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== Introduction ==

== Introduction ==

Laminits is a common and debilitating condition of horses cause by separation of the laminae of the hoof. It can be acute or chronic and can result in the horse being put down. To revise the anatomy of the hoof see [[Equine Phalanges - Anatomy & Physiology]]

Laminits is a common and debilitating condition of horses cause by '''separation of the laminae of the hoof'''. It can be acute or chronic and can result in the horse being put down. To revise the anatomy of the hoof see [[Equine Phalanges - Anatomy & Physiology]]

== Aetiology ==

== Aetiology ==

Laminitis is an acute degeneration of the sensitive primary and secondary Laminae. The cause for this is unknown.

Laminitis is an '''acute degeneration''' of the '''sensitive primary and secondary Laminae'''. The cause for this is unknown.

== Epidemiology==

== Epidemiology==

* Obesity

* Obesity

* Access to lush pastures - particularly in the early morning when high levels of fructans are present in the grass

* Access to lush pastures - particularly in the Spring or Autumn, on cold bright days, and during daylight hours with levels of fructans are highest

* Grain overload (Ingestion of large quantities of soluble carbohydrates)

* Grain overload (Ingestion of large quantities of soluble carbohydrates)

* Retained Placenta, [[Colic|colic]], diarrhoea and any other systemic illness causing endotoxaemia

* Retained Placenta, [[Colic|colic]], diarrhoea and any other systemic illness causing endotoxaemia

[[File:Founder_severe_rotation.JPG|right|thumb|200px|Severe pedal bone rotation with penetration into the hoof sole (Wikimedia Commons)]]

[[File:Founder_severe_rotation.JPG|right|thumb|200px|Severe pedal bone rotation with penetration into the hoof sole (Wikimedia Commons)]]

The separation of the sensitive laminae (originated from the third phalanx/pedal bone) from the laminae lining the inside surface of the hoof.

The separation of the sensitive laminae (originated from the third phalanx/pedal bone) from the laminae lining the inside surface of the hoof.

This allows the pedal bone to '''rotate''' within the hoof capsule and come to rest on the sole. This causes the sole to be pushed downwards and at the toe the pedal bone mat penetrate the sole.

This allows the pedal bone to '''rotate''' within the '''hoof capsule''' and come to '''rest on the sole'''. This causes the sole to be pushed downwards and at the toe the pedal bone may penetrate the sole.

Rotation occurs due to torque from the deep digital flexor tendon.

Rotation occurs due to '''torque''' from the '''deep digital flexor tendon'''.

Also due to the weight of the animal the pedal bone can '''sink''' (displace ventrally). The bone may rotate, sink or both.

Also due to the weight of the animal the pedal bone can '''sink''' (displace ventrally). The bone may rotate, sink or both.

Serum accumulates in the space between the laminae and can breakdown the white line.

Serum accumulates in the space between the laminae and can breakdown the white line.

The mechanism is unknown but theories are:

The mechanism is unknown but theories are:

(1) Ischaemia and necrosis. Ischaemia may be caused by vasoconsriction, arterio-venous shunts, interstitial oedema or a mixture of all three mechanisms.  

(1) '''Ischaemia and necrosis'''. Ischaemia may be caused by vasoconsriction, arterio-venous shunts, interstitial oedema or a mixture of all three mechanisms.  

(2) Inflammation and then degeneration of the sensitive laminae

(2) '''Inflammation''' and then '''degeneration''' of the sensitive laminae

(3) Enzymatic digestion of laminae by Matrix Metalloproteins (MMPs)

(3) '''Enzymatic digestion''' of laminae by Matrix Metalloproteins (MMPs)

(4) Abnormalities in the hoof metabolism or corticosteriods (Endogenous cortisol or iatrogenic) which results in increased glucocorticoid activity.

(4) '''Abnormalities in the hoof metabolism or corticosteriods''' (Endogenous cortisol or iatrogenic) which results in increased glucocorticoid activity.

Subsequent to separation of the laminae a '''pain-hypertension-vasoconstiction''' cycle will occur in acute cases. Pain causes the release of vasoconstictors such as catecholamines, angiotensin II, and vasopressin. This vasoconstriction then causes a reduced blood flow to the foot and systemic hypertension.

Subsequent to separation of the laminae a '''pain-hypertension-vasoconstiction''' cycle will occur in acute cases. '''Pain''' causes the release of '''vasoconstictors''' such as catecholamines, angiotensin II, and vasopressin. This vasoconstriction then causes a '''reduced blood flow to the foot''' and systemic hypertension.

== Clinical Signs ==

== Clinical Signs ==

=== Acute Disease ===

=== Acute Disease ===

Acute disease develops rapidly and most commonly occurs in the front feet. In the early stages of disease or if the case is mild the horse presents as reluctant to move, with frequently shifting of weight between the affected feet and a characteristic stilted gait.

Acute disease develops rapidly and most commonly occurs in the '''front feet'''. In the early stages of disease or if the case is mild the horse presents as '''reluctant to move''', with frequently '''shifting of weight between the affected feet''' and a characteristic '''stilted gait'''.

In more severe cases the horse normally presents with a characteristic posture in which the horse appears to be leaning back on its heels. In this posture the feet are placed normally but the head is low and the back arched as the horse attempts to relieve the pressure on the toe, particularly in the fore-feet. The horse may also be unwilling to move or pick up its feet and can potentially collapse if it is forced to do so. Signs of pain such as anxiety, sweating, increased heart and respiration rate are frequently seen.  

In more severe cases the horse normally presents with a characteristic '''posture''' in which the horse appears to be '''leaning back on its heels'''. In this posture the feet are placed normally but the '''head is low''' and the '''back arched''' as the horse attempts to '''relieve the pressure on the toe''', particularly in the fore-feet. The horse may also be '''unwilling to move''' or pick up its feet and can potentially collapse if it is forced to do so. Signs of pain such as '''anxiety''', '''sweating''', '''increased heart and respiration rate''' are frequently seen.  

In the most severe cases there may be serum like exudate at the coronary band and the hoof may become detached and shed. Although this does indicate a bleak prognosis, with good and dedicated owners, vets and farriers who are prepared for the time and cost of treatment the horse can survive sloughing of the hoof and go back to normal work.

In the most severe cases there may be '''serum like exudate''' at the '''coronary band''' and the '''hoof''' may become '''detached and shed'''. Although this does indicate a bleak prognosis, with good and dedicated owners, vets and farriers who are prepared for the time and cost of treatment the horse can survive sloughing of the hoof and go back to normal work.

=== Chronic Disease ===

=== Chronic Disease ===

In chronic cases separation of the laminae and sinking and/or rotation of the pedal bone will have occurred. The sole drops and the hoof wall spreads which results in marked transverse ridges on the hoof. Also the angle of the hoof as viewed laterally decreases. Degeneration of the white line may allow for infection to enter, potentially resulting in sepsis of the pedal bone. It is common for the animal to become lame with exercise and have repeated bouts of mild laminitis. Often there is a recognised underlying cause such as Cushings disease in chronic laminitis cases.

In chronic cases '''separation of the laminae''' and '''sinking and/or rotation of the pedal bone''' will have occurred. The sole drops and the hoof wall spreads which results in '''marked transverse ridges on the hoof'''. Also the angle of the hoof as viewed laterally decreases. Degeneration of the white line may allow for infection to enter, potentially resulting in sepsis of the pedal bone. It is common for the animal to become '''lame with exercise''' and have repeated bouts of '''mild laminitis'''. Often there is a recognised '''underlying cause''' such as Cushing's disease in chronic laminitis cases.

== Diagnosis ==

== Diagnosis ==

Diagnosis should be based on clinical signs and patient history. Pain may be present on palpation around the coronet and the horse may display a marked withdrawal in response to hoof testers. The height and strength of pulse in the palmer digital artery is normally increased. If the pedal bone has sunk a concavity may be palpable at the junction of the coronet, and in very severe cases the pedal bone may be visible through the sole of the hoof. Definitive diagnosis is achieved using radiography.  

Diagnosis should be based on '''clinical signs and patient history'''. '''Pain''' and '''heat''' may be present on palpation around the coronet and the horse may display a marked withdrawal in response to '''hoof testers'''. The height and strength of '''pulse''' in the '''palmer digital artery''' is normally '''increased'''. If the pedal bone has sunk a concavity may be palpable at the junction of the coronet, and in very severe cases the pedal bone may be visible through the sole of the hoof. Definitive diagnosis is achieved using '''radiography.'''

=== Radiography ===

=== Radiography ===

[[File:Laminitic.jpg|right|thumb|200px|Radiograph of the laminitic foot (Wikimedia Commons)]]

[[File:Laminitic.jpg|right|thumb|200px|Radiograph of the laminitic foot (Wikimedia Commons)]]

Radiographs should be taken of front feet or all feet if all legs are affected. A metal strip should be placed on the dorsal wall of the hoof and the sole should be maked with a similar metal strip or a pin can be used. They the angle of the pedal bone in relation to the hoof can then be analysed and the radiograph should be shown to the farrier who is working with you on the case for corrective farriery. Radiographs are essential for prognosis. There may be no radiographic changes if the case is acute or mild. However, radiographs in more severe cases radiographs may show:  

Radiographs should be taken of front feet or all feet if all legs are affected. A '''metal strip''' should be placed on the '''dorsal wall''' of the hoof and the '''sole''' should be maked with a similar metal strip or a pin can be used. They the angle of the pedal bone in relation to the hoof can then be analysed. There may be no radiographic changes if the case is acute or mild. However, radiographs in more severe cases radiographs may show:  

* Rotation of the pedal bone as a tilting of the distal aspect towards the sole

* '''Rotation''' of the pedal bone as a tilting of the distal aspect towards the sole

* Sinking of the pedal bone (which is the main indicator of prognosis).

* '''Sinking''' of the pedal bone (which is the main indicator of prognosis).

Serum build up may be evident as a radiolucent line between the dorsal hoof wall and the pedal bone. In chronic cases the pedal bone may even develop the appearance of a Turkish slipper, as a result of the pressure placed on tip of the rotated P3.  

'''Serum''' build up may be evident as a '''radiolucent line''' between the dorsal hoof wall and the pedal bone. In chronic cases the pedal bone may even develop the appearance of a '''Turkish slipper''', as a result of the pressure placed on tip of the rotated P3.  

You should measure:

You should measure:

* Distance between the top of the hoof wall the top of the extensor process of pedal bone to assess rotation of P3

* Distance between the top of the hoof wall and the top of the extensor process of pedal bone to assess sinking of P3. This is called the ''''Founder distance''''

* Distance between dorsal hoof wall and dorsal cortex of pedal bone to assess sinking of P3

* Distance between the dorsal hoof wall and the dorsal cortex of pedal bone to calculate the ''''Rotation angle'''' of P3

 

== Differential Diagnosis ==

== Differential Diagnosis ==

* Prevent microthrombi formation

* Prevent microthrombi formation

Analgesics, mainly [[NSAIDs]] (Phenylbutazone) and box rest are the standard treatments. Other available NSAIDs are Flunixin Meglumine, Ketoprofen and Dimethyl Sulfoxide.  

'''Analgesics''', mainly [[NSAIDs]] (Phenylbutazone) and '''box rest''' are the standard treatments. Other available NSAIDs are Flunixin Meglumine, Ketoprofen and Dimethyl Sulfoxide.  

As the pathogenesis of laminitis is not fully understood there is some controversy surrounding the use of some drugs and the theories behind their use - such as vasodilators and anticoagulants. Therefore it is up the individual clinician to decide whether these drugs are indicated. However it is unanimously agreed the box rest and anti-inflammatory drugs are the mainstays of treatment.

As the pathogenesis of laminitis is not fully understood there is some controversy surrounding the use of some drugs and the theories behind their use - such as vasodilators and anticoagulants. Therefore it is up the individual clinician to decide whether these drugs are indicated. However it is unanimously agreed the box rest and anti-inflammatory drugs are the mainstays of treatment.

Mechanical support is important and may provide some pain relief and help prevent rotation or sinking of the pedal bone. It can be done with polystyrene or other packing materials or by keeping the animal on soft, deep bedding. Elevating the heel with a wedge or wedge shoe may be useful to take off some of the strain on the deep digital flexor tendon and help to reduce rotation. The farrier will be able to help with the use of egg bar, heart bar and plastic shoes.

'''Mechanical support''' is important and may provide some '''pain relief''' and help '''prevent rotation or sinking of the pedal bone'''. It can be done with '''polystyrene''' or other '''packing materials''' or by keeping the animal on '''soft, deep bedding'''. Elevating the '''heel''' with a '''wedge''' or wedge shoe may be useful to take off some of the strain on the deep digital flexor tendon and help to reduce rotation. '''Remedial farriery''' can be used to minimise the detrimental effects of disease by; stabilising the pedal bone, decreasing the forces placed on the dorsal laminae, removing infection, and improving blood supply and growth. Techniques include the use of trimming and egg bar, heart bar and plastic shoes. Numerous trimmings will be required.

Horses should be fed on a very low energy diet of soaked hay. Low carbohydrate, high fibre concentrates such as 'Hi-Fi' or 'Happy Hoof' may be added in small quantities if appropriate.  

Horses should be fed on a '''very low energy diet of soaked hay'''. Low carbohydrate, high fibre concentrates such as 'Happy Hoof' may be added in small quantities if appropriate. Supplements such as Biotin may also be given to improve hoof growth.

The response to treatment should be monitored physically and radiographically.  

The response to treatment should be monitored physically and radiographically.  

It should be stressed that management plays a huge role in both the management of an active case of laminitis and in preventing its recurrence in the future. Recovery from laminitis may be prolonged especially in severe cases, and return to work should always be gradual. In the cases where an underlying cause (e.g. Cushing's Disease) is suspected, this should be identified and treated appropriately.

It should be stressed that '''management''' plays a huge role in both the treatment of an active case of laminitis and in preventing its recurrence in the future. Recovery from laminitis may be prolonged especially in severe cases, and return to work should always be gradual. In the cases where an underlying cause (e.g. Cushing's Disease) is suspected, this should be identified and treated appropriately.

In very severe cases the only option may be euthanasia.

In very severe cases the only option may be '''euthanasia'''.

== Prevention ==

== Prevention ==

Identification and management of any predisposing factors is extremely important in preventing the recurrence of laminitis.  

Identification and management of any '''predisposing factors''' is extremely important in preventing the recurrence of laminitis.  

Overweight and unfit animals should be managed appropriately with diet and exercise changes. Horses with a history of laminitis should not be allowed to graze lush pasture, especially in Spring and Autumn and early in the morning. Following injury or lameness to one limb, the other limbs should be monitored closely for signs of laminitis (increased heat and digital pulses) and the animal placed on a deep bed to help prevent it occuring. In horses where endotoxaemia may develop, anti-endotoxic drugs such as NSAIDS should be given as they may prevent the development of laminitis. As mentioned, in the cases where an underlying disease is suspected, this should be identified and treated appropriately.

Overweight and unfit animals should be managed appropriately with diet and exercise changes. Horses with a history of laminitis should not be allowed to graze lush pasture, especially in Spring and Autumn and early in the morning. Following injury or lameness to one limb, the other limbs should be monitored closely for signs of laminitis (increased heat and digital pulses) and the animal placed on a deep bed to help prevent it occuring. In horses where endotoxaemia may develop, anti-endotoxic drugs such as NSAIDS should be given as they may prevent the development of laminitis. As mentioned, in the cases where an underlying disease is suspected, this should be identified and treated appropriately.

Several factors effect the prognosis in laminitis cases. The pursuit of treatment and the likelihood of its success is very dependant of financial and emotional commitment of the owners.  

Several factors effect the prognosis in laminitis cases. The pursuit of treatment and the likelihood of its success is very dependant of financial and emotional commitment of the owners.  

Larger and heavier animals carry a poorer prognosis, as do animals with a greater number of affected feet. Clinical signs help guide prognosis but there are big differences between the signs displayed by stoical and relatively wimpy horses, and it is considered better to use response to treatment in the individual horse as a guide. The Obel grading system was developed (in 1948) to help grade prognosis, with lower grade horses having a better prognosis:

'''Larger''' and '''heavier''' animals carry a '''poorer''' prognosis, as do animals with a '''greater number of affected feet'''. '''Clinical signs''' help guide prognosis but there are big differences between the signs displayed by stoical and relatively wimpy horses, and it is considered better to use response to treatment in the individual horse as a guide. The '''Obel grading system''' was developed (in 1948) to help grade prognosis, with lower grade horses having a better prognosis:

'''GRADE 0'''. There is no lameness at walk or straight trot on a hard surface

'''GRADE 0'''. There is no lameness at walk or straight trot on a hard surface

'''GRADE 5.''' The horse is mostly recumbent and will not stand for more than a few minutes

'''GRADE 5.''' The horse is mostly recumbent and will not stand for more than a few minutes

Radiography is the main tool required for prognostics. It is generally recognised that the worse the rotation of the pedal bone the less chance of returning to athletic function. However there should not be too much emphasis placed on pedal bone rotation when considering the prognosis. A fast rate of rotation is suggestive of further structure collapse - repeat radiographs are useful when assessing this. The level of sinking of the pedal bone is the main prognostic indicator, with distal movement of the pedal bone suggesting a poor prognosis.

'''Radiography''' is the main tool required for prognostics. It is generally recognised that the worse the '''rotation''' of the pedal bone the less chance of returning to athletic function. However there should not be too much emphasis placed on pedal bone rotation when considering the prognosis. A '''fast rate of rotation''' is suggestive of further structure collapse - repeat radiographs are useful when assessing this. The '''acute''' appearance of '''radiolucent lines''' parallel to the dorsal hoof wall suggests structural collapse and a poor prognosis. However, the level of '''sinking''' of the pedal bone is the main prognostic indicator, with '''distal movement of the pedal bone suggesting a very poor prognosis'''.

 

 

==References==

==References==

Rendle, D (2006) '''Equine laminitis 2. Management and Prognosis in the Chronic Stage''' ''In Practice 2006 28: 526-536''

Rendle, D (2006) '''Equine laminitis 2. Management and Prognosis in the Chronic Stage''' ''In Practice 2006 28: 526-536''

Obel, N. (1948) '''Studies on the histopathology of acute laminitis''' ''Almquisst and Wiksells Boktryckeri ab Uppsala''

Obel, N. (1948) '''Studies on the histopathology of acute laminitis''' ''Almquisst and Wiksells Boktryckeri ab Uppsala''

[[Category:Musculoskeletal Diseases - Horse]]

[[Category:Musculoskeletal Diseases - Horse]]

[[Category:To Do - Manson]]

[[Category:To Do - Manson]]

[[Category: To Do - Siobhan Brade]]

[[Category: To Do - Siobhan Brade]]