ABSTRACT
Background:
Shaft fractures of the
femur are commonly treated with
intramedullary nailing, which can release
bone marrow emboli into the bloodstream. Emboli can
travel to the
lungs, impairing gas exchange and causing
inflammation. Occasionally, emboli traverse from the pulmonary to the systemic circulation, hindering
perfusion and resulting in
injuries such as
heart and
brain infarctions, known as
fat embolism syndrome. We studied the extent of systemic
bone marrow embolization in a pig model.
Methods:
Twelve anesthetized
pigs underwent bilateral
intramedullary nailing of the
femur, while 3
animals served as sham controls.
Monitoring included
transesophageal echocardiography (TEE),
pulse oximetry,
electrocardiography,
arterial blood pressure measurement, and
blood gas and
troponin-I analysis. After
surgery,
animals were monitored for 240 minutes before
euthanasia. Post mortem, the
heart,
lungs, and
brain were biopsied.
Results:
Bone marrow emboli were found in the
heart and
lungs of all 12 of the
pigs that underwent
intramedullary nailing and in the brains of 11 of them. No emboli were found in the sham group. The
pigs subjected to
intramedullary nailing exhibited significant
hypoxia (PaO2/FiO2 ratio, 410 mm Hg [95%
confidence interval (CI), 310 to 510) compared with the sham group (594 mm Hg [95% CI, 528 to 660]). The nailing group exhibited ST-segment alterations consistent with
myocardial ischemia and a significant increase in the
troponin-I level compared with the sham group (1,580 ng/L [95% CI, 0 to 3,456] versus 241 ng/L [95% CI, 0 to 625] at the 240-minute
time point; p = 0.005). TEE detected emboli in the right ventricular outflow tract, but not systemically, in the nailing group.
Conclusions:
Bilateral
intramedullary nailing caused
bone marrow emboli in the
lungs and systemic emboli in the
heart and
brain in this pig model. The observed clinical manifestations were consistent with coronary and pulmonary emboli. TEE detected pulmonary but not systemic embolization.
Clinical Relevance Femoral
intramedullary nailing in
humans is likely to result in embolization as described in our pig model. Focused
monitoring is necessary for
detection of
fat embolism syndrome. Absence of visual emboli in the
left ventricle on TEE does not exclude the occurrence of systemic
bone marrow emboli.