When wounds won’t heal

To help fig­ure out why some equine cuts, scrapes and lac­er­a­tions fail to mend, an in­ter­na­tional wound-care ex­pert has com­piled a list of the top 12 heal­ing in­hibitors.

EQUUS - - Equus - By Chris­tine Barakat

To help fig­ure out why some equine cuts, scrapes and lac­er­a­tions fail to mend, an in­ter­na­tional wound-care ex­pert has com­piled a list of the top 12 heal­ing in­hibitors.

For fa­mil­iarhorse most sus­tainedof sce­nario:us, it’s a a Your wound­for your nasty ve­teri­nar­ian enough to come out and tend. It’s been cleaned and de­brided, and now all that re­mains is the daily rou­tine of ban­dage changes. But ev­ery time you go about the task of re­mov­ing the old dress­ing and put­ting on the new, you scru­ti­nize the wound. Is the red­dish color around the edges a sign of trou­ble? Where did that fluid ooz­ing out of the

cor­ner come from? Is this wound heal­ing nor­mally? Take heart. The odds---and bi­ol­ogy ---are on your side. The vast ma­jor­ity of equine wounds, both ma­jor and mi­nor, heal well and rel­a­tively quickly. “There’s no evo­lu­tion­ary ad­van­tage to a wound that doesn’t heal,” says Derek Knot­ten­belt, BVM&S, PhD, DipECEIM. “They want to heal if they can. And most of them do, with very lit­tle in­ter­ven­tion from us.” Knot­ten­belt would know: He is one of the fore­most vet­eri­nary author­i­ties on equine wound heal­ing, hav­ing lit­er­ally writ­ten the book Wound hun­dred­son Man­age­ment---the of topic---cases around Hand­bookand the con­sultedof globe. Equine on taught And hi­mall thatan im­por­tant ex­pe­ri­ence, les­son:he says, “When­has a wound doesn’t heal promptly there’s al­ways a rea­son, and un­til you fig­ure out and ad­dress that rea­son, it never will heal,” says Knot­ten­belt. “Fig­ure it out and cor­rect it, and then the horse’s body takes over and does a re­mark­able job and you can take all the credit.” In fact, Knot­ten­belt has seen so many wound-heal­ing prob­lems that he’s stream­lined the in­ves­tiga­tive process, a check­list. ul­ti­mately“It’s a pretty com­ing fa­mousup with list, ac­tu­ally, among those of us who deal in these things,” he says. “It’s the 12 in­hibitors of wound heal­ing. If I’m faced with a wound that isn’t heal­ing, I go down this list and tick them off, look­ing for each. Any owner or ve­teri­nar­ian can do the same. It may be just one that’s the prob­lem or it may be three or four, but if you iden­tify and cor­rect them, I can as­sure you the wound will heal.” Here is Knot­ten­belt’s list of fac­tors that stop wounds from heal­ing.


Of­ten sig­naled by red, an­gry-look­ing tis­sue that ex­udes pus or has a foul odor, in­fec­tion is the most com­mon rea­son that wounds don’t heal, says Knot­ten­belt, but it’s one of the eas­i­est to rem­edy if you go about it in the right way.

“The in­cli­na­tion among own­ers and some ve­teri­nar­i­ans is to reach for an an­tibi­otic to com­bat in­fec­tion, but that’s not the cor­rect ap­proach,” Knot­ten­belt says. “Wounds be­come in­fected for a rea­son, and you have to fig­ure out why as you be­gin treat­ment or you aren’t go­ing to be suc­cess­ful with med­i­ca­tions alone.”

Some causes of wound in­fec­tions, such as con­tam­i­na­tion or re­duced im­mune func­tion, are found else­where on this list. Others are more sub­tle: “A good ex­am­ple is the pH of the wound. In­fec­tion loves a very high pH wound,” says Knot­ten­belt. “If you can make the wound slightly more acidic, no bac­te­ria can sur­vive that. What you’ve got to do is find out why the wound is al­ka­line. A ve­teri­nar­ian ex­pe­ri­enced in wound heal­ing will know to check for this and how to cor­rect it.”

Sys­temic an­tibi­otics aren’t very ef­fec­tive against wound in­fec­tions, he says: “We all give horses an­tibi­otic in­jec­tions as we are treat­ing wounds as a pre­ven­tive, but if in­fec­tion sets into a wound, the treat­ment needs to be very lo­cal­ized. An­tibi­otics cir­cu­lat­ing in the blood aren’t likely to make it to the wound site in suf­fi­cient lev­els to be ef­fec­tive at that stage.”

Grab­bing a tube of an­tibi­otic cream isn’t al­ways the an­swer ei­ther, he adds: “I’m no fan of put­ting an­tibi­otics on the sur­face of wounds. For starters, they can be dam­ag­ing to tis­sues, de­stroy­ing the very cells you are try­ing to pro­tect. If I’m go­ing to use an oint­ment to kill an in­fec­tion in a wound, I do it know­ing that I’m also go­ing to harm tis­sues, but I’m at the point when I have no choice.” A bet­ter ap­proach, he says, is a thor­ough clean­ing of an in­fected wound to re­move de­bris, dead tis­sue and re­duce the num­ber of bac­te­ria.


Any­thing in­side a wound that shouldn’t be there counts as a for­eign body, in­clud­ing wood splin­ters, dirt, grass and bone frag­ments. The horse’s body will try to ex­pel the ma­te­rial over time, and may ul­ti­mately be suc­cess­ful, but wound heal­ing can’t con­tinue un­til that hap­pens.

“Nearly ev­ery ve­teri­nar­ian has dealt with a wound that just sits there for a long time and dis­charges pus with­out heal­ing,” says Knot­ten­belt. “It can be baf­fling un­til we take an x-ray and see a bit of wire em­bed­ded in the tis­sue. Re­move that and it heals up quickly and com­pletely.”

Knot­ten­belt says that some for­eign bod­ies in wounds cause more prob­lems than others. For starters, not all ma­te­ri­als ap­pear on an x-ray, so a vis­ual in­spec­tion or sur­gi­cal ex­plo­ration of a wound is some­times nec­es­sary to rule out for­eign body con­tam­i­na­tion. And some ma­te­ri­als are more likely to wreak havoc within the tis­sue. “A bit of glass isn’t go­ing to har­bor in­fec­tion as much as, say, a piece of soil or cloth that’s been pushed into the wound,” he says. Some for­eign bod­ies sim­ply de­lay heal­ing un­til the body can eject them; others can lead to a cas­cade of in­fec­tion and greater com­pli­ca­tions. But re­gard­less of what it is, once the ma­te­rial is re­moved or ex­pelled from the wound, the heal­ing starts right back up again.

Some for­eign bod­ies sim­ply de­lay heal­ing un­til the body can eject them; others can lead to a cas­cade of in­fec­tion and greater com­pli­ca­tions. “Wounds be­come in­fected for a rea­son, and you have to fig­ure out why as you be­gin treat­ment or you aren’t go­ing to be suc­cess­ful with med­i­ca­tions alone,” says Derek Knot­ten­belt, BVM&S, PhD.


The nat­u­ral heal­ing process has dis­tinct phases (see “How Wounds Heal,” page 28). With­out ad­e­quate healthy tis­sue within the wound to serve as a foun­da­tion, how­ever, one or more phases may be de­layed or never oc­cur.

“If you’ve got a tis­sue deficit, there may not be enough of a bi­o­log­i­cal foun­da­tion for new tis­sue to form over,” says Knot­ten­belt. “And, if you’ve got a huge wound left to heal by sec­ond in­ten­tion (with­out stitches) it may stay open for­ever.” The so­lu­tion, he says, it to pro­vide what the body can­not.

“For in­stance,” says Knot­ten­belt, “there are new high-tech wound dress­ings that cre­ate a bi­o­logic scaf­fold of sorts, us­ing col­la­gen or am­nion or in­testines from other an­i­mals, that pro­vide the miss­ing foun­da­tion and al­low tis­sue to be­gin to fill in and even­tu­ally de­velop a very nor­mal ap­pear­ance. These can be in­cred­i­bly help­ful with larger wounds that might not ever close on their own.” Your ve­teri­nar­ian will be fa­mil­iar with

these op­tions.


Tis­sue that doesn’t re­main still can­not re­pair it­self, so wounds on a high­mo­tion area of the body may be slow to heal or not heal at all.

“If the wound is over a fet­lock, it’s easy to see how it will move with each step,” says Knot­ten­belt, “but the same thing can oc­cur with a deep wound on the back from the move­ment of the mus­cles un­der­neath it. You may not see it on the sur­face, but it’s just as dam­ag­ing.”

The so­lu­tion is to im­mo­bi­lize the area, which can be done through a va­ri­ety of meth­ods. “Keep­ing the horse in a stall might be enough, but of­ten­times you need to do more,” says Knot­ten­belt. “We do a lot of casts for wounds on the feet. If a horse cuts his heel bulb, tis­sue in that area is go­ing to move with ev­ery step. So we put a cast on the limb to ad­dress that move­ment and when we take the cast off 10 days later, it’s stag­ger­ing how well it has done. Some ar­eas of the body are very dif­fi­cult or im­pos­si­ble to keep still---“you can’t im­mo­bi­lize a tongue,” says Knot­ten­belt---but stall rests and splints can solve the prob­lem for

many lo­ca­tions.


Dead tis­sue within a wound will bring heal­ing to a stand­still, typ­i­cally by in­duc­ing in­fec­tion. A ve­teri­nar­ian deal­ing with a fresh wound will de­bride it dur­ing the ini­tial treat­ment, re­mov­ing tis­sue that is al­ready dead or likely to die quickly. In smaller wounds, you can do the same thing with co­pi­ous flush­ing with wa­ter or sa­line so­lu­tion. But that ini­tial cleanup is not al­ways enough.

“Tis­sue can die within a wound days, weeks or even months after the ini­tial in­jury,” says Knot­ten­belt. “It doesn’t mean the wound was treated poorly. The death of tis­sues is some­times a nat­u­ral part of the heal­ing process.” The only so­lu­tion at that point is to vis­ually in­spect he wound, iden­tify the dead tis­sue and flush or cut it away.

“We typ­i­cally cut it back un­til we see bleed­ing,” says Knot­ten­belt. “Tis­sue with a blood sup­ply is alive, so we as­sume that’s where the necrotic tis­sue ends. We might have to do this a few times be­fore the wound heals.”


Blood brings to the wound site the con­stituents es­sen­tial to heal­ing. With­out ad­e­quate cir­cu­la­tion, tis­sue re­pair fails. “If an artery is oc­cluded [blocked], ev­ery­thing down the line to that can be af­fected,” says Knot­ten­belt, adding that bleed­ing is an in­di­ca­tor of an ad­e­quate blood sup­ply and a ve­teri­nar­ian mak­ing a close vis­ual in­spec­tion can usu­ally iden­tify poor cir­cu­la­tion.

You might think that poor blood sup­ply would cause the de­vel­op­ment of proud flesh---the over­growth of gran­u­la­tion tis­sue that pre­vents ep­ithe­lial­iza­tion of a wound---but that’s not so, says Knot­ten­belt. “It is a fal­lacy that proud flesh de­vel­ops from a lim­ited blood sup­ply,” he says. “There is this idea that lower limbs have re­duced blood flow, so proud flesh is likely to de­velop there. The legs have plenty of blood flow, oth­er­wise they’d fall off. And you can see the blood sup­ply right in the proud flesh if you cut it.” Knot­ten­belt says proud flesh de­vel­ops be­cause heal­ing has stalled due to some other fac­tor on his list.


Wounds re­quire oxy­gen to heal, and they re­ceive that through two routes: The air sur­round­ing the wound and he­mo­glo­bin in the blood sup­ply. “A wound lack­ing oxy­gen, from ei­ther source, will look pur­ple,” says Knot­ten­belt. “A ve­teri­nar­ian will be able to see that. It doesn’t look like a good, healthy wound.”

Leav­ing a wound un­cov­ered can ex­pose it to more oxy­gen, of course, but cov­er­ing it may ac­tu­ally be bet­ter. “If you put a semi-oc­clu­sive dress­ing over a wound, you cut off the oxy­gen it re­ceives from the air,” ex­plains Knot­ten­belt, “but the blood­stream will be­gin to bring in more oxy­gen to com­pen­sate for that and it gets de­liv­ered to the deep­est heal­ing tis­sues, not just those on the sur­face, and in a higher con­cen­tra­tion.”

Knot­ten­belt says that ane­mic horses or those who are oth­er­wise ill may not have the red blood cell vol­ume to de­liver enough oxy­gen, even with this tech­nique, and a ve­teri­nar­ian might try some­thing a bit more dra­matic. “Hyper­baric cham­bers have been used as a means of de­liv­er­ing con­cen­trated lev­els of oxy­gen to slow-heal­ing wounds,” he says. “The horse is placed in a chamber full of con­cen­trated oxy­gen for a par­tic­u­lar length of time each day. These cham­bers do seem to in­crease the rate of heal­ing, but it’s un­clear by just how much.”


A wound that is con­tin­u­ally ag­gra­vated ---by rub­bing tack, chew­ing by the horse or tight ban­dages, for in­stance---will not heal. “This is very com­mon with foot wounds,” says Knot­ten­belt, “par­tic­u­larly wounds to the heel bulb, where the horse may step on it with an­other foot, re­open­ing the en­tire area. Even thick, strong grass can cause enough trauma to wounds on the lower limb to keep them from heal­ing.”

The so­lu­tion is sim­ple enough: Iden­tify and stop the re­peated trauma and the wound will heal. This may mean giv­ing the horse some time off from un­der-sad­dle work, us­ing a neck cra­dle to keep him from fuss­ing with the wound or us­ing a dif­fer­ent ban­dag­ing tech­nique. “Once you stop the trauma, these wounds tend to heal very quickly,” says Knot­ten­belt.


This cat­e­gory of heal­ing in­ter­rupters in­cludes con­di­tions im­me­di­ately in and around the wound. “For in­stance,” says Knot­ten­belt, “a wound may not heal in a very cold or a very hot en­vi­ron­ment ---cells don’t func­tion well in ei­ther of these. Very wet or a very dry con­di­tions can af­fect heal­ing. A wound may not heal if there is pock­et­ing in the tis­sues.” To iden­tify these con­di­tions, a ve­teri­nar­ian will have to look at the big­ger pic­ture and be a bit cre­ative with so­lu­tions.

“You may need to pro­tect the wound with ban­dag­ing---most do well with moist, warm dress­ings---or you may need to move the horse to a less se­vere en­vi­ron­ment,” says Knot­ten­belt. Or, the ve­teri­nar­ian may have to al­ter the wound it­self, re­mov­ing tis­sue to elim­i­nate pock­ets or un­even tis­sue beds.


The gen­eral health sta­tus of a horse can in­flu­ence how his wounds heal. “Cush­ing’s dis­ease is the clas­sic ex­am­ple,” says Knot­ten­belt. “Those horses have low­ered im­mune func­tion, so wounds may be slow to heal or prone to in­fec­tion. A horse on steroid med­i­ca­tions or one with a dis­ease like lym­phoma could have sim­i­lar is­sues.”

In less-de­vel­oped ar­eas of the world, poor nutri­tion can also lead to de­layed wound heal­ing, says Knot­ten­belt. “This isn’t as much of an is­sue ex­cept in Third World coun­tries, but be sure that you are feed­ing a horse prop­erly when he has a heal­ing wound. Make sure he’s get­ting enough pro­tein in his diet. That’s what his body will be us­ing to cre­ate new tis­sue.”


This cat­e­gory, Knot­ten­belt says, boils down to “stupid things peo­ple put on their horse’s wounds” and ranges from un­nec­es­sary com­mer­cial prod­ucts to harm­ful home­made prepa­ra­tions.

“The huge ma­jor­ity of equine wounds do just fine with a thor­ough flush­ing with warm wa­ter or sa­line and then be­ing cov­ered with a sim­ple hy­dro­gel ban­dage,” he says. For first aid treat­ments, he says hy­dro­gel dress­ings, which con­tain a wa­ter-based gel that keeps wounds at an op­ti­mal mois­ture level, can be help­ful, as can hy­dro­gel prepa­ra­tions that pro­tect wounds with­out ban­dages. “Wounds need noth­ing else,” he says. “Horses have a rep­u­ta­tion for wounds that don’t heal and I’m cer­tain it’s be­cause of the ridicu­lous salves own­ers and even some ve­teri­nar­i­ans will put in the wounds.”

Like­wise, says Knot­ten­belt, wounds don’t need phys­i­cal help heal­ing. “Don’t scrub wounds that are heal­ing just fine,” he says, “and don’t pull scabs off. They are there for a rea­son and keep scar­ring to a min­i­mum.”


When the tis­sue in­side a wound de­vel­ops tu­mors, heal­ing stops and man­ag­ing the case can be very chal­leng­ing.

“Sar­coids can de­velop deep in­side wounds,” says Knot­ten­belt. “If the horse has a sar­coid some­where else on his body, it’s easy for those cells to be trans­ferred to the wound by flies. Then you have a sar­coid in the wound and it’s a very se­ri­ous situation that has to be rec­og­nized and dealt with quickly.” Of­ten­times, he says, the form­ing sar­coid is mis­taken for proud flesh and own­ers de­lay call­ing the ve­teri­nar­ian or at­tempt to treat it them­selves, mak­ing the situation worse.

“If you com­pare two wounds, one with proud flesh and one with a sar­coid, they can look iden­ti­cal, but the treat­ments are di­a­met­ri­cally op­po­site,” he says. “You need to treat the tu­mor with cancer drugs; if you try to cut it out like proud flesh, you’re go­ing to make it worse. I be­lieve ve­teri­nar­i­ans should do pathol­ogy on ev­ery sus­pected case of proud flesh to en­sure it’s not a tu­mor.”

If you com­pare two wounds, one with proud flesh and one with a sar­coid, they can look iden­ti­cal, but the treat­ments are di­a­met­ri­cally op­po­site.

CLEANUP: To aid heal­ing, a ve­teri­nar­ian may de­bride the wound, re­mov­ing dead or dam­aged tis­sue.

Con­tin­ued trauma is com­mon in foot wounds, says Derek Knot­ten­belt, BVM&S, PhD, “par­tic­u­larly wounds to the heel, where the horse may step on it with an­other foot, re­open­ing the en­tire area.”

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