Proximal suspensory desmitis is a common injury in equine athletes. It can affect both the front limbs and the hindlimbs, but it is most often seen in the front legs of Thoroughbred racehorses, according to Dr. Rick Arthur, a veterinarian who practices at Southern California tracks. The condition also is known as high suspensory disease because it occurs in the upper portion of the ligament.
"When you are dealing with young Thoroughbred horses early in their careers, they'll come up very marginally sore in a forelimb," said Arthur, who participated in a panel discussion about proximal suspensory desmitis during the recent American Association of Equine Practitioners' convention (The Blood-Horse of Dec. 9, page 7868). "Generally, it (the soreness) is bilateral, and it is very, very difficult to differentiate from third carpal bone changes, which also are very common and also start occurring at this particular time.
"We may use some low-level nonsteroidal anti-inflammatories, generally staying away from steroidal anti-inflammatories," he continued. "If they don't have serious lesions in their suspensory ligament on ultrasound, we will try to train them, to train through it. Basically, we modify their training. We also make sure they are shod properly, and they don't have toe grabs on. Sometimes, if we can, we'll stop and give the horse time to grow up."
In older horses, when the injury reoccurs, Arthur said he will try to keep them in training by using both steroidal and anti-steroidal anti-inflammatory medications. Such horses, according to Arthur, often will perform well, but will need extra time to rest after they work or race "to get sound again."
"When the lesion starts getting quite large, and the horse becomes very sore after a hard work or a race, they don't run well and you probably are just wasting your time," said Arthur, who is a former AAEP president. "The good part about this is that horses do not break down with proximal suspensory desmitis. In California's necropsy program, there has never been a horse that has died of a proximal suspensory desmitis rupture--at least that was the case the last time I talked to anybody (involved in the program) about it."
New treatments for proximal suspensory desmitis include extracorporeal shock wave therapy (ESWT). But Arthur expressed some caution about using the experimental technology, even though it showed promise as a way to deal with suspensory problems in a German study that was presented during the AAEP convention.
"In my limited experience, it did not change the lesion ultrasonographically, but the filly did 'go' better," Arthur said. "The most worrisome aspect, particularly for someone who practices on the racetrack, is that the filly actually went as sound as she does when I block her. I jogged her a couple hours after the procedure, and she stayed that way (sound) for two or three days after the procedure. There is a very profound analgesia in the area that you treat, which I think makes it (ESWT) a cause for concern in performing horses immediately after a procedure. You wouldn't ordinarily intend to do that (race a horse then), but I think it is a potential area of abuse."
The panel discussion also included a report on another new treatment for proximal suspensory desmitis, bone marrow injection, which was developed by Dr. Doug Herthel of the Alamo Pintado Equine Medical Center in Los Olivos, Calif. The procedure involves drawing blood marrow from the injured horse's sternum and injecting it into the affected limbs. Approximately 85% of horses with chronic proximal suspensory desmitis that receive bone marrow injections return to their previous level of function, according to Dr. Mark Rick of Alamo Pintado. He said patients primarily have included horses involved in dressage, jumping, hunting, polo, and Western activities.
In an interview following the convention, Herthel said bone marrow injection also is being used on racehorses. The results have been good, he reported, but it is too soon in Alamo Pintado's research process to talk about the percentage of success. The procedure also has shown promise as a treatment for bowed tendons.