Signalment & History
- This patient presents to your clinic for acute lameness in the right forelimb. The soft tissues of the right carpus are swelling and painful.
- You order Right carpus radiographs.
Findings
- There is a radiolucent line in the dorsal aspect of the third carpal bone. It extends from the intercarpal joint to the carpometacarpal joint in a proximal to distal direction.
Diagnosis
- This patient is diagnosed with a slab fracture of third carpal bone of the right carpus and surrounded by associated soft tissue swelling and/or joint effusion
References
- Murray and Dyson. The equine carpus. In: Thrall DE, ed. Textbook of veterinary diagnostic radiology. 6th ed. St Louis: Elsevier Health Science, 2013;374.
- Incidence, location, and classification of 371 third carpal bone fractures in 313 horses. Schneider et al. (1988) vol 20. S6, p33-42.
- Radiographic investigation of third carpal bone injury in 42 racing thoroughbreds. 1987. De Haan et al. Veterinary Radiology and Ultrasound. Vol 28, No 3, pp 88-92.
Slab carpal fractures
Slab fractures affect more frequently the third carpal bone. Although, fracture of other carpal bones has been reported, they are relatively rare. Racehorses are the most likely to be affected, and they occur more frequently in the right foreleg. The clinical signs differ if the fracture was complete or incomplete. With complete displaced fractures, significant effusion, soft tissue swelling, and severe lameness are usually present, but horses with a nondisplaced incomplete fracture may have no localizing clinical signs.
Radiographic signs of slab fractures
Dorsal plane slab fractures are more likely to occur, particularly affecting the medial facet of the third carpal bone. They may be displaced or nondisplaced. More fractures are associated with an increased opacity of the third carpal bone. Nevertheless, some fractures, and particularly incomplete, can present sclerosis localized in the radial fossa.
Fractures of the radial facet of the third carpal bone are best visualized on lateromedial, flexed lateromedial, and dorsolateral-palmaromedial oblique views and a dorsoproximal-dorsodistal view of the distal row of carpal bones.
Sagittal plane fractures occur less commonly than dorsal plane fractures and may be incomplete. In this case, they primarily affect the medial facet of the third carpal bone. Racehorses with sagittal slab fractures of the third carpal bone can have a favorable prognosis for return to racing, particularly if treated surgically. Sagittal fractures of the third carpal bone are best seen on dorsoproximal-dorsodistal and dorsomedial-palmarolateral oblique views.
Dorsoproximal-dorsodistal radiograph of the distal row of carpal bones. Mild increased radiopacity of the radial facet of the third carpal bone and a nondisplaced slab fracture are visible (white arrows).
