🔬 New Study Reveals Hidden Bone Defect Limiting Airway Surgery Success in French Bulldogs

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

S. L. Yuen, M. A. Genain, J. F. Ladlow, N.-C. Liu

Background

Brachycephalic obstructive airway syndrome (BOAS) is a chronic respiratory disorder in short-nosed dogs caused by anatomical deformities that restrict airflow. While existing surgeries improve dorsoventral airway narrowing, laterolateral (side-to-side) constriction—potentially caused by abnormal pterygoid bone development—has been underexplored. This study aimed to evaluate whether pterygoid bone medialisation (inward deviation) contributes to nasopharyngeal narrowing and poor surgical outcomes in brachycephalic breeds.

Methods

A retrospective CT-based analysis was performed on 144 BOAS-affected dogs (47 Pugs, 64 French Bulldogs, 33 Bulldogs) and 30 non-brachycephalic controls treated between 2015 and 2021. The width of the basisphenoid bone (WB), interpterygoid distance (IPB), and nasopharyngeal cross-sectional area (CSA) were measured. The medialisation index—the WB:IPB ratio—quantified bone inward deviation. BOAS severity before and after surgery was assessed via the BOAS index (0–100%), with ≥50% post-surgery indicating poor outcome. Statistical analyses used Pearson correlations and t-tests.

Results

Brachycephalic dogs exhibited significantly higher medialisation indices (1.982 ± 0.379) than controls (1.646 ± 0.239, P < 0.001). A negative correlation existed between medialisation and nasopharyngeal CSA across all breeds, strongest in Bulldogs (ρ = –0.71, P < 0.001). French Bulldogs with poor surgical outcomes had higher medialisation indices (2.366 ± 0.327) compared to those with good outcomes (1.813 ± 0.271, P < 0.0001). No significant association was found in Pugs or Bulldogs.

Limitations

The study was retrospective and involved a limited sample size, especially among Bulldogs, reducing statistical power. The medialisation index was derived from a single CT slice rather than full 3D reconstruction. Additionally, follow-up was short-term (6–8 weeks), precluding long-term prognostic assessment.

Conclusions

Pterygoid bone medialisation significantly contributes to nasopharyngeal narrowing in brachycephalic dogs, particularly French Bulldogs, and is associated with poorer outcomes after standard airway surgery. Since current procedures cannot correct this bony defect, preoperative evaluation of the pterygoid region via CT may help predict prognosis and guide clinical decision-making. Long-term and 3D imaging studies are warranted to further elucidate its role and potential for selective breeding improvements.

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