RESEARCH

The SCIB's Digital Child Project

Russ Fine and Jay Goldman, University of Alabama at Birmingham

A new, multi-component research initiative known as the Digital Child Project® (DCP) was launched by the SCIB in 2006.

The numerical model development components are being conducted at the University of Alabama at Birmingham (UAB) and Wayne State University (WSU). This collaborative approach takes advantage of expertise in both institutions.

Other projects complementing these two primary research initiatives include identifying: 1) key anthropometries at various pediatric development stages; 2) aggregation and interpretation of injury statistics associated with critically injured organs, body regions, injury severities, and injury sources or etiologies; 3) pediatric biomechanical properties under dynamic loading conditions; and 4) pediatric impact responses and tolerances. These investigation efforts are being conducted by other SCIB member institutions.

Finite element (FE) based computational models can provide more detailed biomechanical responses as compared to physical or rigid body dummy models. Through FE analyses, the stresses, strain, and kinematic information (displacement, velocity, accelerations, reaction forces, etc.) in a specific region of the human body can be obtained. These parameters, which sometimes cannot be measured by experimental approaches, are necessary to investigate the tissue damage and the related injuries of the human body.

Several FE models of the whole adult human body have been developed and used to investigate the injury mechanism of vehicle occupants under different loading conditions. However, recently, pediatric injury has gained much attention, and research efforts have focused on understanding the injury mechanisms and establishment of tolerances to provide a safer environment for children. Some physical child dummy models have been developed for injury research, but they have inherent limitations due to lack of biofidelity. Validated computational models have many advantages because it is very difficult to obtain child cadavers due to ethical issues.

So far, very few pediatric FE models are available in the literature, and most of such models were developed by geometrically scaling from an adult model. Unfortunately, scaled FE models did not consider the anatomical difference between adult and child, so they may not completely reproduce accurate age-dependent biomechanical response. For accurate prediction of injury mechanisms of children, the use of a child FE model with accurate anatomical geometry and material properties is essential.

Together, UAB and Wayne State University are developing finite element meshes of pediatric subjects at 3, 6, and 10 years of age. They are also identifying methods to determine material constitutive laws and their respective constants, and extract component models (such as the femur, tibia, etc.) and regional models (such as the thoracic region, abdominal region) from the whole body finite element meshes for application at other SCIB member institutions where additional experiments will be conducted.

The SCIB’s approach is to develop the whole body model prior to extraction of component models rather than the opposite way. This will ensure mesh compatibility between the local and global models. Subsequently, SCIB member institutions can adjust/modify the regional models according to their experimental boundary conditions, and input material properties using the methods to be developed in the UAB and WSU projects, and input loading conditions to determine if the regional model predictions match experimentally obtained data.

It is well understood that the DCP is too large in scale for any single institution to handle alone. Thus, the SCIB is well positioned to manage this work. In the last phase of the DCP, material constants obtained from all validated regional models will be integrated into whole body models of these three pediatric age groups so that whole body impact responses under various restraint systems can be simulated to improve pediatric transportation safety.

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