Tears of the Accessory Ligament of the Superficial Digital Flexor and Their Relationship to the Carpal Sheath

Abstract

AimsThe study aimed to describe an ultrasonographic technique for evaluation of the accessory ligament of the superficial digital flexor (ALSDF) and to report the presentation, clinical, ultrasonographic and endoscopic features associated with intrathecal tears of the ligament.MethodsThe case records of 83 horses that underwent ultrasonography of the carpal sheath by the author between 2008 and 2012 were evaluated. Injuries of the ALSDF were identified and reviewed.ResultsTen horses had injuries to the ALSDF. All cases were assessed using linear and curved array transducers in caudomedial to craniolateral orientations. The former was used in transverse and longitudinal orientations and with colour Doppler to assess intra‐ and periligamentous vasculature. The curved array transducer was used for transverse studies both with the limb weightbearing and with slight carpal flexion. This combination of imaging studies detected tearing of the ALSDF which communicated with the carpal sheath in all 10 cases. Seven of the 10 cases underwent tenoscopic examination which confirmed the ultrasonographic findings. The areas of torn ALSDF were in consistent locations and with similar lesion morphology.ConclusionsDisruption of the ALSDF can communicate with the carpal sheath resulting in lameness and intrathecal haemorrhage. The latter appears to result from vessels which are primary branches of the median artery and tears in the ALSDF can extend to this. The injuries are reliably predicted by ultrasonography. This also allows assessment of the proximity of the tear to the median artery which in turn is an important guide for subsequent tenoscopic surgery.Practical significanceUltrasonographic evaluation of the ALSDF can identify tears which communicate with the carpal sheath. Tenoscopy should then be considered as a treatment option.Ethical animal researchNot required by this Congress: retrospective clinical study. Sources of funding: None. Competing interests: None.