Agility Total Ankle Arthroplasty

Continuing an earlier discussion on the INBONE ankle arthroplasty, we'll talk briefly about the Agility total ankle arthroplasty, the oldest and most commonly used system in the United States. It has undergone several modifications since initial FDA approval in 1992, but the essential design is a semiconstrained two-component device with a polyethylene disc.

It is important to evaluate follow-up radiographs for periprosthetic lucency, lysis, and component migration or subsidence. Subsidence at the talus is especially important to detect early. The case above is from a bone survey, so we don't have a lateral view, but there is suggestion of talar subsidence on the frontal view.

Because it is the oldest system in use, long term follow-up data are available for the Agility, and the majority don't seem to be good. A recent study of 41 patients with the Agility, for example, found that almost 40% needed revision surgery at some point (follow-up period of 6 months to 11 years), with an average time to revision surgery of 4 years. In addition, the authors found that patients without revisions reported only moderate pain relief and function.

A systematic review of all ankle arthroplasties found that revision rates published in clinical studies were about half the value found in registries, possibly because of the over-representation of publications by implant developers (almost 50% of the published content), who tended to report better results.

References

• Criswell BJ, Douglas K, Naik R, Thomson AB. High Revision and Reoperation Rates Using the Agility(TM) Total Ankle System. Clin Orthop Relat Res. 2012 Jan 24.
• Kopp FJ, Patel MM, Deland JT, O'Malley MJ. Total ankle arthroplasty with the Agility prosthesis: clinical and radiographic evaluation. Foot Ankle Int. 2006 Feb;27(2):97-103.
• Labek G, Klaus H, Schlichtherle R, Williams A, Agreiter M. Revision rates after total ankle arthroplasty in sample-based clinical studies and national registries. Foot Ankle Int. 2011 Aug;32(8):740-5.