Lower extremity injuries remain common in frontal motor vehicle crashes, with
evidence suggesting increased vulnerability among female occupants. While prior
research has established failure tolerances of midsize male lower extremities
under bending and combined loading conditions, limited data exist for small
female specimens. This study aimed to characterize and compare the failure
tolerance of small female and midsize male postmortem human subject lower leg
specimens under combined axial compression and posterior–anterior (PA) bending
using consistent boundary conditions. Twenty-four lower leg specimens, including
the tibia, fibula, and surrounding soft tissue, were obtained from 50th
percentile male (n = 12) and 5th percentile female
(n = 12) donors. Dynamic tests to failure were conducted at
1.5 m/s using a test apparatus designed to apply three-point bending in the PA
direction with varying levels of superimposed axial compression (0, 2, 4, and 6
kN). When paired left and right legs from the same donor were available, they
were assigned to different loading conditions to assess the influence of axial
compression magnitude. Fracture timing was determined using force, strain,
acoustic emission data, high-speed video, and post-test CT imaging. Results
indicated that 18 specimens fractured at the tibial shaft, 5 near the potting
interface, and 1 did not fracture. Under pure bending, mean failure moments were
255 ± 57 Nm for males and 156 ± 15 Nm for females. At 6 kN axial compression,
failure moments decreased to 195 Nm and 72 Nm for male and female specimens,
respectively. Among matched pairs, increasing axial load resulted in an average
21% reduction in bending moment at failure. These findings demonstrate reduced
failure tolerance with increasing axial compression and highlight sex-based
differences. The data provide a foundation for developing improved injury risk
functions and scaling methodologies for diverse occupant populations as well as
informing anthropometric test devices and human body models.
