Basic Considerations for Total Ankle Arthroplasty

Meticulous analysis of the osteoarthritic ankle regarding structural changes is mandatory for successful replacement surgery. Selected components should restore the articular surfaces as close as possible, using all available bones for support. Flat and peg-type tibial implant design may be a promising fixation method with a minimum micromotion, bone resection level, and no disruption on the anterior cortical bone under an extreme axial loading scenario. Talar component positioning, on the other hand, should restore the center of rotation of the ankle. Initially, malpositioned components, and therefore abnormal ligament strains, are correlated with later adverse outcomes. At a minimum, a ligament highly strained at implantation would restrict joint motion and reduce the motion range obtained after postoperative rehabilitation. Furthermore, adequately strained ligaments at implantation contribute to prosthesis stability in a semi-constrained ankle prosthesis. There is evidence that, in a mobile-bearing ankle, abnormal talar motion within the ankle mortise, especially in the coronal plane, may cause polyethylene wear, whereas, in a fixed-bearing ankle, axial malrotation may cause asymmetric polyethylene wear.