Septic Osteitis and Osseous Sequestration of the Distal Phalanx Associated with a Coronary Band Lesion in a Draft Horse: Clinical, Radiographic and Surgical Findings

Inflammatory disorders of the distal phalanx (P3) associated with lesions of the coronary region of the hoof may involve reactive periosteal bone proliferation and focal osseous separation. This report describes a case of focal inflammatory osteal pathology of P3 in a draft horse presenting with severe forelimb lameness and a localized lesion of the coronary region. Radiographic examination revealed a longitudinal radiopaque formation with irregular margins on the dorsal aspect of P3, associated with a corresponding radiolucent area and a tract containing fluid and gas extending toward the coronary region. Surgical intervention was performed under general anesthesia. A progressive distal hoof wall resection was carried out with preservation of the coronary region, followed by evacuation of purulent material and curettage of the affected bone. A detached lamellar bone fragment consistent with focal osseous sequestration was removed, and debridement was continued until macroscopically viable bone was obtained. The excised tissues were submitted for histopathological evaluation. Hematoxylin–eosin-stained sections demonstrated lamellar bone with periosteal thickening and adjacent fibrous connective tissue showing hemorrhagic infiltration and a mixed inflammatory infiltrate composed predominantly of neutrophils and macrophages. No histological evidence of neoplastic proliferation was identified. The findings were consistent with periostitis and osteitis associated with reactive exophytic bone formation and focal osseous sequestration. This case highlights the diagnostic value of radiography and the importance of complete surgical debridement in inflammatory conditions of the distal phalanx associated with lesions of the coronary region.