PROXIMAL ANGLE OR CONTINUOUS BEND IN UNREAMED INTRAMEDULLARY NAILING - AN EXPERIMENTAL-STUDY

The intramedullary tibial nail with a proximal angle according to Herz og was developed in order to facilitate implantation. However, the mod ified technique of unreamed nailing also required a shift of the point of insertion; as a consequence the proximal angle required a consider able increase in the force necessary to introduce the nail. In a study using four cadaver bones and five commercially available unreamed fem oral and tibial nails, the authors demonstrate this considerable incre ase in insertion force and the development of pressure in the medullar y cavity. The measurements made with our experimental setup clearly sh ow that the proximal angle of the unreamed tibial nails available for our series does not have a favourable influence on insertion behaviour . As it appears, it results in an increase in the force required for i nsertion of the nail, thus also causing a greater strain on the bone a nd an increase in pressure in the medullary cavity. In contrast, the c ontinuous bend of the nail results in a much smoother course of pressu re development in the medullary cavity, which does not reach the same high values as with the unreamed tibial nails, despite the fact that l ess time is required for insertion of the nail. In our opinion, modifi cation of the axial shape of the nail would result both in better impl antability and easier removal. We therefore advocate such a modificati on of the axial shape of intramedullary tibia nails.