The diagnosis of lameness associated with distal limb pathology in a horse: a comparison of radiography, computed tomography and magnetic resonance imaging.

The study attempted to compare the effectiveness of radiography, computed tomography (CT), and magnetic resonance imaging (MRI) in diagnosing lameness in a horse, caused by distal limb pathology. Results suggested MRI was the most effective in identifying the specific causes of the ailment, as confirmed by histopathology.

Methodology

• A cadaver limb from an eight-year-old horse that showed lameness in its right forelimb was used for this research. The lameness was relieved when the horse was given an intra-articular distal interphalangeal joint block.
• The limb was subjected to images via radiography, spiral computed tomography (CT), and magnetic resonance imaging (MRI) for comparison.

Findings

• Spiral CT imaging revealed several lucencies or regions of varying darkness in the deep digital flexor tendon, a key tendon in the horse’s hoof, right next to the navicular bone. These dark spots suggest some form of degeneration or injury.
• The MRI scan also showed these same areas with high signals indicating increased water content, a typical sign of inflammation or injury. The MRI also captured an enlargement of the tendon at the site of the lucencies. There was also fluid accumulation observed in the proximal interphalangeal joint and the navicular bursa, which are indicative of internal injuries or infections.
• The MRI also revealed thinning of the fibrocartilage of the navicular bone, a major weight-bearing bone in the horse’s hoof.
• These identified changes were not detected by the radiograph imaging method.

Confirmation with Histopathology

• Upon running a histopathology on the imaged limb, it confirmed that there were indeed areas of collagen necrosis (cell death) in the deep digital flexor tendon. This tissue death is likely to be the cause of the lameness in the horse’s forelimb.
• The histopathology also verified the changes noted in the MRI scan, including the thinning and degenerative changes in the fibrocartilage of the navicular bone.

Conclusion

• The study concludes that MRI proved to be more effective in detecting symptoms of lameness associated with distal limb pathology in the horse, when compared to radiography and CT imaging.
• Specifically, MRI was successful in identifying changes such as collagen necrosis, tendon enlargement, fluid accumulation, and fibrocartilage thinning, that were not visible on radiographs. Thus, it could lead to more accurate diagnoses and treatment protocols.