Do computer tomographic changes of the hyoid correlate with dental pathologies or radiologic changes of the temporomandibular joint?

Introduction: The hyoid apparatus supports the tongue, larynx and pharynx. The connections between the different parts of the hyoid apparatus were investigated in a previous study using CT, micro-CT and histology (Hartl et al., 2021). This study investigated how frequently computer tomographic changes of the hyoid apparatus occur and whether these changes correlate with computer tomographic dental abnormalities or changes of the temporomandibular joint. M&M: The medical records of horses that underwent a CT scan of the head between 2009 and 2019 were reviewed. The information obtained from the medical records included age, breed, sex, use and indication for CT scan of the head. To obtain a more uniform study group, horses with developmental stages (<3 years of age) of the hyoid bone were excluded from the study. The two sides of the hyoid bone were evaluated separately. Results: 167 horses met the inclusion criteria for the study. These were mostly warmbloods (92/167), small horses (23/167), ponies (10/167) and thoroughbreds (10/167). The age ranged between 3 and 29 years, with an average age of 12.3 years. The horses were mainly used as leisure horses (66/167), a small proportion were also used as dressage horses (25/167) or show jumpers (12/167). The reason for CT examination in most cases was sinusitis (39/167), as well as skull fractures (28/167) and space-occupying lesions of the head (25/167). We evaluated 32 parameters, with the following changes occurring most frequently. Marginal exostoses occurred in 170/334 (51%) of the temporal bones, a reduced tympanohyoid in 132/334 (40%) and osteophytes on the stylohyoid in 144/334 (43%) of the temporohyoid joints (THJ). Changes of the epihyoid occurred in 129/334 (39%) of the epiceratohyoid joints. Dental pathologies were found in 40/334 (12 %) of all mandibles and 84/334 (25 %) of all maxillae, and pathologies were found in 60/334 (18 %) of the temporomandibular joints. There were 24/40 (60%) of mandibular, 48/84 (57%) of maxillary dental pathologies and 28/60 (47%) of temporomandibular joint changes together with marginal exostosis of the temporal bone. In addition, 16/40 (40%) of the mandibular, 32/84 (38%) of the maxillary dental pathologies and 21/60 (35%) of the temporomandibular joint changes were found together with a reduced tympanohyoid. Conclusion: We suggest that dental and temporomandibular joint pathologies may have an influence on the development of radiographic temporohyoid joint changes. Reference: Hartl, B; Egerbacher, M; Kneissl, SM (2021): Correlated Imaging of the Equine Hyoid Apparatus Using CT, Micro-CT, and Histology. Front Vet Sci. 2021; 8:652563

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