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Dynamic Response and Injury Mechanism in the Human Foot and Ankle and An Analysis of Dummy Biofidelity
Published May 31, 1998 by National Highway Traffic Safety Administration in United States
Lower Leg injuries are the most frequent severe injury (AIS/3) to car occupants resulting from frontal impacts. Consequently, it is important to be able to detect and quantify the risk of these injuries from car impact tests. The need for a more biofidelic instrumented lower leg and the development of well-founded injury criteria has been clearly identified. At present there are insufficient biomechanical data available to aid the design and construction of such a dummy leg or to define injury risk criteria.
Three phases of a research program are reported. In phase one, a driving simulator trial was carried out using 24 subjects to investigate the positioning and bracing of the driver''s lower leg prior to an emergency-braking event. In the second phase of the work, low energy impact tests have been carried out on post mortem human surrogate (PMHS) legs and volunteers. Comparative tests were performed on existing Hybrid III and GM/FTSS dummy feet/ankles. A new method to generate an Achilles force is reported which has been used to enable studies to be carried out into the effect of bracing by plantar flexion, such as emergency braking. Dynamic tests were based on the EEVC foot certification test procedure. The program included tests to produce inversion and eversion. Additional toe impact tests were performed to assess lower leg behavior with pre-impact bracing, allowing for future comparisons with the ALEx leg.
Difficulties inherent in the interpretation of PMHS testing are reviewed and comparisons between tests on PMHS subjects and human volunteers are presented.
The final part of the paper reports the findings of an in- depth retrospective accident analysis based on data in the UK Cooperative Crash Injury Study database. Accidents in which the front seat occupant had sustained a lower leg injury of AIS/2 in a frontal collision were examined along with the associated hospital notes and X-rays. The injuries are ranked in terms of frequency, severity and impairment in order to determine which lower leg injuries that are a priority for prevention.