Biomechanical study on the effect of atherosclerosis on the vulnerability of thoracic aorta, and it's role in the development of traumatic aorta injury.

Traumatic aorta injury (TAI) is the second most common traumatic cause of death preceded only by head injuries, being responsible for 5% to 30% of all mortalities in high-speed deceleration injuries. Multiple external factors might play a role such as impact speed, impact direction, occupant location, and presence or lack of restraining safety mechanism. Apart from these external factors, also human biological factors can influence its development. Based on the data of scientific literature, age clearly plays a role in suffering TAI, but the role of atherosclerosis-as a disease affecting the structure of the aorta-is unknown. Biomechanical properties of tissue samples of 104 aorta specimens removed during the autopsy from the posterior (Group 'A') and lateral wall (Group 'B') of descending aorta were analyzed. Specimens were examined by a Zwick/Roell Z5.0 biaxial tester. The Young's modulus (E (MPa)) was calculated using a linear regression procedure where the base of the elongation was the parallel length of the sample, the achieved maximal force (Fmax (N)), the elongation at the time of Fmax (Lmax (mm)), the force at the beginning of rupture (Fbreak (N)), the elongation at the time of Fbreak (Lbreak (mm)) were registered. Specimens were categorized based on macroscopic and microscopic appearance. In the posterior (A) samples the difference between Lbreak (p<0.001) and Lmax (p<0.001) was significant between the macroscopic group. Lbreak (p = 0.009) and Lmax (p = 0.003) showed similar pattern in the lateral (B) samples. Comparing the histological groups by the measured parameters (Fmax, Lmax, Fbreak, Lbreak) showed a significant difference in the means (p<0.001, p = 0.003, p<0.001 respectively). The study demonstrated that atherosclerosis decreases the resistance of the aorta. The rupture occurs at lower force (Fmax and Fbreak), and at shorter elongation (Lmax and Lbreak) in case of the presence of atherosclerosis. This effect is most substantial if calcification is present: the resistance of aorta affected by calcification is only two-thirds on average compared to aorta affected by the early phase of atherosclerosis. This phenomenon can be clearly explained by the weakening structure of the tunica intima.

The effect of hepatic steatosis and fibrosis on liver weight and dimensions.

The liver is the most commonly injured abdominal organ, accounting for around half of abdominal organ injuries. The emergence of liver injury is determined by the injury mechanism, force, and tissue vulnerability. The vulnerability of the liver depends on the strength of the capsule and parenchyma, as well as the weight and dimensions of the liver. The common hepatic diseases, like steatosis, fibrosis, and cirrhosis, can change the organ weight and dimensions, but their exact correlation is not well known. This study was designed to evaluate the correlation between liver diseases, weight, and dimensions. The liver weight, horizontal, vertical, and antero-posterior length were measured obtained by 213 forensic autopsies. The recorded data were compared with body height, age, and liver histology. Body height positively correlated with liver weight (R2 = 0.252), but the correlation was much stronger in the case of livers without structural disease (R2 = 0.450). The liver size seems to significantly decrease with age (R2 = 0.081), but the effect is mostly due to structural alterations that are proven by histology. The comparison of the liver weight in various histological groups clearly indicated that steatosis increases the liver size, but fibrosis does not (if no steatosis is present at the same time). In general, liver dimensions increase proportionally to the liver weight. However, hepatic steatosis causes disproportional enlargement: it does not have a significant effect on the horizontal dimension and has only a minor effect on the vertical dimension. Steatosis affects disproportionally the dimensions with a strange tendency to expand liver anteroposteriorly.