["Reduction-effect" ARUM-type intra-focal pins in the osteosynthesis of fractures of the lower end of the radius].

Used for 13 years, the "Intra-Focal Pinning" procedure for the fixation of the Colles fractures, has been criticized on certain points: pin expulsion, risks of injuring the tendons by the cut end of the pin. A new type of pin in proposed, the "ARUM" pin, that is composed of a 20/10 mm screwed pin and a special nut, which has a curved conical form, with a convex base bearing a cruciform groove. Its axial canal has a little space at the base. There are two ancillary tools: a special wire-cutter with asymmetric cutting blades, that can cut the pin close to the nut, and a compound screwdriver and pin-holder. With this tool, it is possible to put the pin in its right place and to screw the "ARUM" nut very precisely: the concave conical form of the nut makes it possible to slide between the tendons without injuring them and widening the fracture site: this is the "reduction effect". In practice, the pins are introduced in the same way as the previously described procedure, by they must protrude beyond the opposite wall by 6-8 mm; the difference is in the screwing of the "ARUM" nut: first it is screwed as the reduction stress is increased so its conical part penetrates between the fracture edges; then the pin is cut; and the nut is unscrewed so the cut end of the pin will be included in the space of its base. Unscrewing is continued until the sharp end of the pin just extends beyond the cortical wall, but without losing the reduction.(ABSTRACT TRUNCATED AT 250 WORDS)