Diagnostic Performance of Digital Tomosynthesis for Detecting Osteophytes and Subchondral Bone Changes in the Equine Distal Interphalangeal and Metacarpophalangeal Joints

Osteoarthritis is a common cause of equine lameness and can involve periarticular osteophytes and subchondral bone (SB) changes. This exploratory ex vivo study evaluated the diagnostic performance of digital tomosynthesis (DT) for detecting these findings in the distal interphalangeal and metacarpophalangeal joints, using computed tomography (CT) classifications as the reference. Sixteen distal forelimbs from nine adult horses underwent imaging with both modalities under simulated weight-bearing conditions. Three independent observers graded osteophytes and SB changes, and the scores were dichotomised as absent or present for analysis. The primary analysis used a majority-based CT reference, defined by agreement of at least two observers. Observer-specific comparisons and within-observer DT–CT agreement were evaluated in a secondary analysis. In the primary analysis, sensitivity ranged from 23.1% (95% CI 9.5–39.3%) to 34.6% (95% CI 13.8–56.0%), specificity from 94.1% to 96.1%, Youden’s index from 19.2% to 30.7%, and Cohen’s κ from 0.249 to 0.377. Sensitivity was numerically higher for osteophytes than for SB changes for all three observers, without formal comparison. DT missed many CT-positive assessments but produced few false-positive classifications. Studies in live horses comparing DT with conventional radiography are needed to determine its additional diagnostic value.