HUMAN FACIAL TOLERANCE TO STEERING WHEEL IMPACT - A BIOMECHANICAL STUDY

In an effort to delineate the tolerance of the human facial skeleton w ith respect to steering wheel impact, research was conducted using hum an cadavers. We reported the biodynamics of steering-wheel-induced fac ial trauma due to impacts at the unsupported rim (Yoganandan, Pintar, & Sances, 1991). The present study was conducted to determine the prob ability of facial bone fracture secondary to impact at the spoke-rim j unction. Either zygoma was impacted once onto the spoke-rim junction a t velocities ranging from 1.4-6.9 m/s. A six-axis load cell placed und er the hub documented the generalized force histories. Interface force at the impact location was computed using the generalized force and d eformation histories recorded at the spoke-rim junction using transfor mation principles. Bone mineral content was also determined. Facial pa thology was evaluated using x-ray, two- and three-dimensional computed tomography, and defleshed skulls. Fractures of the zygoma, orbit, and maxilla were observed. While higher impact velocities resulted in pro pagation of fracture to the contralateral site, unilateral fractures o f less severity occurred at lower speeds. Results indicated that a for ce level of 1525 N corresponds to 50% probability of facial fracture f or the spoke-rim junction. Consequently, significant amelioration of f acial injuries can be achieved if the forces are kept below this limit .