Magnetic Resonance Imaging, Gross Postmortem, and Histological Findings for Soft Tissues of the Plantar Aspect of the Tarsus and Proximal Metatarsal Region in Non-Lame Horses.

This research examines the high-field MRI characteristics of plantar soft tissues (found at the back of the legs) in the tarsus and proximal metatarsus areas of non-lame horses, comparing them to the physical and histological appearances observed in postmortem dissections. The study used single hindlimbs from 42 horses and both right and left hindlimbs from eight horses for the analysis, making a total of 50 single limbs for the MRI study and eight pairs for postmortem and histological comparison.

MRI Scan Findings

• The study reveals that the high-field MRI scans of these tissues showcase different patterns of signal intensity. The superficial digital flexor tendon shows uniform low signal intensity. This tendon is bordered by the flexor retinaculum, which has intermediate to high signal intensity.
• The lateral digital flexor tendon displayed slightly higher signal intensity than its counterparts and was bordered on the plantaromedial aspects by the metatarsocalcaneal ligament, which had low signal intensity.
• The accessory ligament of the deep digital flexor tendon showed variations in both its size and signal intensity.
• The proimal and distal plantar ligaments, the accessory ligaments of the suspensory ligament and the calcaneoquartal ligament all had low signal intensities.

The Long Plantar Ligament

• Scientists also found the long plantar ligament consisted of several related components, separated by lines of high signal intensity. This correlated with fibrous septae seen in gross anatomical specimens.
• Regarding the ligament’s plantar aspect, it had a uniform low signal intensity across all sequences. However, the dorsal half of the ligament was more heterogeneous in its appearance, with multifocal spots or lines of higher signal intensity.

Significance of the Study

• This research provides a better understanding of the high-field MRI characteristics of the plantar tarsal and proximal metatarsal soft tissues in horses.
• Such knowledge could be vital for diagnosing injuries in these regions and providing more effective treatment options. This is especially so as these injuries tend to be a common source of lameness in horses.
• Furthermore, by comparing the MRI findings with postmortem and histological findings, this study bridges the knowledge gap between MRI imaging and actual physical and histological structures.