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

Overview

• This study reports on the diagnostic use of low-field magnetic resonance imaging (MRI) to identify and assess complex bone and ligament injuries in a horse with hindlimb lameness.
• It demonstrates how MRI can detect detailed structural damage not easily seen on radiographs, aiding in appropriate surgical intervention and successful recovery.

Case Description

• A 7-year-old Warmblood mare, involved in show jumping, experienced progressive lameness of the left hindlimb lasting five weeks.
• Clinical examination localized the lameness to the metatarsophalangeal (fetlock) region of the limb.

Initial Diagnostic Imaging

• Radiography was performed first, revealing ill-defined areas of osteolysis (bone loss) at the axial apical regions of both proximal sesamoid bones (PSBs).
• The findings indicated potential pathology but were insufficient to fully characterize the extent and nature of the lesion.

Advanced Imaging with Low-Field MRI

• Due to the horse’s rapid clinical worsening, low-field MRI was used to gain a more detailed assessment.
• MRI identified aggressive axial osteomyelitis (infection and inflammation of bone) affecting both proximal sesamoid bones.
• The imaging also detected:
  • Partial rupture of the intersesamoidean ligament, a critical ligament linking the two sesamoid bones.
  • Damage to the proximal scutum, which is part of the joint’s bony and ligamentous support structure.
  • Herniation of the synovium (joint lining) into the plantar joint recess, indicating joint capsule disruption.
  • An occult penetrating tract, suggesting a hidden pathway for infection or injury.

Surgical Exploration and Treatment

• Endoscopic exploration of the affected joint confirmed the MRI-based diagnosis, verifying the bone infection and ligament rupture.
• Surgical management targeted these identified lesions to control infection and restore joint stability.

Outcome

• Following surgery and recovery, the mare successfully returned to full athletic function, resuming participation in show jumping.

Significance and Implications

• This case highlights the utility of low-field MRI in diagnosing multifaceted orthopedic injuries in horses, especially when radiographs are inconclusive.
• The ability to visualize both bone infection and soft tissue damage provides valuable information for precise surgical planning.
• Early and accurate diagnosis can lead to effective treatment and positive outcomes in equine athletes.