MRI To Evaluate Suspensory, Sesamoid Injuries

Since its inception in the 1930s, the inaugural patent in 1974, and the successful construction of the world’s first whole-body scanner by 1977, magnetic resonance imaging (MRI) has become an indomitable tool in both human and equine medicine. Today, equine practitioners use MRI extensively to help diagnose even the most subtle lameness causes.

“One region of the horse’s body that is a common site for injury is the lower (distal) aspect of the suspensory ligament near the fetlock joint,” explained Alexander Daniel, MRCVS, from Colorado State University’s Veterinary Teaching Hospital, during the 2012 American Association of Equine Practitioners’ (AAEP) convention, held Dec. 1-5 in Anaheim, Calif.

The suspensory ligament originates near the top of the cannon bone at the back of the carpus (knee) and hock, travels down the back of the leg, and splits into two branches—the medial and lateral branches—before each branch inserts onto a sesamoid bone.

“It is known that injury to the suspensory ligament near the fetlock can occur either in isolation or combination with injury to the one or both sesamoid bones,” Daniel said.

What wasn’t known was whether the suspensory ligament’s size or position changed following injury to the sesamoid bone(s). To explore this issue, Daniel and colleagues from the Alamo Pintado Equine Medical Center, in Los Olivos, Calif., reviewed the MRI scans of 26 horses diagnosed with injury to one branch of the suspensory ligament near the fetlock joint (either forelimb or hind limb) after veterinarians had localized lameness to that region.

“We found that the dimensions of the suspensory ligament injury measured on MRI were different between horses that did or did not have concurrent sesamoid bone issues,” relayed Daniel.

This means that the cross area of the suspensory ligament was significantly larger in horses that had injury/damage to the sesamoid bone compared to the area of the ligament in horses without sesamoid bone injuries.

Although the authors were unable to relay specific dimensions (those data will be available upon publication of the full-length article), the researchers suggested that MRI was an invaluable diagnostic tool for identifying suspensory ligament lesions in the fetlock as well as sesamoid bone damage.

Some veterinarians will not pursue MRI for horses with suspensory and/or sesamoid bone injuries, whether it’s about cost or, simply, access to a unit. In such cases, Daniel advised veterinarians to complete a detailed evaluation using radiographs and ultrasound.