Introduction

• Unusual injury, usually in Thoroughbred Thoroughbred or Quarterhorse Quarterhorse racehorses, or occasionally in any breed whilst turned out in a field.  
• Most commonly involve radial, intermediate or third carpal bones.
• Cause: generally occur through acute trauma/impact and can involve more than one bone/carpal row, leading to carpal instability.
• Signs: severe forelimb lameness Musculoskeletal: gait evaluation, synovial distension, pain on flexion Musculoskeletal: manipulative tests and joint instability.
• Diagnosis: radiography Forelimb: radiography, CT Computed tomography, arthroscopy Joint: arthroscopy - overview.
• Treatment: internal fixation, arthrodesis, external fixation - casts Musculoskeletal: external fixation - casts.
• Prognosis: poor, contralateral laminitis Foot: laminitis likely.
• See also:
  • Carpal chip fractures Carpus: fracture - chip.
  • Carpal slab fractures Carpus: fracture - slab.
  • Fractures overview Musculoskeletal: fracture.
  • First aid for fractures Musculoskeletal: fracture - first aid.

Pathogenesis

Etiology

• Comminuted carpal bone fractures generally occur through acute trauma/impact, including kicks, falls and collisions, and can involve more than one bone/carpal row, leading to carpal instability.
• Racehorses are most commonly affected but any breed may be subject to the necessary trauma, particularly when turned out with other animals.

Predisposing factors

• Chronic carpal disease may precede comminuted fractures in racehorses.

Pathophysiology

• The most common combination of fractures involves the third carpal bone (usually radial and intermediate facets) and either the radial or intermediate carpal bone, or both. Occasionally the ulnar carpal and fourth carpal bones are involved which leads to carpal valgus deformity.
• Comminution of one bone, such as the third carpal bone, can be seen in racehorses including Standardbreds Standardbred.

Diagnosis

Treatment

Outcomes