Laminitis: Difference between revisions

[[File:Laminitis radiograph with annotation.jpg|thumb|300px|right|[[Radiograph]] of a horse hoof showing rotation of the [[pedal bone|coffin bone]] and evidence of sinking, a condition often associated with laminitis. The annotation P2 stands for the [[Equine forelimb anatomy#Bones of the distal forelimb|middle phalanx]], or [[pastern]] bone, and P3 denotes the distal phalanx, or coffin bone. The yellow lines mark the distance between the top and bottom part of the coffin bone relative to the hoof wall, showing the distal (bottom) of the coffin bone is rotated away from the hoof wall.]]

'''Laminitis''' is a diseaseinflammation of laminae that affects the feet of [[hooved animals|ungulatesungulate]]s and is found mostly in [[horse]]s and [[cattle]]. Clinical signs include foot tenderness progressing to inability to walk, increased digital pulses, and increased temperature in the hooves. There is also swelling in foot in some cases.Severe cases with outwardly visible clinical signs are known by the colloquial term '''[[#Rotation, sinking, and founder|founder]]''', and progression of the disease will lead to perforation of the coffin bone through the sole of the hoof or being unable to stand up, requiring [[Animal euthanasia|euthanasia]].

{{Main |Horse hoof#Internal structures}}

The bones of the hoof are suspended within the [[Anatomical terms of location#Other directional terms|axial]] hooves of ungulates by layers of modified skin cells, known as '''laminae''' or '''lamellae''', which act as shock absorbers during locomotion. In horses, there are about 550–600 pairs of primary [[epidermis (zoology)|epidermal]] laminae, each with 150–200 secondary laminae projectionprojecting from their surface.<ref name="Equine Emerg">{{cite book | last1 = Orsini | first1 = James | first2 = Thomas | last2 = Divers | name-list-style = vanc |title=Equine Emergencies|date=2014|publisher=Elsevier|location=St. Louis, MO|isbn=978-1-4557-0892-5|pages=697–712|edition=4th}}</ref> These interdigitate with equivalent structures on the surface of the [[coffin bone]] (PIII, P3, the third [[Phalanx bones|phalanx]], pedal bone, or distal phalanx), known as [[dermal]] laminae.<ref>{{cite book | first = Christopher C | last = Pollitt | name-list-style = vanc |year=1995 |title= Color Atlas of the Horse's Foot |publisher= Mosby |isbn= 978-0-7234-1765-1 }}</ref> The secondary laminae contain [[Stratum basale|basal cell]]s which attach via [[hemidesmosome]]s to the [[basement membrane]]. The basement membrane is then attached to the coffin bone via the connective tissue of the dermis.<ref name="Equine Emerg"/>

Laminitis literally means inflammation of the laminae, and while it remains controversial whether this is the primary mechanism of disease, evidence of inflammation occurs very early in some instances of the disease.<ref>{{cite journal | vauthors = Loftus JP, Black SJ, Pettigrew A, Abrahamsen EJ, Belknap JK | title = Early laminar events involving endothelial activation in horses with black walnut- induced laminitis | journal = American Journal of Veterinary Research | volume = 68 | issue = 11 | pages = 1205–11 | date = November 2007 | pmid = 17975975 | doi = 10.2460/ajvr.68.11.1205 | doi-access = free }}</ref> A severe inflammatory event is thought to damage the basal epithelial cells, resulting in dysfunction of the [[hemidesmosome]]s and subsequent reduction in adherence between the epithelial cells and the [[basement membrane]].<ref name="Baxter"/> Normal forces placed on the hoof are then strong enough to tear the remaining laminae, resulting in a failure of the interdigitation of the epidermal and dermal laminae between the hoof wall and the coffin bone. When severe enough, this results in displacement of the coffin bone within the hoof capsule.<ref name="Baxter">{{cite book|last1=Baxter|first1=Gary | name-list-style = vanc |title=Manual of Equine Lameness|date=2011|publisher=Wiley-Blackwell|location=Ames, Iowa|isbn=978-0-8138-1546-6|pages=257–262|edition=1st}}</ref> Most cases of laminitis occur in both front feet, but laminitis may be seen in all four feet, both hind feet, or in cases of support limb laminitis, in a single foot.<ref name="Baxter"/>

[[File:Laminitis embedding hc biovision.jpg|thumb|250px|Hoof sagittal section with massive inflammation and rotation of third phalanx.]]

[[File:2015-09-07. Архипо-Осиповка 026.jpg|thumb|The front feet of this horse exhibit the rings and overgrowth typical of foundered horses.]]

*Anecdotal reports of laminitis following the administration of drugs have been made, especially in the case of [[corticosteroid]]s. The reaction may be an expression of idiosyncrasy in a particular patient, as many horses receive high dose [[glucocorticoid]] into their joints without showing any evidence of clinical laminitis.<ref>{{cite journal |title=Clinical use of triamcinolone acetonide in the horse (205 cases) and the incidence of glucocorticoid‐inducedglucocorticoid-induced laminitis associated with its use |journal=Equine Veterinary Education|volume=16|issue=2|pages=86–89|doi=10.1111/j.2042-3292.2004.tb00272.x|year=2010|last1=McCluskey|first1=M. J.|last2=Kavenagh|first2=P. B.}}</ref> <ref>{{cite journal |title=No Evidence That Therapeutic Systemic Corticosteroid Administration is Associated With Laminitis in Adult Horses Without Underlying Endocrine or Severe Systemic Disease |year=2016|doi=10.18849/ve.v1i1.12|url=https://www.veterinaryevidence.org/index.php/ve/article/view/12/17|last1=McGowan|first1=Cathy|last2=Cooper|first2=Daniel|last3=Ireland|first3=Joanne|journal=Veterinary Evidence|volume=1|doi-access=free}}</ref>

**::* Weanlings will have a greater proximal HL compared to distal HL

**::* Yearlings will have approximately equal proximal and distal HL

**::* Thoroughbreds are usually 17mm proximally, and 19mm distally

**::* Standardbreds have been shown to have a similar proximal and distal HL, around 16&nbsp;mm at 2 years old, and 20&nbsp;mm at 4 years old

**::* Warmbloods have similar proximal and distal values, up to 20&nbsp;mm each

**::* HL tends to increase with age, up to 17&nbsp;mm in most light breeds, or higher, especially in very old animals

In laminitis cases, a clear distinction must be made between the acute onset of a laminitis attack and a chronic situation.<ref>{{Cite web |title=Laminitis in Horses - Musculoskeletal System |url=https://www.msdvetmanual.com/musculoskeletal-system/lameness-in-horses/laminitis-in-horses |access-date=2023-11-30 |website=MSD Veterinary Manual |language=en}}</ref> A chronic situation can be either stable or unstable. The difference between acute, chronic, stable, and unstable is of vital importance when choosing a treatment protocol. There is no cure for a laminitic episode and many go undetected.<ref>{{Cite web |last=Director |first=Stephanie L. Church, Editorial |date=2020-02-05 |title=How to Support Horses With Acute or Chronic Laminitis |url=https://thehorse.com/184663/how-to-support-the-horse-with-acute-or-chronic-laminitis/ |access-date=2023-11-30 |website=The Horse |language=en-US}}</ref> Initial treatment with [[cryotherapy]] and anti-inflammatory drugs may prevent mechanical breakdown if instituted immediately, but many cases are only detected after the initial microscopic damage has been done.<ref>{{CitationCite journal |last1=Van Eps |first1=A. W. |last2=Pollitt |first2=C. C. needed|date=May2004 2009|title=Equine laminitis: cryotherapy reduces the severity of the acute lesion |url=https://beva.onlinelibrary.wiley.com/doi/10.2746/0425164044877107 |journal=Equine Veterinary Journal |language=en |volume=36 |issue=3 |pages=255–260 |doi=10.2746/0425164044877107 |pmid=15147134 |issn=0425-1644}}</ref><ref>{{Cite journal |last1=Jacobs |first1=Carrie C. |last2=Schnabel |first2=Lauren V. |last3=McIlwraith |first3=C. Wayne |last4=Blikslager |first4=Anthony T. |date=2022 |title=Non-steroidal anti-inflammatory drugs in equine orthopaedics |journal=Equine Veterinary Journal |language=en |volume=54 |issue=4 |pages=636–648 |doi=10.1111/evj.13561 |issn=0425-1644 |pmc=9304133 |pmid=35076950}}</ref> In cases of sepsis or endotoxemia, the underlying cause should be addressed concurrently with laminitis treatment.<ref name="Baxter"/> There are various methods for treating laminitis, and opinions vary on which are most useful. Additionally, the each horse and affected hoof should be evaluated individually to determine the best treatment plan, which may change with time.<ref name="Equine Emerg"/> Ideally, affected hooves are re-evaluated on a regular basis once treatment commences to track progress.<ref name="Equine Emerg"/>

In the case of a full-blown case of laminitis, use of a cold water spa proved effective in the treatment of the thoroughbred racehorse [[Bal a Bali]]. For the first three days, Bal a Bali was kept in the spa for eight hours at a time. Once his condition stabilized, he continued to be put in the spa twice a day over the next few months.<ref name=Miracle>{{cite web |last1=Shulman |first1=Lenny | name-list-style = vanc |title=Making of a Miracle |url= https://vet.osu.edu/sites/vet.osu.edu/files/legacy/userimages/u89/BH29-BalABali.pdf |website=vet.osu.edu (reprint from The Blood-Horse)|access-date=20 March 2017|url-status=live|archive-url=https://web.archive.org/web/20161217150726/http://www.vet.osu.edu/sites/vet.osu.edu/files/legacy/userimages/u89/BH29-BalABali.pdf|archive-date=17 December 2016}}</ref> He eventually recovered enough to win two Grade 1 races before retiring to stud.<ref>{{cite web|last1=Scott|first1=Jeff|title=From Off the Pace: Master off Derby trail; Bal a Bali wins Grade 1|url=http://www.saratogian.com/sports/20170313/from-off-the-pace-master-off-derby-trail-bal-a-bali-wins-grade-1|website=Saratogian Pinksheet|accessdate=14 March 2017|language=en}}</ref><ref>{{cite web|last1=Novak|first1=Claire|title=Comeback King Bal a Bali Takes Shoemaker Mile|url=http://www.bloodhorse.com/horse-racing/articles/221912/comeback-king-bal-a-bali-takes-shoemaker-mile|website=BloodHorse.com|accessdate=3 June 2017|language=en}}</ref>

Anti-inflammatories are always used when treating acute case of laminitis, and include Nonsteroidal anti-inflammatory medications ([[NSAIDS]]), DMSO, pentoxpfylline, and cryotherapy.<ref name="Baxter"/> For analgesia, NSAIDs are often the first line of defense. [[Phenylbutazone]] is commonly used for its strong effect and relatively low cost. [[Flunixin]] (Banamine), ketofen, and others are also used. Nonspecific NSAIDs such as [[suxibuzone]], or [[COX-2 selective inhibitor|COX-2]]-specific drugs, such as [[firocoxib]] and [[diclofenac]], may be somewhat safer than phenylbutazone in preventing NSAID toxicity such as [[Horse colic#rightRight dorsal colitis|right dorsal colitis]], [[Equine gastric ulcer syndrome|gastric ulcers]], and kidney damage.<ref name="pmid8420909">{{cite journal | vauthors = MacAllister CG, Morgan SJ, Borne AT, Pollet RA | title = Comparison of adverse effects of phenylbutazone, flunixin meglumine, and ketoprofen in horses | journal = Journal of the American Veterinary Medical Association | volume = 202 | issue = 1 | pages = 71–7 | date = January 1993 | doi = 10.2460/javma.1993.202.01.71 | pmid = 8420909 }}</ref><ref>{{cite conference |first1=David |last1=Sabaté | first2 = Josep | last2 = Homedes | first3 = I | last3 = Mayós | first4 = R | last4 = Calonge | name-list-style = vanc | date = January 2005 | conference = 11th SIVE Congress | location = Pisa |title=Suxibuzone as a Therapeutical Alternative to Phenylbutazone in the Treatment of Lameness in Horses |url=http://www.ivis.org/proceedings/SIVE/2005/free_com/Sabate.pdf |access-date=2008-04-19 |display-authors=etal |url-status=live |archive-url=https://web.archive.org/web/20050529051837/http://www.ivis.org/proceedings/SIVE/2005/free_com/Sabate.pdf |archive-date=2005-05-29 }}</ref><ref name="pmid18167116">{{cite journal | vauthors = Doucet MY, Bertone AL, Hendrickson D, Hughes F, Macallister C, McClure S, Reinemeyer C, Rossier Y, Sifferman R, Vrins AA, White G, Kunkle B, Alva R, Romano D, Hanson PD | display-authors = 6 | title = Comparison of efficacy and safety of paste formulations of firocoxib and phenylbutazone in horses with naturally occurring osteoarthritis | journal = Journal of the American Veterinary Medical Association | volume = 232 | issue = 1 | pages = 91–7 | date = January 2008 | pmid = 18167116 | doi = 10.2460/javma.232.1.91 }}</ref> However, firocoxib provides less pain relief than phenylbutazone or flunixin.<ref name="Equine Emerg"/> Care must be taken that pain is not totally eliminated, since this will encourage the horse to stand and move around, which increases mechanical separation of the laminae.<ref name="Equine Emerg"/>

Besides pain management and control of any predisposing factors, mechanical stabilization is a primary treatment goal once the initial inflammatory and metabolic issues have resolved. No approach has been shown to be effective in all situations, and debate is ongoing about the merits and faults of the numerous techniques. Once the distal phalanx rotates, it is essential to derotate and re-establish its proper spatial orientation within the hoof capsule, to ensure the best long-term prospects for the horse. With correct trimming and, as necessary, the application of [[orthotic]]s, one can effect this reorientation. However, this is not always completely effective.<ref>{{Cite journal |last1=Parks |first1=Andrew |last2=O'Grady |first2=Stephen E |date=2003-08-01 |title=Chronic laminitis: current treatment strategies |url=https://www.sciencedirect.com/science/article/pii/S0749073903000191 |journal=Veterinary Clinics of North America: Equine Practice |series=Podiatry |volume=19 |issue=2 |pages=393–416 |doi=10.1016/S0749-0739(03)00019-1 |pmid=14575166 |issn=0749-0739}}</ref><ref>{{Cite web |title=Tenotomy as a treatment for Laminitis |url=https://www.equipodiatry.com/news/articles/tenotomyhtm |access-date=2023-11-30 |website=www.equipodiatry.com}}</ref><ref>{{Cite journal |last=Baxter |first=Gary M. |date=1994-12-01 |title=Acute Laminitis |url=https://www.sciencedirect.com/science/article/pii/S0749073917303516 |journal=Veterinary Clinics of North America: Equine Practice |series=Emergency Treatment in the Adult Horse |volume=10 |issue=3 |pages=627–642 |doi=10.1016/S0749-0739(17)30351-6 |pmid=7704823 |issn=0749-0739}}</ref>

Successful treatment for any type of founder must necessarily involve stabilization of the bony column by some means. Correct trimming can help improve stabilization. This usually includes bringing the "break over" back to decrease the fulcrum-effect that stresses the laminae. Trimming the heels helps to ensure [[Horse hoof#The frog|frog]] pressure and increases surface area for weight-bearing on the back half of the hoof.<ref>{{Cite nameweb |title="EquineRealigning Emerg"Trim |url=https://www.thelaminitissite.org/realigning-trim.html |access-date=2023-11-30 |website=The Laminitis Site |language=en}}</ref> While horses may stabilize if left barefooted, some veterinarians believe the most successful methods of treating founder involve positive stabilisation of the distal phalanx, by mechanical means, e.g., shoes, pads, polymeric support, etc. Pour-in pads or putty is sometimes placed on the sole to increase surface area for weight-bearing, so that the sole in the area of the quarters, and the bars, will take some of the weight.<ref>{{Cite namejournal |last1="Reilly |first1=Patrick T. |last2=Dean |first2=Emily K. |last3=Orsini |first3=James A. |date=2010-08-01 |title=First Aid for the Laminitic Foot: Therapeutic and Mechanical Support |url=https://www.sciencedirect.com/science/article/pii/S0749073910000490 |journal=Veterinary Clinics of North America: Equine Emerg"Practice |series=Advances in Laminitis, Part II |volume=26 |issue=2 |pages=451–458 |doi=10.1016/j.cveq.2010.06.004 |pmid=20699187 |issn=0749-0739}}</ref><ref>{{Cite web |date=2016-02-14 |title=Managing the Laminitic and Foundered Horse with Sole Support |url=https://www.horsejournals.com/horse-care/hoof-care/managing-laminitic-and-foundered-horse-sole-support |access-date=2023-11-30 |website=Horse Journals |language=en}}</ref>

The deep digital flexor tendon places a constant pull on the back of the coffin bone. This is sometimes counteracted by decreasing the palmar angle of the hoof by raising the heels, often with the use of special shoes which have a wedge in the heel of approximately 20 degrees.<ref>{{Cite journal |last1=Ramsey |first1=G. D. |last2=Hunter |first2=P. J. |last3=Nash |first3=M. P. |date=2011 |title=The effect of hoof angle variations on dorsal lamellar load in the equine hoof |url=https://beva.onlinelibrary.wiley.com/doi/10.1111/j.2042-3306.2010.00319.x |journal=Equine Veterinary Journal |language=en |volume=43 |issue=5 |pages=536–542 |doi=10.1111/j.2042-3306.2010.00319.x |pmid=21496082 |issn=0425-1644}}</ref><ref>{{Cite web |last=MA |first=Christa Lesté-Lasserre |date=2023-10-10 |title=Researchers Compare Therapeutic Shoes for Horses with Laminitis |url=https://thehorse.com/1123873/researchers-compare-therapeutic-shoes-for-horses-with-laminitis/ |access-date=2023-11-30 |website=The Horse |language=en-US}}</ref> Shoes are usually glued or cast onto the foot so painful nailing does not have to take place.<ref>{{Cite web |title=Gluing Shoes To Hoof Boots To Treat Chronic Laminitis |url=https://www.americanfarriers.com/articles/8129-gluing-shoes-to-hoof-boots-to-treat-chronic-laminitis |access-date=2023-11-30 |website=www.americanfarriers.com |language=en}}</ref> The position of P3 within the hoof is monitored with radiographs. Once the horse has improved, the wedge of the shoe must be slowly reduced back to normal.<ref>{{Cite nameweb |last="EquineCF Emerg"|first=Craig Lesser, DVM |date=2022-09-13 |title=Managing Laminitic Horses Using Radiographs |url=https://thehorse.com/1115635/managing-laminitic-horses-using-radiographs/ |access-date=2023-11-30 |website=The Horse |language=en-US}}</ref>

The application of external orthotic devices to the foot in a horse with undisplaced laminitis and once displacement has occurred is widespread. Most approaches attempt to shift weight away from the laminae and onto secondary weight-bearing structures, while sparing the sole.<ref>{{Cite web |title=Laminitis in Horses |url=https://www.acvs.org/large-animal/laminitis-in-horses/ |access-date=2023-11-30 |website=American College of Veterinary Surgeons |language=en-US}}</ref><ref>{{Cite journal |last1=Reilly |first1=Patrick T. |last2=Dean |first2=Emily K. |last3=Orsini |first3=James A. |date=2010-08-01 |title=First Aid for the Laminitic Foot: Therapeutic and Mechanical Support |url=https://www.sciencedirect.com/science/article/pii/S0749073910000490 |journal=Veterinary Clinics of North America: Equine Practice |series=Advances in Laminitis, Part II |volume=26 |issue=2 |pages=451–458 |doi=10.1016/j.cveq.2010.06.004 |pmid=20699187 |issn=0749-0739}}</ref>

Corrective hoof trimming will restore proper hoof form and function. Corrective trimming will allow the hooves to be healthy again.<ref>{{Cite web |title=Disorders of the Foot in Horses - Horse Owners |url=https://www.merckvetmanual.com/horse-owners/bone,-joint,-and-muscle-disorders-in-horses/disorders-of-the-foot-in-horses |access-date=2023-11-30 |website=Merck Veterinary Manual |language=en-US}}</ref>

Realigning trimming trims back the toe so that it is in line with the coffin bone. Realigning trimming pushes the coffin bone back into the correct position. The process of a new hoof capsule totally growing out to replace the old one takes up to a year.<ref>{{Cite journal |last1=Aoun |first1=Rita |last2=Charles |first2=Iyana |last3=DeRouen |first3=Abigail |last4=Takawira |first4=Catherine |last5=Lopez |first5=Mandi J. |date=2023 |title=Shoe configuration effects on third phalanx and capsule motion of unaffected and laminitic equine hooves in-situ |journal=PLOS ONE |volume=18 |issue=5 |pages=e0285475 |doi=10.1371/journal.pone.0285475 |issn=1932-6203 |pmid=37155654 |pmc=10166494 |doi-access=free |bibcode=2023PLoSO..1885475A }}</ref>

Because the rotation of P3 is exacerbated by continued pull on the deep digital flexor tendon, one approach to therapy has been to cut this tendon, either in the cannon region (mid-metacarpus)<ref name="Baxter"/> or in the [[pastern]] region. Over a time period of 6 weeks, tenotomy is thought to allow P3 to realign with the ground surface.<ref name="Baxter"/> Critics claim that this technique is unsuccessful and invasive, with advocates making counter-arguments that it is often used in cases which are too far advanced for treatment to help.<ref name="pmid10029854">{{cite journal | vauthors = Eastman TG, Honnas CM, Hague BA, Moyer W, von der Rosen HD | title = Deep digital flexor tenotomy as a treatment for chronic laminitis in horses: 35 cases (1988-1997) | journal = Journal of the American Veterinary Medical Association | volume = 214 | issue = 4 | pages = 517–9 | date = February 1999 | doi = 10.2460/javma.1999.214.04.517 | pmid = 10029854 | url = http://www.ivis.org/proceedings/AAEP/1998/Eastman.pdf }}</ref> Tenotomy does risk subluxation of the distal interphalangeal joint (coffin joint),<ref name="Baxter"/> which may be avoided with the use of heel extensions on the shoe.<ref name="Equine Emerg"/> Horses may return to work after the surgery.<ref name="Equine Emerg"/> This treatment is often recommended for severe cases of laminitis, and requires proper trimming and shoeing to be successful.<ref name="Equine Emerg"/>

* {{cite book | first = Doug | last = Butler | name-list-style = vanc | title = The Principles of Horseshoeing II and The Principles of Horseshoeing III | isbn = 978-0-916992-26-2 | year = 2004 | publisher = Doug Butler Enterprises }}