Mechanical theory

The simpler mechanical theory proposes that trauma to long bones disrupts fat cells in either the marrow of the fractured bone or in adjacent adipose tissue. The fat droplets enter torn veins and are embolised to the lungs and peripheral circulation.

Strong evidence of the mechanical theory has come from a report from Pell et al. These authors demonstrated (by transoesophageal echocardiography) that at the time a guide wire was inserted into the bone marrow canal for reaming and intramedullary nailing of the femur, echogenic material passed into the right side of the heart. It was noted that reductions in oxygen arterial saturation correlated with the density of echogenic material.