  Medial open-wedge high tibial osteotomy is a surgical treatment for patients
with a varus deformity and early-stage medial knee osteoarthritis. Observations
suggest that this surgery can negatively affect the patellofemoral joint and
change the patellofemoral kinematics. However, what causes these effects and
how the correction angle can change the surgery's impact on the patellofemoral
joint has not been investigated before. The objective of this study was to
develop a biomechanical model that can predict the surgery's impact on the
patellar position and find the correlation between the opening angles and the
patellar position after the surgery. A combined finite element and multibody
model of the lower limb was developed. The model's capabilities for predicting
the patellofemoral kinematics were evaluated by performing a passive deep
flexion simulation of the native knee and comparing the outcomes with magnetic
resonance images of the study subject at various flexion angles. The model at a
fixed knee flexion angle was then used to simulate the high tibial osteotomy
surgery virtually. The results showed a correlation between the wedge opening
angles and the patellar position in various degrees of freedom. These results
indicate that larger wedge openings result in increased values of patellar
distalization, lateral patellar shift, patellar rotation, and patellar internal
tilt. The developed model in this study can be used in future studies to
monitor the stress distribution on the patellar cartilage and connecting
tissues to investigate their relationship with observations of pain and
cartilage injury due to post-operative altered patellar kinematics.
