EFFECT OF PROXIMAL AND DISTAL VENTING DURING INTRAMEDULLARY NAILING

During intramedullary manipulation, 2 main phenomena occur, A dramatic rise in intramedullary pressure occurs followed by intravasation of d amaged marrow tissue. There are concerns about the development of incr eased interosseous pressure during reaming and the potential for this to contribute to fat embolism syndrome. The intramedullary pressures g enerated with various intramedullary devices was determined and the ef fects of a fracture, with and without proximal and distal venting on t hese pressures were studied, Pressures generated in 78 embalmed anatom ic specimen femurs and tibias were studied, leaving all soft tissues i ntact, Pressures were recorded for awl, guide rod, reamer, and nail in sertion, Venting was done by creating a 4.5-mm hole in the cortex dire ctly opposite the transducer, Proximal venting reduced proximal pressu res to 80 mm Hg in the tibia (90% reduction) and 460 mm Hg in the femu r (70% reduction), Distal venting reduced distal pressures to 65 mm an d 30 mm in the tibias and femurs, respectively (90% reduction in press ures), Intramedullary pressures generated during nail or alignment rod insertion in anatomic specimen bone greatly exceeds the critical thre sholds (150 mm Hg) thought to be responsible for fat emboli to the lun g in the dogs, The introduction of a vent may reduce the chance of fat embolism. Despite the high association of raised intramedullary press ures and fat emboli in animal studies, there is no known critical thre shold for humans. Therefore, although venting seems effective in reduc ing the intramedullary pressure in anatomic specimen bones, its effica cy in the patient with trauma remains to be determined.