Femoral Nailing in a Porcine Model Causes Bone Marrow Emboli in the Lungs and Systemic Emboli in the Heart and Brain

Steinar Kristiansen; Anders Hagen Jarmund; Jonas Hilmo; Tom Eirik Mollnes; Martin Leth-Olsen; Siri Ann Nyrnes; Bent Aksel Nilsen; Renathe Henriksen Grønli; Bjørn Ove Faldaas; Benjamin Storm; Arild Espenes; Erik Waage Nielsen

doi:10.2106/JBJS.OA.23.00128

Femoral Nailing in a Porcine Model Causes Bone Marrow Emboli in the Lungs and Systemic Emboli in the Heart and Brain

JB JS Open Access. 2024 Feb 28;9(1):e23.00128. doi: 10.2106/JBJS.OA.23.00128. eCollection 2024 Jan-Mar.

Authors

Steinar Kristiansen^{1

2}, Anders Hagen Jarmund³, Jonas Hilmo^{1

2}, Tom Eirik Mollnes^{4

5}, Martin Leth-Olsen^{3

6}, Siri Ann Nyrnes^{3

6}, Bent Aksel Nilsen^{1

7}, Renathe Henriksen Grønli⁴, Bjørn Ove Faldaas^{3

7}, Benjamin Storm^{1

2

7}, Arild Espenes⁸, Erik Waage Nielsen^{1

2

7}

Affiliations

¹ Department of Surgery, Nordland Hospital, Bodø, Norway.
² Institute of Clinical Medicine, University of Tromsø, Tromsø, Norway.
³ Department of Circulation and Medical Imaging (ISB), Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway.
⁴ Research Laboratory, Nordland Hospital, Bodø, Norway.
⁵ Department of Immunology, Oslo University Hospital, University of Oslo, Norway.
⁶ Children's Clinic, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway.
⁷ Faculty of Nursing and Health Sciences, Nord University, Bodø, Norway.
⁸ Department of Basic Sciences and Aquatic Medicine, Norwegian School of Veterinary Science, Oslo, Norway.

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.