Beschreibung
The clinical relevance of the infraorbital canal is undisputed. For this reason, numerous studies have been carried out in the past regarding the distinct morphology of the infraorbital canal and its surrounding structures such as the paranasal sinuses and the maxillary cheek teeth. Various diagnostic imaging techniques were used in these studies including x-ray, sinuscopy, CT and MRI. Especially the CT-technique has become an important diagnostic tool over the last two decades. In the study at hand the usefulness of the CT for the description of anatomical conditions within the equine skull has been confirmed - even small nerval structures could be identified and described using special tools of the CT-software. The significant increase in knowledge over the last years helps to understand and to improve the treatment of pathological conditions associated with the infraorbital canal. Yet there is a lack of detail information regarding the longitudinal morphology of the infraorbital canal especially its dorsoventral course. The study at hand produces results to that specific topic and confirms a greater morphological variability (even comparing the two sides of one equine skull) to what has been presumed in literature up to this point.
Relating the question to which age horses show direct contact between the alveoli of the maxillary cheek teeth and the infraorbital canal the study at hand delivers comparison data as well as new findings. This new data includes the documentation of the diameter of cross sections of the infraorbital canal in relation to every single position of the maxillary cheek tooth.
The bony lamella which carries the infraorbital canal in adult horses has not been officially named in the NAV (2017); therefore, in the study at hand the nomenclatory suggestion of “Ponticulus canalis infraorbitalis” (PCI) was made. The PCI was described to be physiologically consistent and for this reason the distinct paranasal sinuses were permanently separated from each other. Furthermore, the PCI displayed a great variability especially in adult horses (age group 2) and comparing two sides of the individual equine skull.
The data collected from this study partly contradicts other authors’ findings for in all investigations the infraorbital foramen could only be found at the level of Triadan 07 and 08 and was generally located more caudally in adult horses (age group 2) compared to juvenile horses (age group 1).
Compared to the infraorbital canal there are much fewer studies dealing with the description of the Canalis mandibulae and the alveolar inferior nerve, respectively. Yet this nerve is not of little clinical importance. The findings of the study at hand suggest a much greater anatomical variability of the longitudinal course of the nerve in relation to the mandibular cheek teeth roots than anticipated in literature. Collectively 10 different courses of the alveolar inferior nerve could be described. Furthermore 15% of all investigations performed showed asymmetrical longitudinal courses of the nerve comparing two sides of an individual equine skull.
Generally, the alveolar inferior nerve was easier to be identified in juvenile horses (age group 1) compared to adult horses (age group 2). Furthermore, the visibility of the nerve was decreased in the caudal aspect of its course for in this area a distinct bony lamella within the mandible was less frequently detectable using CT. For this reason, HU-values for the alveolar inferior nerve were determined in this study which can be used as comparison data to identify the nerve by discriminating it from other tissues in cases of difficult visibility in the CT.
