Biomechanical Tests and Clinical Application of Unicortical Pin by the External Fixator System

ABSTRACT

The paper outlines characteristics of the unicortical pin, its biomechanical features, as wel as its application in the clinical practice. The plastic models are used for parallel tests of biomechanics of unicortical and Schanc's pins that are mounted together with the external fixator M.9. Their stability in LL direction is almost the same, but in AP direction the unicortical pin offers lower stability. This can be explained by the direction and position of placing of these pins. Special advantage and feature of the unicortical pin is its saving role toward the bone vascularization. It passes only into the bone cortex, and this in spots, and it doesn't pass thrugh the medullary channel and doesn't damage medullary vascularization. In clinical practice the unicortical pin is most frequently applied with the comminuted fractures. It puhes the free bone fragment and attaches it to the basic one so that greater stability is assured at the fracture core and the fracture gap, i.e. hematom, is diminished. This procedure stimulates the osteogenesis process. Unicortical pins are less frequently used for independent fixing of the bone fragments—this only if there is counterindication for the general anesthesia, in which case the unicortical pins are applied under local anesthesia.