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

Overview

• This study investigated how well digital tomosynthesis (DT), an imaging technique, detects bone changes related to osteoarthritis in horse joints compared to computed tomography (CT), a standard reference method.
• Using images of horse limbs, researchers assessed DT’s ability to identify osteophytes and subchondral bone changes, important features of joint disease causing lameness.

Background and Purpose

• Osteoarthritis is a frequent cause of lameness in horses and involves abnormal growths called osteophytes and changes in the bone beneath the joint surface, known as subchondral bone (SB) changes.
• Detecting these changes accurately is crucial for diagnosis and treatment planning.
• Digital tomosynthesis is an imaging method that can produce sectional images of bone and may provide better detail than standard radiography.
• The study aimed to evaluate DT’s diagnostic performance in detecting osteophytes and SB changes in the distal interphalangeal (coffin) joint and metacarpophalangeal (fetlock) joint of horses, comparing it to the results of CT, which is more detailed but less accessible clinically.

Methods

• Specimens: 16 distal forelimbs were collected from 9 adult horses.
• Imaging Techniques:
  • Each limb was imaged using digital tomosynthesis and computed tomography under simulated weight-bearing conditions to mimic the horse standing.
• Observers:
  • Three independent observers reviewed the images from both modalities.
  • They graded the presence or absence of osteophytes and SB changes.
• Data Analysis:
  • The observer scores were simplified into binary categories: presence or absence of the bone changes.
  • The main reference standard (“gold standard”) was determined by majority agreement among at least two of the three observers reviewing the CT images.
  • Key measures calculated included sensitivity (ability to correctly detect bone changes), specificity (ability to correctly identify absence of changes), Youden’s index (overall diagnostic effectiveness), and Cohen’s kappa (agreement measurement).
  • Additional analyses examined observer-specific results and agreement between DT and CT assessments within each observer.

Results

• Diagnostic Performance:
  • Sensitivity (true positive rate) of DT was relatively low, ranging from 23.1% to 34.6%, indicating many true cases detected by CT were missed by DT.
  • Specificity (true negative rate) was high, between 94.1% and 96.1%, showing DT rarely falsely identified bone changes that weren’t present on CT.
  • Youden’s index values ranged from 19.2% to 30.7%, reflecting moderate overall diagnostic ability.
  • Cohen’s kappa values ranged from 0.249 to 0.377, suggesting fair agreement between DT and CT findings.
• Osteophytes vs. Subchondral Bone Changes:
  • Sensitivity for detecting osteophytes was higher than for detecting SB changes in all observers, although no formal statistical comparison was made.
• Error Patterns:
  • DT missed many positive assessments seen on CT (false negatives).
  • DT produced few false positives—wrongly identifying changes not present on CT.

Conclusions and Implications

• Digital tomosynthesis showed strong specificity but limited sensitivity for detecting osteophytes and subchondral bone changes in the horse distal limb joints in this ex vivo study.
• This suggests DT is reliable in confirming absence of changes but often misses actual lesions compared to CT.
• Because CT is less practical for routine clinical use in live horses, DT might be a useful tool but requires further evaluation.
• Future studies are needed involving live horses that compare DT with standard radiography to better understand if DT adds valuable diagnostic information in clinical settings.
• Overall, DT may contribute to improved imaging diagnostics for equine osteoarthritis but currently has limitations in sensitivity that must be addressed.