Biomechanics and Motion Analysis

Unfavorable Influence of Malpositioned Total Ankle Arthroplasty (TAA) of Ankle Stability

Principal Investigator: Harold B. Kitaoka, M.D.
Project Coordinator: Lawrence Berglund — berglund.lawrence@mayo.edu

Historically TAA has had disappointing results. Previous designs were geometrically constrained, and often loosened and failed. The second generation of these devices are less constrained, often with a flat intermediate articulating component. Due to the mid term promising clinical results from these new devices there has been renewed interest in TAA. Malpositioning of the TAA is a recognized problem adversely affecting results. The purpose of this study was to evaluate the effects of TAA malposition on mechanical stability.

Anterior-posterior calcaneal-tibial combined displacement averaged 6.9±2.0mm for neutral TAA, 5.0±1.3 mm for 10 deg. valgus, and 5.9±1.9 mm for 10 deg. varus malposition. Displacements of both malalignments were significantly reduced. In medial-lateral calcaneal-tibial combined displacement, there was no significant difference between the groups. For external-internal rotation, calcaneal-tibial combined values averaged 11.8±1.6 degrees for neutral alignment, 6.3±1.6 degrees for valgus, and 8.1±1.9 degrees for varus malalignment. Rotation ranges were significantly reduced for both valgus and varus malalignment.