ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

show that patellar mal-positioning seems not to affect AA rotation and AP translation
kinematics too much apart from the IE rotation (Figure 2).
The sensitivity analysis showed that, generally, patellar mal-positioning do not affect
tibio-femoral kinematics (Figure 2).
Although tibial component mal-positioning and ligaments shifting could alter internalexternal
rotation up to 6.8º, tibial components mal-positioning alter mainly the
abduction-adduction tilting and the antero-posterior translations (up to 3.8º and 2.9 mm
respectively).
Figure 2: a) influence of mal-configurations for IE rotation, b) influence of malconfigurations
for AA rotation, c) influence of mal-configurations for AP translation
5. DISCUSSION
In this project a numerical analysis of the effects of tibial mal-positioning, patellar malpositioning
and ligament shifts on knee kinematics for different TKA designs was
performed.
For that reason the aim of this work was to evaluate and compare TF kinematics during
a loaded deep squat for TKA with simulated device mal-positioning and for different
soft-tissues anatomies. Although each prosthesis type in this study is represented by a
specific design, the purpose of this study is not to analyze the behavior of those specific
TKA designs but rather to determine, in general, how mal-positioning and ligaments
anatomy can alter the TF kinematics compared to its own reference configuration.
This project presents several limitations because just only one cadaver leg and only one
size for each TKA were used. We analyzed the knee model using a generic soft tissue
model and not a patient specific one.
In the sensitivity analysis, only one parameter was changed at a time even if a
combination of deviations for more than one parameter would represent a very
interesting sensitivity analysis. However, this was not considered in this first
investigation and will be addressed in future studies.
We did not consider any femoral component deviations from the reference models and
we did not consider all the tissues and muscles.
The model was simplified considering only the quadriceps and the hamstrings.
even with these limitations, the results demonstrated that, irrespective of TKA implant
design, TF kinematics can be altered considerably up to 6.8º for IE rotation, up to 3.8º
for AA tilting and up to 2.9 mm for AP translation. The results concerning changes in
implant positioning are in agreement with Thompson et al. [24].
Understanding how the effects of components mal-positioning alter the biomechanical