Age Effects on Thoracic Injury Tolerance

It is well known that the ability of the human body to withstand trauma is a function of its inherent strength, i.e., the strength of the bones and soft tissues. Yet, the properties of the bones and tissues change as a function of the individual's age. In this paper age effects on thoracic injury tolerances are studied by analyzing the mechanical properties of human bones and soft tissues and by examining experimental results found in the literature of thoracic impact tests to human cadavers. This work suggests that the adult age range can be divided into three age groups. Using piece-wise linear regression analyses, it has been determined that the reduction in injury tolerance from the “young” age group to the “elderly” group is approximately 20% under blunt frontal impact loading conditions and is as much as 70% under belt loading conditions. By comparing cadaver data and living human data, it has been also found that cadaver data on the elderly overestimate the decreases in mechanical properties with age. The reductions in injury tolerance with age can be used to scale tolerances between age groups so that existing experimental data of injury tolerances for a specific age range can be extrapolated to other ranges. The results of this paper may also be useful in the design of automotive restraint systems which are tunable to occupant age.