How can a femoral shaft fracture be lethal?
A femoral shaft fracture in isolation should not cause death. Yet a patient with a femoral fracture can die from this injury.
Recall that bone is vascular and fractures let marrow contents (fat especially) out into the circulation.Fat could embolize to the brain or the lungs.
This photo of Pork Neck Bone Soup with Lotus Root with glistening fat droplets on the surface will remind you of this more than an MRI of a brain showing a fat embolism
MRI of a brain showing a fat embolism–see, wasn't I right??
These marrow contents are inflammatory in the lungs, and thus, after a femoral fracture, some patients develop ARDS (adult respiratory distress syndrome).
Also, the marrow contents are thrombogenic. Patients with fracture, especially if immobilized can get extremity venous clots, and when a clot embolizes to the pulmonary artery unhappiness is the result.
Other serious co-morbidites of femoral shaft fractures include shock from significant blood loss and visceral injuries from the initial injury force that broke the bone.
In this CT angiogram a pseudoaneurysm of medial branch of the profunda femoral artery is seen. Bleeding from this location is not apt to be lethal, but the picture should remind you of the interplay between vascular injury and bone fracture
Below a femur fracture is shown in yellow with a pelvic diastasis (suggestive of a visceral injury) is shown in red