title: COMPUTED TOMOGRAPHIC APPEARANCE OF THE TEMPOROMANDIBULAR JOINT IN 1018 ASYMPTOMATIC HORSES: A MULTI-INSTITUTION STUDY.
abstract: Published descriptions of nonseptic arthritis of the equine temporomandibular joint (TMJ) are rare and large studies investigating variations in the TMJ for asymptomatic horses are lacking. The objectives of this cross-sectional, retrospective, multi-institutional study were to describe anatomical variations in the TMJ detected using computed tomography (CT) in an equid population asymptomatic for TMJ disease and determine whether these variations were associated with patient signalment, reason for CT examination, or CT slice width. Medical records at eight hospitals were searched for horses that had head/neck CT scans and no clinical signs of TMJ disease. Age, breed, sex, clinical presentation, and CT slice width data were recorded. Alterations in CT contour and density of the mandibular condyles, mandibular fossae, and TMJ intra-articular discs were described for each horse. Generalized logistic regression was used to test associations between anatomical variations and horse age. A total of 1018 horses were sampled. Anatomical variations were found in TMJ CT images for 40% of horses and 29% of joints. These were dichotomous with regard to age. Horses <1 year old commonly had alterations in the shape and density of the mandibular condyle. Older horses commonly had spherical hypodensities within the mandibular condyles consistent with bone cysts; and hyperdense regions of the intra-articular disc consistent with dystrophic mineralization. Findings indicated that TMJ anatomic variations were common in CT images of younger and older horses asymptomatic for TMJ disease. Future studies are needed to more definitively characterize these CT variations using gross pathology and histopathology.
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, S7N5B4, Canada.
authors.forename: James L
authors.initials: JL
authors.lastname: Carmalt
authors.affiliation: Unit of Diagnostic Imaging, Department of Small Animals and Horses, University of Veterinary Medicine, Vienna, 1210, Vienna, Austria.
authors.forename: Sibylle
authors.initials: S
authors.lastname: Kneissl
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado.|Department of Clinical Sciences, College of Veterinary Medicine Cornell University, Ithaca, New York.
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Rawlinson
authors.affiliation: Tierärztliche Klinik, Grasweg 2, 86459, Gessertshausen, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Zwick
authors.affiliation: Department of Veterinary Clinical Sciences, Ohio State University, Columbus, Ohio.
authors.forename: Lisa
authors.initials: L
authors.lastname: Zekas
authors.affiliation: Clinic for Diagnostic Imaging, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse, 285c, 8057, Zurich, Switzerland.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Ohlerth
authors.affiliation: Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Buenteweg 9, 30559, Hannover, Germany.
authors.forename: Astrid
authors.initials: A
authors.lastname: Bienert-Zeit
mesh_terms: D000818:Animals; D003430:Cross-Sectional Studies; D005260:Female; D006736:Horses / Q000033:anatomy & histology*; D008297:Male; D008335:Mandibular Condyle / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D012016:Reference Values; D012189:Retrospective Studies; D013704:Temporomandibular Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000662:veterinary
keywords: TMJ; computed tomography; equine; horse; temporomandibular