Magnetic resonance anatomy of the carpus of the horse described from images acquired from low-field and high-field magnets.

The research focused on the anatomy of the carpus (wrist joint) in horses, using magnetic resonance imaging (MRI) to analyze cadaver samples. The study aimed to describe normal anatomy and any variations, which could be useful in interpreting MR images of lame horses.

Research Methodology

• The study involved 30 mature horses with no history of carpal (wrist) or proximal metacarpal (upper part of the hind limb or forelimb) pain.
• The carpi (plural for carpus) of these horses, not alive at the time the study was performed, were examined using low-field (0.27 T) and high-field (1.5 T) magnetic resonance imaging (MRI).
• The images acquired were analyzed to identify the normal MRI anatomy in transverse (cross-sectional), sagittal (longitudinal), and dorsal (backside) planes.
• The researchers measured the thickness of the subchondral bone (the bone just below the cartilage in a joint) and cortical bone (the outer layer of bone) at standardized sites.

Research Findings

• The study found variations in the thickness of the subchondral bone in the radius (the larger of the two bones in the forelimb) and carpal bones.
• They also found that the thickness of the subchondral bone was relatively larger at the backside compared to the palmar (front) in the proximal row of carpal bones.
• The inner surface of the subchondral bone appeared smooth, and the shape of the ulnar carpal bone (one of the bones in the carpus) was variable.
• In 5 out of the 30 limbs, one or more small skeletal fragments were identified near the bone, however, researchers found no evidence suggesting pathological fractures or ligament damage.
• The amount of muscle tissue present in the flexor tendons at the top of the carpus varied among the horses, with none present at the middle joint and distally (farthest from the body).
• The researchers were able to evaluate several structures using MRI that could not be examined using other methods such as radiography (x-rays), ultrasonography, or arthroscopy (inspection using a thin tube called an arthroscope).
• A few anatomical variations not previously described were identified, including in the layers of the medial aspect (inside edge) of the carpus’s fascia (a band of connective tissue).
• These findings provide valuable knowledge about the variations in the appearance of the carpus in horses which aren’t lame, which can assist in interpreting MR images of horses that are suffering lameness.