The Dreaded Cyst After Total Ankle Replacement
There is much is to be discovered concerning cysts and total ankle arthroplasty, but we do know is that cysts may lead to aseptic loosening and failure.
Hip arthroplasty has connected peri-prosthetic cysts to the degree of porous ingrowth on the femoral stems (smooth versus porous). No previous study had chased this perspective in vertically stemmed, total ankle replacements, until recently: “A Study of Tibial Cyst Formation in Modular Stemmed Total Ankle Arthroplasty: Exploring a Possible Relationship to Smooth and Porous Coating on the Stem Segments.” This new research from the Orthopedic Foot & Ankle Center is available from the Journal of Foot & Ankle Surgery.
In a retrospective comparative cohort, the authors compared INBONE-2 stems with and without porous-coated stems to assess for any correlation with tibial cyst formation. The cohorts were matched based on radiographic follow-up, and the relative risk for reoperation was calculated.
Overall, porous-coated stems proximally showed considerable bonding on radiographs and computed tomography scans, with cyst formation observed distally in proximity to the tibial tray (63% incidence), secondary to stress shielding. By comparison, the smooth stems did not show cyst formation.
In this study, the cysts were not associated with an adverse outcome and the relative risk reoperation (0.74) between the two was similar.