Radiographic detection and characterization of palmar lesions in the equine fetlock joint.

The study primarily involves investigating the presence, characteristics, and impact of subchondral lesions located in the distal palmar region of the third metacarpus in Thoroughbred horses. It was found that such lesions can be effectively identified through radiographic techniques, and these lesions are associated with secondary joint disease. The size and irregularities of these lesions have an apparent correlation with the severity of the joint disease.

Research Process and Findings

• The study involved 15 Thoroughbred horses and focused on 21 fetlock joints. The horses were subjected to radiographic analysis to identify and examine subchondral lesions located in the distal palmar region of their third metacarpus.
• These lesions were more easily detected on the lateromedial and flexed lateral projections. The flexed lateral projection provided the best visibility for assessing these lesions.
• Subchondral lesions were characterized as poorly marginated, radiolucent defects found at the base level of the proximal sesamoid bones. The shape and distribution of these defects varied widely, taking forms such as crescent, flattened, shallow concavity, deep concavity, oval, or circular.

Association with Secondary Joint Disease

• The presence of these palmar lesions was found to be associated with secondary joint disease in the Thoroughbred horses.
• The severity of this joint disease was found to be intensified with an increase in size and irregularity of the lesions on the subchondral bony surface.
• Three of the horses with these lesions were rested and re-examined after varying periods of time (16, 40, or 56 weeks). Two of these horses showed a decrease in the size and definition of the lesions, but all three exhibited an increased degree of secondary joint disease.

Implications of the Study

• The identification of small palmar lesions is crucial in predicting potential joint health issues, and therefore important for determining the suitability of a Thoroughbred horse’s return to racing.
• The study puts forth an effective method – radiographic analysis – for early and accurate detection of these lesions, which can help in formulating appropriate interventions before the development of severe secondary joint diseases.