Injuries to the lower leg are still a frequent occurrence in
frontal crashes and the most serious injuries have been found to be
associated with the ankle region (pilon, calcaneal and talar neck
fractures). These injuries are not only of a high severity, they
are also associated with long-term impairment, which contributes
significantly to the societal cost associated with road traffic
accidents. In order to reduce these injuries, the ability to
determine the potential injury risk in legislative crash tests as
well as the capability to assess the performance of proposed
enhanced safety measures in the vehicle footwell region is
essential. If this is to be achieved a biofidelic assessment tool
with appropriate injury criteria is required.
In Europe, the protection afforded against injury in frontal
impacts is currently assessed by the Hybrid III dummy in an offset
deformable barrier test. For the lower leg the tibia index injury
criterion is used, however this relates primarily to the risk of
tibia fracture and is not appropriate for the determination of the
risk of injury to the ankle.
This paper reports an overview of the biofidelity of existing
dummy legs and the results of a series of PMHS tests which have
recreated in the laboratory the more serious ankle injuries seen in
real-world crashes. The limitations of this work in terms of its
application to an ankle injury criterion using peak tibia force for
the Hybrid III are discussed and proposals for future work using a
different approach are made in order to obtain these important
criteria.
The results show the significantly enhanced biofidelity of the
THORLx lower leg compared to the Hybrid III leg. The paper
concludes that the early introduction of a more biofidelic leg such
as the THORLx lower extremity is essential if additional and
reliable lower leg criteria are to be usefully implemented.