Static, dynamic and non‐weightbearing ultrasound evaluation of the digital flexor tendon sheath improves sensitivity and specificity of manica flexoria tears diagnosis in cobs and ponies

Abstract

SummaryBackgroundUltrasonography (US) is commonly used as a first‐line imaging modality in horses with lameness localised to the digital flexor tendon sheath (DFTS). The reported sensitivity of US for the detection of manica flexoria (MF) tears is low.ObjectivesTo report sensitivity (Se), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) of US for diagnosing MF tears.Study designProspective observational study.MethodsSixty‐seven horses (70 limbs) with lameness localised to the DFTS were enrolled. All the horses underwent a standardised US examination of the DFTS including weightbearing (WB), nonweightbearing (NWB) and dynamic NWB US examination. The presence or absence of a MF tear was recorded. All the horses underwent tenoscopic examination as part of the treatment plan. The US diagnosis was recorded and compared with tenoscopic findings. Sensitivity, Sp, PPV and NPV were calculated.ResultsCobs and ponies were over‐represented (46/67 horses). Ultrasonographic examination correctly predicted the presence of a MF tear in 34/37 (92%) limbs (true positive). In 31/33 (94%) limbs, the MF was considered normal during US examination and this was confirmed during surgery (true negative). In two of 33 (6%) cases, US led to a false‐positive diagnosis. In three of 37 (8%) cases, US failed to identify the presence of a MF tear (false negative (FN)). In all three cases, the MF was only partially torn. The calculated sensitivity of ultrasonography for the detection of MF tears was 92%, specificity 94%, PPV 94% and NPV 91%. There was no significant difference in the ability of operators to identify MF tears.Main limitationsTwo different operators (both DECVS) performed the ultrasonographic examination. The operator performing the US examination was not blinded to the results of the lameness examination. The tenoscopic examination was performed by the same surgeon who had performed the lameness and ultrasonographic examination.ConclusionsUltrasonographic examination of the DFTS is an accurate diagnostic modality to rule in or out the presence of a MF tear. Partial MF tears that do not affect its distal border and/or its attachment onto the SDFT can be challenging to diagnose during US examination.