[Insertion of distal screws in interlocking nailing using a new free-hand control device].

While it is technically easy to introduce the proximal screw in interlocking nailing, the torsion of the nail being driven into the medullary canal can make distal locking more difficult. There are two approaches to the insertion of the distal screws: the c-arm-mounted device and the free-hand technique. The Grosse-Kempf c-arm device was introduced in 1978, but it requires modification of the fluoroscopy unit and is time consuming. The free-hand technique has certain disadvantages because of involuntary movement during the change from aiming to drilling. Furthermore, the bulky power drill makes monitoring of the path of the drill bit impossible, and the radiation time can be considerable. A new free-hand distal aiming device for the interlocking nail was therefore designed in our department. The main objectives were to provide a simple, yet precise instrument with few parts that would allow monitoring of the direction during process of penetrating the nail hole. The device consists of two metal rings on both ends of an X-ray translucent cylinder with a central 4-mm hole in it. A pin with a sharp tip (diameter 4 mm, length 160 mm) is inserted through the hole. Using the image intensifier, the device is then placed so that the sharp tip of the pin points to the bone. The device is moved until the two metal rings are superimposed on each other and give the impression of one ring with the nail hole in the middle. On the screen the pin then appears as a dot inside the nail hole.(ABSTRACT TRUNCATED AT 250 WORDS)