Biomechanical response of the human clavicle: the effects of loading direction on bending properties

The purpose of this study was to determine the influence of loading direction on the structural response of the human clavicle subjected to three-point bending. A total of 20 clavicles were obtained from 10 unembalmed fresh-frozen postmortem human subjects ranging from 45 to 92 years of age. The right and left clavicles from each subject were randomly divided into two test groups. One group was impacted at 0 degrees from the transverse plane, and the second group was impacted at 45 degrees angle from the transverse plane. There was no statistically significant difference in peak force (p = .22), peak moment (p = .30), or peak displacement (p = .44) between specimens impacted at 0 degrees versus 45 degrees from the transverse plane. However, there was a significant difference in the structural stiffness (p = .01) and peak strain (p < .01) between specimens impacted at 0 degrees versus 45 degrees from the transverse plane. The peak strain, however, must be evaluated with caution because of the variation in fracture location relative to the strain gauge. Due to the controlled matched data set, the differences in the structural stiffness with respect to loading direction can be attributed to the complex geometry of the clavicle and not material differences.