Radiographic features of pelvis and hip joint development of English Bulldogs

Objectives: To evaluate distinctive features of pelvis and hip joint development of English Bulldogs throughout the first year of life.Methods: The pelves of 20 English Bulldogs were radiographed at three different ages (<4, 6–8, and 12–14 months). At each time point, the dogs were clinically evaluated and the abnormal hip joints were classified as mild, moderate, or severely deformed. The pelves were compared to a phantom study in which external rotation of a normal hemipelvis around its long axis was artificially created at different degrees, with different pelvic inclinations, and classified as either normal and without deformity, or as mild, moderate, or severely deformed. Hip joints and pelvic scores were statistically compared.Results: Although none of the dogs were considered lame at the end of the study, none of the hips showed normal development; 77.5% were moderately to severely deformed at 12–14 months of age. At this age, 75% of the hemipelves had moderate to severe torsional deformity (>5.2° of external rotation), with retroversion of the acetabulum confirmed by the presence of the crossover sign. An external rotation of the hemipelvis on its long axis >5° was likely associated with a moderate to severely altered hip joint conformation.Clinical Significance: Abnormal hip conformation was common in this series of English Bulldogs. Torsional deformity of the pelves with acetabular retroversion was a common and distinctive feature, which has not yet been thoroughly studied in dogs. These findings need further evaluation in English Bulldogs as well as in other breeds.