Ankle Fusion or Total Replacement? This Study May Help You Decide

In a large study of British patients needing surgical treatment for advanced arthritis in the ankle, fusion appeared to be a better option than total ankle replacement.

Among some 10,000 patients undergoing total ankle replacement and about 31,000 having ankle fusion, subsequent revision procedures were dramatically higher after joint replacement, with relative risks about eight times greater at 5, 10, and 20 years, according to Adrian Kendal, BMBCh, DPhil, of the University of Oxford in England, and colleagues.

And the common belief that fusion comes with increased need for later hindfoot fusion surgery was not borne out, the group reported in a manuscript posted on the medRxiv preprint server. The 25-year risk was estimated to be 8.6% with ankle fusion (95% CI 7.8-9.6) versus 6.8% with total ankle replacement (95% CI 5.4-8.7), falling short of statistical significance.

Some perioperative complications were more frequent with one procedure than the other, but overall they balanced out, Kendal and colleagues found.

“Overall, these observations alone do not support the use of [replacement] over [fusion] in treating end-stage isolated ankle arthritis,” the researchers wrote.

Degenerative ankle arthritis is often overlooked in comparison with its hip and knee counterparts, but it remains a common condition: Kendal and colleagues indicated that about one in 100 people worldwide are affected. If patients live long enough, or the disease starts early enough, they eventually run out of medical therapy options. Only surgical procedures can offer quasi-definitive relief at this stage, and total ankle replacement and ankle fusion are the two choices.

Deciding between the two is complicated. As Kendal and colleagues explained, fusion (whether open or arthroscopic) has a substantial non-union rate; moreover, some studies have found high rates of subsequent hindfoot fusion surgery (26% within 9 years in one analysis). “This remains a major concern of ankle fusion surgery; that it predisposes patients to developing adjacent joint degeneration, requiring a hindfoot fusion. This can shift a patient from a high functioning individual to someone with a rigid ankle hindfoot complex,” Kendal’s group wrote.

“In contrast, [total replacement] is thought to protect against the development of adjacent joint disease by preserving a range of motion at the ankle,” they continued. But multiple studies have documented that subsequent revisions are common, in the 25%-30% range within 10 years. And, full-scale revision is often preceded by other, relatively minor surgical efforts to save the implants, such as arthroscopic debridement or bearing exchange.

Yet no previous study has sought to compare outcomes from ankle fusion versus replacement with population-level data. Here, Kendal and colleagues drew on U.K. National Health Service hospital records to identify all patients undergoing these procedures from 1998 to 2023. Mean patient age was 64 when undergoing total replacement and 55 for ankle fusion. About 60% in both groups were men.

Revision rates after 10 years stood at 10.9% following replacement, reaching 13.5% at year 20; corresponding figures for ankle fusion were 2.5% and 3.1%. These translated to relative risks of 0.12 at both time points as well as at year 5, with the 95% confidence interval’s upper bound not exceeding 0.23 — thus, a highly significant difference. Adjustments for age, race, sex, socioeconomic deprivation, and comorbidity burden led to a hazard ratio of 3.28 for revision with total ankle replacement versus fusion (95% CI 2.92-3.67).

Kendal and colleagues also examined shorter-term complications, including 90-day mortality, intra-operative fracture, wound infection requiring additional surgery, and pulmonary embolism. Death within 90 days was somewhat less common after total replacement (0.23% vs 0.41%, RR 0.57, 95% CI 0.37-0.89); so was pulmonary embolism (0.23% vs 0.58%). As well, re-intervention for “metalware complications” occurred more frequently after fusion surgery.

But fusion did better than replacement for intraoperative fracture (0.10% vs 0.43%) and for wound infection re-intervention (0.15% vs 0.26%). Additionally, late all-cause mortality (beyond 7 years) was greater among patients having total ankle replacement (about 48% with fusion versus 60% with replacement at year 20).

In some respects these findings showed better outcomes than might have been expected from previous studies. In particular, revision rates following both procedures were much lower than were reported from Norwegian and Swedish national registry data.

On the other hand, though, Kendal and colleagues suggested that revision rates after replacement may underestimate the true failure rate. “It is possible there is a large cohort of patients currently living with symptomatic and failing [replacements] that are being dissuaded from surgery,” they observed. “The large number of observed minor operations performed enroute to a far more complex… revision operation supports this understandable procrastination.” Between years 1 and 5, some 2,400 of the original 10,355 underwent some kind of re-intervention. (However, minor procedures during this time frame were nearly as common among fusion patients as well.)

Limitations to the study included, chiefly, the “inherent selection bias” in comparing patients receiving the two procedures, with unmeasured factors helping to dictate which they underwent. As well, database records are always susceptible to coding errors.

“Further work will focus on subgroup analysis of open versus arthroscopic ankle fusion as well as an economic analysis of TAR [total ankle replacement] versus AF [ankle fusion],” the authors concluded. “Can we justify the additional implant cost of TAR over AF based on this long-term data?”

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