An assessment of trochlear groove morphology with the severity of medial patellar luxation using ultrasonography in dogs presented to a clinic in Japan

Background: Ultrasonography is a valuable tool for the preoperative morphological evaluation of the femoral trochlear groove in dogs with medial patellar luxation (MPL). This study aimed to objectively evaluate the femoral trochlear groove morphology using ultrasonography and compare it with the severity of MPL in dogs. Methods: Small-breed dogs weighing 10 kg or less and diagnosed with normal stifle joints or MPL were included. Pelvic limbs without any orthopaedic disease served as the normal group. Pelvic limbs with MPL were divided into grade 1, 2, 3 and 4 MPL groups according to the Singleton grading system. In this study, the heights of the medial and lateral trochlear ridges, the femoral trochlear depth and the sulcus angle (SA) were objectively measured using ultrasonography. Results: A total of 125 pelvic limbs (in 88 dogs) were evaluated: normal (n = 29) or grade 1 (n = 9), grade 2 (n = 42), grade 3 (n = 34) and grade 4 (n = 11) MPL groups. The heights of both the medial and lateral trochlear ridges were significantly lower in the grade 4 MPL group than in the normal and grade 1 MPL groups. The femoral trochlear depth was significantly shallower with increasing MPL grade. The SA was significantly higher in the grade 4 MPL group compared to the other groups. Conclusion: The morphology of the femoral trochlear groove can be easily and objectively evaluated using ultrasonography. Significant hypoplasia of the femoral trochlear groove was observed in the grade 4 MPL group.