The effect of a venous filter on the embolic load during medullary canal pressurization: a canine study

Acute intramedullary stabilization of femoral shaft fractures in multiply injured patients is controversial. Intravasation of medullary fat during canal pressurization has been suspected to trigger adult respiratory distress syndrome. The goal of the present study was to evaluate the effect, on the lungs, of a filter placed into the ipsilateral common iliac vein during medullary canal pressurization in a canine model.

With use of an established model of fat embolization, twelve mongrel dogs were randomized into two groups. In six dogs, a special filter was inserted percutaneously into the left common iliac vein while the dogs were under general anesthesia. In all dogs, the left femur and tibia were then pressurized by injection of bone cement and insertion of intramedullary rods. Hemodynamic measurements and echocardiographic images were recorded throughout the experiment. After one hour, the animals were killed and the lungs were harvested for histomorphometric analysis.

Without the filter, the mean pulmonary artery pressure increased by 11.8 +/- 2.1 mm Hg (p < 0.001). With the filter, the mean pulmonary artery pressure increased by only 2.2 +/- 0.8 mm Hg (p < 0.02). Without the filter, there was a significant increase in the index of pulmonary vascular resistance as compared with the baseline value (p < 0.05). With the filter, there was no such increase. Histomorphometric analysis demonstrated that the presence of the filter reduced the absolute area of embolization and the volume percentages of lung and pulmonary vasculature embolized.

In this canine experiment, temporary placement of a venous filter prior to medullary canal pressurization reduced the embolic load and minimized its hemodynamic effects.