It has been reported that lower extremity injuries represent a
measurable portion of all moderate-to-severe automobile crash-
related injuries. Thus, a simple tool to assist with the design of
leg and foot injury countermeasures is desirable. The objective of
this study is to develop a mathematical model which can predict
load propagation and kinematics of the foot and leg in frontal
automotive impacts.
A multi-body model developed at the University of Virginia and
validated for blunt impact to the whole foot has been used as basis
for the current work. This model includes representations of the
tibia, fibula, talus, hindfoot, midfoot and forefoot bones.
Additionally, the model provides a means for tensioning the
Achilles tendon.
In the current study, the simulations conducted correspond to
tests performed by the Transport Research Laboratory and the
University of Nottingham on knee-amputated cadaver specimens. These
tests include non-destructive local dynamic impact to the heel and
toes of the foot. For each test, the loads registered at loadcells
implanted in the mid-tibia and in the Achilles tendon, the
accelerations registered at the impactor accelerometer, and the
kinematic response was compared to their counterparts in the
model.
In order to improve the model response to the local and blunt
impact test data, a more biofidelic shape of the hind and midfoot,
a distal-to-proximal translation capability at the ankle joint, and
modified contact properties were included in the model. Other model
parameters that were found to significantly influence the load
propagation are the ankle and subtalar joint location, the
configuration of the midtarsal joint and the knee joint properties.
In addition, the impact location, foot initial state and level of
Achilles tension influenced the model response.
The conclusions are that the model now is valid in local impacts
to the foot and still maintains validity in blunt impacts to the
foot. Thus the model can potentially improve our understanding of
the load distribution in the foot and leg and of the foot and leg
injury mechanisms, which in turn can help improve injury risk
assessment.