[Jamming a child's finger: an experimental study to determine elastic resistance and the point of onset of bone/joint deformation].

Knowledge of the elastic properties of children's fingers is very important to understand the potential hazard for jamming injuries that exists in modern motor vehicles with automatic power-operated windows. This study determined the elastic resistance and the point of onset of bone/joint deformation at each of 5 different jam positions of a child's finger under continuous dorsal-palmar compression. An unembalmed finger that recently had been surgically removed from a polydactylic 8 month-old girl was jammed in a custom hydraulic test apparatus. A subminiature force sensor and an electrometric path sensor measured force and deflection values. To visualise the respective point of onset of bone/joint deformation, jamming of the finger was performed under fluoroscopy. The mean force at the point of onset of bone/joint deformation was 78.4 N. The current statutory limit of 100 N for the maximum closing force of an automatic power-operated motor vehicle window is thus well beyond the point at which finger injuries can occur in children. Assuming finger injuries in children can occur at a jamming force below approximately 80 N, a reduction of the statutory limit to us higher than 50 N is reasonable.