Pterygoid bone malformation and its limitations on the effectiveness of brachycephalic airway corrective surgery in brachycephalic dogs.

Objectives: This study aimed to examine the association between pterygoid bone medialisation and treatment outcomes after upper airway surgery in three brachycephalic breeds.

Materials and methods: Dogs that underwent CT of the head followed by routine surgery for brachycephalic obstructive airway syndrome were recruited in this study. Measurements obtained from the CT images included the width of the basisphenoid bone, interpterygoid distance and cross-sectional area of the nasopharynx. A ratio of width of the basisphenoid bone to interpterygoid distance allowed quantification of pterygoid bone medialisation. Pearson's correlations were calculated to assess the relationship between width of the basisphenoid bone: interpterygoid distance and cross-sectional area of the nasopharynx. Additionally, width of the basisphenoid bone: interpterygoid distance was compared across breeds, as well as between dogs with good and poor surgical outcomes (post-operative brachycephalic obstructive airway syndrome index ≥50%).

Results: One hundred and forty-four brachycephalic dogs (47 Pugs, 64 French Bulldogs and 33 Bulldogs) and 30 non-brachycephalic controls were included in the analysis. The width of the basisphenoid bone: interpterygoid distance ratio in brachycephalic dogs was significantly higher (1.982 ± 0.379) than that of controls (1.646 ± 0.239, P < 0.001). A negative correlation was observed between width of the basisphenoid bone: interpterygoid distance and cross-sectional area of the nasopharynx in Pugs (ρ = -0.29, P = 0.048), French Bulldogs (ρ = -0.47, P < 0.001), Bulldogs (ρ = -0.71, P < 0.001) and controls (ρ = -0.55, P = 0.002). French Bulldogs with poor surgical outcomes exhibited a significantly higher width of the basisphenoid bone: interpterygoid distance (2.366 ± 0.327) than those with good surgical outcomes (1.813 ± 0.271, P < 0.0001).

Clinical significance: Pterygoid bone medialisation is associated with nasopharyngeal narrowing, which limits the effectiveness of surgical interventions in brachycephalic obstructive airway syndrome in affected French Bulldogs. As there are no surgical options currently reported to address this condition, these findings are important in guiding clinicians in providing prognostic information to owners during elective brachycephalic obstructive airway syndrome surgery.