Virginia Therapeutic Farriery

Management of Clubfoot in Horses: Foals to Adult.

Reprinted with permission from the American Association of Equine Practitioners.
Originally printed in the 2012 AAEP Convention proceedings

Robert J. Hunt, DVM, MS, Diplomate ACVS

1. Introduction

Clubfoot, or a distal interphalangeal (corono-pedal) flexural deformity, may affect the horse at any stageof life from neonate through adulthood. The deformity may be congenital or acquired and in manyinstances has a genetic basis.1-3 The etiology, clinical manifestations, management, and expectationsdiffer between age groups; however, commonalitiesbetween the groups do exist. Treatment and longterm management vary depending on the age ofonset, underlying etiology, severity, duration, secondary complications, and client expectations. Theprognosis for long-term soundness is generally favorable with appropriate management but may beadversely affected by the severity of the deformity and/or the presence of secondary complications.3

The origin of the term "clubfoot" is unclear because it bears little resemblance to the clubfoot deformity in children referred to as congenital talipes equinovarus.4,5 Presumably, the term was coinedto describe the upright or straight tubular appearance of the foot, where there is little expansion of the hoof capsule, giving a "club-like" appearance, but this is an overly simplistic definition. The clinical presentation in the horse can range from a mildly upright and a small foot to one that is buckled forward with an angle greater than 90° at the distal interphalangeal joint, or may have advanced pedal osteitis and hoof wall deterioration. A clubfoot has been classically defined as a hoof that meets the ground at an angle greater than 60°6 and can be further classified into two types: stage 1 or type 1, in which the hoof axis is less than or equal to 90°, and stage 2 or type 2, in which the hoof to ground angle is greater than 90°.7 A recently proposed classification system designates four grades of clubfoot.2,8 A grade 1 clubfoot has a hoof axis 3° to 5° greater than the contralateral foot and displays fullness at the coronary band but is mild enough that the hoof-pastern axis is aligned. A grade 2 clubfoot is slightly more severe, with a hoof axis measuring 5° to 8° greater than the contralateral foot. In a grade 2 foot, the hoof-pastern axis is steep and slightly broken-forward. Growth rings of the hoof are wider at the heel than at the toe, and after trimming excess hoof wall from the heel, the heel may not touch the ground. A grade 3 clubfoot is a more severe deformity, which has a broken-forward hoof-pastern axis and mild concavity present in the dorsal hoof wall. The growth rings are twice as wide at the heels as those at the toe, and, radiographically, there is demineralization and lipping along the apex of the distal phalanx. A grade 4 clubfoot is the most severe classification and has a hoof angle of greater than or equal to 80°, with a severely broken-forward hoof-pastern axis. A grade 4 clubfoot has a markedly concave dorsal hoof wall, and the coronary band height at the heel is equal to that at the toe. Radiographic changes include rounding of the distal phalanx due to extensive demineralization, and rotation may be present.

Despite the degree of deformity or age category at presentation, the most widely accepted explanation of the underlying mechanical cause is shortening of the musculotendinous unit of the deep digital flexor tendon relative to the bony column. This shortening ultimately results in hyperflexation of the distal interphalangeal joint.2,9-11 This hyperflexation is due to an inability to fully extend the distal interphalangeal joint because of the rigid tension band formed by the accessory ligament of the deep digital flexor tendon to the bony insertion on the distalphalanx combined with the shortening of the musculotendinous unit of the deep digital flexor tendon. Clinical observation suggests that the joint affected in a flexural deformity is determined by the proximity of the joint to the point of insertion of the affected musculotendinous unit. The joint immediately proximal to the tendinous insertion of the primarilyinvolved ligament is the point of least resistance and therefore exhibits deformation. Thus, when the musculotendious unit of the deep digital flexor tendon is affected, the joint affected is the distal interphalangeal, whereas if the superficial digital flexor tendon musculotendinous unit is affected, the joint deformity occurs at the metacarpophalangeal joint because the insertion of the superficial flexor tendon is on the distal first phalanx and the proximal second phalanx. The initiating event behind this musculotendinous shortening is often undetermined and may be related to lameness, nutrition, or genetic predisposition

Although the clinical presentation, causal factors, complications, treatment, and long-term management of the clubfoot varies with the age of the horse at presentation, some basic principles may be applied to management of all cases. Client communication and determination of client expectations is critical to achieving a satisfactory outcome; the more severe the deformity, the worse the prognosis. Deformities that have greater than a 90° hoof angle and advanced pedal osteitis rarely become good sales prospects or sound athletes. Additionally, the potential genetic association of clubfoot in some breeds should be discussed with owners before initiating treatment.

2. Neonatal Presentation

Congenital distal interphalangeal flexural deformity is recognized shortly after birth and ranges in severity from mild to severely contracted and unable to ambulate. Two distinct variations of clubfeet or distal interphalangeal flexural deformity occur in neonates. The deformity may occur as an isolated unilateral deformity; however, the more common form occurs along with, and is probably secondary to bilateral flexural deformity of the carpi and/or metacarpophalangeal joints. The etiology for this deformity is generally undetermined, but factors incriminated include genetics, intrauterine malposition, teratogens, influenza virus exposure, or sudan grass ingestion.1,12

Evaluation of the neonate includes observation ofthe stance of the foal and the ability of the foal toambulate. Foals that exhibit bilateral carpal flexural deformity with clubfeet require minimal to nointervention if they have the ability to stand, ambulate, and nurse unassisted. Manual extension ofthe lower limb almost always produces a normalangle and alignment of the distal interphalangealjoint. Management is conservative because as theprimary carpal or metacarpophalangeal deformityresolves, so does the foot. A more severe flexuraldeformity requires therapeutic intervention, and theearlier in the clinical course, the faster the resolution of the deformity. Treatments include aggressive physical manipulation and stretching of the legsin conjunction with a variety of forms of externalcoaptation aimed at fatiguing the muscular sectionof the musculotendinous unit. Bandaging, transient static splinting with PVC bracing or dynamicsplinting with an articulating brace, application of aflexible tension band along the dorsal aspect of thelimb, and casting are accepted techniques whenproperly applied and managed. Application of acast in a mildly extended position in the first hourafter birth will often improve the condition enoughto allow splinting or bandaging until the conditionfully resolves. Administration of oxytetracycline(44 mg/kg IV, SID) will also facilitate improvementof the deformity.13

The less common variation of clubfoot in neonatesoccurs as an isolated unilateral deformity of thedistal interphalangeal joint and does not correctwith manual extension applied to the joint. Thedeformity occurs in all degrees but is often severeand difficult to manage. Contrary to common practice, toe extensions are not beneficial and typicallycause the foal to stumble. Although it is difficult toapply useful external coaptation to this area, articulating extension braces attached to a foot cuff, application of a cast, or application of a flexible tensionband with surgical tubing will provide appropriatemechanics to this area. Oxytetracycline is a beneficial treatment; however, administration will typically result in excessive laxity of the normal regionssuch as the carpi and fetlocks.

In extreme situations, surgical resection of theaccessory ligament of the deep digital flexor tendonor transection of the deep digital flexor tendon isnecessary. Although the author is unaware of anyrecognized, specific guidelines for surgical interventionin the neonate, with a primary unilateral clubfootin which the hoof angle is approaching orexceeding 90°: if no improvement is seen with conservative treatment within 2 weeks, surgery shouldbe considered.

Fig. 1.
Grade 1 clubfoot. On the lateral view, note the mildflexural deformity and the heels slightly off the ground. On thedorsal view, note the lack of flare in the hoof capsule as it growsdistally and the disparity in width between the coronet and theground surface of the hoof that would indicate decreased loading.

Fig. 2.
Before and after appropriate trimming. Note the improvementin the hoof-pastern axis and the bevel (arrow) createdin the solar surface of the hoof.

3. Juvenile Presentation

The most frequently recognized form of clubfoot inhorses occurs in sucklings or weanlings at approximately2 to 8 months of age.1-3,6-8 It is commonlya unilateral condition but occasionally affects bothlimbs. The first clinical sign recognized is an uprightappearance of the foot combined with the inabilityof the heels to contact the groundimmediately after trimming the foot. As the conditionprogresses, the coronary band develops a squareor full appearance dorsally. As the toe wears, theupright nature of the foot becomes more evident andthe foot assumes a contracted shape, losing its flareas it grows distally (Fig. 1). The dorsal hoof wallbegins to dish and widens at the white line. Concurrently,the carpus often assumes a back-of-the kneeconformation. The toe may become bruisedand ultimately abscess, resulting in severe lameness.Because of the abnormal forces on the distalphalanx and inflammation associated with excessiveloading, bruising, and abscessation, pedal osteitis isa common occurrence.

Differentiation should be made between a developingclubfoot and a foot that is upright from excessivewear at the toe. The latter is a self-limitingproblem as long as lameness is not severe or fromabscessation. If lameness is present, a protectivedevice over the toe will generally alleviate the problemonce the foot grows sufficiently. A foot of thistype responds well to most treatments, and unduecredit is often given to aggressive therapy that wasunnecessary in the first place.

Clinical management of clubfoot is influenced bythe severity, duration, and the etiology of the clubfootas well as the degree and source of lameness, ifpresent. Evaluation of the foot should be performedat rest and in motion. The angle and balanceof the foot should be determined and the foot should be inspected for under-run or separated wallor sole. Sensitivity to hoof testers or response tofirm pressure from fingers should be assessed.If lameness is present, peripheral nerve blocksshould be performed to isolate and confirm the originof the lameness. Radiographs of the foot shouldbe taken to assess the position and the integrity ofthe distal phalanx or presence of other pathology.If there is evidence of pedal osteitis, especially in thepresence of a severe clubfoot, venographic evaluationmay aid in prognostication. If the clubfoot issecondary to lameness of other origin, it is imperativeto isolate and resolve the other lameness priorto attempting therapy for the clubfoot.

The shoe can be further modified to unload painful areasof the sole or if the sole has dropped or prolapsed byrecessing the shoe's solar surface. Shoe modifications areeasily added or subtracted (i.e. rasping the toe of theshoe to adjust breakover), with the foot in the farrierposition. The wooden shoe being malleable will often bemodified by normal wear which allows the horse to finda comfort zone unique to its individual needs.

Treatment in the early stages of development ofclubfoot involves establishing a normal hoof angleby lowering and spreading the heels as long as thefoal remains sound. One should adhere to theguidelines for trimming and providing a sound, balancedfoot.14-16 The bars should be removed todecrease as much restrictive mass of the hoof capsuleas possible, and the frog should be trimmed tohealthy, compliant tissue to enhance loading. Thewall through the quarters and heels should be loweredto the plane of the frog and parallel the frog.It has been suggested to apply a reverse wedge padunder the toe to determine the amount of heel tolower before reaching a level of discomfort of thefoal.2 If the toe is worn excessively, a protectivedevice applied to the toe to prevent bruising andsubsequent lameness may be applied. The toe maybe rounded, squared, or beveled to promote breakoverand alleviate any lever effect of the toe as wellas to reduce stress on the lamellae (Fig. 2). Toeextensions applied to provide a lever arm using ashoe or composite material are contraindicated becausethey may exacerbate wall separation in additionto delaying break-over. Extensions may alsocontribute to lameness from excessive tension of thedeep digital flexor unit if the foal fully loads the foot.

Fig. 3.
Lateral view of a grade 3 clubfoot. Note the flexuraldeformity, the disparity of hoof wall growth between toe and heel,and the concavity in the dorsal hoof wall. The palmar viewshows contracted heels and the frog recessed between the hoofwall at the heels.

In the event of lameness isolated to the foot, itmay be necessary to elevate the heels to establishweight-bearing on the involved foot. Presumablythis is beneficial if the pain originates from tensionof the flexor apparatus. In the author's experience,heel elevation is temporarily beneficial, but attemptsto resume a normal hoof angle should commence as soon as the foal is comfortable and bearingfull weight. The hoof angle may be reduced graduallyover a period of weeks; however, if pain recurs,the foal should be considered for surgery. Otherforms of hoof appliances in common used to treatthis condition include slipper shoes and springloadedspreader shoes. These devices appear to increasethe width of the distal portion of the foot;however, this occurs by shearing and separationof the laminae through the quarters, which ultimatelyundermines the integrity of the hoof. Actualspreading of the foot must begin from withinthe foot at the coronary band by increasing loadthrough the bony column to the axial and load-bearingsurfaces of the foot, with the foot properlytrimmed. Application of flexible synthetic shoes, awhich are nonrestrictive and allow expansion of thefoot with compliant properties similar to the hoofcapsule, have promise in horses that have a footwith deficient wall for sustaining load during regrowth.Other methods of obtaining expansion ofthe hoof include variations on resecting sections ofwall through dorsal wall thinning or removal to thelevel of the lamina or placing multiple verticalgrooves the full length of the wall. Although thereis no body of evidence to substantiate the efficacy ofthese techniques, there are anecdotal testimonies oflarger foot growth after these procedures have beenperformed.

A severe clubfoot is usually complicated with contractureof soft tissues surrounding the distal interphalangealjoint, including the joint capsule andpresumably the collateral ligaments or other supportivestructures in the region. Therefore, thereare inherent limitations on the effectiveness of correctiveprocedures. Alleviating tension of the deepdigital flexor tendon (DDFT) by transection of theDDFT accessory ligament or transection of theDDFT may not yield a normal angle of the hoof andmay not produce soundness, although it is unusualnot to obtain some degree of improvement withsurgery.

Other alternative modalities of therapy to considerinclude the use of oxytetracycline (44 mg/kg,IV, SID)13 or other medications aimed at reducingtension on the DDFT tension apparatus. Theoretically,oxytetracycline produces chelation of calciumions with the net effect of relaxation of musclegroups.17,18 Unfortunately, with clubfoot disorderhaving a propensity to be accompanied by back-of the-knee conformation, the drug typically worsensthe carpal conformation while having limited effectson the foot. The author routinely administersoxytetracycline in conjunction with performing surgeryto enhance relaxation of the muscle unit andrelax other involved soft tissues. Other antimicrobials,such as enrofloxacin,b clinically produce asimilar effect of relaxation of the flexor tendons andmay have benefit similar to oxytetracycline. Botulinumtoxin is used in people and has been reportedfor use in horses with laminitis to achieve relaxation of the DDFT to prevent distal phalangeal rotation.19With appropriate application, the drug may havemerit in the management of clubfoot in horses in thefuture.

Clubfoot may develop in the yearling or may be acontinuum of the process initiated earlier in life.In general, the older the animal is at the onset, theless likely of obtaining a normally conformed foot,although this does not necessarily preclude a successfulathletic career. If the condition is acquiredas a yearling, it is almost always secondary to alameness or gait deficit resulting in inappropriateloading of the foot, such as with a neurogenic disorder.If the primary disorder is rapidly rectified, thefoot may return to normal if the gait is restored tonormal before the development of irreversiblechanges in the foot. The mechanical principles involvedin therapy are the same as for the weanling,and the primary objectives with any of the proceduresare to maintain comfort and to obtain a mechanicallysound foot. Changes in hoof shapeachieved in yearlings (and adults) are often lessthan those obtained in younger horses.

4. Adult Presentation and Management

Adult clubfoot disorders may be present as the resultof previous clubfoot as a juvenile, may be secondaryto other lameness, or may result as a sequelto chronic laminitis. The principles of managementof clubfoot in the adult are the same as in otherage groups; however, pathologic changes of the footare often more advanced because of the duration ofthe deformity (Fig. 3). Expectations for a favorableoutcome are largely determined by the followingfactors: the severity of the deformity, the durationthe deformity has been present, the integrity of boththe hoof capsule and third phalanx, and the intendeduse of the horse (breeding versus athlete).Many horses are able to compete athletically with aclubfoot as long as they are maintained on a consistenthoof management program.

Fig. 4.
Clubfoot illustrated in Fig. 2 after appropriate farriery.Note the concavity in the dorsal hoof wall reduced theimprovement in the hoof-pastern axis and the heel elevationnecessary to load the heels.

Mild deformities are managed in large partthrough routine farriery aimed at trimming for optimal and uniform load-bearing of the entire hoofwall. The hoof angle required to achieve this typeof load-bearing is usually steeper than normal but isa necessary compromise to avoid lameness associatedwith either hyperextension of the distal interphalangealjoint and accompanying structures orexcessive stress on other soft tissue structures,which often occur secondary to an attempt to establisha normal hoof angle. Break-over may be enhancedin these individuals by rolling or rockeringthe toe. As in the management of all clubfeet, thefoot must not be allowed to grow to extremes andundergo separation of the wall. The general guidingprinciple is to trim the foot at an angle thatallows full loading of the heels or landing flat-footedwhen ambulating. Mild heel elevation may be necessaryto accomplish fully loading the heels. Theheels should not be lowered to the point of allowingtoe contact before heel contact at the walk (Fig. 4).

If the hoof wall integrity is poor and the footundergoes recurrent bruising and abscessation, protectionof the wall and sole through shoeing or castingmay be necessary. Similar principles applyregarding uniform loading of the wall and enhancingbreak-over to reduce shear forces along the dorsallaminae, as in milder cases of clubfoot.

Adult breeding horses with a clubfoot are subjectto excessive trauma at the toe and subsequently areprone to develop subsolar abscessation and eventualpedal osteitis. Extra measures in these horses maybe useful, such as shoeing to protect the toe. Inprotracted, severe cases of clubfoot deformity withadvanced pedal osteitis, desmotomy of the accessoryligament of the DDFT or DDF tenotomy may bebeneficial. Desmotomy of the accessory ligament ofthe DDFT is usually reserved for less severe cases ofclubfoot deformity in which the individual is intendedfor athletic endeavors. Clinical experiencehas yielded favorable results from these proceduresin the form of improved integrity of the wall, expansionof the hoof capsule, and an angle that is closerto normal in addition to a reduction of hoof abscessation.If the decision is made to perform a deepdigital flexor tenotomy, although improvement isusually achieved whether the tenotomy is performedmid-metacarpal or mid-pastern, clinical impressionis that the mid-pastern tenotomy produces morerelaxation of the tendon and therefore more derotationof the distal phalanx.

5. Surgical Procedures

The underlying premise supporting surgery fortreatment of clubfoot is to relieve the rigid tensionband of the DDFT extending from the third metacarpusvia the accessory ligament of the DDFT toinsert on the distal phalanx. The two methods ofaccomplishing this include transection of the accessoryligament of the DDFT and transection of theDDFT. Several techniques have been described toaccomplish each procedure.20-24

Transection of the accessory ligament of theDDFT has been described, using conventional surgicaldissection from a lateral or medial approach,using ultrasound guidance, using tenoscopic guidance,and performing the surgery in lateral or dorsalrecumbency. Each technique has advantages anddisadvantages; the main disadvantage all techniquesattempt to avoid is the cosmetic blemish associatedwith the surgery. I do not believe there isa difference in cosmetic outcome with one techniqueover another, provided the surgery is performed proficientlyand the patient is tractable for appropriatebandaging and exercise for the first 3 months aftersurgery. There is variation in the amount of exerciseallowable, depending on the condition of thefeet. With conventional surgical descriptions, amedial approach is often described; in my experience,this approach requires significantly more dissectionand there is a higher likelihood of a blemishas a result. Personally, I find a blemish on themedial aspect of the limb as offensive as on thelateral.

The most straightforward technique and commonlyperformed technique is accomplished by usingconventional surgery in lateral recumbencypositioned for a lateral approach, with the affectedleg up. The skin may be rolled palmarly beforeincising, so the final placement appears over thefourth metacarpal bone. The skin incision begins 2cm distal to the head of the fourth metacarpal boneand extends distally 2 cm. Sharp dissection is continuedthrough the subcutaneous tissue, the fasciaof the flexor carpal sheath and paratenon, exposingthe junction of the accessory (inferior check) ligamentwith the DDFT. A pair of curved hemostatsare passed along the dorsal border of the accessoryligament and the DDFT and spread, then withdrawn.Next, the hemostats are passed along thepalmar border of the ligament in a similar fashion.Care must be taken to avoid the neurovascular bundle along the medial aspect of the limb. Digitalpalpation of the superficial digital flexor tendon(SDFT) and DDFT is performed to confirm that theproper structure has been isolated. The lower limbmay be slightly flexed to relax the ligament that isisolated, exposed, and exteriorized with the hemostaticforceps, and then transected. I generally removea 1-cm section of the ligament, althoughremoval of this section is not necessary, it requiresmore tissue dissection, and the second transectingcut can be difficult to accomplish neatly. The limbshould undergo extension and flexion, and the operatorshould observe the movement of the structureto ensure complete transection. Interestingly, withsevere clubfoot deformity, the ligament is often significantlylarger than normal. Closure should beperformed in three layers, being careful to leave a0.5-cm opening in the distal portion of each layer toallow for drainage, should a seroma occur. Thebandage should extend above the knee and be tapedto prevent slippage and exposure of the incision.If there is no slipping of the bandage, the first bandageshould remain in place 4 to 5 days beforechanging. The foot should be trimmed appropriately,and, if a corrective device such as a toe cap isneeded, it should be applied. I routinely administer2 to 3 days of oxytetracycline (44 mg/kg IV SID)13in addition to a nonsteroidal anti-inflammatory drugin the postoperative period to encourage loading thefoot.

Deep digital flexor tenotomy may be performed forstage 2 deformities. As a general rule, even withsevere deformities, I attempt correction with a checkligament desmotomy before this. Mid-metacarpalor mid-pastern tenotomy is acceptable, but greaterrelease is achieved with a mid-pastern approach andis my preferred technique in adults that have repeatabscessation or septic osteitis of the distal phalanx.Reports vary regarding the level of success aftersurgical intervention. In general, soundness isachieved, but racetrack performance is decreasedfrom that of unaffected siblings.20

6. Long-Term Management and Prognosis

Although clubfoot deformity in horses is common,there is a sparse amount of evidence-based workdefining the syndrome and its management. Therapyis often empirical and based on clinical experience.The primary goal of therapy andmanagement of any clubfoot horse is to obtain asound horse with a normal or near-normal foot thatwill be maintained with routine hoof care. Oneimportant principle of clinical management is todetermine if discomfort or lameness is present, andif so, to localize the source of the lameness anddetermine the association of the lameness to theclubfoot (primary or secondary). If the foot is improperlyloaded, a normal-contour hoof capsule willnot be possible to obtain and the underlying lamenessmay be the limiting factor on the future athleticcapacity.

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