Morphologic and Morphometric Description of the Temporomandibular Joint in the Domestic Dog Using Computed Tomography

Abstract

The temporomandibular joint (TMJ) in the domestic dog is a synovial joint with 2 articular surfaces, the mandibular fossa of the squamous portion of the temporal bone and the articular head of the condylar process of the mandible. Although different diagnostic imaging techniques have been used to study the TMJ in dogs, morphologic and morphometric studies based on computed tomography (CT) are scarce. The purpose of the present study was to describe the morphologic and morphometric features of the TMJ in domestic dogs using CT. Width and depth of the mandibular fossa and 2 different angles between the mandibular fossa and the condylar process were measured in 96 TMJs of 48 dogs of different breeds (Labrador retriever, German shepherd, cocker spaniel, boxer, English bulldog, pug, shih tzu, and Cavalier King Charles spaniel). Temporomandibular joint conformation differed between breeds. Mid- and small-sized dogs had mandibular fossae that were more shallow, less developed retroarticular processes, and irregularly shaped condylar processes. The TMJs were more congruent in large dogs, presenting with deeper mandibular fossae, prominent retroarticular processes, and more uniform condylar processes. The measurements proposed in this study demonstrated 3 different morphologic conformations for the TMJ in the dogs of this study.

Comparative morphometry of the temporomandibular joint in brachycephalic and mesocephalic cats using multislice CT and cone beam CT

“…12 In dogs, mesocephalic and brachycephalic skull types also showed important differences in the TMJ, and conformations associated with specific breeds were also encountered. 10 Although cats do not present as much phenotypical variability as is observed in dogs, the differences reported here were consistent.…”

“…The head of the mandible was significantly shorter in the brachycephalic group compared with the mesocephalic group, whereas the length was not significantly different. Angle 1, which quantifies the ventral extension of the retroarticular pro-cess over the head of the mandible, 10 was not significantly different between the two groups. However, angle 2, which reflects the congruence between the articular head of the condylar process and the mandibular fossa of the temporal bone, was wider in the brachycephalic group.…”

“…The morphometric description of the TMJ in the cat adapted a previously described work performed in the dog. 10 In our work, the supramastoid crest was used as an anatomical landmark instead of the nuchal crest, as used in the dog, 10 because it was not consistently observed in all sagittal slices in the cat. The supramastoid crest is a strongly marked prolongation of the squamous part of the temporal bone, and runs backwards from the upper border of the zygomatic process, above the external acoustic meatus.…”

“…These anatomical landmarks were used to identify the estimated axis of rotation of the condylar process (EARCP) adapted from a similar study in the dog (Figure 1). 10 The supramastoid crest was always the first to be identified and marked with a dot, using the three-dimensional surface rendering option in the software (Figure 2a). The left and right supramastoid crests were subsequently visualised on the coronal reconstruction and aligned with the axial axis (Figure 2b).…”

“…The EARCP corresponded to the centre of a circle drawn at the sagittal reconstruction transected by the supramastoid crest, over the mandibular condylar pro-cess, being carefully adapted to the articular contour, according to a previous report. 10 Two angles (1 and 2) were determined. Anlge 1 was calculated using the following lowing anatomical points: the maximal lateral extension of the supramastoid crest, the EARCP and the maximal ventral extension of the retroarticular process (Figure 3a).…”