Magnetic resonance imaging findings in the equine deep digital flexor tendon and distal sesamoid bone in advanced navicular disease–an ex vivo study.

The research article investigates abnormal findings on magnetic resonance imaging (MRI) scans of the deep digital flexor tendon and distal sesamoid bone in horses affected by advanced navicular disease. In this ex vivo study, these findings are then compared to physical assessments and histological evaluations post-mortem.

MRI Methodology and Findings

• The researchers used thirteen post-mortem specimens of horses with radiographic changes indicative of navicular syndrome. The specimens underwent an MRI scan using a 1.5-T magnetic field with various sequences.
• MRI scans revealed tendon abnormalities in 12 of the deep digital flexor tendons (DDFTs). These lesions were predominantly located at the distal sesamoid bone and the proximal recess of the podotrochlear bursa.
• Based on their MRI features, the tendon lesions were categorized into core lesions, dorsal lesions, dorsal abrasions, and parasagittal splits.
• Increased MRI signal in the DDFTs suggested a disturbance and lack of continuity in the tendon fibers, spots of edema (swelling due to fluid collection), hemorrhages, and the formation of bodies containing specific materials.
• Signal alterations in the distal sesamoid bone marrow were observed in all specimens.

Comparison with Gross Assessment and Histologic Examination

• The researchers then physically dissected the specimens to compare the MRI findings with the gross assessment results and histologic examination of the DDFT and distal sesamoid bones.
• The histological examination identified spots of edema, hemorrhaging, necrosis (cellular death), and fibrosis (excessive growth of connective tissue) in the bone marrow, consistent with the MRI findings.
• Additionally, cyst formation and disorganization, thinning, and remodeling of trabecular bones were seen in areas of abnormal signal intensity.
• An increase in bone density due to the thickening of trabecular bones resulted in decreased signal across all MRI sequences.

Conclusion

• This study demonstrates that MRI scans can effectively identify lesions and structural abnormalities in the DDFT and distal sesamoid bone in cases of advanced navicular disease in horses.
• The findings highlight the potential of MRI as a diagnostic tool in veterinary orthopedics, particularly in identifying and characterizing tendon and bone changes due to advanced navicular disease.