May newsletter: Interesting Hoof Pathologies – Causes And Treatments

hoof-sidebone-fourways-equine-clinic

The foundation of your horse’s soundness starts at the foundation of its limbs… the hooves!

As any horse owner can attest to, an unsound horse can be one of the most frustrating things to deal with. The importance of having a professional team of vets and farriers working together to resolve lameness issues is often understated. In this article we will look at some of the more common, and some slightly less common but interesting, causes of lameness localised in the hoof.

Seedy Toe/White Line Disease (WLD)

This condition predominantly affects the hoof wall in the toe area. There is separation of the outer hoof wall portion from the inner portion. This can occur for a number of reasons i.e. poor conformation, poor hoof care, environmental and mechanical stresses, poor hoof trimming etc. If the separated portion of hoof wall is invaded by bacteria or fungi, a painful infection results and this often causes a greater portion of hoof wall to “run up” and become separated in an upwards direction.

The disease is often discovered during routine farriery and is noted as an area of different, powdery consistency along the white line. Generally, no clinical signs are seen in affected horses, but if the disease is not caught and dealt with early, lameness can result from infection and mechanical separation of affected areas.

Treatment involves removing all affected portions of the hoof wall. If a large portion of the toe’s solar area needs to be removed, your farrier may decide to place a bar shoe to provide support. The removed portion should be kept clean and dry and depending on the individual case, an appropriate topical treatment may be prescribed.

Radiographs are a useful tool for the vet or farrier to use in order to determine how far up the hoof wall is separated and therefore how much of the affected portion of hoof wall needs to be removed.

In this radiograph, the affected portion which has been removed from the toe area can be seen; however gas lines (indicating hoof wall separation) can be seen creeping higher than the removed section – these are seen as darker lines on a radiograph and are indicated above the dashed yellow lines.

 

Left: Hoof wall separation
Right: An affected portion of hoof wall removed in a chronic, longstanding case

 

Sidebone

This is caused when the cartilages which form the “wings” of the hoof become calcified. This most often occurs in heavier breeds (draft horses and Warmbloods), however many causes have been identified such as poor conformation, repetitive trauma (jumping, eventing, working on hard surfaces) and so on

Typically there are no clinical signs of sidebone, however lameness may occur if the sidebone is still in the active, developing stage or if fracture of the calcified cartilage occurs. Most often, sidebone is found incidentally during routine hoof radiographs. If there is unevenness between the sidebone on the inside and outside of the hoof, this is cause for closer evaluation and often requires corrective farriery in order to identify and treat the cause (medio-lateral hoof imbalance/poor heel conformation/rotational fault of the hoof).

A relatively normal hoof radiograph above.

 

The hoof above has sidebone formation on the inside and outside cartilages, however the cartilage on the lateral side (the outside of the limb) is greater in height when compared to the inside.

 

Pedal Bone and Navicular Bone Fractures

These usually occur through trauma of some sort. Lameness is often severe and occurs acutely. A rim bar shoe is placed (there are various different types) to prevent expansion of the heels and effectively keep the hoof “quiet”. This is combined with strict stall rest and judicious use of anti-inflammatory treatment.

Fracture through P3 (pedal bone)

 

The navicular bone is outlined in green. A fracture (indicated by the orange arrow) is shown through the navicular bone.

 

A rim shoe after being forged (above). And once fitted to the hoof (below).

 

Often an acrylic material is placed between the rim and the hoof wall in order to form a good bond and ensure that the hoof is well encapsulated.
Laminitis
One of the most frustrating problems for both vet and farrier.

 

There are many different potential causes:

  • Toxic causes (septicaemia due to placental retention, major gut disturbances, severe illness etc.)
  • Mechanical trauma (work on hard surfaces, supporting limb laminitis etc.)
  • Metabolic disorders (equine metabolic syndrome, cushings disease, etc.)

Laminitis causes massive inflammation of the laminae which form the interdigitations of the hoof wall. This causes instability of the dorsal hoof wall and can lead to rotation or sinking of the entire bony column within the hoof capsule.

The inciting cause of laminitis should be identified and treated as far as possible. Corrective farriery is of utmost importance in trying to ensure that the toe wall is maintained and the weight is removed off the damaged laminae in the toe wall and distributed to the healthy leftover hoof structures for support (frog, bars, sole, heels and quarters).

Reverse shoes – These can be combined with some form of frog support such as high density polystyrene foam/impression putty/heartbars. Reverse shoes are relatively easy to apply but do require the nailing of shoes on to an already painful hoof.

Reverse shoe

 

Reverse shoe with an impression putty for additional support

 

Wooden clogs – These are used on acute cases of laminitis. They utilise the entire hoof as a way to distribute weight off the toe and do not require any nailing.

Coronary groove – A groove is made through the hoof wall through to the sensitive laminal layer. This is done just over the toe region of the hoof wall, just below the coronary band. This provides relief from the pressure in the toe area.

Chronic laminitis – These are often maintained using a type of trim called a “laminitis trim” whereby the toe of the affected hooves are shortened and rolled to ease breakover on the affected foot. Alternatively, reverse shoes can be applied if needed.

A foot with chronic laminitis showing typical slipper formation.

 

A laminitic foot – note the reverse shoe which it has had applied.
A gas line running up the front of the toe area indicates separation of the laminae in the hoof wall in this region.
There is rotation of the pedal bone in a downwards direction.

Keratoma

A keratoma is a tumorous growth of the keratin layer within the hoof wall. The tumour will often cause a pressure atrophy on the pedal bone and this causes a classic feature on radiographs where a distinct circular-shaped defect in the pedal bone can be seen (see the purple box on the radiograph below).

Keratomas cause insidious lameness issues and may be accompanied by visible distortions in the hoof wall and chronic, recurring hoof abscesses.

Keratomas are treated through removal of the affected portion of the tumour and hoof wall.

Whilst up to a third of the solar surface area of the hoof wall can be comfortably removed, removal of more than that will require the addition of some form of stability at the base of the hoof – this is often provided in the form of a bar shoe.

Application of acrylics, or other covering materials, over the defect in the hoof wall where the tumour was removed is often contraindicated as it is often applied on to sensitive laminae and has the potential to seal in bacteria and incidental contaminants.

Penetrating Foreign Object

Any time a foreign object penetrates through the sole of the hoof, it should be viewed as an EMERGENCY. This is due to the fact that there are so many critical anatomical structures which lie relatively shallow to the sole of the hoof and are thus easily damaged by something poking through the sole.

If you are ever faced with this emergency, it is important to immediately immobilise the horse and prevent the object from penetrating deeper through the sole. DO NOT REMOVE THE FOREIGN OBJECT! Instead, keep the horse quiet and keep the hoof off the ground. Alternatively, apply supports around the object which can keep the hoof elevated without pushing the object even deeper into the hoof. Immediately call your vet whilst all of these things are being done!

If the object is removed, it becomes difficult to visualise in which direction the object penetrated and to what depth. In this way, it complicates the matter of determining whether or not important structures had been damaged. If the object is removed, a radiographic dye, or a metallic probe, can be inserted through the entrance tract but this is not the preferred way of assessing the trauma caused.
A radiograph as seen on the figure above is less likely to cause panic compared to the one seen on the figure below.

If the nail has penetrated important structures within the hoof (digital synovial sheath, navicular bursa, pedal bone, navicular bone), the tract must be surgically opened up and cleaned in order to prevent the formation and spread of infection.

Thereafter, the application of a specialised hospital plate horseshoe is performed. This plate allows for complete protection of the affected sole and prevents dirt from accessing the area. It has a removable plate so that it may be removed on a daily basis, or as needed, to allow for cleaning of the sole and tract.

As always, please feel free to contact any of our team of vets with questions or concerns.
Fourways Equine Clinic is available to assist you 24 hours a day, 7 days a week.

Fourways Equine Clinic: 011 468 3393
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Website: www.fourwaysequine.co.za

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