CT tenography for digital flexor tendon sheath

Gross anatomy, computed tomographic contrast tenography, and needle endoscopy of the equine medial digital flexor tendon sheath

Maria P Kerbert 1, Uta Delling 1, Nicole Verhaar 1

Background
Understanding the internal topography of the equine digital flexor tendon sheath (DFTS) is essential for accurate diagnostic imaging and therapeutic interventions in cases of distal limb lameness. While various methods exist to examine this structure, comprehensive descriptions correlating gross anatomy, computed tomographic (CT) tenography, and needle endoscopy have been lacking. This study aimed to describe and correlate the internal anatomy of the DFTS using these three modalities in equine cadavers, with an emphasis on evaluating their utility for guiding clinical and surgical approaches.

Methods
The study utilized eight forelimbs from adult equine cadavers. Each DFTS was distended with a contrast solution, followed by CT imaging to produce detailed tenograms. Needle endoscopy was then performed using a 1.9-mm arthroscope introduced into the distended sheath. Anatomical dissection followed to validate imaging and endoscopic findings. Structures of interest included the superficial and deep digital flexor tendons, mesotendons, manica flexoria, and synovial folds. Observations were documented and compared across all three assessment modalities.

Results
CT tenography successfully delineated the course and spatial relationships of the flexor tendons, mesotendons, and synovial recesses, particularly identifying the proximopalmar recess and its extension. Needle endoscopy allowed real-time visualization of internal structures, albeit with a limited field of view compared to CT. Gross dissection confirmed the anatomical accuracy of both imaging modalities. Discrepancies included occasional difficulties in visualizing the distal sheath margins endoscopically and overestimation of synovial folds in CT due to contrast pooling.

Limitations
The study was conducted exclusively on cadaveric limbs, which may not fully replicate in vivo tissue characteristics, distension, or fluid dynamics. The small sample size and absence of pathological specimens limit the generalizability to clinical populations. CT artifacts and variability in contrast distribution could affect image interpretation. Additionally, needle endoscopy's constrained field and potential for missed lesions were acknowledged.

Conclusions
The combined use of CT tenography and needle endoscopy provides complementary insights into the equine DFTS anatomy. CT offers a comprehensive spatial overview, while endoscopy enables targeted inspection of synovial structures. These findings support the utility of these modalities in diagnostic and surgical planning, warranting further investigation in live and pathological specimens.

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