Surgical Treatment of an Osseous Cyst-Like Lesion in the Middle Phalanx Communicating With the Distal Interphalangeal Joint of a Horse

Abstract Subchondral or osseous cyst-like lesions within the distal aspect of the middle phalanx are not commonly reported in equids. These osseous lesions, which can communicate with the distal interphalangeal joint, can result in significant lameness and may not respond well to medical management. This report describes the clinical, diagnostic imaging, and surgical management of a 4-year-old mixed breed gelding where medical management of a chronic subchondral osseous cyst-like lesion of the middle phalanx, which communicated with the distal interphalangeal joint, was unsuccessful. A successful outcome was accomplished after surgical cyst debridement and packing with tricalcium phosphate, a bone marrow aspirate, and platelet-rich plasma.