Thermographic imaging of police working dogs with bilateral naturally occurring hip osteoarthritis

Background: Digital thermal imaging is a physiologic, non-invasive, contactless, and non-radiating diagnostic tool that can assess a wide range of musculoskeletal conditions, including hip osteoarthritis (HOA). Fifty police working dogs were evaluated to compare the dorsoventral (DV) and lateral (LT) thermographic images in dogs with naturally occurring bilateral HOA. A DV, and left and right lateral LT images were obtained for each animal in six different moments. They were positioned standing in a symmetrical upright position for the DV view. Each image included the area from the last lumbar to the first coccygeal vertebrae. Each LT view was set with the greater trochanter in the centre of the image. Images were taken with a thermographic camera from a distance of 60 cm. Mean and maximal temperatures were recorded, analyzed with ANOVA, dependent samples t-test, and Spearman correlation, with P < 0.05. Results: Nine hundred images were considered, collected from 30 males and 20 females, with a mean age of 6.5 +/- 2.2 years and bodyweight of 26.7 +/- 5.3 kg. The overall value recorded on the DV view was 25.3 degrees +/- 9.1 and 28.4 degrees +/- 2.8 on the lateral view. These were significantly different (P < 0.01) and with a low correlation (r = 0.10, P = 0.03). German Shepard dogs showed significantly lower values on all views than other breeds (P < 0.01), and heavier dogs had higher values on the lateral view. Conclusions: This is the first study that describes digital thermography's diagnostic use to evaluate working dogs with naturally occurring HOA, comparing two different views. Future studies should address each one's value in the diagnosis and response to treatment of this disease.