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Histology of the Alar and Transverse Ligaments

SALDINGER, P., MD*; DVORAK, J., MD; RAHN, B. A., MD*; PERREN, S. M., MD*

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Seven sets of human transverse and alar ligaments, after tensile testing, and eight corresponding ligaments without testing, were examined histologically with respect to their fiber composition and fiber orientation. Variaous staining techniques were supplemented by polarized light microscopy. Both the transverese and the alar ligaments consist of collagen fibers, with very few elastic fibers in the peripheral layer. In the central portion of the transverse ligament, the collagen fibers cross each other at an angle of approximately 30°. Close to the dens, the transverse ligaments show on their ventral side a transition into fibrocartilage. Except for the immediate site of failure, no differences became evident between tested specimens and controls. The collagen, as the almost exclusive consitituent, together with the fiber orientation determine the mechanical properties of these ligaments. This supports the hypothesis that the ligaments could be irreversibly overstretched or even ruptured when the head is rotated and, in addition, flexed by impact trauma, especially in unexpected rear-end collisions.

*Laboratory for Experimental Surgery, Swiss Research Institute, Davos

† Department of Neurology, Wilhelm Schulthess Hospital, Zurich, Switzerland

© Lippincott-Raven Publishers.