Accuracy of B-mode ultrasonography and ARFI elastography in the evaluation of the hip joint and hip musculature for the early and late diagnosis of hip dysplasia in dogs

Abstract Background: Canine hip dysplasia is common orthopedic disease in veterinary, characterized by hip instability in puppies and secondary degenerative joint disease in adult. Radiographic examination has been the main diagnostic method of hip dysplasia. Different radiographic studies, in addition to diagnosing joint laxity and degenerative joint disease, facilitate patient screening and selection of optimal treatment. However, radiographs do not allow for the assessment of capsular characteristics and adjacent muscles, which can be thoroughly evaluated using various ultrasound techniques. Radiographic examinations require anesthetic management, often causing discomfort in the patients and an inconvenience to owners. This study aimed to evaluate the accuracy of B-mode ultrasonography and acoustic radiation force impulse elastography in the evaluation of the joint capsule and periarticular musculature of dogs using the classification of the Orthopedic Foundation of Animals (OFA) and the distraction index (DI) in the early and late diagnosis of hip dysplasia. This study sought to propose a protocol for the ultrasonographic evaluation of the structures involved in canine hip movement. Results: Radiographic and ultrasonographic evaluations were performed on 108 hip joints of 54 dogs. Thirty dogs were older than 2 years and 24 were aged between 4 and 10 months. It was verified that an increase in pectineus muscle stiffness (cutoff value >2.77 m/s) by elastography and an increase in the thickness of the joint capsule (cutoff value >0.9 mm) in B-mode ultrasonography, were associated with a distraction index >0.5, with both having a positive correlation. In B-mode ultrasonographic evaluation, the presence of signs of degenerative joint disease, such as irregularities of the cranial edge of the acetabulum and femoral head, were associated with a distraction index >0.5 in canines, with a specificity of 94%. In adult dogs, the findings of degenerative joint disease on ultrasound were associated with a diseased OFA classification (P<0.05). Measurement of the joint capsule >1.10 mm was diagnostic for dysplasia in unhealthy dogs by OFA. Conclusions: Ultrasound can be used as an adjuvant diagnostic modality in the diagnosis of hip dysplasia in association with radiographic evaluation in young and adult animals.