Evaluation of biofidelity and repeatability of THOR-Lx metric under axial impact loading

Abstract

This study evaluated biofidelity and repeatability of THOR-Lx under two axial impact loading conditions. Four cadaveric lower limbs were tested under a 3.1 m/s axial impact condition. Then, the responses were normalized to those of the 50th percentile male and the 5th percentile female using a mass scaling technique. The response corridors for foot plate displacement and three axial loads measured at foot plate, mid-sections of tibia and fibula, and knee plate were developed for the two target anthropometries. The THORLx was tested under matching conditions to evaluate its biofidelity and repeatability. Lastly, the responses of THOR-Lx with foot and MIL-spec shoe and molded shoe configurations were compared under a 5.3 m/s impact loading condition. THOR-Lx exhibited biofidelic and repeatable responses regarding Biorank scores and ISO rating scores, respectively. Under the 5.3 m/s impact conditions, the THOR-Lx with MIL-spec shoe exhibited greater ankle inversion and tibial bending moments than that of THOR-Lx with molded shoe. Lastly, THOR-Lx with both shoe configurations exhibited a stiffening behavior when the axial load exceeded around 4 kN. It was concluded that THOR-Lx is biofidelic under an axial impact loading condition until 4 kN, but it requires a modification to be biofidelic under a higher load.