AKILE™ total ankle arthroplasty: Clinical and CT scan analysis of periprosthetic cysts

IntroductionDespite good clinical results following total ankle replacement (TAR), the development of large periprosthetic cysts (> 400 mm2) in the medium-term is a source of concern.ObjectiveThe primary objective of this study was to detect any large periprosthetic cysts in a cohort of AKILE™ patients using radiographs and CT scans, and then to compare these findings to published ones.Material and methodsA total of 127 TAR procedures were performed between June 1995 and January 2012. We retrospectively reviewed 68 cases with the newest AKILE™ implant design that had a minimum follow-up of 36 months. The average follow-up was 81 ± 33 months; eight patients were lost to follow-up. The outcomes consisted of analyzing radiographs (A/P and lateral weight bearing views, Meary view and lateral views of flexion/extension) and helical CT scans, performing clinical evaluations (range of motion, AOFAS score, Foot Function Index, pain levels) and determining the survivorship of TAR implants.ResultsTAR survival at 5 years was 79% for in situ implants and 62% for revision-free implants. The AOFAS score improved from 33.7 ± 14.7 to 77.1 ± 15.1 (out of 100) and the pain sub-score was 30.2 ± 9.7 (out of 40) at the last follow-up. The average ankle range of motion was 32.3° ± 12.7° on the radiographs. CT scan revealed Type A cysts (< 200 mm2) under the talar implant in 52% of cases and in the tibia in 50% of cases; these cysts were smaller than 100 mm2 in 80% of cases and had no effect on the implants. No periprosthetic cysts larger than 400 mm2 in size were identified.DiscussionThe medium-term functional results and survivorship are comparable to those reported for other TAR designs. The incidence of cysts was low overall and there were no large-diameter cysts, which should improve long-term survival. The implant's design and materials likely played a role in preserving the periprosthetic bone stock. The AKILE™ TAR has distinctive features related to the low rate of large periprosthetic cysts in the medium-term.Level of evidenceIV (retrospective case series).