When your horse is lame, a diagnosis of suspensory trouble can be discouraging, particularly if it’s termed proximal suspensory desmitis (PSD). Inflammation of the upper suspensory ligament in this area can be tough and expensive to treat successfully, particularly in the hind limbs. Why? Because not all PSD cases are accurately diagnosed with common diagnostic methods and, thus, are not effectively treated, according to new research presented at the American College of Veterinary Surgeons meeting on Oct. 20.

Proximal suspensory desmitis is usually diagnosed with nerve blocks to localize the pain followed by radiographic and ultrasonographic examination to visualize lesions and guide treatment. However, Rich Redding, DVM, MS, Dipl. ACVS, clinical associate professor of equine surgery at North Carolina State University (NCSU) and lead author on the study, found that ultrasound was only accurate in diagnosing PSD in 43% of the horses that MRI confirmed as having PSD. The study used MRI as the “gold standard” for PSD diagnosis in horses that had pain localized to the proximal suspensory region.

“MRI shows that just because you block pain that originates in this region, you don’t necessarily have a problem in the suspensory ligament,” he explained.

MRI on 25 anesthetized horses showed that six (24%) had primary PSD without bony lesions (the “typical” PSD case), seven (28%) had PSD with co-existent bony lesions, while eight horses (32%) had only bony lesions in that area, and the other four (16%) had no focal suspensory lesions (just adhesions and mild enlargement).

Redding explained that if the diagnosis is inaccurate, expensive treatment might be directed incorrectly. Obviously, this reduces the horse’s chance of a successful return to performance as it might be a little like putting a Band-Aid on a broken arm, or a splint on a cut–it’s just not what that injury needs to heal.

“It’s relatively expensive to do an MRI (about $2,700 at NCSU for PSD examination, which includes anesthesia and evaluation of paired front or hind limbs), but you need to know what the diagnosis is before you initiate treatment,” he commented. Diagnosing PSD based on nerve blocks and ultrasonography alone is unreliable, he concluded.