Facial injury: a review of biomechanical studies and test procedures for facial injury assessment.

A review of biomechanical studies that have attempted to measure fracture tolerances of facial bones has been carried out. The particular bones of interest were the mandible, the zygoma, the maxilla and the nasal bones. Numerical values have been given for the peak force and pressure fracture tolerances for these bones. A study of these values illustrates just how variable the bone strength of various individuals is. A review of various methods that have attempted to measure and quantify the physical effects of a blow to the face has also been carried out. Three major types of test procedure exist, namely frangible elements, peak force and pressure sensing elements and deformable elements. Frangible and deformable elements generally replace the face of a standard test dummy, fracturing and deforming at appropriate impact force levels, respectively. These surrogate face forms are used for two different reasons; either they are used to measure the damage to the human face for some impact scenario or they are simply used to better simulate the response of the whole head to impact by simulating the compliance of the face. Peak force and pressure sensing elements take the form of piezoelectric sensors and pressure-sensitive, colour 'Fuji film'. Both these methods are complicated and really only suitable for research purposes only. Finally, it is recommended that a mathematical model approach be used to establish the principal injury mechanism and support further development of an acceptable face form test.