Osteomyelitis of the lateral humeral epicondyle secondary to trauma in a Franches‐Montagnes gelding

Summary Osteomyelitis secondary to trauma of the distolateral humerus is a rare diagnosis in horses. Although common in foals, mainly due to haematogenous spread, osteomyelitis is uncommon in adult horses and usually associated with traumatic injuries and infected wounds. This case report describes the diagnostic findings, treatment and outcome of a 4‐year‐old gelding with osteomyelitis of the lateral humeral epicondyle. The horse presented with acute lameness associated with marked swelling of the elbow region. Radiographs showed fragments in the region of the proximal lateral collateral ligament attachment of the elbow joint. Ultrasonography revealed a fistula and an abscess reaching the lateral humeral epicondyle with local periostitis as well as two avulsion fragments within the lateral collateral ligament. The intraoperative computed tomography (CT) scan revealed a focal osteolytic lesion within the lateral humeral metaphyseal medulla with adjacent periostitis, indicative of osteomyelitis of the distolateral humerus. The avulsion fragments were surgically removed, and the wound was debrided. Recurrent swelling of the region and sequestrum formation resolved without treatment. Inactive osseous changes were still visible radiographically upon re‐examination 9 months later, but the gelding remained sound.