Evaluation of experimentally induced injury to the superficial digital flexor tendon in horses by use of low-field magnetic resonance imaging and ultrasonography.

This research examines how effectively ultrasonography and low-field magnetic resonance imaging (MRI) can evaluate tendon injuries in horses. Findings suggest that ultrasonography may underestimate long-term injury extent, while MRI provides a more sensitive approach for evaluating tendon injuries lasting more than four weeks.

Study Methodology

In this study:

• The tendons of 8 young adult horses were used.
• Experimentally induced tendon injuries were assessed using MRI and ultrasonography. This was done by injecting the tendons with collagenase, an enzyme that breaks down collagen in the tissues, therefore simulating injury.
• These assessments were made at varying time points of 3, 4, 6, 8, and 16 weeks after the collagenase injection.
• In addition to imaging assessments, histologic characteristics of each tendon, including collagen and proteoglycan content and fiber alignment, were determined at the same time points.

Results of the Study

The experiment yielded several noteworthy results:

• At four weeks after inducing the injury, both MRI and ultrasound returned comparable results—indicating that ultrasonography can be effective for short-term tendon injury evaluation.
• However, with injuries lasting over four weeks, ultrasonography tended to underestimate the area of the injury by about 18% when compared to MRI.
• The MRI provided different levels of signal intensity based on the type of imaging used (T1-weighted images were the most hyperintense, followed by short tau inversion recovery images, and T2-weighted images which were the most hypointense).
• The signal intensity of tendon injuries was significantly higher than that for the unaltered deep digital flexor tendon.
• From a histological standpoint, there was a decrease in proteoglycan content, an increase in collagen content, and minimal change in fiber alignment during the 16 weeks of the study.

Conclusion

This study concludes:

• Ultrasonography might not be the most effective method for evaluating the extent of long-term tendon damage in horses, as it tends to underestimate the area involved.
• In contrast, low-field MRI offers a more sensitive technique for this purpose and should be considered for horses with tendonitis lasting for more than four weeks.