Injury Mechanisms and Injury Criteria

Abstract

Traumatic injuries occur when the mechanical tolerance limits of body structures are exceeded. Injuries are generally believed to result from excess strain induced by direct or indirect (i.e. inertial) loading and the most important advance in impact biomechanics has been the development of injury criteria relating the probability of trauma to mechanical parameters which can be measured using instrumented crash test dummies or cadavers, or evaluated in a numerical model. Without injury criteria, the severity of trauma in a staged test or an accident reconstruction cannot be evaluated. Injury criteria are mostly estimated from experimental tests on cadavers or animals, but tolerance thresholds are sometimes derived from human volunteer tests. There are many problems associated with the development of injury criteria including sample size, age of cadaver subjects, scaling from animal tests to humans, inherent variability in biological samples and differences between cadavers and living people. Furthermore, limitations in sensor technology and in dummy biofidelity have resulted in injury criteria that correlate injuries with structural parameters (forces and accelerations etc) rather than tissue level loading or deformations (stress or strain). These factors should be considered when assessing the validity of a proposed injury criterion.