Coping with osteochondroma

Q:I adopted a just-retired 5-year-old Thoroughbred racehorse gelding two months ago. Upon arrival, he was faintly lame in the left fore when trotted on pavement, and he had a soft swelling running down the inside of his left front suspensory ligament.

After ultrasound and radiography, he was diagnosed with a solitary osteochondroma of the distal radius. The osteochondroma has the peaked shape of a shark’s tooth, and has damaged his superior check ligament and deep digital flexor tendon.

Fluid was drained from the back of my horse’s knee, and he was given two platelet-rich plasma injections two weeks apart. He was confined to a stall, then to a small pen that does not give him space to run, and he was walked once a day for 10 to 20 minutes.

A second ultrasound after one month found improvement in the tissues, and he was sound at the trot. I was advised to keep him on a graduated walking schedule, beginning at five minutes twice a day and increasing by five minutes a week to 45 minutes two to three times a day. The horse remains sound at the trot, and he is still confined to a pen. The filling in the leg, though, continues, with no apparent relationship to his activity. There are days when it is virtually nonexistent and days when it is quite marked.

My veterinarian doesn’t want to try surgery to remove the osteochondroma as long as the horse trots sound, because he feels it’s too likely that surgery would

leave the horse lame. But the fact that he is not lame when briefly trotted, and otherwise almost totally inactive, is not that reassuring to me, especially since at times he shows a lot of swelling. My concern is that the fluid must indicate continuing irritation, and as long as the osteochondroma remains, any significant activity will lacerate the tissues.

How risky is osteochondroma surgery, and how concerning is it that the filling in the leg continues when there is no lameness?

Name withheld upon request

A:Without examining your horse myself, I am going to answer on the assumption that the diagnosis and other details of this case are correct. The description of the signs is consistent with osteochondroma, but of course, many orthopedic issues can look similar.

An osteochondroma is an overgrowth of bone and cartilage that protrudes above the normal bone surface.

Osteochondromas are fairly rare in horses. When they do occur, the back of the lower radius, just above the horse’s knee, is a common site.

These noncancerous tumors are harmless by themselves, but depending on their location, they may cause lameness if they either interfere with movement or if they injure tendons or other soft structures in the vicinity.

Osteochondromas are fairly rare in horses. When they do occur, the back of the lower radius, just above the horse’s knee, is a common site. Some horses may have multiple lesions, which are thought to have a hereditary link.

In addition to lameness, signs of

osteochondroma include a bony lump that can be felt under the skin and can be associated with warmth and swelling in the affected area. When diagnosed, osteochondromas that do not interfere with vital structures or cause clinical signs may be left alone, but surgical removal of the excess growth is recommended when they are causing lameness. The surgical correction of the problem described here is a relatively straightforward and safe arthroscopic procedure. The outcomes of the procedures I have performed have been very successful, which means that 80 to 90 percent of the horses I treated returned to their previous work.

In this case I, too, would be concerned that if the surgery is not performed, the osteochondroma would continue to cause further injury to your horse’s deep digital flexor tendon, and that lameness would return, once he resumes a normal level of activity. David Frisbie, DVM, PhD Colorado State University Fort Collins, Colorado