Findings:
- In the dorsal aspect of the third carpal bone, a well-defined and sharply marginated fracture extends from the middle carpal joint to the carpometacarpal joint in a proximal to distal direction (yellow arrows). The fracture is non-displaced.
- Centered on the carpal joint, there is severe circumferential thickening of the soft tissues.
Conclusions:
- Acute, complete and biarticular slab fracture of right third carpal bone with associated severe joint effusion +/- extracapsular soft tissue swelling (e.g. edema, hemorrhage)
A little bit more…
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 (DeHaan et al., Schneider et al.).
- Racehorses are the most likely to be affected, and they occur more frequently in the right thoracic limb (Tallon et al.).
- 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 (Schneider et al.).
Radiographic signs of slab fractures
- Dorsal plane slab fractures are more likely to occur, particularly affecting the medial facet of the third carpal bone (Nelson et al., DeHaan et al.). They may be displaced or nondisplaced. More fractures are associated with sclerosis of the third carpal bone. Sclerosis localized in the radial fossa may be seen, especially with non-displaced fractures (DeHaan et al., Schneider et al.).
- Fractures of the radial facet of the third carpal bone are best visualized on lateromedial, flexed lateromedial, and dorsolateral-palmaromedial oblique projections, as well as on a dorsoproximal-dorsodistal projection of the distal row of carpal bones (DeHaan et al., Schneider et al.).
- Sagittal plane fractures occur less commonly than dorsal plane fractures and may be incomplete (Tallon et al.). 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 (Schneider et al.).
- CT is superior to radiography for characterization of carpal fractures in horses. Radiography often underestimated the degree of displacement and fracture extent. More fractures may be classified as incomplete using radiography when compared to CT (Dash et al.).
Treatment
- Surgical repair is indicated for unstable fracture as severe degenerative joint disease or compensatory laminitis of the contralateral limb may ensue (Dash et al.).
- The prognosis for return to prior or other ridden work is poor (Dash et al.).
- Although sagittal plane slab fractures are more often non-displaced and may be managed conservatively, they tend to carry a more guarded prognosis. Arthroscopy may be considered for debridement of the affected joint and placement of a transcortical screw for stabilization of the fracture (Tallon et al., Dash et al.).
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.
- Schneider RK, Bramlage LR, Gabel AA, Barone LM, Kantrowitz BM. Incidence, location and classification of 371 third carpal bone fractures in 313 horses. Equine Veterinary Journal. 1988 Sep;20:33-42.
- DeHaan CE, O’Brien TR, Koblik PD. A radiographic investigation of third carpal bone injuryin 42 racing thoroughbreds. Vet Radiol 1987;28:88-92.
- Tallon R, O’Neill H, Bladon B. Sagittal plane slab fractures of the third carpal bone in 45 racing Thoroughbred horses. Equine veterinary journal. 2020 Sep;52(5):692-8.
- Nelson BB, Lawless SP, McIlwraith CW. Slab fractures of the third carpal bone involving both radial and intermediate facets and outcomes after surgical repair in racing Quarter Horses. Equine Veterinary Journal. 2022 May;54(3):556-62.
- Dash RF, Minshall GJ, Wright IM. Comparison of radiography and CT for the evaluation of third carpal bone slab fractures in Thoroughbred racehorses. Veterinary Radiology & Ultrasound. 2023 Jul;64(4):661-8.
