Journal of Equine Veterinary Science 31 (2011) 89-96

Journal of Equine Veterinary Science

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Clinical Techniques

Long-term Prognosis Using Deep Digital Flexor Tenotomyand Realignment Shoeing for Treatment of Chronic Laminitis

Scott Morrison DVMFrom the Rood and Riddle Equine Hospital, Lexington, KY

Keywords:Chronic laminitisDeep digital flexor tenotomyRealignment shoesLaminitis prognosis

Corresponding author at: Scott Morrison, DVMEquine Hospital, P.O. Box 12070, Lexington, KY 40580

E-mail address: smorrison@roodandriddle.com

0737-0806/$ - see front matter � 2011 Elsevier Inc. Adoi:10.1016/j.jevs.2010.12.008

a b s t r a c t

Transection of the deep digital flexor tendon is a controversial treatment for chroniclaminitis largely because of the variation in personal experience with the procedure andthe varying success rates reported in the previously published data. Differences inreported success rates are more likely because of the dissimilarities in foot pathology andthe foot management associated with the procedure. This report presents 245 tenotomycases, in which all cases received the same shoeing protocol (realignment shoeing).Outcomes were determined for the following categories: degree of bone disease, solarpenetration, sinking, number of limbs involved, and front or hind feet affected. Thesuccess rates by different categories of disease may assist the clinician in formulatinga prognosis for similar cases.

� 2011 Elsevier Inc. All rights reserved.

1. Introduction

Chronic laminitis is defined as radiographic confirma-tion of displacement of the coffin bone. Displacement isfurther defined as rotation, medial or lateral sinking(horizontal plane laminitis), and vertical sinking. The typeof displacement depends on the location and/or severity oflamellar failure. The degree of damage in a chronic lam-initic foot can be classified as compensated (stable) oruncompensated (unstable) [1]. The compensated caseshave displacement; however, the change in the position ofthe third phalanx has stabilized and the foot is still able togrow and regenerate hoof wall and sole in all areas of thefoot. The growth pattern is commonly abnormal, creatinghoof capsule distortion. The uncompensated case hasprogressive displacement and instability, resulting inconstant compression of the sole corium and thereforecannot produce or regenerate sole tissue in parts of thefoot. Pedal bone displacement within the fixed, rigid hoofcapsule causes shearing and compression of the coronarydermis resulting in no hoof wall production in areas. The

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case in which the wall and/or sole growth has stopped istermed uncompensated. These cases often suffer fromchronic pain and infections if the instability is not reversed.

Rotational displacement is the most common form ofchronic laminitis (Figs. 1, 2). There are different theories asto the causes which are as follows: (1) During an acutelaminitis episode, lamellar damage may affect the entirelamellar interface, but because the anterior laminae areunder the greatest stress, theyare the first to fail. Force platestudies indicate the center of pressure (COP) in the normalloaded foot to be located in the toe region, just behind theapexof the frog apex and slightlymedially [2,3]. This ismostlikely because of the pull of the deep digital flexor tendon(DDFT) on the pedal bone during weight bearing, resultingin rotation around its center of articulation and subsequentstress on the anterior lamellar attachments; (2) The heeland quarters are supported by other structures, the frog andbars, whereas the toe is supported by the suspensoryapparatus of the third phalanx (P3); and (3) Because themajor blood flow to the foot comes from the heel region, theblood supply of the toe can be easily altered if laminitiscauses a change in perfusiondthe toe suffering the greatestdamage. The vascular hypothesis is controversial for mostforms of laminitis [4-7] but may have merit in the sup-porting limb laminitis case.

Fig. 1. Acutely foundered foot with severe rotation and prolapse of sole.

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Rehabilitating rotational displacement usually involvesshoeing changes that: (1) move the COP caudally; (2)decrease tension on the DDFT; (3) provide axial support orload structures within the perimeter of the wall (sole, frog,bars); and (4) eases break over in all directions (medial,lateral, and dorsally) [8] in an effort to take stress off thelaminar interface during movement. Methods to move theCOP caudally and decrease tension on the DDFT use barshoes and a heel elevation. Using a wedge to counteractrotational forces has been shown to be effective in clinicalcases. Venogram studies have shown increased perfusionto anterior regions in the wedged loaded foot comparedwith the unwedged loaded foot [9]. Severe uncompensatedcases that do not respond to shoeing may require a deepdigital flexor (DDF) tenotomy to relieve the displacementand realign the pedal bone.

Transection of the DDFT as a treatment for chronic lami-nitis has been reported with variable success rates in thepreviously published data. Eastman et al. [10] reported theresults of 35 cases between 1988 and 1997. A total of 77% ofthe cases survived aminimumof 6months, 59% survived>2years. Allen et al. [11] reported on 13 cases. Five of thesereturned to limited athletic activity, six were pasture sound,one case improved initially, but further deteriorated after 9months andwas euthanized, and one case improved, butwaseuthanized foreconomicreasons.Huntetal. [12] reported theexperiencewith20 cases. In these cases,11 survived less than1 month, six survived longer than 6 months, three of theseremained lame. None of the cases in that study returned toathletic performance. These studies had a large variation inthe degree of third phalanx injury at the time of initialpresentation, chronicity, shoeing and/or trimming protocolsat the time of surgery, and follow-up care. In Hunt’s study,therewere several caseswhich all received the same shoeingprotocol and postsurgical foot management. To better eval-uate the efficacy of the tenotomy procedure we considered:the degree of injury to the coffin bone of each case andincluded coffin bone disease (BD) and whether or not therewas sinkingdmedial, lateral, or verticaldof the coffin boneas part of the syndrome and whether or not the coffin bonepenetrated the sole.

2. Materials and Methods

A total of 245 chronic laminitis case records werereviewed which received the same tenotomy and realign-ment shoeing (derotation) procedure. Realignment shoeingis also known as derotation shoeing [13], but in this study,the term realignment was used to describe the farrieryprocedure. Transection of the DDFT allowed immediaterealignmentof the coffinbone relative to thegroundsurface.The procedure was a two-part processdrealignmentshoeing first and then DDF tenotomy. The realignmentshoeing was performed before surgery to minimize theeffect of the surgical preparation on the adherence of theglue to the hoof wall because of a wet field. Each case wassedated with detomidine (Dormosedan, Pfizer, New York,NY 10017) IV and an abaxial sesamoid block using carbo-caine (Carbocaine-V, Pharmacia andUpjohnCo., Kalamazoo,MI, 60064) was performed to allow the shoeing and radio-graphic procedure. After the radiographs were completed,each limbwas anesthetized using a high four point and ringblock at the proximal meta-carpal/-tarsal region. Thechronic laminitis cases seemed to stand better for shoeingand surgery using an abaxial sesamoid and a high four-point/ring anesthetic block. After the regional nerve block,the mid cannon bone areawas covered with gauze paddingand a wrap to reduce the swelling from the perineuralinjections for the shoeingprocedureandaid identificationofthe anatomical structures during surgery.

2.1. Realignment Shoeing/Foot Management

The goal for the realignment shoeing was to glue a shoeonto the foot parallel to the ground surface of the coffinbone [13]. Additionally, the shoe should have a heelextension to prevent the distal interphalangeal (DIP) jointfrom hyper-extending after transection of the tendon. Thecaudal extension of the shoe was fit to a plum line droppedfrom the proximal palmar aspect of the first phalanx withthe horse standing squarely (Fig. 3). The shoe was forgedfrom aluminum or a keg shoe is used with a heel platewelded onto the shoe. The heel plate served to improve sole

Fig. 2. Radiographs of same horse. This bone has only been displaced for less than a week. Note the indentation and/or cavitation of anterior coronary band.Quarters appear healthy with no signs of sinking and the coffin bone is healthy.

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support and provided additional support to the palmar partof the foot. The hoof was sanded and prepared for gluing ofthe shoe to the hoof wall. The sole support material (elas-tomer [Advanced Cushion Support, Nanric, Inc., Versailes,KY 40383]) was mixed and applied to the sole (Fig. 3). Theshoe was firmly placed onto the foot at the same angle asthe solar surface of P3 as viewed on the radiographs. Often,

Fig. 3. The shoe is firmly placed into the elastomer. Pressing the shoe firmly onto th

the sole support material was molded at this point intoa toe wedge to achieve proper shoe alignment (Fig. 4). Oncethe proper angle is achieved, the shoe is glued in placeusing fiberglass cloth impregnated with the adhesive(Equilox [Equilox Adhesive System, Equilox International,Pine Island, MN 55963]) leaving the toe open to minimizethe chances for abscess formation if the toe is covered with

e heel region allowing the shoe to sit directly on the hoof in the heel region.

Fig. 4. Note the shoe position aligns the ground surface of the coffin bone to the shoe. The shoe sits directly on the hoof in the heel region and is wedged up in thetoe region.

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the adhesive material (Fig. 5). This shoeing method isadequate for the majority of severe cases of chronic lami-nitis in which mechanical failure is limited to the toeregion. However, if the foot also shows injury in the heel orquarter regiondmedial or lateral sinkingdthe shoewas setslightly lower to the opposite side of the foot, the sinkingside. For clarification of the methoddif the foot is sinkingto the medial side, the shoe is set on the sole slightly loweron the lateral side to shift the weight distribution of thefoot to the lateral heel, causing the “ground/”ventralsurface of the coffin bone to be parallel to the ground asviewed on the dorso-palmar/plantar radiographic view.Coronary band grooving [14] was performed if a palpableledge or cavitation of the coronary band was present. Ahorizontal groove was performed below the coronary bandat a minimum of half-inch below the hairline and extendedthe entire length of the palpable cavitations.

2.2. Deep Digital Flexor Tenotomy

After shoeing, the feetwerewrapped inplastic to keep theacrylic adhesivedryduring the sterilepreparationof theDDFTsurgery site. The acrylic required a minimum of 6 hours ofdrying time to cure completely. The tenotomies were per-formed in the mid-cannon region, unless scar tissue orevidence of an old tendon lesion was evident and if so, thesurgery procedure was performed at the level of the pastern(Fig. 6). If the procedure was performed at the level of thepastern, the abaxial nerve block was used as the regionalanesthesia of choice. After adequate preparation of thesurgical site, a three-fourth toone-inchskin incisionwasmadeon the lateral aspect over the DDFT in themid-cannon region.The tissuewas dissected around theDDFTusingMetzenbaumscissors; small, malleable retractors were used to isolate thetendon and the DDFT transected using a number 15-scalpelblade. The skin was closed with 1-0 nonabsorbable suture invertical mattress pattern. The surgery site was covered witha sterile nonadherent dressing and cotton bandage.

If the procedure was performed at the level of thepastern, the incision was made on midline of the palmarpastern just proximal to the heel bulbs. The incision

was continued through the subcutaneous tissues to theDDFT sheath and 1.5-2” in length. The DDFT was isolatedusing hemostatic forceps to exteriorize, isolate, and transectthe tendon. The tendon sheath was closed using a 2-0absorbable suture material in a simple continuous patternand a 1-0 nonabsorbable suture material in a verticalmattress pattern. The incision was covered with a sterilenonadherent dressing and bandaged from the hoof to themetacarpal region. After the shoeing and DDF tenotomyprocedure, lateral radiographs were taken to ensure idealshoe alignment; subluxation of the DIP joint was a normalfinding on the radiographs (Fig. 7). The subluxation wasmore pronounced in some cases but did not create any long-term problems such as osteoarthritis of the DIP joint andusually “self” corrected over several shoeings. Each case wasreshod the same way at 5-6-week intervals. Following theprocedure, successful cases demonstrated rapid anterior solegrowth, and required less realignment and toe wedging ateach shoeing. Once the sole depth at the toe equaled the soledepth in the heels, the foot was shod flat orwas left barefoot.The improvements in sole depth usually took 2-3 shoeingcycles and even in cases in which the third phalanx pene-trated the sole (Fig. 8). Cases with radiographic evidence ofsevere bony disease could be rarely left without a shoe.

Caseswere categorized on the basis of: (1) degree of BD ofthe third phalanx; (2) sinking; (3) rotation; (4) sole penetra-tionof P3; (5) thenumberof feet affected; and (6) frontversushind feet and the effect on prognosis. BD was classified assevere, moderate, or not present. Severe bone disease wasconsidered to be a sign of chronicity and was defined in thestudyas significant shorteningof thedorsal surfaceof P3 seenon the lateral radiographic view. The apex of P3 had demin-eralization characterized as loss of density seen on the lateralradiographic view approaching the terminal arch. Moderatesigns of bonediseasewas described asmild demineralizationor roughening of the anterior and distal margins seen on theproximaledorsal radiographic view, but not seen on thelateral view. Remodeling or “lipping” of the distal border andmarginal rim fractures were also considered to be a sign ofmoderate bone disease. Some cases developed a divot orsmall area of demineralization on the distal dorsal surface of

Fig. 5. Once the shoe is positioned correctly it is adhered to the foot with fiberglass and acrylic. The adhesive is only used in the heel and quarters.

S. Morrison / Journal of Equine Veterinary Science 31 (2011) 89-96 93

P3, which was also classified as a moderate change. Nodetectablebonediseasewasclassifiedasahealthycoffinbonewithout any radiographic signs of demineralization orremodeling.

There are various indicators or signs of sinking. Founderdistance [15,16] or the distance between the proximalaspect of extensor process and the coronary band is variable

Fig. 6. Tenotomy procedure perform

in normal healthy feet, but a change in the distance overtime is considered to be an evidence of sinking. On physicalexamination, palpation and close inspection of the coronaryband is probably the most sensitive and accurate indicatorof sinking [17]. In our study population, sinkingwas definedas a palpable coronary band ledge or cavitations on eitherthe medial, lateral, or both quarters. Close examination of

ed in the mid-cannon region.

Fig. 7. Post-tenotomy and realignment shoeing radiograph. Note the ground surface of coffin bone is parallel to shoe. The subluxation seen here is a normal effectof the procedure. The shoe also provides adequate caudal extension.

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the compromised coronary band reveals displacement ofthe hairline beneath the hoof capsule. This is considered tobe a sign of acute vertical displacement (sinking). Radio-graphs usually show a coronary band “halo” or linear soft-tissue opacity in the quarter and heel coronary regions onthe lateral view. Separation or a palpable ledge in theanterior coronary band was considered part of pedal bonerotation and was not considered sinking in our study.

Solar penetration was defined as a visible exposure ofprolapsed sensitive sole corium/dermis or if the coffin bonewas exposed, denuded of the corium/dermis layer.

3. Results

Since 2000, a total of 1,031 chronic laminitis cases weretreated and aDDFTwas performedon301 cases. This is 29% ofthe chronic laminitis cases treated with a DDFT. The podiatrycenter is a referral center for chronic lamintis cases that havenot responded to routine shoeing prescriptions and thereforemany of the less severe cases responded to routine shoeingprocedures, eliminating these cases from our laminitis casepopulation. Of the 301 tenotomies performed, 245 cases metthe criteria for inclusion on the basis of completion anddocumentation in the medical record. Of the 245 cases, 124(51%) were considered a successdthe case survived fora minimum of a year after surgery, maintained good bodycondition, and was no more than an Obel grade 2 lameness(moved freely at the walk but may have a stiff gait, soreon turning, and able to pick up each foot when asked). To

determine the relationship each factor had on the successrate, the following was used to summarize the results in thestudy.

3.1. Effect of BD on Prognosis

� Cases with no BD and no signs of sinking or penetrationhad an 83% (72/87) success rate.

� Moderate BD and no sinking or penetration had a 93%success rate.

� Cases with severe BD and no sinking or penetrationhad a 44% (21/48) success rate.

3.2. Effect of Sinking on Prognosis

Cases with signs of sinking (medial, lateral, or vertical)had an overall success rate of 18% (17/95). Nonsinkers hada 71% (107/150) success rate.

3.3. Effect of Solar Penetration on Prognosis

Cases with penetration and no sinking had an 88%(22/25) success rate. With penetration and sinking, thesuccess rate was 25% (4/16).

3.4. Effect of Number of Limbs

Success rate for one limb was 52% (42/81), two limbs50% (79/158), four limbs 50% (3/6).

Fig. 8. Same foot observed 3 months later. The sole depth in toe region is now at a normal thickness. The subluxation has resolved. Note the ridge of new wallgrowth one-third way down the wall. At this time the foot can go barefoot.

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3.5. Effect of Front versus Hind

Success for front limb was 51% (120/237), hind limbs50% (4/8).

4. Discussion

All the study cases received the same treatmentdDDFTand the realignment/derotation shoeing protocol. Caseselection for inclusion was important to minimize differ-ences between and among study participants. Foot care andshoeing at the time of surgery and pre- and/or postsurgicalmanagement after transection of the DDFT leads us toconclude that this combination is an effective and viableoption for treatment of chronic laminitis cases in our caseseries. Categorizing the cases on the basis of presentingpathology was important to establish a more accurateprognosis. The combination procedure has the greatestsuccess in cases that have mechanical failure isolated to thetoe and no radiographic and clinical signs of sinking. Therewas no negative outcome on prognosis if the coffin bonepenetrated the sole, as long as there was no advanced BDand no physical signs of sinking in the quarters; theygenerally had a success rate of 88%. The finding that thedegree of rotation was not a factor in the long-term prog-nosis is consistent with other studies [16,17]. The highsuccess rate for the chronic laminitis cases penetrating thesole has much to do with how they were treateddas anemergencydwith the procedure performed immediately.

Although the DDFT procedure is useful in the rehabilitationin the acute sinker syndrome, it should be remembered thatthese cases have an extremely poor prognosis regardless ofthe treatment protocol used. We estimate that only 5%-10%of our clinical acute sinker population is successfully treated.In the group of sinker cases, they were believed to havea reasonable chance for rehabilitation and received a tenot-omy as part of the treatment, only 18% were considereda success using our established criteria. Bone changesviewed on radiographs take some time to develop and area consistent sign of chronicity. It is interesting that studycases with moderate BD had a better success rate, 93% (13/14), compared with the cases with no BD, 83% (72/87). Thiscan be because BD is a sign of chronicity and takes time todevelop, therefore concluding that some degree of stabilityof P3 occurs. In cases with severe instability and structuralcollapse, humane destruction is frequently recommendedbefore bone changes are evident radiographically. Except forthe extensor process, the third phalanx has a thick fibrouscovering,which is less reactive than the periosteum coveringlong bones [18]. Therefore, the coffin bone shows bonereactive changes at a much slower rate. It has been observedthat demineralization and remodeling at the distal border ofP3 in the chronic laminitic foot usually occurs about 45-60days after displacement; however, if infection is part of theclinical presentation, the radiographic changes are muchmore rapid. The number and location of limbs involved inthis case series did not seem to have an important effect onsuccess ratedabout 50% success ratedversus the overall

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success rate for the study populationwas 51% (124/245). Thelong-term prognosis appears to be dependant on the degreeof pathology of the most severely affected foot. In otherwords, if one foot is not successful the case outcome is poor.

In all, 13% or 16/124 of cases returned to some form ofathletic soundness or use. Of these 16 cases, four werediagnosed as sinkers. None of the cases with severe BDreturned to athletic use.

We believe that there are several criteria needed for thetenotomy to be successful: (1) thoughtful case selection;(2) timing of the procedure; (3) realignment shoeing as partof the tenotomy procedure; and (4) physical therapy withhandwalking or small paddock turnout if possible. The DDFTprocedure should also be performed before the patientexperiences advanced BD. If the coffin bone is severelycompromised, the BD serves as a chronic source of pain. Only44% of these cases in our series were considered successfulafter a tenotomy. We believe this is because after surgery,these cases do not mechanically load and use the limb nor-mally and rapidly heal with a contracted tenotomy withexcessive scar tissue at the surgery site. Additionally, a repeattenotomy is needed and usually results in short-term reliefwitheach repeatprocedure. Thesecases tend tohealwith lotsof scar tissue and adhesions to the superficial digital flexortendon and suspensory ligament with tissue shortening,creating a combined superficial and DDFT contracture.Recognizing that returning the limb to full weight bearing assoon as possible after surgery is important, we also believe itmay be beneficial to treat any infection or perform debride-ment before the planned tenotomy. This may not be possiblein all cases, asmost infections are secondary to compromisedtissue by displacement of P3; the DDFT and the realignmentshoeing is frequently important to successfully treat theunderlying infection. After the DDF tenotomy, a controlledexercise program with hand walking or turnout in a smallpaddock is recommended to encourage physiological loadingof the limb. If the case remains on strict stall rest for anextended period, the potential for contracture of the DDFTand ultimate loss of benefit from the surgical procedure canresult. Therefore, performing the DDF tenotomy as soon asindicated in this study leads to the best outcome. It shouldalso be emphasized that before secondary complications ofosteomyelitis and coronary band separations occur, usingshoeing alone in this study, is failing to rehabilitate the footappropriately; thus, surgeryneeds tobeperformedas soonaspossible.However,manyclinicians viewtheDDF tenotomyasa “salvageprocedure,” anddelayperforming it before the footsuffers permanent and irreversible bony pathology. This isone of the main reason the procedure has not receiveduniformacceptance and validation in other studies. Themostcritical part of the protocol is managing the foot with theappropriate trimming and shoeing in combination withsurgery, as the “key” for long-term success. The DDFtransection without realignment shoeing results in onlya short-term clinical improvement and rarely improves theprognosis. BD appears to be the determining factor in futurequality of life and clinical soundness. For this reason alone,preserving the health of the distal phalanx should be theprimary goal in rehabilitation of a chronic laminitis patient,even if this entails transection of the DDF tendon.

The three reasons to perform the DDF tenotomy andrealignment shoeing are:

1. If the foot is not growing new “horn” tissue and thereis insufficient depth of sole, the foot will remainuncompensated.

2. Clinically acceptable comfort for pasture soundnesswithshoeing alone has not been achieved. Some cases growandmaintain adequate depth of solewith shoeing alonebut are not clinically comfortable; I believe the source ofpain is frompulling on the sensitive lamina and not fromthe sole corium. These cases generally improve after theDDF tenotomy procedure.

3. The cost of maintaining a chronic laminitis case intherapeutic shoes indefinitely versus performing a DDFtentotomy and realignment shoeing, with the goal ofthe equine patient being able to be barefoot afterseveral shoeing cycles.

In conclusion, as with any surgical and therapeuticprocedure, the timing and proper case selection is essentialfor thebest long-termoutcome. The informationpresented inthis study provides useful information that can assist theequine clinician in formulating a prognosis for chronic lami-nitis cases requiring the DDF tenotomy and the realignmentshoeing procedure.

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