The correlation of canine patellar luxation and the anteversion angle as measured using magnetic resonance images

Measurements from magnetic resonance (MR) images can be used to examine the anteversion angle (AT-angle) and its influence on the lateromedial or medi olateral luxating forces on the patella, The AT-angle of the femoral neck w as measured with the aid of MR imaging in 45 pelvic Limbs without patellar instability, in 33 limbs with patellar luxation and in 6 limbs with rupture of the cranial cruciate ligament, The limbs with medial patellar luxation were divided into three groups based on clinical examination. The mean (ran ge) AT-angle was 7.6 degrees (0 degrees to 24 degrees) in the "normal" grou p, 8.6 degrees (-10 degrees to 29 degrees) in the group "grade II," and -0. 4 degrees in the group "grade III" (-28 degrees to 12 degrees), A mean (ran ge) AT-angle of 4.8 (-4 degrees to 11 degrees) was measured in the pelvic l imbs with rupture of the cranial cruciate ligament. Compared to literature that described AT-angles based on radiographs of normal limbs, reduced AT-a ngles were found in this study due to different lines of measurement of the femoral neck. This study documents that the AT-angle of the femoral neck d oes not influence patellar instability. This study also demonstrates that M R images can be used to make exact measurements of the canine AT-angle that represent the true anatomy of the femoral neck.