revise previously inserted talar components and a corresponding shortening or “lowering the profile” of the tibial component side walls by 2 mm to accommodate the talar wings.
A second modification was the ability to mismatch component sizes by upsizing one talar component relative to the tibial component. This allows for more precise insertion and revision capabilities since the tibial component from an earlier generation can remain in situ and one can insert a bottom-loaded full column +2 mm UHMWPE into an LP talar component. The third modification was developing a front-loaded polyethylene locking mechanism with 0 mm (i.e., neutral) and +1 mm thickness, making subsequent replacement easier.14,19,31,32
Unfortunately, a recently completed but not yet published U.S. National Institutes of Health two-year outcome study of 50 non-cemented Agility LP Total Ankle Systems revealed complications similar to the older Agility designs.33 Additionally, the Agility LP Tibial Tray is no longer being manufactured. This foretells the end of the LP version as a primary total ankle replacement and complicates revision options.
There has been much attention focused on intraoperative complications (i.e., malleolar fracture, nerve or tendon injury) and incision healing-related problems (i.e., wound coverage, infection). However, the intermediate and long-term complications (i.e., aseptic osteolysis, subsidence, component loosening and progressive malalignment) require careful consideration as the secondary procedure options for revision remain limited and the potential need to revise previously revised implants exists.2,3,9-13,16,19,20,34-61