[Comparative theoretical study of various external fixation devices for the stabilization of distal radius fractures]

In the treatment of comminuted Colles' fractures different types of external fixation devices are used. Three main types are compared: (1) Fixation with two pins in each plane: Ace-Colles' type; (2) fixation with four or more parallel pins in one plane: Wagner/Hoffmann type; (3) fixation with four pins in one plane, two pins on each side of the fracture forming an angle of 60 degrees: ASIF-type fixator. These three types are compared with reference to the different forces that have to be neutralized by the seating of the pin in the bone. To minimize these forces with the aim of preventing pin-loosening, the theoretical results are used as the basis of practical surgical advice: (1) The distance between skin and fixator should be as short as possible. (2) The fixator should be fixed as close as possible to the fracture. (3) The diameter of the pins should be as great as possible. (4) If more than two pins per plane are used (Hoffmann/Wagner type), the pins should be wide apart. (5) If only two pins per plane are used (Ace-Colles Type) the bending stress on each pin is high (6) If more than two parallel pins per plane are used (Hoffmann/Wagner type), the axial forces on each pin are high. (7) The pins should be fixed at right angles to the fractured bone. Pins at other angles do more harm than good.