Intraosseous pressure and pathologic changes in horses with navicular disease.

This study investigates the intraosseous pressure and pathological changes in horses suffering from navicular disease, highlighting significant differences in pressure and pathologies compared with control horses.

Methodology

• The study was conducted on 12 horses in total; 8 with navicular disease and 4 healthy horses acting as control subjects. Both the left and right forelimbs of each horse were studied.
• Under general anesthesia, three types of pressure – navicular bone intraosseous, medial palmar arterial, and saphenous venous pressures – were measured.
• Gross pathological evaluation was carried out. This involved grading the changes observed on the flexor surface of the navicular bone which is the curved surface in contact with the deep digital flexor tendon.
• Histologic-histochemical grading was done on the articular and fibrocartilage surfaces of the navicular bones using sections stained with Safranin-O-fast green. This staining method helps to differentiate between various types of tissue due to colour differentiation. Here, the aim was to observe and grade the integrity of the hyaline cartilage and fibrocartilage of the navicular bone.
• Hematoxylin and eosin-stained sections were used for the morphological evaluation of the navicular bone’s marrow spaces.

Findings

• Significant differences were found in the navicular bone intraosseous pressure between horses with navicular disease and control horses. With statistical significance (P < 0.001), it was found that the intraosseous pressure was considerably higher in horses afflicted with navicular disease.
• There was no statistically significant difference in the medial palmar arterial or saphenous venous pressures across the two groups.
• On evaluating the pathological changes on the flexor surface of the navicular bone, significantly higher severity was reported for horses with navicular disease compared to the control horses.
• While grading the cartilage surfaces of the navicular bones, it was found that significant differences were present in fibrocartilage scores but not in hyaline cartilage scores between control horses and those with navicular disease.
• Lastly, a greater level of fibrosis (the thickening and scarring of connective tissue) was observed in the marrow spaces beneath the flexor cortex (the outer layer of the bone) of horses with navicular disease compared to control horses.

The findings, therefore, highlight the significant variations in pressure and pathology in horses afflicted with navicular disease, contributing to the understanding of the disease’s impact and possible routes for therapeutic intervention.