Tricky X-Rays

The im­ages ap­pear in black and white, but answers lie in shades of gray. Learn why your horse’s ra­dio­graphs may mean dif­fer­ent things to dif­fer­ent peo­ple.

Horse & Rider - - Table Of Contents - By Barb Crabbe, DVM

Iwas re­cently asked to eval­u­ate a set of ra­dio­graphs for a client pur­chas­ing a (very ex­pen­sive) horse. “Ev­ery­thing is great,” the seller had told her. Need­less to say, she and I were both sur­prised to see a large bone frag­ment right in the mid­dle of the horse’s hock. Was the horse OK? Maybe. Did my client want to take the risk with her hard­earned cash? No way. So why did the seller and her ve­teri­nar­ian think that chip was “no big deal,” yet my client and I felt dif­fer­ently? Ra­dio­graphic find­ings aren’t al­ways 100-per­cent ac­cu­rate or pre­dictable, and de­pend­ing on whether you’re the seller, buyer, or sim­ply an owner try­ing to make a de­ci­sion about your horse’s fu­ture, your per­spec­tive might be dif­fer­ent.

In this ar­ti­cle, I’ll ex­plain why ra­dio­graphs aren’t as black and white as they might seem. I’ll start by ex­plain­ing fac­tors that make it dif­fi­cult to de­ter­mine whether some­thing we think we see on ra­dio­graphs is re­ally there, and how we can de­ter­mine if it’s real. Then, I’ll de­tail why even some­thing real might not be all that sig­nif­i­cant. Fi­nally, I’ll of­fer real-life ex­am­ples to help you un­der­stand why a find­ing on a ra­dio­graph might seem in­signif­i­cant in one sit­u­a­tion, and im­por­tant in an­other.

Is It Real? Or Is It…

The first thing your ve­teri­nar­ian asks when she sees some­thing ques­tion­able on a ra­dio­graph is “is it real, or is it just an ar­ti­fact?” An ar­ti­fact is some­thing that ap­pears on the im­age, but doesn’t re­ally cor­re­spond with the un­der­ly­ing anatomy. In some sit­u­a­tions, an ar­ti­fact can be some­thing that’s re­ally there, like a speck of dirt on your horse’s hair or a small piece of a horse­shoe nail. De­pend­ing on the lo­ca­tion, these types of things can eas­ily be mis­taken for a bone frag­ment or cal­ci­fied soft tis­sue. In oth­ers cases, an ar­ti­fact is more an er­ror in per­cep­tion, such as an over­lap­ping line that ap­pears be­tween two bones that could be mis­taken for a frac­ture. Fi­nally, ar­ti­facts can be the re­sult of equip­ment mal­func­tion—such as a “ghost im­age” that shows up on the screen un­der­ly­ing the cur­rent im­age.

How does your vet iden­tify an ar­ti­fact? Of­ten, it’s a ques­tion of re­peat­ing a ra­dio­graph af­ter brush­ing off the skin or repo­si­tion­ing the leg to see if the ar­ti­fact dis­ap­pears. If your vet still can’t de­cide, she might opt to send films to a board-cer­ti­fied ra­di­ol­o­gist for re­view. Ve­teri­nary ra­di­ol­o­gists spend years in train­ing, and much of their time re­view­ing ra­dio­graphs. They’re highly skilled at read­ing ra­dio­graphs. Even sur­geons and vet­eri­nar­i­ans who spe­cial­ize in lame­ness rely on ra­di­ol­o­gists to help de­ci­pher ques­tion­able find­ings. Of­ten, a ra­di­ol­o­gist can ex­plain what your vet is see­ing or of­fer a sug­ges­tion to help eliminate the ar­ti­fact with a unique view or ex­po­sure.

Is It the Prob­lem?

Once your ve­teri­nar­ian de­ter­mines that a ra­dio­graphic find­ing is real, she next ex­plores what’s caus­ing a prob­lem. We’ve all seen horses that have a chip in a hock or fet­lock, yet stay com­pletely sound for their en­tire ca­reer. How does that hap­pen? Chances are the chip is buried in the soft tis­sues away from the joint and never causes any dam­age. This is es­pe­cially im­por­tant if that chip gets blamed for your horse’s lame­ness when it’s re­ally some­thing else, be­cause in that case your treat­ment isn’t likely to be suc­cess­ful. For ex­am­ple, if your horse strains his sus­pen­sory lig­a­ment and your vet iden­ti­fies a

bone chip in his fet­lock, sur­gi­cal re­moval of that chip won’t solve your prob­lem.

In some sit­u­a­tions, sub­tleties in the ap­pear­ance of the ra­dio­graph can help de­ter­mine whether a find­ing is sig­nif­i­cant. For ex­am­ple, if your horse comes up sud­denly ex­tremely lame, a bone frag­ment iden­ti­fied in the ra­dio­graph that’s rounded and smooth is likely old and not the source of the sud­den lame­ness. If it’s jagged and fresh-look­ing, how­ever, there’s a good chance it’s the cul­prit. If your vet’s un­sure, a ra­di­ol­o­gist’s re­view of im­ages can help your vet eval­u­ate these sub­tleties.

In other sit­u­a­tions, ad­di­tional di­ag­nos­tic tests can help de­ter­mine the sig­nif­i­cance of a ra­dio­graphic ab­nor­mal­ity, be­gin­ning with a clin­i­cal exam and di­ag­nos­tic blocks. If your horse is lame, your vet prob­a­bly de­cided what area to ra­dio­graph based on the re­sults of an ex­am­i­na­tion, and blocks can be es­pe­cially help­ful. When your vet blocks your horse, she’ll in­ject a lo­cal anes­thetic sub­stance into nerves sup­ply­ing an area, or di­rectly into a joint or other en­closed struc­ture. If your horse’s lame­ness dis­ap­pears when a spe­cific area is blocked, it helps your vet to lo­cal­ize the source of lame­ness. Let’s take the ex­am­ple of the fet­lock chip in the horse with a lig­a­ment in­jury. If that horse con­tin­ues to be lame af­ter lo­cal anes­thetic has been injected into his fet­lock joint, chances are that chip is not the rea­son for the lame­ness. Your vet will con­tinue to in­ves­ti­gate. If, how­ever, the block re­solves the lame­ness, the chip might be wor­thy of more at­ten­tion.

In other sce­nar­ios, the ques­tion might be whether a ra­dio­graphic find­ing is ac­tive or quiet. A ra­di­ol­o­gist may be able to shed some light on whether some­thing seen on ra­dio­graphs ap­pears ac­tively in­flamed. If it’s still a ques­tion, a bone scan can pro­vide the an­swer. For a bone scan, your horse will have a ra­dioac­tive sub­stance injected into his blood­stream. Be­cause ac­tive in­flam­ma­tion means in­creased blood flow, an in­flamed area will ac­cu­mu­late ra­dioac­tiv­ity that can be de­tected with a spe­cial cam­era. For ex­am­ple, if your horse has ra­dio­graphic ev­i­dence of arthri­tis in his hocks and de­vel­ops a sud­den hind-limb lame­ness, your vet might ques­tion whether the arthri­tis re­ally is to blame. And be­cause the hind sus­pen­sory lig­a­ment orig­i­nates just be­low the hocks, re­sults or di­ag­nos­tic blocks of that area can be un­clear. Add that hock in­jec­tions can ac­tu­ally in­crease the risk of mak­ing a sus­pen­sory in­jury worse, and you see that it’s es­pe­cially im­por­tant to make an ac­cu­rate di­ag­no­sis. A bone scan can tell you that the hock joints are quiet and un­likely to be caus­ing the lame­ness. It might even show ac­tiv­ity at the ori­gin of the sus­pen­sory lig­a­ment, con­firm­ing that to be the more likely un­der­ly­ing cause of your horse’s lame­ness.

The take-home mes­sage here is just be­cause there’s some­thing on a ra­dio­graph, it doesn’t guar­an­tee it’s caus­ing lame­ness. It’s im­por­tant to con­sider all the fac­tors when mak­ing a di­ag­no­sis—es­pe­cially if you want your treat­ment to be suc­cess­ful.

The Crys­tal Ball

Fi­nally comes the hard­est ques­tion of all: What does an in­ci­den­tal find­ing on a ra­dio­graph mean for the horse’s fu­ture? A num­ber of fac­tors come into play, and so an in­ci­den­tal find­ing is likely the sit­u­a­tion that causes the most dis­agree­ment be­tween buyer and seller re­gard­ing sig­nif­i­cance of the is­sue.

As a gen­eral rule, the horse’s age and work his­tory pro­vide the best in­for­ma­tion you can get about the po­ten­tial im­pact of an in­ci­den­tal find­ing on a ra­dio­graph taken of a per­fectly sound horse. If you’re con­sid­er­ing an older horse that’s in full work and has been per­form­ing his job with no un­sound­ness for years, there’s a good chance he’ll con­tinue to stay sound as long as his de­mands don’t change. If the horse is young and hasn’t been in work for very long, how­ever, the risks that some­thing might cause a prob­lem in the fu­ture will in­crease.

Let’s go back to our ex­am­ple of the chip in the horse’s fet­lock joint. As­sume it’s smooth and round—so ob­vi­ously it’s been there for a while. And the horse is per­fectly sound. But he’s only 3 years old. So is the chip a prob­lem? Maybe so, maybe not. The only way to know for sure is to have that chip re­moved, which not only al­lows for an ac­cu­rate as­sess­ment of the health of the joint, but also elim­i­nates the po­ten­tial for the chip to cause a prob­lem mov­ing for­ward. If that horse were an older, sound per­for­mance horse, re­mov­ing a chip is un­likely to be rec­om­mended. If it hasn’t caused a prob­lem yet, there’s a good chance it’s buried in the soft tis­sues where it’ll never cause an is­sue.

Of course, a clin­i­cal ex­am­i­na­tion and ad­di­tional di­ag­nos­tics such as ul­tra­sound, bone scans, or MRI can also give more in­for­ma­tion about whether an in­ci­den­tal find­ing on a ra­dio­graph is likely to cause prob­lems over time.

Real-Life Ex­am­ples

Let’s take a look at some ra­dio­graphs wor­thy of de­bate, and see why the answers aren’t al­ways black and white.

EX­AM­PLE #1: FET­LOCK CHIP Is it real? This small chip in the horse’s fet­lock joint isn’t an ar­ti­fact—it’s re­ally there. Does it mat­ter? The chip ap­pears round and smooth—it’s most likely been there for a while. If I found it on a horse that was sud­denly lame, this chip is un­likely to be the cause. How­ever, it’s in a lo­ca­tion where it could cause joint dam­age over time un­less it’s buried in soft tis­sues where it won’t im­pact the joint at all. Can you find out more? Sur­gi­cal re­moval would tell you whether the joint has been dam­aged and pre­vent the chip from caus­ing dam­age over time. Most ex­perts will agree that this is the best an­swer for a young horse. How­ever, if the chip were iden­ti­fied in an older horse that’s com­pletely sound, surgery might be con­sid­ered risky and un­nec­es­sary. Ad­di­tional ra­dio­graphic views might show if there are signs of arthri­tis that could be prob­lem­atic if they progress, and more ad­vanced di­ag­nos­tics such as an MRI would give a de­tailed look at the area. What’s the true story? This chip was iden­ti­fied on a 2-year-old as part of a set of screen­ing ra­dio­graphs be­fore the horse was put to work. The chip was re­moved, the joint looked great, and the horse never looked back.

EX­AM­PLE #2: HOCK LINE Is it real? This faint line on this horse’s hock could be a hair­line frac­ture. It’s in an un­usual lo­ca­tion, how­ever, and could also be an ar­ti­fact caused by over­lap. Does it mat­ter? If this line is a hair­line frac­ture, it’d sig­nif­i­cantly change the treat­ment rec­om­men­da­tions for this horse. Hock in­jec­tions to treat his arthri­tis and con­tin­ued work could eas­ily lead to a much more se­ri­ous in­jury if the frac­ture blew apart. If it’s just an ar­ti­fact, this horse’s hocks could be treated with min­i­mal risk. Can you find out more? A ra­di­ol­o­gist might be able to de­ter­mine if this line is just an ar­ti­fact. If the an­swer still isn’t clear, a bone scan of the area would show whether this line shows a lot of ac­tiv­ity, in­creas­ing the chance that it’s a frac­ture. What’s the true story? This ra­dio­graph was re­viewed by sev­eral dif­fer­ent sur­geons and ra­di­ol­o­gists, and no one could agree whether the line was re­ally sig­nif­i­cant—es­pe­cially be­cause the horse had come up sud­denly lame and the area was sen­si­tive to touch, which would be un­usual for sim­ple hock arthri­tis. The owner de­cided against ad­di­tional di­ag­nos­tics, and opted to play it safe. He al­lowed the horse to rest for three months to give time for a pos­si­ble stress frac­ture to heal, be­fore treat­ing the arthri­tis and care­fully putting his horse back to work. →

EX­AM­PLE #3: FET­LOCK FRAG­MENT Is it real? This bone frag­ment isn’t an ar­ti­fact— it is re­ally there. Does it mat­ter? The frag­ment is in a lo­ca­tion that can be prob­lem­atic, where it might im­pact the joint or in­volve some of the small lig­a­ments that at­tach in this area. It does ap­pear fairly smooth, in­di­cat­ing it’s most likely been there for a while. Can you find out more? The age and work his­tory of this horse could be ex­tremely im­por­tant. If the horse is older, sound, and has a his­tory of suc­cess­fully work­ing hard, the frag­ment might be less con­cern­ing. If he’s a young­ster, risks for fu­ture prob­lems would in­crease. Ad­di­tional di­ag­nos­tics such as ul­tra­sound or MRI might of­fer more about the over­all health of the joint and soft tis­sues in the area. What’s the true story? This frag­ment was iden­ti­fied in a sound, older horse work­ing at a very high level. It had first been iden­ti­fied years ago, and ra­dio­graphs taken six years apart looked iden­ti­cal. Al­though there’s no guar­an­tee it won’t cause prob­lems in the fu­ture, the horse’s his­tory makes it much less of a risk.

EX­AM­PLE #4: FIBULA FRAC­TURE Is it real? This line looks just like a frac­ture, but it’s not! It’s a nor­mal find­ing that oc­curs when the fibula is de­vel­op­ing. Does it mat­ter? No. Al­though it looks a bit un­usual, this frac­ture-like line is ac­tu­ally com­pletely nor­mal. Can you find out more? Some­times nor­mal vari­a­tions in anatomy can be con­fus­ing, and even your ve­teri­nar­ian might ques­tion the sig­nif­i­cance. A sim­ple way to check is to take a ra­dio­graph of the op­po­site leg to see if it looks the same. What’s the true story? This horse came up acutely “frac­ture lame” with swelling in this area of the leg, which caused the vet to ques­tion whether this line was re­ally nor­mal, or if the horse had been in­jured. In the end, the horse had a soft-tis­sue in­jury com­pletely un­re­lated to this ra­dio­graphic find­ing.

EX­AM­PLE #1

EX­AM­PLE #2

EX­AM­PLE #4

EX­AM­PLE #3

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