Introduction: Early stabilization of the skeleton in multiply injured patients has shown to reduce mortality and chest morbidity. Reamed intramedullary nailing is the current method of choice for stablizing femoral and tibial shaft fracture. However several investigators have highlighted the adverse effect of early reamed nailing in polytrauma patients. Intravasation of medullary fat during canal pressurizaton has been suspected to produce a ‘second hit’ and trigger pneumonia and ARDS. The objective of this study is to investigate the effect of a filter placed into the ipsilateral common iliac vein during medullary canal pressurization.

Methods: Using an established model of fat embolization, twelve mongrel dogs were randomized into two groups. Under general anaesthesia, cannulations of carotids and jugular veins and transesophageal echo-cardiography were performed in all animals. Under fluoroscopy control, a special filter was inserted percutaneously into the left common iliac vein in half the animals, where as the other half served as controls. In all dogs, the left knee was exposed; the femor and tiiba were sequentially reamed and then pressurized by injection of bone cement and insertion of intramedullary rods. Hemodynamic measurements and trans-esophageal echocardiography images were recorded continuously during the surgical procedure. After 45 minutes from pressurization, the dogs were sacrificed and the lungs and kidneys were harvested and fixed for histological analysis.

Results: There was significant difference noticed in the right-sided pressures and oxygen tension between the filter and the control groups. The mean pulmonary artery pressure at 3 minutes of pressurization was 12mm of Hg in the filter group and 28mm of Hg in the control group. Transesophageal echocardiography showed less embolic shower in the filter group and also lesser dilatation of right ventricles. Histomorphometry with special staining demonstrated much less proportion of lungs to be occupied by fat in the filter group as compared to the control group.

Discussion and Conclusion: This canine study has demonstrated that mechanical blockade by a venous filter can significantly reduce the emobilic load on the lungs in an established model of fat embolization. A suitable filter with suction system is being designed for possible use in high-risk patients.