BACKGROUND: Definitive and successful treatment of end-stage ankle arthritis is either total ankle replacement (TAR) or ankle fusion (AF). The long-term implications of both treatments remain unclear. AF may predispose patients to subsequent hindfoot joint fusion, and TAR potentially risks high rates of complex revision surgery. The study investigates the risks of further surgery, adjacent joint surgery, and rare but serious complications following AF and TAR. METHODS: An England population cohort study was performed using the Hospital Episode Statistics database, linked to Office of National Statistics (ONS) mortality data (1998-2023). The primary outcome was Kaplan-Meier curve analysis of revision surgery-free survival of TAR vs AF. Secondary outcome measures were the rates of adjacent joint/hindfoot fusion, any further re-intervention to the ankle, peri-operative mortality, 90-day complications, and serious adverse events. RESULTS: A total of 10 335 TARs and 30 704 AFs were analyzed. The AF revision rate was significantly lower than TAR at all time points including 5 years (2% vs 6.1%, relative risk [RR] 0.12, 95% CI 0.10-0.16), 10 years (2.5% vs 10.2%, RR 0.12, 95% CI 0.08-0.18), and 20 years (3.1% vs 13.55%, RR 0.12, 95% CI 0.01-0.23). There was no significant difference in the 25-year risk of adjacent joint fusion following AF (8.64%, 95% CI 7.79%-9.58%) vs TAR (6.82%, 95% CI 5.36% to 8.66%). TAR was associated with higher risks of intra-operative fracture (0.42% vs 0.10%, RR=4.35) and re-intervention for wound infection (0.26% vs 0.15%, RR 1.74) but a lower observed 90-day pulmonary embolus rate than AF (0.23% vs 0.58% respectively). CONCLUSION: Both TAR and AF are definitive treatments of ankle arthritis with low peri-operative risk. In this England-wide registry cohort, TAR showed higher cumulative revision risk than AF over long-term follow-up. Estimates at the furthest time points have lower certainty. Furthermore, AF did not appear to pre-dispose patients to hindfoot fusion and was not associated with a higher 25-year rate of hindfoot fusion than TAR. These estimates do not capture joint degeneration managed non-operatively.