Long-Term Outcomes of Infinity Total Ankle Arthroplasty Compared to Ankle Arthrodesis

Abstract

Category: Ankle Arthritis; Ankle Introduction/Purpose: End-stage ankle arthritis causes severe pain and disability. The most common treatment has been ankle arthrodesis (AA) with proven long-term results. However, total ankle arthroplasty (TAA) has become a viable option to preserve ankle joint motion, relieve pain and shield adjacent joints. And with the evolution of TAA prostheses over the past 2 decades, the use of TAA has been steadily increasing. Nevertheless, long term outcome data on the latest generation of TAA prostheses is scarce. The primary purpose of this study is to evaluate long-term PROMs after Infinity™ TAA and to compare the outcome to a patient cohort of ankle arthrodesis (AA) performed during the same time period. Methods: Patients with end-stage ankle arthritis who received surgical treatment with a primary Infinity TAA or AA performed between 2013-2015 were included in this study. All surgeries were performed by four fellowship trained foot and ankle surgeons. Patient reported outcomes (PROMs) comprising the AOS and SF-36 PCS score were prospectively collected for patients who were willing to enroll into the Canadian Orthopaedic Foot and Ankle Society (COFAS) database. PROM data was compared between the TAA and AA patient cohorts. Implant survivorship as well as revision and reoperation rates were also analyzed. Results: 33 patients/ankles underwent primary Infinity™ TAA and 59 patients/ankles underwent AA. Of these, 25 TAA and 46 AA were enrolled in the prospective database, 20 and 46 had PROMs available for follow-up, respectively. Mean TAA PROM follow- up was 6.8 years (3-9) and for AA 6.4 years (2-9). Mean TAA age at surgery was 67 years (54-85) and 58 years for AA (27-84). TAA total AOS score pre-operatively was 52.9, which improved significantly to 23.9. SF-36 PCS scores improved from 33.1 to 43.3. Pre- and post-operative PROMs were similar to the AA cohort. At clinical follow up of 8-10 years, TAA implant survival was 97% with one metal component exchange. Two TAA patients had two reoperations each. In the AA cohort, the reoperation rate was 10.8%. Conclusion: This is the first report on patient reported outcomes and implant survival at 8 or more years after primary Infinity™ TAA. PROMs remain significantly improved at long term follow-up and are comparable to a cohort of long-term AA patients. Revision rates were low with a single component revision in 33 patients resulting in an implant survivorship of 97%. Long-term outcome of the Infinity™ total ankle arthroplasty is promising.