Simple SummaryThe extent of injury in horses with third carpal bone (C3) fracture is not fully appreciated using conventional radiography. Computed tomography (CT) enables more detailed imaging of bone needed for accurate diagnosis and is becoming more widely available in equine practice. We describe the CT findings in racehorses with a variety of C3 fracture configurations (15 cadaver carpi and 27 carpi from 26 horses with C3 fracture) and report agreement with radiographic findings in those with ante-mortem digital radiographs (DR). CT detected more concurrent bone pathology and enabled more accurate determination of fracture configuration. Agreement between DR and CT was good for recognition of fracture displacement, fair for fracture comminution, bone loss at the articular surface and concurrent osteochondral fragmentation, and poor to slight for recognition of whether the fracture was complete in each plane, and whether additional fissures and bone lucencies were present. This study highlights the limitations of radiography and the benefits of CT in the accurate diagnosis of bone pathologies in horses with C3 fracture.AbstractRadiographs underestimate the extent of bone injury in horses with third carpal bone (C3) fractures (Fx). We aimed to describe bone pathologies identified using computed tomography (CT) and compare the diagnostic value of digital radiography (DR) and CT in horses with C3 Fx. CT images of 15 racehorses with C3 Fx and 10 controls were reviewed (Part 1) then DR and CT images of 26 racehorses (24 Thoroughbred, 2 Standardbred) with C3 Fx (Part 2) were evaluated. Agreement on fracture geometry and concomitant bone lesions was tested between DR and CT using the kappa statistic (Part 2). For agreement analysis, 38 limbs were used (27 Fx carpi from 26 horses and 11 contralateral carpi). Intermodality agreement was good for recognition of displacement, fair for comminution, articular surface bone loss and osseous fragmentation, and poor–slight for recognition of whether the Fx was complete, additional fissures and lucencies. CT provides more detailed information than DR regarding bone pathology and fracture configuration in horses with C3 fracture. Correlation of CT findings with clinical information and outcome needs to be explored; however, the more accurate diagnosis possible with CT is likely valuable when deciding on the most appropriate management and for surgical planning.