A comparison of 3-T magnetic resonance imaging and computed tomography arthrography to identify structural cartilage defects of the fetlock joint in the horse.

The researchers were comparing the effectiveness of 3-Tesla magnetic resonance imaging (MRI) and computed tomography arthrography (CTA) in identifying structural defects in the fetlock joint cartilage of horses. The study found the CTA showed higher sensitivity and specificity in detecting these defects, making it a more reliable tool compared to MRI. However, the MRI provided supplementary information about soft tissues and the subchondral bone, constituting part of an overall evaluation.

Study Design and Methodology

• The researchers sought to determine and compare the sensitivity and specificity of 3-Tesla magnetic resonance imaging (3-T MRI) and computed tomography arthrography (CTA) in identifying structural defects in the cartilage of the equine MCP/MTP joint.
• They took forty distal cadaver limbs and imaged them with CTA (after injecting a contrast medium) and 3-T MRI. Two specific sequences were used for MRI: dual-echo in the steady-state (DESS), and sampling perfection with application-optimised contrast using different flip-angle evolutions (SPACE).
• The reliability of these imaging techniques was assessed using gross anatomy as the gold standard.

Results and Analysis

• The study found that CTA showed higher sensitivity (0.82) and specificity (0.96) than MRI (with 0.41 and 0.93 respectively), particularly when identifying overall cartilage defects.
• The intra and inter-rater agreements that measure consistency of the collected data were also better for CTA (0.96 and 0.92) compared to MRI (0.82 and 0.88).
• Despite these results, the positive predictive value for MRI, which indicates the probability that subjects with a positive screening test truly have the disease, was low (0.57).

Conclusion and Implications

• The results suggest that CTA could be considered a better technique for assessing cartilage defects in the MCP/MTP joint. This is due to the technique’s short acquisition time, high specificity, sensitivity, and accuracy.
• However, the study also suggests that MRI can still provide valuable information about soft tissues and subchondral bone, which can help in the overall evaluation of the joint.
• Nevertheless, the researchers caution clinicians regarding the limitations of MRI as a diagnostic technique, particularly considering its reduced accuracy in picking up defects in structural cartilage.