Acute and Chronic Laminitis: an Overview
Individualized approach based on adherence to principles produces best results
Reprinted with permission from the American Farrier Journal.
|FIGURE 1.The arrow denotes the point of breakover after the toe has been beveled on the ground surface.|
|FIGURE 2. Lateral and dorsopalmar radiographs of a horse with severe distal displacement taken 10 days after the onset of symptoms.|
|FIGURE 3. A dorsopalmar radiograph showing displacement of the distal phalanx in a horizontal plane.|
|FIGURE 4. A schematic drawing of a radiograph used for realignment of distal phalanx. It shows the lines drawn parallel to the solar surface of the distal phalanx (Line 1) and the line drawn parallel to the dorsal surface of the distal phalanx as well as the desired position of the point of breakover (Point B).|
2. We have no practical means to counteractthe vertical load of the horse'sweight that is placed on its feet. In otherwords, we have no method that allows usto take weight off the inflamed lamellae.If the horse is shod or if the horse standson a hard surface, weight bearing is transferredfrom the perimeter of the hoofwall onto the compromised lamellae.
In acute laminitis, it may be appropriateto remove the shoes if the horse isshod and apply some type of deformablematerial to the solar surface of the footsuch that the sole, bars and frog in thepalmar/plantar section of the footbecome load sharing with the hoof wall.Frog pressure has become ingrained inthe veterinary and farrier literature as amethod to support the weight of thehorse. The anatomy of the bottom of thehorses' foot, the horny frog (which variesin thickness) and the digital cushionabove it, both are readily compressiblestructures under pressure.
When pressure is placed over the frog,it quickly deforms, compresses and theinterface between the outer surface ofthe frog and the solar surface of the distal phalanx (P3) is diminished. These structurescan be irreversibly damaged by frogpressure and the animal will often feelmore discomfort. To counteract the forces acting on the bottom of the foot,it may be more advantageous to recruitthe entire solar surface of the foot insteadof relying on one structure.
This can be accomplished byapplying either thick styrofoam, one ofthe deformable impression materials orplacing the horse in sand. Applying shoesin the acute stage of laminitis, in myopinion, has not been shown to offer anyadvantages.
3. The distractive force placed on thelamellae by the deep digital flexor tendon(DDFT). In the acute stage this can bedecreased to some extent by moving thebreakover in a palmar /plantar direction.A line is drawn across the solar surfaceof the foot dorsal to the frog and a raspis used to bevel the foot in a dorsal directionfrom this line. This effectivelymoves the breakover palmarly, decreasesthe moment on the dorsal lamellae andmay lessen the forces created by theDDFT (Figure 1). Raising the heelsexcessively in the acute stage has been advocated by some but should be donewith caution, as there is no scientificproof of a beneficial effect.
Laminitis as a consequence of systemic disease such as gastrointestinalproblems, respiratory disease, retainedfetal membranes or contralateral limblaminitis results in distal displacement(sinking) of the distal phalanx ( Figure 2).In this case the entire lamellae attachmentsare damaged, allowing the distalphalanx to sink uniformly within thehoof capsule.
Raising The Heels
There is minimal involvement of thedeep digital flexor tendon during thissinking process. A common treatmentregimen for distal displacement is to raisethe heels with the theory that it decreasesstresses on the DDFT, a practice that Ihave not seen to be successful. Movingthe breakover back and placing a uniformlayer of a deformable impression materialon the bottom of the foot or placingthe horse in sand may be a better option.
Recently, I have applied wooden shoesto horses with acute laminitis that areexpected to rotate or sink. These shoes have the border of the ground surface atthe toe and sides cut on an angle and theresults are very encouraging. They will bedescribed later in the text.
Baseline radiographs consisting of alateral and dorsopalmar view (to diagnoseunilateral displacement of the distalphalanx in a horizontal direction) shouldalways be taken during the initial examinationof acute laminitis. They can beused to determine previous damage, tofollow the progression of the disease andas a guide to trimming and shoeing thehorse at the appropriate time.
Rehabilitation of the horse withchronic laminitis is not a “cookbook”process as affected horses with chronic laminitis will vary from horse to horseand foot to foot and our understanding ofthe disease is still vague. However, theunderstanding of digital mechanics hasimproved and technological advances inshoe design and materials and techniquescontinue to expand.
Chronic laminitis by definition meansthat the distal phalanx (P3) has displacedwithin the hoof capsule. The distalphalanx can rotate downward at the toe,rotate to either side (laterally or medially)or it can totally displace (sink) withinthe hoof capsule. Rehabilitation of thehorse with chronic laminitis will againdepend on the amount of viable lamellaethat remain intact, the conformation ofthe foot and the ability to realign thedistal phalanx within the hoof capsule.
The question is often asked as to whena horse with chronic laminitis should beshod. The guidelines are:
I have never been successful nor haveI observed improvement in the laminitic state when having to use local anesthesiain order to lift the horses foot and applya shoe before the foot has stabilized.
The lateral radiograph is often theonly film taken for evaluating chroniclaminitis but it does not allow identificationof asymmetrical medial or lateraldistal displacement. Therefore, theauthor considers it crucial that adorsopalmar (AP) radiographic projectionis included as part of the radiographicstudy for either acute or chroniclaminitis. High quality radiographs arerequired to visualize the osseous structureswithin the hoof capsule as well asthe hoof capsule itself.
Radio-opaque markers can be usedto determine the position of the distalphalanx in relation to surface landmarks.The radiographic features of chroniclaminitis are well documented.
The following observations from thelateral radiograph are important in determiningthe prognosis and guiding treatment:
The dorsopalmar radiograph is examinedto determine the position of thedistal phalanx in the frontal plane.Asymmetrical distal displacement of thedistal phalanx on either the lateral ormedial side is present if an imaginaryline drawn across the articular surface ofthe distal interphalangeal joint orbetween the solar foramens of the distalphalanx is not parallel to the ground, thejoint space is widened on the affectedside and narrowed on the opposite side,and the width of the hoof wall appearsthicker than normal on the affected side (Figure 3).
Finally, radiology will form the guidelines to be used in realigning the distal phalanx and applying any type of farriery (Figure 4).
Trimming and shoeing has alwaysbeen the mainstay of treating chroniclaminitis and is directed at reducing andorremoving the adverse forces on thecompromised lamellae. In consideringhoof care in horses with chroniclaminitis, there are three goals fortherapy:
Realignment of the third phalanx tocreate a better relationship of the solarsurface of the distal phalanx with theground is used as the basis for treatingchronic laminitis. Realignment of thedistal phalanx should promote andproduce hoof wall growth at the coronetand sole growth under the distal phalanx.
Applying any type of shoe followingthis procedure should complement therealignment of the distal phalanx andfurther decrease the forces on thelamellae.
The principles applied to all shoeingmethods used in treating chroniclaminitis are to recruit ground surface,reposition the breakover palmarly andto provide heel elevation as needed. Ourshoe of choice is usually some type ofwide web aluminum shoe with heelelevation either incorporated within theshoe, in the form of rails or a heel wedgeinsert if an adequate heel base is present.
Deformable impression material isapplied between the branches of the shoeto increase the surface area and redistributethe load. Breakover can easily becut into the shoe in the appropriate placeusing a grinder. The center of rotation canbe used for accurate placement of theshoe on the foot.
|FIGURE 5.This is a wooden shoe with impression material. The black arrow signifies the widest part of the foot. Red line denotes the point of breakover on the ground surface of the shoe.|
|FIGURE 6. A wooden shoe applied to the foot with screws placed against the foot at the heels to act as struts to accommodate fiberglass-casting tape.|
Recently this writer has been verysuccessful using a wooden block cut inthe shape of the foot with the border ofthe ground surface cut on an angle of atleast 45 degrees (Figure 5). The foot istrimmed appropriately to addressrealignment, impression material isformed to create an interface betweenthe solar surface of the foot and thewooden shoe, heel elevation is used ifnecessary and the shoe is applied atraumaticallyusing screws, casting tape andor a composite (Figure 6).
With this procedure flat, even pressureis placed across the palmar section ofthe foot and all the mechanics are placedin the block while preserving the hoofcapsule.
Deep digital flexor tenotomy remainsa very useful procedure for treatingchronic laminitis. I consider this surgerynecessary if the margin of the distalphalanx has prolapsed through the soleor on those cases that fail to stabilize once they begin displacing.
As stated earlier, two of the maindetriments when treating chroniclaminitis are the weight of the horse andthe distractive force of the DDFT. One ofthese detrimental forces can be removedthrough this surgery. but knowing whento use it may pose a dilemma. It is oftennecessary to use this procedure in orderto realign the distal phalanx.
|FIGURE 7. A radiograph showing marked rotation with a flexural deformity involving the DIP joint. A DDF tenotomy is necessary to realign the distal phalanx.|
Further indications for this surgeryare progressive rotation, persistent pain,minimal hoof wall and/or sole growthand secondary flexor apparatus contracture.If a marked flexural deformityinvolving the distal interphalangeal joint(DIP) is present, this is an indication ofshortening of the musculotendonous unitand a release procedure is necessary toaccomplish realignment of the distalphalanx (Figure 7).
It has to be emphasized that if a deep digital flexor tenotomy is utilized, it must be accompanied by realignment of the distal phalanx to decrease the adverse forces on the lamellae. Following a DDFT tenotomy, the second phalanx will move distal and palmarly relative to the distal phalanx (P3). This concentrates the load on the palmar soft tissue structures of the foot rather than redistributing the load on the solar surface of the distal phalanx.
The author has found it helpful to usea shoe or a cuff to extend the groundsurface beyond the heel and add a fewdegrees of heel elevation. This willrealign the digital axis and appears toimprove the clinical perimeters (comfort,hoof capsule changes, sole growth, etc.)following surgery.
Unfortunately, many of the treatmentregimens — both medical and farriery —that are used to treat acute and chroniclaminitis are based on tradition, theoreticalassumptions that a given treatmentshould work and anecdotal evidence thata certain type of treatment has worked onprevious cases.
There are no controlled studiescomparing efficacy of the numerous treatments in use nor is there any scientificproof that one treatment is superiorto another. What are well documentedare the forces and mechanics applicableto the equine foot. As clinicians (veterinarians and farriers), we may be betterserved by a thorough knowledge andunderstanding of the anatomy, physiologyand function of the hoof.Understanding the foot in a mechanicalsense may allow us to better apply ourpreferential treatment.
Treatment of laminitis has to be agroup effort equally shared betweenveterinarian, farrier and owner. The intentof this paper is not to discourage treatmentof laminitis but to create expectationsthat are realistic, humane and basedon the cause of the disease, amount oflamellar damage, pain, duration and thefinancial constraints invo l ved inprolonged treatment.
At the onset of treating chroniclaminitis, certain guidelines should beoutlined to indicate the efficacy of the chosen treatment method along with areasonable timeframe for improvement.
These guidelines could be a change instance, decreased digital pulse, increasedcomfort, horn growth at the coronet, solegrowth, etc. If the desired improvementis not observed or the condition getsworse, the overall farriery methodsshould be reassessed and changed wherenecessary.
With severe laminitis cases, we areoften unable to rehabilitate the horse towhere it has an acceptable quality of life.The main reason being that there areinsufficient soft tissue structuresremaining within the hoof to achieverealignment.
I think it is important from a humaneperspective to know when to discontinuetreatment that has not been effective.Often we persevere with various treatments,put the horse through muchunnecessary suffering only to achieve anunsatisfactory outcome.
It is unlikely that there will ever be asingle drug or other line of therapy totreat acute or chronic laminitis so ourresearch efforts need to be directedtoward prevention.
Dr. Steve O'Grady is both a veterinarianand a farrier. He operatesNorthern Virginia Equine in Marshall,Va., which is an equine podiatry practiceand also offers a podiatryconsulting service. He is the chairmanof the AAEP veterinarian-farriercommittee and a member of theInternational Equine VeterinariansHall of Fame.
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