The objective of this study was to determine the biomechanics of the human thorax in a simulated frontal collision. Sled tests were conducted using unembalmed human cadavers at velocities of 32 or 48 kph. Specimens were restrained using air bag - knee bolster, air bag - lap belt, or air bag - three-point belt combinations. Deformation contours derived from the chest bands indicated regional differences in the biodynamic response. Nondisplaced rib fractures occurred without internal injuries or without the laceration of the costal pleura through the fractured rib. The number of rib fractures identified on routine clinical radiographs were consistently smaller than the number found at autopsy. The rib trauma mechanism was determined to be compression and/or bending-related for the air bag - three-point belt restraint system wherein fractures were concentrated around the shoulder harness region and the lateral-most area of the rib cage on the right side. The skeletal injury mechanism for the air bag - knee bolster system was secondary to a compressive force directed along the anteroposterior axis and applied bilaterally over the lower torso regions. The biomechanical response of the thorax is different between air bag - three-point belt loading, compared to the air bag -knee bolster restraint combinations.
Abstract