Bipartite distal phalanx and navicular bone in an Andalusian stallion.

This study details the medical conditions and radiographic abnormalities observed in an Andalusian stallion suffering from divided or bipartite distal phalanx and navicular bone in its right forelimb. Associated occurrences including a likely keratoma and degenerative joint disease at the distal interphalangeal joint are also reviewed, with potential causes being explored.

Clinical Findings

In this study, a horse, specifically an Andalusian stallion, was found to have a divided, or bipartite, distal phalanx and navicular bone in the right forelimb.

• A bipartite distal phalanx involves the phalanx (a bone in the foot) consisting of two parts instead of its usual single structure.
• Simultaneously, a bipartite navicular bone means that the navicular bone (a small bone found in the feet of horses) is also split into two parts rather than being intact.

Associated Findings

Alongside these main findings, additional signs related to these conditions were observed:

• The horse was observed to have a suspected keratoma. Keratomas are a type of benign tumour that can occur in horses, characterised by hard, corn-like growths in the foot.
• The study also identified the presence of degenerative joint disease in the distal interphalangeal joint of the horse. This is a condition that affects the joints, leading to pain and potentially limiting movement over time. This condition most often occurs due to wear and tear to the cartilage in the joint but can also arise due to trauma or inflammation.

Possible Etiologies

Several potential causes for these conditions were considered and discussed in this study.

• Genetics potentially play a role in these conditions. As both the distal phalanx and navicular bone are made up of cartilage that ossifies (hardens) over time, issues in this process could lead to a bipartite structure.
• External factors such as physical trauma could also potentially cause these conditions by damaging the structure of the bones, leading them to heal in a bipartite manner. This is, however, speculation and the study does not provide solid evidence for this.
• As both the bipartite distal phalanx and navicular bone were found in the right forelimb, there may be a correlation between these conditions and the horse’s dominant foot, though further investigation would be necessary to confirm this.