Abstract
Category:
Ankle Arthritis; Ankle
Introduction/Purpose:
Fourth generation total ankle arthroplasty (TAA) implants minimize tibial resection and utilize small pegs or posts for fixation. The components are designed to facilitate osseous integration. However, a number of studies have identified concerning rates of lucencies around the tibial components of all newer generation implants. In this study, we evaluated a consecutive series of patients receiving a fourth generation TAA prosthesis to describe the incidence and characteristics of tibial component lucencies at minimum one year follow-up. Of these patients, we aimed to identify the rate of revision surgery. Secondary aims included identifying any difference in patient factors between patients with global lucencies and a cohort of patients without lucencies.
Methods:
A prospectively-collected TAA registry was queried to identify eligible patients. All patients greater than 18 years old who underwent primary TAA with a Cadence, Infinity, Infinity Adaptis, or Vantage prosthesis through January 2021 were identified. Each surgery was performed by one of six fellowship-trained orthopedic foot and ankle surgeons. For radiographic analyses, lucency was defined as a radiolucent line adjacent to the tibial tray of at least 1 mm in thickness, comprising at least 50% of the zone (Figure). Poorly-defined lucency around the tibial component in all four tibial zones, as agreed upon by two independent reviewers, was considered “global lucency.” Intraoperative, one year, and two year postoperative radiographs were assessed for periprosthetic lucencies. Pre- and postoperative coronal tibiotalar alignment was recorded. Additional data collected included age, sex, BMI, diagnosis, presence of diabetes, smoking status, presence of ipsilateral hindfoot fusion, pre- and postoperative PROMIS scores, and reoperation and complication data.
Results:
616 ankles were analyzed: 274 Vantage (44.4%), 253 Infinity (41.1%), 52 Cadence (8.4%), and 37 Infinity Adaptis (6.0%). Mean radiographic follow-up was 27±20 months. There were 28 revisions (4.5%), 21 (3.4%) for symptomatic tibial component loosening. 36 patients (5.8%) had global tibial lucency at one year. Of these, 15 (42%) were eventually revised and the remaining 21 (58%) were doing well clinically at final follow-up. When comparing patients with global lucency at 1 year and revision for loosening (42 patients, 6.8%) with the remaining patients, there were no significant differences in any of the factors assessed (Table). PROMIS pain interference scores were higher at 2 years in the loosening group (p = 0.03). Intraoperative lucencies were not predictive of global lucency or revision for loosening.
Conclusion:
Aseptic loosening is the most common mode of failure of TAA, and has been reported with all of the low-profile fourth generation implants. We found a 6.8% incidence of tibial loosening (global radiographic lucency at 1 year or revision for tibial loosening). We were unable to identify any patient factors associated with loosening. Although 50% of these patients did not require revision and were doing well clinically at early follow-up, tibial loosening was associated with higher PROMIS pain interference scores at 2 years. Further research will be required to determine how patients with tibial loosening fare over longer-term follow-up.
