Vet Corner: Equine hoof distortions - Part 2

In his last post, veterinarian Andrew Conway BVSc from The Vet Centre Richmond touched on how External Hoof Mapping can be used as a useful tool to evaluate the conformation of your horse's feet. This ensures that any distortions in hoof growth can be recognised early to prevent potential discomfort or lameness. In this follow up post, Andrew now looks at another area of hoof conformation that is easily overlooked, but can often have subtle to severe impacts on your horse's movement.

Firstly, have you ever noticed any of these things about your horse?

• Moves better on one lunge direction compared to the other
• Rushes after landing from a jump
• Bucking after a jump
• Often places feet to either side of the midline when standing at rest
• Hard swellings, sometimes sensitive, on the medial or lateral aspect above the coronet on the hoof (see Figure 2 further below).

The joints in a horse's leg, from the stifle down in the back leg and the elbow down in the front, are known as hinge joints. This means that they can only move in one direction (compare that to your wrist, which can move in all directions). All these joints have minimal tolerance for side to side movement.

Put another way, if you were to ask your horse to walk around a hill side in the same direction continually, it would soon become lame. The persistent pressure on one side of the hoof being greater than the other side will eventually cause irritation to joints, in particular between the coffin bone (also known as the Phalanx 3 or P3) and the Phalanx 2 (or P2).

Figure 1: The exfoliated functional sole thickness is equal
beneath the lateral and medial ventral border of P3 and,
therefore, is reliable as a reference guide for medial-lateral balance.

A similar effect results from uneven hoof wall lengths between the medial and lateral sides of the hoof. The distance between the lateral and medial borders of P3 to the ground surface must be equal. If one side is higher than the other (even only 3 or 4 millimetres) for long periods of time, irritation will occur in the joint between P2 and P3, resulting in discomfort and lameness. This is shown here in Figure 1.

Over a long period of time, the collateral ligaments become calcified due to being under constant strain and irritation, and are then called ‘sidebones’ (see Figure 2).

Figure 2: The head of arrow 'A' shows an example of hard swellings on the medial or lateral
aspect above the coronet. Arrows 'B' show sidebones.

How can you tell if your horse’s feet have a medial-lateral imbalance?

One way is to have your horse's feet X-rayed (see Figure 3). Even if the problem is not currently present, the presence of sidebones can suggest that there has been a problem. Generally, sidebones are not an issue in themselves - they are just the end result or symptom of irritation or strain to the collateral ligaments, usually due to medial-lateral imbalance.

Figure 3: X-raying to check for medial-lateral imbalance

Another way is to have the sole exfoliated in the region of the widest part of the foot (discussed earlier in Part 1). When the functional sole is identified, the height of the hoof wall on each side should be equal. The functional sole thickness is a reliable reference for medial and lateral heights of the distal border of P3 from the ground and is, therefore, an accurate guide in achieving medial-lateral balance in the hoof.


What can I do about it?

The solution is generally simple and the results can be dramatic. Have all your horse's feet trimmed for medial-lateral balance - either from X-rays (a very reliable check method, especially if the problem persists), or from exfoliation of the sole down to ‘live’ sole, measuring the hoof wall in the area of the widest part of the sole and trimming for equal heights medial to lateral.

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Vet Corner: Equine hoof distortions - Part 1

This is the first of planned regular posts by veterinarian Andrew Conway BVSc. Horses form a substantial part of The Vet Centre Richmond's activities, and Andrew has developed a special interest in equine hoof care and lameness issues. In this post, Andrew looks more closely at hoof distortions - what are they and how can you recognise them?

Around half a tonne of horse weight is supported by a bony column ending in a supporting structure called the 'HOOF' - a capsule of keratin, ligaments, tendons, bone, blood vessels and nerves that is the last supporting structure between the horse and the ground. It is not surprising then, that 80% of horse lameness issues are associated with the hoof or its adjacent structures and, equally, it is not surprising that the hoof's health and conformation is critical to the athletic function and comfort of the horse it supports.

COA should be halfway along the ground contact surface of
the hoof. That is, the breakover point to the most caudal part
of the heel touching the ground (usually part of the frog).

Although there is considerable opinion on what is normal hoof conformation, there are some very established and well-recognised guidelines. One of these is what is called the ‘Centre of Articulation’ or COA, which is a point in the middle of the distal condyle of P2. Draw a line to the ground from this point and you should have equal amounts of ground contact area behind that point as you do in front.

The tendency is that with poor trimming or infrequent trimming/wear, you end up with much more area in front of this line than behind. In turn, this can cause discomfort, poor function, incorrect gait and lameness. When this occurs, it is called ‘Hoof Distortion’.

In the arid, wild environment of the native horse, wear occurs on a daily basis and 99% of these horses' feet have no distortions. However, the way we care for our horses and use them in domestic life is quite different to that wild environment. We put shoes on them, stable them and we graze them on soft ground. All these actions take away any natural wear of the hoof structures that are growing relentlessly 24-hours a day. We become reliant on regular trimming to look after the conformation of the hoof.

As the hoof wall grows, without natural wear or correct trimming
occurring, distortions start to appear. These include loss of frog
ground contact, elongated frog, long heels and toe, bent and
cracked bars, etc.

The difficulty is that, from the outside, it is difficult for the horse owner to know where this point (COA) is without X-rays. That is, until more recently.

At a specialist conference I attended in Colorado, USA, External Hoof Mapping was presented as a tool to identify and grade hoof distortions. This is for the purposes of monitoring the process of correcting hoof distortions and lameness, and also as an aid to predict potential lameness, such as Navicular syndrome, on the basis of the grade of hoof distortion present. For example, a Grade 1 distortion is the normal growth of the hoof that you would expect between trimmings. Whereas a Grade 3 distortion may show altered gait and discomfort, with the toe becoming elongated, the heels long, and the frog elongating and losing ground contact.

One of the key markers used is what is called the ‘Widest Part of the Hoof’ or WPH (or more correctly, the widest part of the sole). By finding this point, we know where the COA is. The COA is consistently located one inch behind the WPH. The WPH can be located by three methods - which are best demonstrated on a horse rather than described here - but it is something very valuable for a horse owner to know so that they can make some assessment of their horse's conformation and need for corrective trimming. Even apparently normal looking hooves can be slightly distorted, but the correction is simple, and the results on a horse's movement and comfort can be remarkable.

Look out for Part 2 of Andrew Conway's informative hoof distortion post, to be published here shortly.

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The story of George

Six years ago, Nelson woman Helen Bowler wrote down the special story of her Warmblood-X-Thoroughbred horse, George, and his long struggles with lameness - as the eventual happy ending meant so much to her.

Even though scientific research into hoof care and lameness prevention has continued to advance rapidly since that time, and we are learning more and more as the years go by, the foundations of George's rehabilitation are still just as relevant today. Six years on, this story still makes interesting reading.

Helen has kindly asked that this story, told largely from George's point of view, now be shared here for anyone who may be interested: Select here to access to The Story of George.

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