Intramedullary pressure, strain on the diaphysis and increase in cortical temperature when reaming the femoral medullary cavity--a comparison of blunt and sharp reamers.

Clinical application has shown intramedullary nailing to be a safe therapeutic procedure, although damage to the vascular system and fat embolism have been demonstrated in animal experiments. The main negative factors were presumed to be the increase in intramedullary pressure and the increase in cortical temperature. In this study, the effect of the blunting of the reamers on the increase in intramedullary pressure, the tangential strain on the diaphysis and the increase in cortical temperature was to be clarified. The measurements were carried out on pairs of human femora reamed with sharp and blunt AO reamers. The pressure was measured in the middle of the diaphysis and in the metaphysis, the strain in the middle of the femur and the temperature on four aspects of the femur. The femora were reamed with identical compression and traction forces in a water bath at 37 degrees C. In comparison with the sharp reamer, the blunt reamer develops 2.1 times the positive diaphyseal pressure, 1.7 times the positive metaphyseal pressure, 1.6 times the negative diaphyseal pressure, 1.5 times the positive tangential strain, 55 times the negative tangential strain and 2.8 times the increase in cortical temperature. There is no difference in the negative metaphyseal pressure. Since blunt reamers produce greater intramedullary pressure values, greater tangential strain on the diaphysis and a greater increase in cortical temperature, the attention of surgeons and operating staff must be drawn to the fact that they should treat the reamers gently and replace them whenever necessary.