Does Low-Field MRI Tenography Improve the Detection of Naturally Occurring Manica Flexoria Tears in Horses?

Abstract

Diagnosing digital flexor tendon sheath (DFTS) pathologies, particularly manica flexoria (MF) tears, can be challenging with standard imaging modalities. Standing low-field MRI tenography (MRIt) may improve the detection rate of MF tears. This study aimed to compare ultrasonography, contrast radiography, pre-contrast MRI, and MRIt to detect naturally occurring MF lesions in horses undergoing tenoscopy. Ten horses with a positive DFTS block, which underwent contrast radiography, ultrasonography, MRI, MRIt, and tenoscopy were included. Two radiologists evaluated the images and recorded whether an MF lesion was present and determined the lesion side. Sensitivity and specificity were calculated for each modality using tenoscopy as a reference. MRIt and contrast radiography detected MF lesions with the same frequency, both showing 71% sensitivity and 100% specificity. Pre-contrast MRI and ultrasonography detected MF lesions with a lower sensitivity (57%); however, the MRI (100%) demonstrated a higher specificity than ultrasonography (33%). Adding contrast in MRI changed the sensitivity from (4/7 lesions) 57% to (5/7 lesions) 71%, with a constant high specificity (100%). MRIt diagnoses MF tears with a similar sensitivity to contrast radiography, with the same specificity, but with the added benefit of lesion laterality detection. The combined advantages of the anatomical detail of the T1 sequence and the post-contrast hyperintense appearance of the fluid may help diagnose MF tears and identify intact MFs. However, this needs to be substantiated in a larger number of cases.

Keywords: MRI; horse; manica flexoria; tenoscopy.

Figure 1

(A) Transverse ultrasound image of the fetlock area (medial to the left). There is an asymmetrical thickened and hypoechoic appearance of the lateral aspect of the manica flexoria at its attachment to the superficial digital flexor tendon. The floating edge of the manica flexoria within the synovial fluid of the digital sheath is visible at the lateral aspect (arrow). (B) Transverse ultrasound image of the fetlock area obtained on the non-weight bearing limb. There is a medial displacement of the superficial digital flexor tendon relative to the deep digital flexor tendon (arrows).

Figure 2

Lateromedial contrast radiograph demonstrating two diagnostic criteria used for assessment of manica flexoria lesions. The two parallel lines which delineate the manica flexoria just above the proximal sesamoid bones, at the dorsal border of the deep digital flexor tendon, are not visible (arrow), and there is an isolated area of contrast overlying the dorsal border of the deep digital flexor tendon at the level of the manica flexoria (arrowhead).

Figure 3

Magnetic resonance images (MRI) indicating a manica flexoria lesion (arrow): transverse T2-fast spin echo sequence (A), transverse T1 sequence (B), and a transverse T1 sequence following intrathecal gadolinium administration (C) of the same limb. In this case, the manica flexoria lesion could only be diagnosed in the transverse post-contrast T1 sequence clearly (C). In the T2 sequence, a tear could have been suspected (A).

Figure 4

Magnetic resonance images (MRI) indicating a manica flexoria lesion (arrow): transverse T2-fast spin echo sequence (A), transverse T1 sequence (B), and a transverse T1 sequence following intrathecal gadolinium administration (C) of the same limb. The manica flexoria lesion, as well as tendon thickening and rounding, is visible in all sequences.