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Response of the Knee Joint in Lateral Impact: Effect of Bending Moment
Published September 08, 1993 by International Research Council on Biokinetics of Impact in Switzerland
During the 80's a new type of crash impact dummy, the rotationally symmetrical pedestrian dummy (RSPD), suitable for the assessment of car front aggressiveness in pedestrian impacts was developed. This dummy enables measurement of biomechanical parameters, such as forces and moments at the knee joint level related to the injury mechanisms. To determine the resistance of the human knee to shear force or bending moment and to describe the injury mechanisms, it was necessary to make separate in-vitro experiments with human cadaver specimens, where only one of those two parameters affects the biological material at the time.
In the present study an experimental method for assessing the tolerance to bending moment in the lateral direction of the extended knee joint has been developed. The load response of the lower extremity was measured by means of force transducers. The bending moment transferred through the entire knee joint was calculated and the motion of the specimen was registered by high speed photography. The bending moment in the lateral direction at the first sign of damage of the entire extended knee joint was determined. Damages were assessed by measuring the knee joint condition (valgus-varus and anterior drawer increment) and by dissecting the knee region. Seventeen tests were carried out under dynamic conditions, seven at a velocity of 16 km/h and ten at 20 km/h on human cadaver lower extremities.
The first and most common damage type to entire knee joint in this loading configuration was stretching and rupture or avulsion of the medial collateral ligament (MCL). These damages are generated by dentical mechanisms i.e. tensional forces acting on the medial knee structures. The mean peak moment correlated with this damage mechanism was 101 (±21) Nm for an impact velocity of 16 km/h, and 123 (±35) Nm for an impact velocity of 20 km/h. The mechanisms led to damage of the knee joint when the lower extremity was bent approximately 10 degrees in the lateral direction at the knee joint