Osteochondral necrosis of the femoral condyles in Thoroughbred foals: eight cases (2008-2018)

OBJECTIVE To describe clinical, imaging, gross, and histopathological abnormalities associated with osteochondral necrosis of the femoral condyles in foals and identify features suggestive of a common pathogenesis. ANIMALS 8 Thoroughbred foals euthanized with a presumptive diagnosis of necrosis of the femoral condyles. PROCEDURES Postmortem CT was performed on all distal femoral epiphyseal samples. The articular epiphyseal cartilage complex (AECC) of affected distal femurs was examined grossly and histologically, focusing on lesions of interest identified on CT images. RESULTS 7 foals were between 9 and 23 days old at the time of euthanasia; 1 foal was 85 days old. Concurrent illness (neonatal maladjustment syndrome, neonatal isoerythrolysis, or infection such as enteritis and omphalitis) was diagnosed in 7 foals. The characteristic antemortem radiographic and postmortem CT finding was a crescent-shaped osteochondral flap displaced from the affected medial femoral condyle. Synovial fluid cytology from affected joints was either within normal limits or consistent with mild inflammation. Histologically, all lesions were characterized by osteochondral necrosis and detachment of the AECC. In 6 foals, polymorphonuclear cells were found within growth cartilage canals, representing septic cartilage canals.

Automated summary

This study describes the clinical, imaging, gross, and histopathological abnormalities associated with osteochondral necrosis of the femoral condyles in foals, and identifies features suggestive of a common pathogenesis.