Introduction/Purpose: All primary total ankle replacements (TARs) over a seven year period were retrospectively reviewed. This was a single surgeon consecutive case series involving primary TARs using a low profile tibial component. The senior author noticed a trend of increased early revision of metal components starting in 2024 and undertook a study to identify potential root causes. This study evaluates patient factors, radiographic factors, degree of deformity, and prosthetic type on incidence of early revision.
Methods: A single surgeon, community practice retrospective review was undertaken from 2018 -2024. Only primary total ankle replacements with the Infinity or Infinity Adaptis prosthesis were considered. As most modern ankle replacements are press fit, and rely on bony ingrowth and on growth, we hypothesized a number of factors that might impact rates of loosening and subsidence. In this study, early revision (within the first two years) was evaluated, but infections and gutter debridement surgeries were excluded. Asymptomatic loosening and presence of radiographic lucency was also excluded. Early revision was defined as need for revision surgery during the first two years after the index surgery.
Rates of complication were compared over two implant designs. We also looked at the effect of patient factors such as weight, and presence of osteoporosis / osteopenia, and preoperative hounsfield unit measurements. Further, we investigated the role of pre-operative deformity and decreased ankle dorsiflexion.
Results: From 2018 - 20220, a total of 88 Infinity total ankle prostheses were implanted. There were no revisions for loosening or implant subsidence (0.0%). From 2020 -2024, a total of 165 Adaptis Infinity total ankles were implanted. There were five incidences of implant subsidence, and four incidences of aseptic loosening, requiring revision within the first two years of implantation (5.45%). This difference was found to be statistically significant (p = 0.0293).
Overall, the sample size was too small to identify patient factors, such as age, limited dorsiflexion or presence of osteopenia /osteoporosis to account for the higher complication rate. Presence of preoperative deformity in the ankle or foot may have been a contributing factor, but did not reach statistical significance.
Conclusion: TAR remains a challenging operation. Prosthesis choice may have an impact on complications. Low profile implants may have a higher rate of loosening / subsidence due to the smaller surface area for bonding and higher contact pressure at the bone / implant interface.
This study examined various factors associated with early revision for two different low profile TAR prostheses. There was a significant increase in early revision after adoption of the Infinity Adaptis Prosthesis, compared to the Infinity prosthesis. As this was a single surgeon series, our findings may not be generalizable, but warrant further investigation.
