Stress-driven collagen fiber remodeling in arterial walls.

A stress-driven model for the relation between the collagen morphology and the loading conditions in arterial walls is proposed. We assume that the two families of collagen fibers in arterial walls are aligned along preferred directions, located between the directions of the two maximal principal stresses. For the determination of these directions an iterative finite element based procedure is developed. As an example the remodeling of a section of a human common carotid artery is simulated. We find that the predicted fiber morphology correlates well with experimental observations. Interesting outcomes of the model including local shear minimization and the possibility of axial compressions due to high blood pressure are revealed and discussed.

[Factors of severity in the fractures of the odontoid process (author's transl)]. / Elements de pronostic des fractures de l'odontoïde.

The authors think that the prognosis in fractures of the odontoid process could be based on an evaluation of the stability and on the direction of the fracture line. The stability depends on the integrity of the common posterior spinal ligament. When it is disrupted, the spine should be surgically fixed. When it is intact, conservative treatment is indicated. The stability should be appreciated on dynamic X rays 15 days after the trauma. The fracture lines oblique anteriorly are more stable than the fracture lines oblique posteriorly. The comminuted type, like "English policeman's hat" are very unstable.