Biomechanical characterization of internal layer subfailure in blunt arterial injury.

Blunt carotid artery injuries occur in 0.3% of blunt injured patients and may lead to devastating neurological consequences. However, arterial mechanics leading to internal layer subfailure have not been quantified. Twenty-two human carotid artery segments and 18 porcine thoracic aorta segments were opened to expose the intimal side and longitudinally distracted to failure. Porcine aortas were a geometrically accurate model of human carotid arteries. Internal layer subfailures were identified using videography and correlated with mechanical data. Ninety-three percent (93%) of vessels demonstrated subfailure prior to catastrophic failure. All subfailures occurred on the intimal surface. Initial subfailure occurred at 79% of the stress and 85% of the strain to catastrophic failure in younger porcine specimens, compared to 44% and 60%, respectively, in older human specimens. In most cases, multiple subfailures occurred prior to catastrophic failure. Due to limitations in human specimen quality (age, prior storage), young and fresh porcine aorta specimens are likely a more accurate model of clinical blunt carotid artery injuries. Present results indicate that vessels are acutely capable of maintaining physiologic function following initial subfailure. Delayed symptomatology commonly associated with blunt arterial injuries is explained by this mechanics-based and experimentally quantified onset of subcatastrophic failure.