Diagnosis and treatment of intrathecal tears of the accessory ligament of the superficial digital flexor

Abstract

SummaryReasons for performing studyTears of the accessory ligament of the superficial digital flexor (ALSDF) that communicate with the carpal sheath are not reported in the literature. The study describes ultrasonographic techniques for evaluation of the ALSDF and reports clinical, ultrasonographic and endoscopic features associated with intrathecal tears of the ligament.ObjectivesTo investigate whether tearing of the ALSDF can be: 1) intrathecal with respect to the carpal sheath; 2) cause lameness and distension of the carpal sheath; and 3) result in intrathecal haemorrhage by tearing vessels that appear to be direct branches of the median artery, as well as to confirm that these lesions are reliably predicted by ultrasonography.Study designRetrospective case series.MethodsCase records and diagnostic images of horses with ALSDF injuries were reviewed retrospectively, and follow‐up information was obtained.ResultsUltrasonographic examination using a combination of linear and curved array transducers identified 10 cases with intrathecal tears of the ALSDF. This was confirmed in 7 cases that underwent tenoscopy. Tears were consistently in the caudal ALSDF and in 3 cases exposed the median artery. Extruded torn fibres were removed. Of the 7 surgical cases, one horse returned to competitive work, one was back in full training, 2 were retired from racing but performing riding club activities, 2 were convalescing and one was lost to follow‐up. Of the 3 cases that did not undergo surgery, one was subjected to euthanasia and the other 2 failed to return to training.ConclusionsTears of the ALSDF can communicate with the carpal sheath, resulting in lameness and intrathecal haemorrhage. The latter appears to result from vessels that are primary branches of the median artery, and tears in the ALSDF can extend to this. These injuries are reliably predicted by multimodal ultrasonography, which also allows assessment of the proximity of tears to the median artery.