Morphological Assessment of the Temporomandibular Joint in Asymptomatic Brachycephalic Dogs Using Computed Tomography

Abstract

Temporomandibular joint (TMJ) incongruity and morphological variations can result in clinical signs but have also been reported in asymptomatic brachycephalic dogs. The purpose of this study was to assess TMJ morphology in a group of brachycephalic dogs using computed tomography (CT). French Bulldogs, English Bulldogs, Boxers, Cavalier King Charles Spaniels (CKCS), Chihuahuas, Lhasa Apsos, Pugs, Shih Tzus, and Staffordshire Bull Terriers were retrospectively enrolled. The severity of the TMJ morphological changes was determined using a modified 5-grade classification system. The intra- and inter-observer agreements were calculated. One hundred fifty-three dogs were included. When evaluating the medial aspect of the TMJ in the sagittal plane, there was a spectrum of variations in the shape of the head of the condylar process of the mandible, the mandibular fossa and the retroarticular process ranging from a rounded concave TMJ with a long retroarticular process to a flattened TMJ with an absent process. Variations in the articular surface of the head of the condyle in the transverse plane ranged from flat, through curved and trapezoid to sigmoid. The prevalence of severe TMJ dysplasia (grades B3 and C) in the CKCS and French Bulldog was high (69.2% and 53.8%, respectively). The intra- and inter-observer agreements were moderate. Variations in TMJ morphology exist in asymptomatic brachycephalic dogs. Marked changes seem to be highly prevalent in the French Bulldog and CKCS and should be considered a breed variation. The TMJ classification described in this study could be used to standardize assessment of canine TMJ morphology. However, further research is needed to determine its clinical application.

Morphological and morphometric measurement of the temporomandibular joint of small and medium-weight dogs with different skull shapes

“…As in two of the previous studies, this study also showed that the Cavalier King Charles Spaniel, the Dachshund, and the French Bulldog had particularly low values for the respective TMJ measurements. These results support the hypothesis of an existing breed predisposition in these dog breeds ( 10–12 ). The French Bulldog was especially different because of its particularly wide and extremely flat joint cavities.…”

“…The canine TMJ has only been studied to a limited extent. This study builds on three previous studies in which morphometric measurements of the canine TMJ were performed ( 5 , 10 , 18 ). In two of the above studies, different breeds of brachycephalic and mesocephalic dogs were analyzed and it was shown that there are breed differences in the congruency of the TMJ, the arrangement of the retroarticular process and the shape of the mandibular fossa.…”

“…In two of the above studies, different breeds of brachycephalic and mesocephalic dogs were analyzed and it was shown that there are breed differences in the congruency of the TMJ, the arrangement of the retroarticular process and the shape of the mandibular fossa. However, these studies were limited to breed-specific evaluations ( 5 , 10 ). Furthermore, the 2016 study acknowledges that the group size of low- and medium-weight dogs was not sufficiently investigated in this study.…”

“…Large breed variations have already been described in the literature in regard to the alignment of the TMJs ( 9 ). Most recently, the extent of breed disposition is illustrated by an additional publication, using a classification system for TMJs of various brachycephalic dog breeds ( 10 ).…”

“…Poor joint congruency due to insufficiently developed joint cavities as well as joint processes can lead to a pronounced instability of the TMJ and can be accompanied by subluxations and luxations of the joint. These studies mainly concluded breed dispositions in French Bulldogs ( 10 ), Cavalier King Charles Spaniels ( 11 ), Dachshunds ( 12 ), American Cocker Spaniels ( 13 ), Basset Hounds ( 14 , 15 ), Irish Setters ( 16 ), Boxers, Golden, and Labrador Retrievers ( 17 ).…”