C7: Biomechanics

PARAMETRIC ANALYSIS ON PELVIC INJURY IN AN UNDERBELLY BLAST - A FINITE ELEMENT STUDY


Kwong Ming Tse1, Dale Robinson1, Melanie Franklyn1,2, Peter Vee Sin Lee1


1The University of Melbourne, Australia;
2The Defence Science and Technology Group, Australia


With the recent increase in underbelly (UB) blast attacks using improvised explosive devices (IEDs), severe injuries to the pelvis, which are often fatal or result in permanent impairment, have been reported to occur to occupants of military vehicles subjected to these events. In the current study, a finite element (FE) model of the pelvis was used in order to analyse the factors influencing pelvic injury potential from applied vertical loading, thereby providing an enhanced capability for risk assessment of military armoured vehicle occupants in UB blast events. 

Experimental boundary and loading conditions from high-speed pneumatically-driven impact tests using
cadaveric defleshed pelves were applied to the FE pelvis model and experimental measurements such as seat force, pelvic rotation and pelvic displacement relative to the fixture were used for validating the model. Using the FE pelvis model, parametric analyses were then conducted to assess the effects of different variables such as the presence of muscle forces, thoracic mass, abdominal mass, bone density, seating postures and compliance of the sacroiliac and sacrococcygeal joints on pelvic injury potential. 

A preliminary analysis of these simulations showed that the sacrum was highly susceptible to fracture, while muscle forces, which mainly contribute to intraabdominal pressure and are acting inferiorly on the pelvis brim, increased the likelihood of pelvic bone fractures. A smaller pelvic tilt, which occurs when a vehicle occupant seats with his or her upper body flexed forward, resulted in a higher stress in the  pelvis. The importance of intra-abdominal pressure in the loading path and fracture patterns in the dynamic blast event was also highlighted in the findings. The results of this preliminary work provide insights which can be used in the development of improved operational standards for the mitigation of complex pelvic injuries in UB blast events.

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