# Comparison of Ultrasonography, Contrast Radiographic Tenography, Cone-Beam Computed Tomographic Tenography, and Tenoscopy for Lesion Detection Within the Digital Flexor Tendon Sheath of Horses—A Prospective Clinical Trial

## TL;DR

This study compares imaging techniques for detecting tendon sheath lesions in horses and finds that computed tomographic tenography is most accurate.

## Contribution

The study provides a direct comparison of diagnostic imaging modalities for equine tendon sheath lesions without using a gold standard.

## Key findings

- CTT showed the highest agreement with tenoscopy for diagnosing DDFT, SDFT, and MF lesions.
- Agreement between imaging modalities for diagnosing PAL constriction was poor.
- Combining RXT and ultrasonography improved agreement with CTT compared to using either alone.

## Abstract

Lesions of the superficial (SDFT) or deep (DDFT) digital flexor tendons, manica flexoria (MF) or palmar/plantar annular ligament (PAL) within or adjacent to the digital flexor tendon sheath (DFTS) are common causes of lameness in horses. A comprehensive diagnostic imaging workup is critical for accurately defining the underlying cause and ensuring successful case management. This prospective study compared and quantified the agreement between different imaging modalities and tenoscopy. The imaging included radiography (RXT) and computed tomography (CTT), with contrast medium injected into the DFTS to visualize the tendons and MF, and ultrasonography. Eighteen horses with naturally occurring DFTS distention were evaluated. For DDFT, SDFT and MF lesions, the highest agreement was found between CTT and tenoscopy. Agreement between imaging modalities for the diagnosis of PAL constriction (PALco) proved to be poor, as none of the modalities agreed on affected cases. Therefore, CTT is considered the best modality to diagnose the lesion causing distention of the DFTS when the SDFT, DDFT or MF are affected, showing lesions unreported both on ultrasonography and tenoscopy. Combining RXT and ultrasonography increased the agreement with CTT compared to either modality alone and should be considered when CTT is not available pre-surgery.

Lesions of the tendons and manica flexoria (MF) within the digital flexor tendon sheath (DFTS) are a common cause for lameness in horses. This prospective study compared and quantified the agreement and disagreement of positive contrast computed tomographic tenography (CTT), positive contrast radiographic tenography (RXT), ultrasonography (US) and tenoscopy for diagnosing naturally occurring lesions within the DFTS, without application of a gold standard. Lesions affecting the deep (DDFT) and/or superficial digital flexor tendon (SDFT), and/or the MF and/or constriction of the palmar/plantar annular ligament (PAL) were evaluated in eighteen horses with distention of the DFTS. For DDFT lesions, comparing CTT with tenoscopy, US, and the combined results of US and RXT (US+RXT) attained the highest agreements, with 83% matching results (κ: 0.65). For SDFT lesions, CTT and tenoscopy showed the highest agreement with 94% matching results (κ: 0.89), followed by tenoscopy with US+RXT (78%; κ: 0.56). The highest agreement for MF-tear detection was found comparing CTT with tenoscopy (83%; κ: 0.67), followed by CTT with RXT (78%; κ: 0.56). None of the modalities agreed on positive diagnoses of PAL constriction. CTT achieved the highest agreement with tenoscopy and US for the diagnosis of lesions within the DDFT and is, therefore, considered the most useful modality for preoperative evaluation.