Low-Field Magnetic Resonance Imaging Features of Axial Proximal Sesamoid Osteomyelitis and Intersesamoidean Ligament Rupture in a Horse.

A 7-year-old Warmblood mare used for show jumping was evaluated for progressive left hindlimb lameness of 5 weeks' duration, localized clinically to the metatarsophalangeal region. Radiography revealed ill-defined osteolysis of the axial apical regions of both proximal sesamoid bones (PSBs). Due to rapid clinical deterioration, low-field magnetic resonance imaging was performed and demonstrated aggressive axial osteomyelitis of both PSBs, partial rupture of the intersesamoidean ligament and proximal scutum with herniation of synovium of the plantar joint recess, and an occult penetrating tract. Endoscopic surgical exploration confirmed the imaging findings. Following surgical treatment, the horse returned to full athletic function.