The primary goal of the current study was to determine ATD lower extremity loading characteristics seen in frontal crash tests and apply these characteristics to isolated PMHS lower extremity impacts. Essentially, the study attempted to re-create the kinetics experienced by the Hybrid III 50th percentile ATD (HIII) in frontal crash tests and apply this crash test loading scenario directly to PMHS specimens efficiently and while maximizing the utilization of a small number of cadaver subjects. The secondary goal of this study was to determine the relationship between PMHS and HIII lower extremity impact response. Based on this comparison, it was anticipated that PMHS posterior cruciate ligament (PCL) injury threshold and timing could be related to knee shear in the HIII ball-bearing knee slider mechanism.
HIII lower extremity loading was analyzed from a series of twenty-eight (28) frontal barrier or vehicle to vehicle crash tests from late model vehicles. Specific loading parameters, including knee shear, upper tibia force, lower tibia force and femur force, were examined. Phase I testing involved thirty-four (34) full body HIII lower extremity impact tests with a linear impactor to replicate the crash test loading acting on the HIII lower extremity in the frontal crash tests. Phase II consisted of twenty-five (25) isolated HIII lower extremity impact tests. These tests used the results from Phase I as an initial starting point, and were performed and correlated with the crash test and Phase I results. Finally, Phase III testing involved eight (8) isolated PMHS lower extremity impacts. These impacts were conducted utilizing the impact setup from Phase II testing in an attempt to determine a method for predicting PCL injury threshold.
This study found (1) that a PMHS impact setup that duplicates ATD loading seen in crash tests was feasible and could be created in a short period of time while making the most of available cadavers, (2) full-body PMHS testing can be eliminated where isolated body segment testing is more desirable, (3) knee injury location and type was different when using full lower extremities potted only at the mid-femur as opposed to lower extremities in previous studies potted at both the femur and tibia with surrounding tissue removed and (4) the accurate determination of a PCL injury threshold and timing requires additional PMHS impact testing.