A technique for using strain gauges to evaluate airbag interaction with cadaveric upper extremities

Radius and ulna fractures from airbag deployment onto the forearm have been reported in the literature. Based on laboratory experiments with eight cadaveric upper extremities, this paper presents a method for using strain gages to evaluate upper extremity loading during airbag deployment. The technique provides strain rates, bending moments, and time of fracture for the radius and ulna. Planar rosettes (350 omega, 5% strain) were selected as the best choice given the application to bone with a rosette being placed mid-shaft on both the anterior and posterior surfaces of the radius and ulna. Forearm incisions were intended to be minimally invasive and to limit damage to the interosseous membrane. The bone surface was prepared with Ether, and the gauges were bonded to the surface with methyl-2-cyanoacrylate. A thin latex cover was installed over the surface of the rosettes to isolate the gauges from the surrounding tissue. Strain relief of the gauges was provided by securing the wire leads to the bone with tie-wraps, as well as suturing the wires to the skin. With this technique all gauges reported accurate data throughout the duration of the impact.