Midterm Outcome of the Agility Total Ankle Arthroplasty.

BACKGROUND

Ankle arthritis is a debilitating condition that causes severe functional impairment. While arthrodesis has been the gold standard of surgical treatment for this condition, significant improvements in total ankle arthroplasty have made it a viable alternative. The purpose of this study was to look at the midterm follow-up of the Agility total ankle.

METHODS

A retrospective review of prospectively collected data was conducted on 127 consecutive Agility total ankles implanted between 2002 and 2009. Charts were reviewed to collect patient demographics. In addition, coronal alignment, overall arc of motion, tibiotalar component motion, syndesmotic fusion, zones of osteolysis, and subsidence were determined. A Kaplan-Meier survival and linear regression analysis were used to predict implant failure. A multivariate regression analysis was used to assess whether radiographic measures were predictive of patient satisfaction.

RESULTS

Ninety (78.2%) of 115 patients retained their primary implant, of which 105 were available for evaluation, with an average follow-up of 9.1 years. Twenty-five had their implant removed. The average score for the Foot and Ankle Ability Measure (FAAM) activities of daily living subscale was 82.4, FAAM sport subscale 55.3, postoperative visual analog scale (VAS) for pain 12.7, and Short Form-12 (SF-12) Health Survey physical component 45.8 and SF-12 mental component 56.1. Average arc of motion across the implant was 22.3 and 6.3 degrees in adjacent joints. Osteolysis most commonly occurred in zones 1 and 6. No statistical differences were found in the rate or location of subsidence. Linear regression analysis demonstrated that age at the time of surgery was predictive of failure ( P = .036). Inflammatory and atraumatic arthritis demonstrated higher likelihoods of revision. No correlation was detected between radiographic parameters and outcomes scores ( P > .05; rho >0.2). A significant reduction in mean VAS pain scores by 67.6% was maintained at an average of 8 years.

DISCUSSION

Our results were improved over the nondesigner outcomes published in the current literature. Survivorship approached 80% at 9 years, with Kaplan-Meier 14-year survival calculated at 70.4%. Patients with their original implant were functioning with a high level of satisfaction based on statistically validated outcome scores, which was independent of the radiographic appearance of their implant. Age at the time of surgery and inflammatory/atraumatic arthritis were predictive of failure.

LEVEL OF EVIDENCE

Level IV, case series.