Biomechanics of the Intramedullary Interlocking Nail (An Experimental Work On Distal Locking Screw)

Abstract

In order to compare the biomechanical performances of the distal lock screws placed in varying distances from the fracture line under axial tension, twenty sheep tibias with locked intramedullary nails were compressed wth Universal Haunsfield machine and loads in fracture region were measured by means of strain-gauges that are placed at the fracture line and then graphics were drawn. Whenever the axial load is beyond 500 Newton or the bone tension is less than 1 Newton/mm2 it was found that the shortening at the bone is large and there is no load on the fracture line. As fixing screws are placed far from the fractured region it was found that the fracture line is less affected from the loading. It is concluded that locked intramedullary nails should be placed in a distance that makes the tension along the fracture no less than 1 Newton/mm2.