Fractures of the Small Tarsal Bones in Horses

Fractures of the central and third tarsal bones (see central tarsal bone fracture images) occur most commonly in Standardbred or Thoroughbred racehorses, but they can also occur in other horse breeds and during other high-speed disciplines. Fracture of the third tarsal bone is more common. These fractures most often occur as a result of trauma to an already sclerotic tarsal bone. However, horses with wedging of the tarsal bones from incomplete ossification as a foal seem to be more predisposed to such fractures.

Fracture, central tarsal bone, CT images, horse

Image

Courtesy of Dr. Hilary Rice.

In racehorses, fractures of the small tarsal bones typically present as slab fractures in the dorsal plane of the central and third tarsal bones. In warmblood breeds and nonracehorses, a more sagittal orientation of central tarsal bone fractures has been described. These fractures usually cause acute-onset severe hindlimb lameness that diminishes over time.

Lameness resulting from fractures of small tarsal bones is exacerbated by hock flexion, and persistent tarsocrural joint effusion is typically present when the central tarsal bone is involved. intra-articular analgesia of the tarsocrural joint typically resolves the lameness when central tarsal bone fractures are present.

Diagnosis of fractures of the small tarsal bones is based on standard radiographic views of the tarsus; however, multiple oblique projections can be required for accurate diagnosis. When radiography is not sensitive enough to diagnose a fracture, nuclear scintigraphy can be useful in confirming the presence of a fracture in the small tarsal bones.

CT and MRI provide better images for the evaluation of fracture lines in small tarsal bones, because these fractures can occasionally be comminuted. The use of CT for preoperative planning is essential to ensure adequate diagnosis and fracture assessment. The treatment of choice to maintain the horse's athletic function is fixation of the fracture with one or two screws placed in lag fashion.

When surgical repair is not an option, conservative management, including stall rest and controlled exercise, may be considered; however, it carries a higher risk for the development of osteoarthritis.