Measurement of Ulnar Subtrochlear Sclerosis Using a Percentage Scale in Labrador Retrievers with Minimal Radiographic Signs of Periarticular Osteophytosis

ABSTRACT
Objective—To report the development of a measurement method for quantifying ulnar subtrochlear sclerosis (STS) in Labrador Retrievers.
Study Design—Prospective blinded study.
Sample Population—Radiographs of Labrador Retrievers elbows (n=30) with minimal radiographic signs of periarticular osteophytosis.
Method—Measurement of STS as a % of the distance between 2 standardized radiographic landmarks (%STS) was developed. Mediolateral radiographic projections of flexed elbows were collected from 2 cohorts termed diseased (n=15; confirmed disease of the medial coronoid process) and control (n=15; free from clinically evident disease). Five observers blindly assessed each radiograph for radiographic technique, elbow positioning, periarticular osteophytosis, and STS, which, if present, was measured and assigned a %STS score. Intraobserver and interobserver variations in measuring STS and the ability to differentiate study cohorts were assessed using receiver operator curve (ROC) characteristics. A P-value of <.05 was considered significant.
Results—Median %STS for diseased elbows was 47% (range, 0–74%) and 0% (range, 0–62%) for control elbows. Correlations were not significantly different between each observer's assessments of %STS, with a median Spearman's P-value of .75 (range, .67–.86). All observers differentiated the 2 cohorts with "fair-good" accuracy, with a median ROC value of 0.81 (range, 0.75–0.88).
Conclusion—Measurement of %STS in Labrador Retrievers was repeatable for each observer and repeatable between observers.
Clinical Relevance—A method for measuring STS allows comparison of Labrador Retrievers of different sizes, is easy to perform, and could be used to investigate the clinical significance of STS in this breed.