Biomechanically based criteria for rib fractures induced by high-speed impact.

Biomechanically based correlations for rib fractures induced by high-speed impact were developed from animal studies, finite-element simulations, and statistical analysis. Using subject-specific finite-element models of swine thorax developed from medical images and customized for each animal subject, simulations were conducted for animal tests. The peak motions, internal forces, stresses, and strains were calculated for individual ribs. Statistical analysis then was used to determine represented variables that were statistically significant and that better fit the test data. The findings showed that the main loading modes during impacts are local bending and shearing. Stress-based variables fit the injury data very well. Strains also were relevant, but did not correlate with the data as well as stresses. The results also indicate that motion responses, such as displacement and velocity, and internal forces are not good correlates in high-speed impacts. The regression risk curves were developed using the stresses as correlates, and the threshold values are given consistent with bone strength data.