Pathophysiology

There are two main suggested theories for fat embolism:

Mechanical theory 

Fatty tissue is directly released into the vascular circulation as a result of trauma in adipose tissue or bone marrow.

Biochemical theory

Inflammatory response to the trauma causes release of free fatty acids into the venous system from the bone marrow or cellular plasma.

The formed  fatty emboli cause a severe inflammatory response in the local tissue including increases in vessel permeability and can lead to systemic complications.