NEGATIVE PALMAR ANGLE SYNDROME HOOF CARE & SHOEING

BY ANDREA E. FLOYD, D.V.M.

YOUR HORSE is trainingwell, but you notice that hisheels are starting to get thin-

ner, and they look like they are col-lapsing. Soon,his foot looks longer,and he may be off his game. Histendons may be getting puffy, andhis ankles are starting to fill. Hemay be developing quarter cracksand heel fractures.

You are icing him and trying tokeep him in training, but he is sore.Although he looks good in everyother way, you start injecting hisjoints, which helps, but he just isnot coming back to where he was.

As the condition worsens, osteo-phytes, or bone chips, may becomeapparent in the coffin, pastern, orfetlock joints. Superficial and deepflexor tendinitis may occur withnavicular bruising and adhesions.

Sound familiar? What you see happening to his

feet on the outside is just the tip of

the iceberg. What is happening tohis feet on the inside is the biggerproblem. You are doing everythingyou can to keep your horse in topshape, but this aspect of his carehas gone untreated. Why? Because,until now, we have not had a goodway to explain and treat negativepalmar angle syndrome (NPAS).

NPAS has been associated witha number of factors:

• Research has shown that Thor-oughbreds lose hoof-wall angle asthey start galloping;

• Foals born and raised in sandy,humid soil conditions also have beenobserved not to develop good heels;

• Surgery called deep flexor teno-tomy can produce NPAS; and

• A genetic predisposition forNPAS may exist.

Farriers have to fight to keepgood feet on the Thoroughbredright from the start. So what canyou do to help? Request good, soft-tissue lateral radiographs of yourhorse’s feet. Your veterinarian prob-ably is using a digital X-ray ma-chine now, and with this machineyou will be able to see all the tis-sues of the foot.

Essential measurementsThere are some basics you need

to know and questions to ask when

Sore-heeled ThoroughbredConditioning the racehorse’s foot is as valuable as general conditioning

For further information on NPAS,read the November 2010 article forveterinarians and farriers in the Jour-nal of Equine Veterinary Science.Further information on NPAS alsowill be available at www.serenityequine.com.

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observing the radiographs with yourveterinarian. What does normal looklike? What does a negative palmarangle look like? What does an in-creased palmar angle look like?

The palmar angle is measuredalong the bottom of the third pha-lanx (also called P3 or the coffinbone) inside the foot and the ground

surface or standing surface ofthe hoof. This angle is a loteasier to read when your horseis standing on hoof blocks thathave a wire in the center out-lining the standing surface ofthe block. A normal palmarangle is a positive palmar angleof 3° to 5°. An abnormal pos-itive palmar angle exceeds thatmeasurement and is seen in

clubfeet and laminitic(foundered) feet.

The focus here is a neg-ative palmar angle, andwhat you need to avoid.The NPAS feet have moresole under the tip of thecoffin bone than under thewings of the coffin bone.(See Figure 1,which showsan example of NPAS in aThoroughbred, where

more sole is under the tip of the cof-fin bone than under the wings ofthe coffin bone,and the digital align-ment is not a straight line.)

The next measurement to lookfor is the digital alignment. Thismeasurement should be 180°, ora straight line when drawn downthe front of the three bones belowthe fetlock. Those bones are thefirst (P1), second (P2), and third(P3) phalanges. The measurementstarts at the lower half of the frontface of P1 and should be a straightline through the face ofP2 and the face of P3.(See Figure 2, whichshows a normal digitalalignment where thefaces of the bones arein a straight line.)

Correcting theproblem

If, after measuringthe palmar angle anddigital alignment, youfind they are incorrect,you need to do some-thing to change them.Change begins first withtrimming the groundsurface of the foot to anoptimum palmar angle.(See Figure 3.)

If trimming alone cannot achievethe proper palmar angle, the horsehas a higher grade of NPAS andwill require specialized shoeing.

The digital alignment usually willcorrect itself with the proper palmar-angle trim. If it does not, a specialshoeing will correct the palmar angleand digital alignment.

Figure 3 shows the line, in red,of the correction that is to be madewith the rasp on the solar-surfacehoof wall or the load-bearing hoofwall. This will increase the digitalalignment while making the pal-mar angle positive. This radiograph

was taken of a two-year-old Thoroughbred takenout of training due to sorefeet. The feet were cor-rected and the colt becamesound.

It has been observed thatit is not necessary to re-move sole. In fact,we rarelytouch the foot with a hoofknife. We do like to see thebars about a millimeterbelow the bearing surfaceof the hoof, though. If thereis a little load-bearing onthe sole at the white lineof the toe, we consider thatnormal, as that area iscalled the solar callous andis load-bearing in the feetof wild, unshod horses.However, instead of paringout the sole with a knife,wegrind out the shoe so thereis no load-bearing on thesole at any point of hoof-wall coverage. All shoes—aluminum, titanium, orsteel—can be ground to pre-vent sole pressure.

If, after trimming the footto a zero palmar angle or apositive palmar angle, a ra-diograph reveals that youhave not corrected the dig-ital alignment, a full-rockershoe is used. Full-rockerracing shoes are available

on the market today, and they havemet with great success. (See Fig-ure 4, which shows the final digi-tal alignment correction on an NPASfoot that has a zero palmar angle.The next shoeing should yield apositive palmar angle.)

It is a wise idea to follow at leastthe first few trims with radiographsto ensure you have achieved the

SORE HEELS from page 23

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correction. This mayrequire synchronizingthe farrier and the vet-erinarian and allottingthe time required forthe work.

More severeNPAS

There are highergrades of severity inNPAS. The highergrades require a two-plane trim of the solaror load-bearing surfaceof the foot to achievea positive palmar anglewhile allowing for good growth ofthe heels. Figure 5 shows the trimwith the red line indicating theachievement of a positive palmarangle on the dorsal or toe plane.

The green line indicates the re-moval of the hoof wall of the heelson the palmar or heel plane to ahealthy level of heel. The heelplane has been rasped back to thewidest point of the frog, thus plac-ing load-bearing back where it be-longs.

The two-plane trim is done infront of the quarters and behindthe quarters. The shoe is nailed tothe toe while suspending the heelsin the air. Do not put the foot downuntil the heel area has been prop-erly filled with a material such asEquipak, which provides a softplatform for the heels to rest on.(See Figure 6.) Healing will occurto the heels over several months’time, and then they may be allowedto be trimmed and shod normally.

Remember that as the foot elon-gates and slides forward,away fromperfect conformation, the heels willbe where the quarters should be andthe quarters will be where the toeshould be. The actual toe becomesa fulcrum point that tears the sen-sitive lamina of the toe, elongatesthe hoof further, and weakens theheels. Having the load-bearing andlanding spot of the heels so far for-ward causes another fulcrum spotthat starts heel crushing or heel frac-tures and quarter cracks.

The horse with NPAS always isgoing to need proper alignment. Ifone is aware of those needs andlearns how to care for them, the ac-tual trimming and shoeing will be-come second nature,and will preventthe deterioration of the conditionand prolong the racing athleticismof the horse. You work hard everyday to ensure that they are in thebest condition possible, and nowyou have a way to condition the footas well.

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Andrea E. Floyd, D.V.M., is co-author of the textbook Equine Podiatry and founder of Serenity Equine in Evington,Virginia, a veterinary facility that specializes in the equine

hoof. To read more about her work, visitwww.serenityequine.com._______________________________________

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