Implant loosening
-
commonly linked with elevated initial
micromotion
-
is the primary indication for total ankle replacement (TAR)
revision. Finite element modelling (FEM) has not been used to assess
micromotion of TAR implants; additionally, the biomech
anical consequences
of TAR malpositioning
-
previously linked with higher failure rates
-
remain unexplored. The aim of this study was to estimate implant
-
bone
micromotion and peri
-
implant bone strains for optimally positioned and
malpositioned TAR prosthe
ses, and thereby identify fixation features and
malpositioning scenarios increasing the risk of loosening. Computational
models simulating three of the most commonly used TAR devices (BOX®,
Mobility® and Salto®) implanted into the tibia/talus and subjected
to
physiological loads were developed. Mobility and Salto demonstrated the
largest micromotion of all tibial and talar components, respectively. Any
malpositioning of the implant creating a gap between it and the bone
resulted in a considerable increase i
n micromotion and bone strains. It
was concluded that better primary stability can be achieved through
fixation nearer to the joint line and/or while relying on more than a
single peg. Incomplete seating on the bone may result in considerably
elevated impl
ant
-
bone micromotion and bone strains, thereby increasing
the risk for TAR failure.