Comparison of Radiographic Measurements of the Femur in Yorkshire Terriers with and without Medial Patellar Luxation

Abstract

Objective This article aimed to compare measurements of anatomical angles of the femurs, based on radiography, in Yorkshire Terriers without or with various grades of medial patellar luxation (MPL) based on radiography. Methods The skeletally mature Yorkshire Terrier dogs without MPL and with various grades of MPL were included in this prospective study. Cases with other orthopaedic disorders were excluded. For inclusion of the dog, it was required that standardized digital radiographs of both femurs in craniocaudal and axial directions were available. Measurements of the anatomical lateral proximal femoral angle, anatomical lateral distal femoral angle, femoral varus angle, anteversion angle and femoral inclination angle were performed. Results Forty-two Yorkshire Terriers (84 hindlimbs) were included in the study. They were divided into five groups according to grade of MPL as healthy (n = 12), grade I (n = 9), grade II (n = 44), grade III (n = 10) and grade IV (n = 9) dogs. The anatomical lateral proximal femoral angle and anteversion angle were significantly lower in dogs with grade IV MPL, while anatomical lateral distal femoral angle and femoral varus angle were significantly higher. The femoral inclination angle values did not differ significantly. Clinical Significance Yorkshire Terriers affected with grade IV MPL had severe femoral deformities or femoral varus and external rotation of the distal femur. Reference range can be used as an aid in diagnosis, determining indications and surgical planning for corrective osteotomy.