Computed Tomography Evaluation of Morphological Types of Femoral Trochlear Dysplasia in Small-Breed Dogs-A Retrospective Study.

Abnormal trochlear morphology is one of the most important factors for patellar luxation occurrence in dogs, yet no studies have investigated its prevalence in the general population. This retrospective computed tomography study was designed to evaluate the trochlear groove morphology in four small dog breeds and the prevalence of trochlear dysplasia types according to Déjour's classification depending on the breed, sex, and medial patellar luxation (MPL) presence and grade. A total of 174 joints (68 healthy, 96 grade II MPL, and 10 grade III MPL) from Mini-Pinschers, Yorkshire Terriers, Pomeranians, and Chihuahuas were included in the study. The morphological type of trochlear dysplasia (TD) was evaluated on axial scans and 3D reconstruction images according to the four-type classification of Déjour, sulcus angle, trochlear depth, and lateral/medial inclination angles. Of all 174 joints, 140 had trochlear dysplasia-all joints with MPL (n = 106) and 50% of healthy joints (n = 34). The classification of Déjour for trochlear dysplasia types (A, B, C, and D) corresponds to the morphology of the femoral trochlea in the studied small breeds of dogs. The results demonstrated three types of trochlear dysplasia according to Déjour: most commonly, type A, followed by type C, and most infrequently, type D. The Déjour type B was an incidental finding. The large proportion of clinically healthy joints with TD (50%) emphasises the significance of early trochlear morphology evaluation for the orthopaedical health of dogs from susceptible breeds, especially in female breeders.