[Traumatology of the alar ligaments].

A postmortem study of craniocerebral traumas of varying severity was done to determine the pattern of injury of the alar ligaments. It was found that in the entire group of patients (n = 30) the alar ligaments were ruptured or suffused with blood 11 times. No close relationship was found between the massive nature of the cranial trauma and the severity of the injury of the alar ligaments. In some cases the alar ligaments were not at all involved even though the skull had suffered extensive osseous lesions, whereas on the other hand the ligaments were injured even though only soft parts had been involved (e.g., haematoma or dehiscent wounds of the scalp). Ruptures of the alar ligaments were typically involved in extended ruptures of the ligamentous apparatus (see Figure 6a involving the ligamentum apicis dentis, ligamentum transversum atlantis, m.atlanto-occipitalis anterior, m.tectoria, m.atlanto-axialis anterior et posterior). In some cases the pattern of injury of the alar ligaments was found to be decisive in enabling reconstruction of the course of the accident. Damage to the alar ligaments near the dens axis represent rotation injuries. On the other hand, insertion tears out of the condyli occipitales must be related to a lateral thrust tendency in indirect fracture of the skull (bursting fracture). Within this overall framework a new mechanism of fracture of the condylus occipitalis is described. As a matter of principle, the alar ligaments can become involved in consequence of rotation, traction and compression of the cranium.