Farriery for the foal: A review part 2: Therapeutic farriery
Reprinted with permission from Equine Veterinary Education (EVE).
Conservative treatment such as restricting exercise toreduce further trauma to the foot is paramount. Correctingthe nutritional status of the foal (i.e. weaning the foal toavoid possible excessive nutrition from the lactating mareand/or decreasing carbohydrate intake), administering ananti-inflammatory agent (NSAID) to relieve pain, administeringoxytetracycline to foals with acquired flexural deformities tofacilitate muscle relaxation and carefully trimming the palmarsection of the hoof are, in the author’s opinion, is areasonable starting point. The NSAIDs should be administeredshort-term and judiciously in foals due to the potential sideeffects, such as gastroduodenal irritation and nephrotoxicity.For analgesia, the author will administer firocoxib (0.1 mg/kgbwt q. 24 h) or flunixin meglumine (1.1 mg/kg bwt q. 24 h)combined with a gastric protectant. Hoof trimming isdirected towards improving the hoof angle by lightly trimmingthe heels from the middle of the foot palmarly until the hoofwall at the heels and the frog are on the same plane. Overtrimming of the heels should be discouraged as this willinvariably cause the heels to lift off the ground which can benoted on firm footing. The bars can be thinned in thisinstance as an attempt to spread and possibly improve heelexpansion. Additionally, the heels of the hoof capsuleadjacent to the frog sulci may also be rasped to a 45° anglein an attempt to promote spreading. If the sole thickness issufficient in the dorsal foot (does not deform with hoof testersor thumb pressure), breakover is moved palmarly by creatinga mild bevel with a rasp, which begins just dorsal to the apexof the frog and extends to the perimeter of the dorsal aspectof the hoof wall (Fig 1). If improvement is noted, this trimmingregimen is continued and optimally performed at 2-weekintervals. If the toe is constantly being bruised or undergoingabscessation, an acrylic or urethane composite (Equilox® orVettec®) can be applied to the dorsal aspect of the sole andthe distal dorsal aspect of the hoof wall to form a protectivetoe ‘cap’. The acrylic composite-impregnated fibreglasscombination or urethane composite used to form the toecap will cover the solar surface with a thin layer of compositefrom the margin of the dorsal hoof wall to the apex of thefrog, protecting that area from further damage and creatingor exacerbating lameness. Caution is advised when acomposite cap is applied as the sole-wall junction may bestretched or have separations/fissures present which make it
The above treatment for a mild flexural deformity is oftentemporary as many foals will progress to a more severedeformity and thus the farriery appears to work best wheninitiated at the first sign of abnormal foot conformationbefore a marked flexural deformity is apparent. Wheneverpossible, the elimination of any possible or suspected incitingcauses should be pursued.The farriery for a mild flexuraldeformity should always be combined with restrictedexercise. If the affected foot continues to improve or doesnot regress, conservative treatment is continued. If a mildflexural deformity progresses in severity to the stage where amarked flexural deformity is present, the foal becomes asurgical candidate.
Severe acquired flexural deformities of the DIPJ
A mild acquired flexural deformity may progress in severitydespite conservative treatment or a severe acquired flexuraldeformity may be acute in onset. A severe acquired flexuraldeformity is characterised by a foot with a hoof anglegreater than 80°, a prominent fullness at the coronary band,a broken forward hoof-pastern axis, disparity in hoof wallgrowth distal to the coronet at the heel relative to growth atthe toe and heels that fail to contact the ground (Fig 2). Ifthe flexural deformity is allowed to persist, the foot eventuallyassumes a boxy, tubular shape due to the overgrowth of theheels to accommodate the lack of ground contact; heellength will approach the length of the toe (Fig 3). Increasedstress on the hoof wall at the toe will eventually cause aconcavity along the dorsal surface of the hoof wall. Stressexerted on the sole-wall junction in the toe area will cause itto widen, allowing separations to occur.
Farriers have traditionally applied toe extensions to createa lever arm using a shoe or a composite to force the heel to the ground, but this will only exacerbate damage to thedorsal section of the foot, promote hoof wall separation anddelay breakover (Hunt 2012; O’Grady 2017). As it is importantto consider the use of a toe extension in biomechanicalterms and to understand the effect of this leverage, it isnecessary to briefly consider the moments about the distalinterphalangeal joint. The moments about the DIPJ are theflexor moment and the extensor moment (a moment is equalto force x distance). At rest, the extensor moment is theproduct of the weight born by the limb (a force) and thehorizontal distance from the point at which the groundreaction force GRF acts on the foot (centre of pressure CoP)and the centre of rotation of the distal interphalangeal joint(a distance). The flexor moment opposes the extensormoment and is the product of the force (tension) in thetendon and the shortest distance of the deep digital flexortendon (DDFT) from the centre of rotation. Normally thesetwo moments are balanced at rest, the GRF is dorsal to thecentre of rotation of the joint and the heels are on theground. In foals with a flexural deformity of the DIPJ, thetension in the tendon increases (as a result of the shortenedmusculotendinous unit), which increases not only the flexormoment but the opposing extensor movement which movesthe CoP dorsally in the toe. At the point where the tension inthe tendon increases such that the CoP is at the dorsal limitof the toe, any further increase in tendon tension cannot bebalanced by movement of the CoP because it is already atthe perimeter of the toe and can't move further dorsally,therefore, the heels lift off the ground (Eliashar 2012). Addingan extension to the toe of the foot allows the centre ofpressure to move further dorsally in the toe in an attempt tocounteract the tension in the tendon and force the heels tothe ground. The ability of the toe extension to do this isdependent on the integrity of the tissues (hoof wall,lamellae), however, the tissues are not generally strongenough to withstand the additional stress and separationoccurs within the dorsal hoof wall. Therefore, placing anextension or leverage on the dorsal hoof wall to counteractthe forces in the shortened deep digital flexor muscle tendonunit is unrealistic and, in the author’s opinion, contraindicated(Fig 4). Furthermore, extensions may contribute to lamenessdue to excessive stresses on the DDFT when the foal puts fullweight on its foot and at the initiation of breakover.
Radiographs should be used to assess changes in the jointand the integrity of the distal phalanx. The author willadminister mild sedation (xylazine [0.33 mg/kg bwt, i.v.]combined with butorphanol [0.022–0.066 mg/kg bwt i.v.]) andplace each of the foal’s feet on separate wooden blocks ofequal height, which allows normal or equal loading of bothforefeet. The forelimbs are positioned such that the thirdmetacarpal bone is perpendicular to the ground. Lateral-medial weight-bearing images of both forefeet should beacquired. The degree of flexion of the DIPJ, the angle of thedorsal hoof wall and abnormalities at the margin of the distalphalanx should be assessed (Fig 5). When a marked flexuraldeformity is noted during radiographic examination of thefeet, conservative treatment and hoof trimming alone aregenerally unsuccessful in resolving the foot conformation.Elevating the heels has been advocated to reduce tension inthe DDFT and to promote weight-bearing on the palmarsection of the hoof. However, although elevating the heelswill load the palmar section of the foot, improve the hoofpastern axis and make the foal more comfortable initially, theauthor has not been able to subsequently lower the heel orremove the wedge and establish an acceptable hoof anglewith the heel on the ground. Once a marked flexuraldeformity of the DIPJ with the heels of the hoof capsule liftedoff the ground or a distorted hoof capsule characterised by afoot with a steep hoof angle, a prominent fullness at thecoronet, a broken forward hoof-pastern axis, a disparity in thelength of the heel relative to the toe of the hoof and somedegree of concavity in the toe is apparent; the authorrecommends transection of the accessory ligament of theDDFT combined with the appropriate farriery.
The farriery is generally performed prior to the surgeryeither before or while the foal is anaesthetised to preventmanipulating the limb and handling the surgical site followingthe procedure. A toe extension is not used; rather an acryliccomposite is applied to the solar region of the toe to createa reverse wedge (Stone and Merritt 2009; Hunt 2012; O’Grady2012, 2017). The wedge affords protection for the toe regionand appears to redistribute the load to the palmar aspect ofthe foot, thus mildly increasing the stresses on the DDFT, andappears to restore the concavity to the sole. The heels arelowered with a rasp from the point of the frog palmarly, untilthe sole adjoining the hoof wall (sole plane) at the heelsbecomes solid. This will generally place the hoof wall and thefrog on the same horizontal plane. Any concavity or bendingin the dorsal aspect of the hoof wall is removed with a rasp inorder to redirect the forces directly under the coronet atbreakover. The ground surface of the foot dorsal to the frogand the perimeter of the dorsal hoof wall are sanded andprepared for the composite wedge using a rasp or motorisedburr (Dremel® tool). Deep separations in the sole-wall junctionat the toe are explored and filled with clay, if necessary, toprevent tracts for infection beneath the composite. Foalsundergoing this procedure are usually between 3 and5 months old; therefore, due to their size and weight,reinforcing the composite with fibreglass is necessary toprevent excessive wear.
The surgical aftercare is at the discretion of the attendingclinician. Oxytetracycline may be used with the surgeryduring the perioperative period to facilitate relaxation ofother soft tissue structures secondarily involved (joint capsule,collateral ligaments) (Hunt 2012). Controlled exercise in theform of daily walking or turn out in a small paddock with firmfooting such as a round pen is essential. There is the potentialfor pain with the initiation of exercise due to the shortening ofsoft tissue structures such as the joint capsule and suspensoryligaments to the navicular bone, requiring close monitoring ofthe foal, and exercise should be increased sequentially. Thefoal is trimmed at roughly 2-week intervals, based on theamount of hoof growth at the heels with the objective ofestablishing normal hoof capsule conformation. Thecomposite wedge is removed one-month post-surgery. Atsubsequent trimmings, the heels are trimmed as necessaryfrom the middle of the foot palmarly such that the frog andhoof wall are on the same plane and hoof wall at the toe istrimmed from the dorsal aspect of the hoof wall until thedesired conformation is attained. No sole dorsal to the frog isremoved. This type of trim promotes sole growth and createsapproximate proportions on either side of the COR. When thedesired foot conformation is reached, the foot is trimmed in aroutine manner monthly. It is important to emphasise thatwhen the hoof capsule returns to an acceptableconformation, only that portion of the sole that is sheddingshould be removed. This avoids causing discomfort in thedorsal solar section of the foot that can result in the foalredeveloping, to some degree, the original flexural deformity.The higher-grade clubfoot appears to have a tendency torevert back to the original deformity if not managed properly.
Angular limb deformities
Angular limb deformities (ALD) are common in foals andrequire early recognition and treatment (Greet 2000; Hunt2000; Greet and Curtis 2003; Auer 2006; Witte and Hunt 2009;Garcia-Lopez 2017; O’Grady 2017). This subject receivestremendous attention in any discussion of foal conformationand it refers to a lateral or medial deviation in axial alignmentof the limbs when the animal is viewed from the frontalplane. It is understood that a certain amount of deviationcan be normal in young foals and does not require anyspecial farriery or surgical intervention (Hunt 1998, 2000; Auer2012; O’Grady 2017). Objective data is lacking regarding thedynamics involved in the development of acquired angularlimb deformities, however, it is recognised that many foalschange axial alignment during various stages of theirdevelopment. Serial evaluation and treatment of limbdeviations is an integral component of management on mostbreeding operations.
Angular limb deformities may occur anytime during theanimal’s life but are most commonly treated from birththrough the yearling growth period. The primary lesionappears to be an imbalance of physeal growth; for assortedreasons, growth proceeds faster on one side of the physis vs.the other. Although this is described as a discrepancy of limblength of the medial vs.
Limb alignment of young foals should be observedstanding and walking without restriction on the head andneck (not leaning) toward and away from the examiner.Overall body development and maturity should be noted. Itis important to take note of foot placement especially whenworking with distal limb deviations. This will determine thenecessity for corrective measures on the feet such astrimming or placement of a composite extension on the hoofcapsule to alter the forces on the physis and change therotation of the limb on contact with the ground. This practiceis especially beneficial with a fetlock varus deviation withinward rotational deformities in foals 2–4 weeks of age inwhich there is a limited time frame for correction.
It is apparent that a mild carpal valgus of 2–5 degrees offersthe newborn foal a comfortable stance while nursing andeating off the ground and is considered acceptable. If thedeviation exceeds 5–8 degrees then it becomes a concernand should be monitored (Hunt 1998, 2000; Auer 2012). A fewdays of stall confinement on firm bedding or limited exercisein a small paddock (2–3 times a day) is a rewarding, costeffective treatment for early carpal or tarsal valgus (GarciaLopez and Parente 2011).
It may be helpful to digress and briefly mention routinehoof care before discussing treatment of angular limbdeformities. The technique for using farrier tools whentrimming foals was discussed under the trim in Part 1 of thisreview. The veterinary and farriery literature abounds withvarious trimming methods that are thought to affect thevarious limb conformations; however, none of these methodshave been substantiated or documented to be efficacious.The author trims the heels such that the heels of the hoof walland the frog are on the same plane, visualises a line acrossthe middle of the foot (located just dorsal to the COR) andthen reduces the toe to make the foot proportional on eitherside of the line across the widest part of the foot. When thetrim is complete, the solar surface of the foot will be levelrather than having the lateral to medial orientation of thefoot changed by rasping one side of the foot more than theother (Fig 8). Farriery texts describe trimming a foal lower onthe outside of the foot when the foot turns out and trimmingthe foal on the inside of the foot when the foot turns in;however, remembering that a toe-out or toe-in stanceoriginates from the limb, this practice will do nothing morethan place excessive stress on one side of the hoof capsule
If the angular limb deformity is greater than 5–8 degrees orshows no improvement in the first few days of life, radiographsshould be part of the physical examination of a foal with ALD(Garcia-Lopez and Parente 2011; Garcia-Lopez 2017).
Occasionally, osseous abnormalities such as hypoplasticcarpal/tarsal bones will preclude correction of the problemwithout splints or a cast. Radiographs will also reveal the siteand degree of deviation which will allow comparison later.Carpal valgus deformities of less than 10 degrees aregenerally handled successively with conservative treatment(Garcia-Lopez and Parente 2011; Garcia-Lopez 2017).
Conservative therapy for the management of many mildto moderate congenital angular limb deformities may besuccessful in the newborn foal. Restricted exercise would beeither strict stall confinement or brief periods of turnout (1 htwo times daily) in a small area with firm footing. This allowsthe physis to be stimulated but prevents stress, fatigue andcompression on the overloaded side of the growth platefrom excessive exercise. If the carpus can be corrected byapplying pressure with one hand on the inside of the carpusand counter pressure with the other hand applied to theoutside of the fetlock, some form of coaptation such assupport tape, splints, dynamic splints or tube casts may behelpful. The author uses a splint made from polyvinylchloride(PVC) pipe, cut in half and fitted from the elbow to belowthe fetlock applied for a few hours 1–2 times daily. It islabour intensive, but the splints must be removed andreplaced periodically to prevent laxity. A full-length thickcotton bandage is applied to the entire limb, and then thePVC pipe is placed on the outside of the limb and securedto the bandage with elastic tape. This will distract thecarpus laterally and load the limb more proportionally. Thesplint is often the most cost-effective treatment availablebut must be applied with caution, paying strict attention tothe details of application. Meticulous attention to applyingthe splint is essential to prevent focal pressure and thepropensity of the foal to develop decubital ulcers. As thefoal improves, brief periods of turnout in a small area withfirm footing can be considered.
Acquired carpal/tarsal valgus deformities can be gradedfrom one to four according to severity (Fig 9). Mild tomoderate carpal valgus will generally respond to restrictedexercise and the use of a composite extension applied to themedial side of the foot while the more severe cases requiresurgical intervention combined with farriery (Hunt 1998, 2000;Greet 2000; Auer 2006; Witte and Hunt 2009; Garcia-Lopez2017; O’Grady 2017). Various clinicians have describedtrimming the lateral side of the foot aggressively when there isa valgus deformity in an attempt to increase the groundsurface on this side of the foot (Greet and Curtis 2003).However, it is this authors’ opinion that the foal does not growsufficient horn at this age to make an appreciable differenceand changing the medial to lateral orientation of the footmay have detrimental effects on the immature hoof capsuleas well as the physis. Using some form of extension toincrease the ground surface of the foot and change theforces on the physis seems to be more beneficial (Cheramieand O’Grady 2003; Greet and Curtis 2003; O’Grady 2017).
Periosteal elevation is a controversial surgery that isroutinely performed on foals with mild to moderate angularlimb deformities (Garcia-Lopez 2017). However, the authorhas not referred a foal for this surgery in 20 years as theauthor saw no difference when compared with foals thathad controlled exercise (brief turnout in a small paddock withfirm footing) and the application of a hoof extension(O’Grady unpublished data, 2014). If stall confinement is usedinitially, the mare and foal should be bedded on firm footing(such as a thin layer of sawdust) for the foot extensions to beeffective. Initially, the author prefers using some form ofextension to increase the ground surface area of the foot ona given side and change the forces on the affected joint.Some type of composite applied to the hoof wall is preferredrather than a cuffed shoe that is attached with glue as thistype of shoe appears to restrict movement of the hoofcapsule and contracts the foot especially the heels. As notedpreviously in Footcare in foals: A review part 1, the author willnot apply a composite to a foal’s foot before 3 weeks of agebecause of the potential detrimental effects of the excessiveheat
For carpal valgus, the composite extension is placed onthe medial side of the hoof and toward the heels whichappears to redirect the forces on the physis on theoverloaded side of the limb by moving the axis of weightbearing towards the centre of the limb (Fig 10).
Varus deformities involving the fetlock are common in eitherthe front or hindlimb of newborn foals (Fig 11).
Carpal varus deviations are also recognised in young foalsand weanlings. Foals that develop carpal varus from birth to1–2 months of age often have an ‘over at the knee’appearance and buckle forward when standing. These foalstypically worsen with exercise and improve with rest. Dietarycontrol is important as is the judicious use of analgesics andcontrolled exercise. Lateral extensions placed on the foot maybe useful but surgical intervention may be necessary if thevarus deformity is severe. Weanlings that develop carpal varusare typically offset at the carpus, sometimes pigeon toed andoften have accompanying physeal dysplasia. If the physealdysplasia is kept under control; the deviation will often resolve.If the condition fails to respond, surgery such as transphysealbridging or placement of a transphyseal screw in the physis ofthe distal lateral radius may be necessary. In general, valgusdeviations are far easier to manage and are more prone tospontaneously correct and appear much more forgiving froma soundness standpoint than varus deviations.
The concept of protecting the foot from the deleteriouseffects of mal-loading created by many FLDs and ALDs is justas important as using the symptomatology as an instrumentto correct the deformity. Flexural and angular limb deformitiesare often controversial and have a multitude of purportedtreatments; it is therefore essential that appropriatecommunication occur among the responsible parties toavoid any misunderstanding and unnecessary or jobthreatening miscommunications. Management of limbdeformities in foals, irrespective of the type, severity or origin,are best managed through a coordinated effort betweenthe owner, farm manager, farrier and veterinarian. Whentreating valgus and varus limb deformities especially fetlockvarus, prompt early recognition and treatment is best forconsistent correction. Most veterinarians are not able toperform the farriery required to address foot and limb issues infoals, so their reliance on a farrier becomes obvious. Aveterinarian not well versed in farriery should familiarisethemselves with good basic farriery and have a workingknowledge of this discipline. An avenue of communicationbetween the professions is not only necessary but mandatory.Hoof care in the first few months of life is serious business andshould never be taken lightly. Appropriate farriery combinedwith medical/surgical input from the veterinarian is essentialwhen confronted with orthopaedic disorders related to thelimbs. Farriery plays a vital role in both the development ofthe hoof and the conformation of the limb. A planned footcare programme is time consuming whereas assembly-linetrimming is quick and easy, but the former thoughtfulapproach is much more rewarding with a better outcome
Conflict of Interest
No conflicts of interest have been declared.
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