Cop­ing with osteochondroma

EQUUS - - Consultants -

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

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