3D Osteolysis Patterns in TAR

Total ankle replacements (TARs) have higher rates of osteolysis than hip or knee replacements.

New problem or old problem getting worse?

It has been postulated that the underlying mechanism for cysts post TAR is a pathological immune response to wear debris. This concept is supported by biopsy studies showing increased ligand (RANK-L) and inflammatory cells in the osteolysis. Others would debate that they are pre-existing cysts that continue to grow after the TAR.

Support for bone cyst disease and not immune mediated osteolysis

In a descriptive study evaluating the pattern of bone cysts and resection margins for TAR it was found that only 14% of ankles had no cysts and 8% would have their cysts completely removed by the planned bone resection. Bone cysts found outside of the planned resection occurred in 78% of patients scheduled for a TAR. Maybe it is the old cysts growing that is manifesting as later cysts around implant.

Ideas for bone cysts around implants

In the setting of a TAR with no symptoms but a progressively enlarging bone cyst bone grafting has been shown to be effective; although not all cysts achieve complete healing and cyst progression rate post grafting is relatively high at 68%. Grafting in this study was done in the setting of non-implant revision so maybe a combination of factors is in play.