Lameness and Distortions
Horses commonly develop a range of hoof distortion, due to a number of causes. Many of these can lead to lameness. Some of them can be caused by lameness or body imbalance elsewhere. Below you will find some basic information.
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Navicular Disease / Syndrome These get their own page
An overview of causes
Diet, trimming and environment are huge factors, which can damage lamellar connections, allow hooves to overgrow, increase susceptability to infections... fail to provide what is needed to develop a strong, functional hoof in the first place.
Mechanical factors, such as too much pressure being placed on the walls and too little support under the foot can lead to 'distal descent' as the internal structures 'sink' within the capsule and the sole thins. Leverage forces on long walls cause capsule distortion such as stretching and separation of the laminae, flares, cracks and allowing infection. Ground parallel or lower angles of the back of P3 cause a 'broken back' pastern angle, putting a lot of stress on both the extensor process(top/front of pedal bone) region and the navicular region.
Environment and lifestyle can be behind weak caudal foot development, due to lack of development or previous damage will cause sensitivity and result in toe-first impacts and a horse who doesn't want to weight his heels fully. Lack of movement/use will lead to general lack of growth and thickness of sole and frog too.
Diet, nutrition and feeding has a huge effect on hoof health and problems here can cause laminitis, weak or 'shelly' walls, breakdown of wall material, increased susceptibility to infections such as 'seedy toe' or 'thrush'.
Body imbalance/injury is another cause of hoof problems, which includes hoof imbalances such as 'clubbed' feet, medio-lateral imbalances, low/negative angles in hind feet, dragging toes and 'supporting limb l lameness'.
An overview of specific problems;
Flares, cracks, chipping, 'run forward' heels & toes
When hooves are flared, walls disconnected, feet running forward, this is the result of mechanical problems - incorrect, insufficient, imbalanced trimming. Edges chipping can be due to this too, if walls are too long or not 'dressed' with a 'roll'(bevel) at the outer edges. And vertical cracks can result from this imbalance too, when stressed walls give way. Distorted hairlines are also an indication of mechanical problems.
Treatment involves ensuring hooves are well trimmed and balanced correctly, that they are kept well maintained and walls are not allowed to get too long(depending on the footing).
In addition, cracks may nee to be 'relieved' of all ground pressure to remove all force that is perpetuating them. IF the crack extends more than half way up the hoof capsule and is through the entire wall, then holding it together with a screwed on brace, 'staples' or such may be helpful as *part* of the treatment.
Alternative methods of treatment, such as 'dressing' flares on the outside or 'dubbing' flared toes without addressing the mechanical forces underneath will further weaken walls, leaving them more 'prone' to cracks and infection, without addressing the real issues. 'Wedging' crushed heels will put more pressure on what should be the vertical part of the heel wall, ensuring it stays crushed.
Scoring the hoof horizontally above a crack does nothing. Attempting to hold the crack together at the ground surface with shoes will actually put more stress on the walls, generally perpetuating the crack. Cracks are commonly perpetuated due to infection, so treating the hoof mechanically without addressing infection may manage the crack but not allow it to grow out.
Seedy Toe / White Line Disease and Thrush
This is 'opportunistic infection' caused by soil organisms. In the wall material it is known as 'seedy toe' or 'white line disease', while when it infects the frog, it is called 'thrush'. Healthy, strong, well functioning hooves are not so susceptible to infection, regardless what organisms are around. But when hooves are compromised, by cracks or separation, by weak, contracted heels, by chronically wet or mucky footing, then the 'opportunistic' bugs get in. Infection can be fungal, bacterial or protozoa. They are all 'anaerobic' meaning they love dark, moist environments and dislike being open to the air. Seedy toe and thrush doesn't generally make a horse lame, but if severe enough it can do.
Treatment includes topical antiseptic application. It should be a broad spectrum solution, to kill all possible bugs. The horse needs to be kept - at least part time, if full time cannot be managed - on dry, clean footing. Trimming of infected frog material, and removing flaps which can harbour infection is important.
**It is important to realise that strong antiseptics and heavy chemicals, such as 'Thrush Buster' and even iodine or 'Dettol' can damage and therefore seriously retard growth and healing of live tissue. Therefore while killing infection is vital, it's best to avoid use of strong chemicals on deep frog thrush or otherwise close to live tissue. Save the 'heavy guns' for those infections which are in the hoof wall or shallow frog infections.
Cutting out infected horn and opening up cracks with a knife is also often vital in order to effectively get the antiseptic everywhere it needs to be. Infection can be present just as a 'hairline' crack in otherwise solid horn, although it can be insideous and far worse further in. Infection can also eat away horn faster than it can grow, so it's impossible in many instances to address purely topically. This is called 'resecting'. If a large resection is necessary, protecting the live tissue inside may be necessary and as with large, full depth hoof cracks, bracing the face of the resection may be helpful.
Diet and nutrition are often a vital link, and it has been shown that appropriate low-carb diets and well balanced nutrition will help hooves be less susceptible to infection. Studies done into supplementing MSM have also been promising.
Thin, flat soles
Inadequate protection of the internal structures under the foot will cause sensitivity and potential damage. This is very often due to peripheral loading, of long hoof walls or rim shoes, causing the unsupported foot to 'drop' within the hoof walls. This is called 'distal decent'. Hooves that are flared with weak lamellar connections will also become thin soled. Hooves which are 'broken forward' with the tip of the pedal bone angling too sharply into the ground, such as laminitis with 'rotation' and clubbed feet, will become thin soled at the toe.
It is worth noting that it is still not uncommon for some farriers to routinely pare(or even rasp into) sole material. Some schools of thought on 'natural trimming' hold that concavity should be carved into a sole if it is flat. In these ways, farriers can directly cause thin, sensitive soles! As explained in the trimming principles, it is sometimes necessary to remove sole material, but it should generally be left in place where possible and the live sole plane should never be invaded.
Treatment includes removing shoes and other causes of peripheral loading and correct, well balanced trimming to treat any flares and distortion - it seems, from Dr Bowker's and Pete Ramey's observations, that the sole cannot begin to grow thicker, more concave until the walls are grown down strongly attached without undue mechanical force.
In addition, support and protection may be needed underneath the foot, in the form of padding.
Abscesses come about due to damage to the corium. The bruising, if beneath wall or sole, sandwiched between bone and horn, can cause a 'pocket' of high pressure fluid, just like if you bash you're thumb with a hammer. This is why abscesses are generally so painful. *Though they're not always painful and owners often don't even realise their horse has had an abscess until there are telltale signs at the next trim!
Treatment - along with getting the hoof in shape, is, if the horse is lame and abscess suspected, to soak hooves in a warm solution magnesium(Epsom Salts) solution, to soften the horn and allow the abscess to burst. The horse should be kept in an area it is able to get free movement, but not forced to move on it's tender hoof. It is rarely necessary or desirable to have a vet 'open up' an abscess IMO. Once the abscess has burst, soaking in, or applying a strong saline solution and keeping the foot clean and dry should clear up and prevent infection. After a week or so, when there should be a thin layer of horn over the corium, then it may be a good move to treat the spot with 'heavy guns' for seedy toe, to prevent this insideous infection taking hold until the 'blow out' has grown out.
In addition, if the abscess burst at the hairline, causing a horizontal wall crack, then once it gets close to ground surface, it may be necessary to trim this part of the hoof slightly shorter, to prevent the weak section from breaking away too soon.
Abscesses are often 'diagnosed' and found with 'hoof testers' - a sort of pincer tool. This can be helpful, but it's important to realise it is not a reliable method. Any part squeezed in between the pincers may be damaged and therefore reactive, due to an abscess or otherwise - I've known of unfortunate horses who were diagnosed with an abscess at the toe sole, which was 'opened up' by the vet, only to discover there was precious little sole there, and the pain was due to P3 pressure being right there!
Imbalance, Asymmetry and Body Issues
Ground parallel or lower angles of the back of P3 cause a 'broken back' pastern angle, putting a lot of stress on both the extensor process(top/front of pedal bone) region and the navicular region. Alternately, high heels cause 'rotation' of P3 the other way, with the toe pointing into the ground.
A horse may have 'clubby' feet for a variety of reasons. One reason is failure of development of the back of the foot, which causes him to be uncomfortable impacting on his heels. Landing toe first naturally wears the toes shorter and allows heels to grow high.