Carpal lameness is a common cause of wastage in Thoroughbred racehorses, with the middle carpal joint most frequently affected. Evaluation of the dorsoproximal–dorsodistal oblique (DPr–DDiO) radiographic projection of the third carpal bone (C3) is fundamental in clinical and prepurchase assessment of Thoroughbred racehorses. A standardized grading system is needed to improve consistency of diagnosis and reporting between clinicians.
Retrospective Study: Novel Grading System for C3 Radiographs
In a retrospective multirater agreement study, researchers aimed to develop and assess interrater reliability of a novel grading system for evaluating radiological features of the third carpal bone on the C3 skyline projection.
The novel grading system assessed bone radiopacity changes (Grades 0-4) and lucency characteristics (Grades A-C). Bone density ranged from Grade 0 (even trabecular distribution) to Grade 3 (severe radiopacity), with Grade 4 indicating overt evidence of fracture. Lucencies were classified as A (small, dorsal), B (linear or curvilinear, central), or C (extensive). Six observers independently graded 250 radiographs from a first-opinion Thoroughbred racehorse caseload. Interrater agreement was determined using Kappa statistics.
Category-specific bone density grading revealed moderate agreement for Grades 0, 1, and 3 (κ = 0.45, 0.41, and 0.53); fair agreement for Grade 2 (κ = 0.36); and moderate to substantial agreement for Grade 4 (κ = 0.68). Interrater agreement on lucency classification ranged from fair (Grade B, κ = 0.28; Grade A, κ = 0.39) to moderate (Grade C, κ = 0.52). Unweighted kappa for bone density grading was 0.44 and 0.47 for presence of lucency grading. Weighted kappa for bone density grading was 0.59, indicating moderate agreement.
Bottom Line
Interrater agreement using a novel grading system to evaluate the C3 “skyline” radiographic projection was generally moderate and substantial for fracture. Adoption of this grading system in clinical practice will help standardize diagnostic and prognostic evaluation of this important injury site.
https://beva.onlinelibrary.wiley.com/doi/epdf/10.1002/evj.70301
Related Reading
- Advanced Imaging-Based Assessment of Proximal Sesamoid Bones in Thoroughbred Racehorses
- 20 Risk Factors for Fatal Musculoskeletal Injury in Thoroughbred Racehorses
- Using Advanced Imaging for Lameness Workups
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