Standing computed tomographic tenography is reliable in identifying soft tissue lesions within the digital flexor tendon sheath in horses

OBJECTIVE: To determine the diagnostic performance of standing computed tomographic tenography (CTT) in detecting naturally occurring intrathecal lesions of the superficial digital flexor tendon (SDFT), deep digital flexor tendon (DDFT), manica flexoria (MF), and in identifying palmar/plantar annular ligament (PAL) desmitis and constriction in horses undergoing tenoscopy. STUDY DESIGN: Retrospective observational study. ANIMALS: Client-owned horses of various breeds and use, median age of 12.5 years (range: 6-20 years). METHODS: A total of 24 horses with inconclusive ultrasonographic and contrast tenographic examinations were included. All underwent DFTS anesthesia, CTT, and tenoscopy. CTT images were retrospectively evaluated by one ECVDI radiologist and a third-year ECVDI resident, both blinded to tenoscopy findings, reaching a consensus. For each structure within the DFTS (SDFT; DDFT; MF and PAL), lesions were recorded as present or absent. Diagnostic performance of CTT for lesion detection was calculated using tenoscopy as the reference. RESULTS: CTT demonstrated high overall diagnostic performance, with a sensitivity and specificity of 93% for detecting intrathecal lesions. Identification was improved for lesions of the DDFT (sensitivity: 100%; 12/12; 95% confidence interval [CI]: 51%-97%; specificity 83%; 95% CI: 51%-97%) and MF (sensitivity: 90%; 9/10; 95% CI: 66%-99%; specificity: 93%; 95% CI: 66-99%), compared to the SDFT (sensitivity: 71%; 5/7; 95% CI: 29%-99%; specificity: 94%; 95% CI: 71%-99%) and PAL (sensitivity: 64%; 14/22; 95% CI: 15%-100%; specificity: 100%; 95% CI: 15%-100%). CONCLUSION: CTT demonstrated a high diagnostic performance in detecting intrathecal lesions, particularly those involving the DDFT and MF. CLINICAL SIGNIFICANCE: CTT is a valuable advanced imaging modality for evaluating DFTS pathology, particularly when standard imaging techniques do not provide definitive diagnosis.