Hoof Cracks And Wall Defects - AAEP PDF

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FARRIER PROGRAMHoof Cracks and Wall DefectsG. Kent Carter, DVM, MS; and Jason Maki, Dipl WCF, CJFAuthors’ address: Department of Large Animal Clinical Sciences, Texas A&M University, College of Veterinary Medicine and Biomedical Sciences, College Station, Texas 77843;e-mail: [email protected] 2010 AAEP.1.IntroductionHoof cracks and wall defects are common problemsencountered in equine practice that vary in severityand clinical significance to the individual horse.Many simple cracks or defects may require nothingmore than adequate trimming and shoeing of thefoot. However, unstable complicated cracks andlarge or unstable defects will require removal of theaffected tissues or stabilization and therapy to address the complications (e.g., infection) to prevent ortreat lameness. The major goals of treating hoofwall cracks and defects are to correct the cause,when possible, debride affected tissues, and stabilizethe hoof wall, when necessary. Other supportivetreatments, such as treatment of local infections andtherapeutic shoeing, can also be important to a successful outcome.2.Hoof CracksHoof-wall imbalances from conformational abnormalities and/or improper trimming and shoeing canbe associated with the occurrence of hoof-wallcracks. However, there are a number of horseswith apparently structurally sound feet and goodshoeing practices that develop hoof cracks. If imbalance or shoeing abnormalities exist, correctingthe observed abnormalities should help in the resolution and prevent recurrence of the crack. If, how-NOTES5222010 Ⲑ Vol. 56 Ⲑ AAEP PROCEEDINGSever, imbalances and shoeing or trimming problemsare not observed, therapeutic shoeing options maybe less apparent.Poor hoof care and neglect are causes of hoofcracks. Excessive hoof length, which predisposesthe hoof wall to break off, can lead to hoof cracks,usually originating at the solar surface and migrating proximally. Hoof cracks are not uncommon inhorses maintained barefoot. However, the cracksthat we are asked to deal with in most performancehorses are in shod horses, and most occur at thecoronary band at the quarter and migrate distally.A true quarter crack usually leads to instability,inflammation, and infection.1 Feet that are longtoed with short-shod underrun heels is a commonhoof conformation that is observed in horses presented with quarter cracks, particularly in racehorses.2 A sheared heel is apparent on mostcases of quarter cracks in performance horses seenby the authors. In observing a typical foot affectedby a sheared heel and a quarter crack, one can see adistinct proximal deviation of the coronary band atthe site of origin of the crack (Fig. 1). This deviation of the coronary band is not typically seen on theopposite side of the foot. In the authors’ experience, this occurs far more commonly on the medialheel of the forefeet. However, sheared heels andquarter cracks can occur on the lateral heel, partic-

FARRIER PROGRAMFig. 1. A foot with a quarter crack.the coronet in the area of the crack.Note the displacement ofularly in horses with excessive toe-in conformation.Quarter cracks are not common in the rear feet, butthey are occasionally encountered. Althoughsheared heels are usually conformation-related,they can be exacerbated by trimming and shoeingwhen the abnormal hoof growth and distortion arenot recognized and appropriately addressed. Insome cases, therapeutic shoes applied for lamenessproblems can create distortion of the hoof capsuleand lead to a sheared heel and a quarter crack.An example is a wedged-egg bar shoe applied to helprelieve pain from navicular disease that leads to aquarter crack.3.TherapyAppropriate attention to the imbalances that occurin the foot, both medial lateral balance as well asdorsal to palmar balance, is as important as anyother therapy done to the foot. You can repair ahoof crack by a number of techniques and employseveral shoeing options, but continued appropriatetrimming and balance of the foot are necessary toeffectively heal and manage a foot affected with aquarter crack for the long term. It is not uncommon for the authors to examine horses that havehoof cracks that stabilized and then reoccurred, because the original hoof imbalances were not addressed. The authors have successfully managednumerous quarter cracks by properly applied trimming and shoeing without stabilization of the crackby other described methods. However, many of thehorses presented with quarter cracks are intendedto perform, and time out of training is undesirable tothe owners. Therefore, stabilization of the hoofcrack in concert with appropriate trimming andshoeing is often employed to allow the horse to perform while the crack grows out. A commonly occurring hoof imbalance seen by the authors in a footwith a medial quarter crack is a long medial shearedheel, a long lateral toe, and usually to some degree,an underrun heel. Trimming to address these ab-normalities includes shortening the medial heel,particularly from the crack or bulge in the coronaryband palmar, shortening the lateral toe, and backing up the bearing surface of the heels to the widestpart of the frog combined with backing up the toe toallow for a better break-over of the hoof. Floatingof the heel palmar to the hoof crack, although not auniversally accepted concept, has been useful inthese authors’ hands. By removing ground forcespalmar to the crack, it allows the hoof capsule’sproximal distortion to somewhat correct. In fact,when trimming a horse with a crack, it is common tofloat the affected heel, trim the opposite toe quarter,and then, allow the horse to stand on a flat surfacewhile the other three feet are trimmed and shod.In most cases, there will be a discernable change inthe coronary band; usually, the affected heel willhave settled to some degree and in some cases, become weight-bearing on the ground surface. It maybe of further advantage to allow the horse a period inthe stall with sole and frog support to effectivelyfloat the affected heel for a longer period of time,allowing for more accommodation before shoeingand repair. Allowing the hoof palmar or plantar tothe crack opportunity to correct as much as possiblebefore stabilizing it with a rigid repair will afford abetter long-term outcome. Therefore, these authors usually shoe the horse with a bar shoe, floatthe medial heel, and postpone rigid repair for 1–2wk. This period allows more opportunity to correctthe sheared heel and for the coronet to assume amore normal position; it also allows time to ensurethat the infection in the crack is controlled. Various configurations of bar shoes can be used to effectively increase the bearing surface of the foot,provide palmar support, and decrease the independent vertical movement of the heels. Types of barshoes commonly employed include straight-bar, eggbar, z-bar, and heart-bar.3Hoof-crack stabilization, although not always necessary, can be an important aspect of dealing withcracks that are causing lameness, increasing in size,or occurring in horses that must perform. Thereare numerous techniques and materials describedfor repairing hoof-wall cracks that have merit inindividual circumstances. Methods of repair can berather complicated and require some expertise toapply, whereas others, although simple, may notprovide adequate stabilization for the horse to compete and the crack to heal. Regardless of whichmethod of repair is applied and what supportive careis provided, the goal of any repair technique is toprovide adequate stability of the hoof wall adjacentto the crack. The degree of stabilization andstrength of the repair required can vary with the useof the horse and whether a period of rest from athletic use can be afforded. The challenge often facing the practitioner is the importance of the horse’scontinued performance with a hoof crack that iscreating lameness. One important aspect of treating hoof-wall cracks that is often not stressedAAEP PROCEEDINGS Ⲑ Vol. 56 Ⲑ 2010523

FARRIER PROGRAMenough is to not make a bigger problem with yourtreatment. There are several techniques describedthat use screws placed into the hoof wall as part ofthe repair. Screws are incorporated into fiberglassrepairs4 and screw and wire repair; additionally,screws with an adjustable tension-band device5 andplates of a variety of materials attached across thecrack with screws are used. Although these can beeffective and are routinely used, problems such aslameness or submural abscesses can be encounteredif the screws impinge on the sensitive lamina. Inthe authors’ experience, most horses will toleratethe use of 0.375-in sheet-metal screw, but some willnot. Horses with thin hoof walls and cracks nearthe heels or coronary band have the highest risk forproblems with screws. If a screw used in a composite hoof-crack repair penetrates the sensitive laminaand creates a submural abscess, it may require removal of the hoof-wall repair and part of the hoofwall to resolve the complication. The horse couldbe out of use for an extended period of time if thishappens.There are a number of repair techniques describedthat use stainless-steel wire or synthetic material indifferent suture patterns across the crack. Toachieve these repairs, holes are drilled into the hoofwall to accommodate the sutures. It is extremelyimportant that these drill holes not penetrate thesensitive laminae, because if the drill holes exposesensitive laminae and the suture is used in conjunction with a composite repair, a submural abscessand associated complications could arise. Lacingthe crack with synthetic material and incorporatingit into the composite repair has been described as aneffective method of repair that provides good stabilization of the crack.6 A more recently describedsimilar approach uses a relatively fine-gauge wiresuture that incorporates a small metal tab,a whichprevents the wire from cutting through the hoofwall.3 One advantage to this technique is that thesmall-size wire requires a much smaller hole anddrill bit, and therefore, there is less damage to thehoof wall and less likelihood of exposing the sensitive lamina with the drill bit.Several materials have been used in compositereconstruction of hoof-wall cracks and hoof-wall deficits. Flexible polymethylmethacrylate,b seems tobe most commonly used for this purpose, and thesematerials can be used by themselves or in combination with several methods used to stabilize the hoofwall crack. It is not uncommon for hoof-walldefects to be filled with the polymethylmethacrylatematerial alone, but most veterinarians recommendincorporating fabric such as spectra, fiberglass, orkevlar in the repair. Incorporation of a compositein the repair of the hoof-wall crack will aid in thestrength and stability of the repair. It is imperative that proper application principles be followedwhen performing these repairs, because the material may not adhere to the hoof properly or absces5242010 Ⲑ Vol. 56 Ⲑ AAEP PROCEEDINGSsation of sensitive tissues could occur under therepair.If a composite is to be used in the repair, thefollowing principle should be followed to improvechances for success and decrease potential forcomplications. Clean the crack with a Dremelctool and a cross-cut tungsten carbide bur.d Allloose horn and debris should be removed from thecrack. Cracks that are infected and/or have exposed non-keratinized tissue should be opened toenhance drainage and treatment of the crack.If non-keratinized tissue or infection is present,either (1) delay further repair until lamellar tissues are keratinized and can be safely covered,providing stabilization (for example, wire fixationwithout a composite covering can be done at thistime, and composite reconstruction can be done ata later date), or (2) if immediate repair is required,use a technique to allow drainage and treatmentof the crack and prevent abscessation under thecomposite repair. Infected or exposed areas canbe protected by applying modeling clay/doughe orhoof puttyf over the tissues and placing a draintube of small silastic or rubber tubing along thecrack for the length of the repair. The tubing canbe removed after cure of the polymethylmethacrylate, leaving a tunnel that transverses the crackand provides drainage that is accessible to therapy. Although it is the authors’ preference toallow infections to resolve and the tissue to keratinize before application of the polymethylmethacrylate, there are times where rapid return toathletic use warrants the application of a polymethylmethacrylate before healing. If this is done,it is extremely important that adequate drainagebe afforded.The hoof wall should be sanded, dry, and cleanbefore application of the polymethylmethacrylate.If the hoof is not dry, it can be slowly dried with aheat gun (paint stripper) and then treated with acetone or denatured alcohol before application of thepolymethylmethacrylate. A wrap of elastic bandageg at the coronary band prevents the polymethylmethacrylate material from contacting the skinand hair above the coronary band.When applying the polymethylmethacrylate, itis desirable to incorporate fiber (kevlar, spectra, orfiberglass) into the repair for strength and coverthe repair with plastic wrap to improve the appearance and cure of the resin. After curing, therough edges are trimmed and sanded and then thehorse is shod with the appropriate shoe. The authors prefer a bar shoe in many cases, but thelocation and severity of the crack will affect theshoeing regimen chosen. If the horse is exposedto excess moisture and mud, this will affect thelongevity of the composite repair and hoof qualityunder the repair. Therefore, it is important toavoid excess exposure to moisture.

FARRIER PROGRAMFig. 2. A hoof with white-line disease.into the affected area of the hoof.4.Note the probe insertedHoof-Wall Removal for Hoof-Wall DefectsIndicationIndications for removal of hoof wall are commonlyencountered in the equine practice and can be accomplished in several ways. Currently, the mostcommon condition that we see when hoof-wall removal is indicated as part of the therapy is thestructural damage and separation at the stratummedium and stratum lamellatum, commonly knownas white-line disease. The term white-line diseaseis a misnomer, because the white line is anatomically defined as the junction of the hoof wall andsole. However, white-line disease is the most common term used to describe the separation of hoofwall proximal to the white line. In the authors’experience, this is a distinct and separate conditionfrom other forms of separation, such as a seedy toeseen in chronic laminitis. White line disease seemsto be a progressive deterioration of the attachmentof the hoof wall that seems to be the result of keratolytic fungal and/or bacterial agents. This loss ofattachment can occur in hooves that appear healthyon the surface and have no known injury or disease.It is not uncommon for an outwardly normal-appearing hoof wall to have a significant

crack in concert with appropriate trimming and shoeing is often employed to allow the horse to per-form while the crack grows out. A commonly occur-ring hoof imbalance seen by the authors in a foot with a medial quarter crack is a long medial sheared heel, a long lateral toe, and usually to some degree, an underrun heel. Trimming to address ...