Enthesopathy of the radial tuberosity in two thoroughbred racehorses.

This research article discussed two cases of enthesopathy (a disorder involving the attachment of a tendon or ligament to a bone) in the radial tuberosity (a bony prominence in the forearm) in Thoroughbred racehorses, with symptoms closely resembling Osgood-Schlatter disease in humans.

Key Findings

• The researchers used soft X-ray imaging to identify and study the disorder. This imaging process revealed separated bony fragments in the front of the radial tuberosity, similar to lesions seen in Osgood-Schlatter disease in children.
• Osgood-Schlatter disease in humans is caused by the detachment of part of the apophysis (a growth area where a tendon attaches to a bone) of the tibial tuberosity (a bony prominence near the knee).
• In the affected horses, the detached bony fragments were made up of cortical bone tissue, a sturdy type of bone that forms the outer layer of most bones in the body. This tissue contained trabeculae (small, lattice-like structures) with osteons (cylindrical structures that carry nutrients in bones), similar to the structure of lamellar bone, the main component of the radial tuberosity.

Implications and Speculation

• Tendon fibrils were found to be inserted into the front portions of these detached fragments. Moreover, scar tissue filled the gap between the back part of the fragments and the radial tuberosity. This suggested that the detached fragments could have been due to an avulsion fracture due to repeated high tension caused by muscle contraction.
• Specifically, the avulsion fracture may have occurred at the location where the tendinous part of the biceps brachii muscle (one of the main muscles of the upper arm) attaches to the bone tissue of the radial tuberosity. This location is subjected to repeated high-tensile force due to muscle contraction, particularly in racehorses.
• This study provides new insight into a specific type of enthesopathy in horses, offering a reference for future studies on bone and joint disorders in animals.