Digital sheath synovial ganglion cysts in horses.

Abstract

OBJECTIVES: To report the clinical features of horses with fluid-filled masses associated with the digital flexor tendon sheath (DFTS) and outcome after surgery. STUDY DESIGN: Case series. ANIMALS: Horses (n=10) METHODS: Medical records of horses with fluid-filled masses associated with the DFTS were reviewed and the clinical features, diagnostic methods, treatment, histopathology, and outcome reported. RESULTS: Masses were unilateral (7 hind limb, 3 front limb) and in 8 horses were associated with lameness. In 6 horses, lameness improved by >50% with intrathecal DTFS anesthesia, whereas 2 were less positive but were further improved with perineural anesthesia just proximal to the cyst. Communication between the DFTS and mass was identified in all horses ultrasonographically. Resection of the mass resolved lameness in 7 horses. Histologically (5 specimens), the mass was characterized by a fibrous outer layer without a synovial lining, consistent with a ganglion cyst. CONCLUSION: The histologic appearance of ganglion cysts suggests that they arise from trauma to the sheath wall and may subsequently be a cause of lameness.