AUTHOR=Válega Ana , Alves-Pimenta Sofia , McEvoy Fintan J. , Nielsen Dorte H. , Ginja Mário 

TITLE=Digital Analysis of Subtrochlear Sclerosis in Elbows Submitted for Dysplasia Screening

JOURNAL=Frontiers in Veterinary Science

VOLUME=Volume 8 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2021.664532

DOI=10.3389/fvets.2021.664532

ISSN=2297-1769

ABSTRACT=Ulnar trochlear notch (UTN) subchondral bone sclerosis is observed in elbow dysplasia (ED) associated with the medial coronoid disease. However, its evaluation is based on a simple visual examiner assessment of bone radio-opacity level and is considered subjective. The purpose of this study was to objectively characterize the radiographic opacity of the UTN subchondral bone in mediolateral elbow projections classified, using the International Elbow Working Group guidelines.  Records and mediolateral flexed elbow images from the Danish Kennel Club database for the ED screening scheme between 2012 and 2018 were available. Of the dogs in the database those with an ED negative status in the left limb were identified. From these, 20 dogs each having a status free from ED, or with Grades 1, 2 or 3 in the right limb were randomly chosen. Joints with primary ununited anconeal process were excluded from the sample.  A template was developed using the Image J software, for computer UTN sclerosis analysis. It was overlaid onto each image to define five regions of interest (ROI): ROI-1– distal UTN; ROI-2– middle UTN; ROI-3– caudal UTN; ROI-4– cortical bone; ROI-5– bone marrow. Mean pixel intensity for each UTN ROI was divided by the mean pixel intensity of ROI-4 to normalise the data. The mean ± standard deviation (SD) of the normalised pixel intensity in the disease joints (ED Grades-1, 2 and 3) were 1.18±0.17, 1.03±0.12   and 0.92±0.09 for ROI regions 1, 2 and 3, respectively.  The corresponding values for the contralateral normal left joints were 1.16±0.17, 1.01±0.1, and 0.91±0.08.  There was a significant difference (p<0.05) between the normalised mean pixel intensity in dysplastic vs non-dysplastic elbow joints for ROIs  1 and 2. The raw mean pixel intensity from right and left cortical and marrow bone ROIs sometimes showed relatively large differences. Digital radiography is associated with exposure and post-processing variabilities. Differences in apparent radiopacity (as indicated by pixel intensity) though statistically significant in dysplastic joints compared to contra lateral normal joints are slight and are thus problematic for computer aided assessment of UTN sclerosis.