Magnetic resonance imaging of the palmar aspect of the equine podotrochlear apparatus: normal appearance.

This study focused on detailing the normal magnetic resonance (MR) imaging characteristics of specific structures within the equine podotrochlear apparatus using MR imaging studies of 16 horse limbs post-mortem. The results showed a clear picture of the various anatomical structures of the apparatus. The findings provide necessary baseline information for further research into detecting pathological changes in horses’ feet using MR imaging.

Magnetic Resonance Imaging Approach

• The study employed a retrospective evaluation of MR imaging studies that were conducted on 16 cadaver limbs of horses.
• The limbs of the equine test subjects were imaged using a 1.5 Tesla magnetic field and a human knee radiofrequency coil. Also, different types of MR imaging sequences were used such as spin echo (SE) T1-weighted, turbo spin echo proton density (TSE PD)-weighted with and without fat saturation (FS), and FS TSE T2-weighted sequences.
• However, the articular region of the distal sesamoid bone was not evaluated as part of this study.

Post-Imaging Dissection

• After all image capturing, the limbs were dissected to confirm the absence of any gross abnormalities. This validation process covered the flexor aspect of the distal sesamoid bone, of the deep digital flexor tendon, and the distal impar sesamoidean ligament.
• The deep digital flexor tendons of seven limbs were subjected to a histologic examination to rule out any microscopic tendon pathology.

MR Imaging Findings

• The MR images clearly showed the anatomical structures associated with the podotrochlear apparatus.
• Compact bone of the flexor cortex of the distal sesamoid bone showed a low-intensity signal across all scanning sequences. However, in 11 digits, an increased signal was noticed within the thickness of the sagittal eminence of the flexor cortex in SE T1-weighted images and in TSE PD-weighted images without fat saturation.
• The trabecular bone demonstrated a granular appearance and high signal in the SE T1-weighted sequences along with the TSE images without fat saturation.
• On the other hand, the deep digital flexor tendon showed a low signal on FS T2-weighted images, while on shorter echo time sequences like T1- and PD-weighted sequences, the tendon signal fluctuated depending on the relative positioning between the tendon’s fibers and the static magnetic field.

Conclusion

• The findings demonstrated that MR imaging provides a comprehensive evaluation of the anatomical structure of the podotrochlear apparatus.
• Such a detailed understanding of the MR imaging appearances, the anatomy, and potential pitfalls could enhance diagnostic specificity when detecting pathological changes.
• Hence, researchers and veterinarians could use this information as a benchmark for identifying abnormalities in the equine podotrochlear apparatus in live horses.