Signalment & History
- This patient presents for left thoracic limb lameness that occurred while turning at the canter.
- On physical examination, her vitals are normal. There is Grade 4 lameness of the left thoracic limb, moderate soft tissue swelling, and pain on palpation of the left carpus.
Findings
The soft tissues surrounding the left carpus are moderately thickened. There is a comminuted fracture within the fourth carpal bone, with multiple angular, well-defined fracture fragments. There is a mild palmar, lateral, and proximal displacement of the fracture fragments. Multiple ill-defined fissure lines are present within the fourth carpal bone, with mild sclerosis of the surrounding trabecular bone. There is a mild amount of angular, amorphous mineral opacity within the soft tissues on the palmarolateral aspect of the fourth carpal bone.
Diagnosis
- This patient is diagnosed with a comminuted, subacute, mildly displaced, fourth carpal bone fracture, with soft tissue swelling (likely edema, with or without hemorrhage)
Conclusions
Fractures of fourth carpal bones of horses
- Fractures of the fourth carpal bone are uncommon in horses
- They appear to be the end result of abnormal concentrations of force on the bone resulting in bone failure
- Fractures typically arise at a 45 degree angle to the direction of the applied force
- They can occur in both racing and pleasure horses and may be the result of either direct trauma or abnormal force concentration in the carpus
References
- Field JR, Zaruby JF. Repair of a fracture of the fourth carpal bone in a yearling standardbred horse. Can Vet J. 1994;35: 371-2
