Numerical simulation of crash phenomena in rigid multi-body approach brings up problems when the various bodies constituting the mechanical system come into contact. The planar modeling of contact requires bodies' geometry to be taken into account. The method used permits the simultaneous management of constraints due to their contact and to kinematic joints, by introduction of holonomic constraints. We validate this method on biomechanical applications. The results arising from a numerical model, and from a sled test, where we recreated the dummy seating conditions, are compared.