The clinical question
An ankle arthrodesis done well is a durable operation. The problem is not the fusion itself. It is what happens in the subtalar and transverse tarsal joints ten and fifteen years later — the slow overload that turns a pain-free ankle into a painful hindfoot. A subset of these patients is a candidate for takedown of the fusion and conversion to total ankle replacement. Most are not.
This episode is about how to tell the difference.
Key decision points
Three things separate a good candidate from a poor one, and none of them are the imaging.
- Functional complaint. The best candidates are not complaining about the fused ankle. They are complaining about the way the foot moves — or fails to move — distal to it.
- Alignment history. If the fusion is in malalignment, or if the hindfoot has drifted into compensatory varus or valgus over a decade, the conversion is a reconstruction, not a replacement.
- Bone stock. CT is non-negotiable here. The lateral fluoroscopic view will under-read tibial and talar cystic change, and the surgeon who trusts it alone will be surprised on the table.
The question is never whether you can take a fusion down. You can always take a fusion down. The question is whether the ankle underneath is worth replacing.
What the literature shows
The Gross systematic review (FAI 2022) gathered eleven studies and a little over three hundred patients. Reoperation rates were meaningfully higher than primary TAR — roughly twice, depending on definition — and survivorship at five years trailed the primary arthroplasty cohort by a predictable but real margin. The classic Coester paper from 2001 remains the clearest long-term look at adjacent joint degeneration after fusion and is worth rereading before the clinic visit.
The take-home is not that conversion is a bad operation. It is that conversion is a technically demanding revision procedure being performed on a patient whose functional baseline has already compensated for a decade of altered mechanics.
What Anish took away
The longer I do this, the more the expectations conversation feels like the operation. A patient who understands that conversion is a reconstruction — that the first year will look different from a primary TAR, that hardware removal is likely, that the functional ceiling is lower than a native ankle — can arrive at a good outcome. A patient who expected a new ankle will be unhappy with a good result.