ARCHIVE - ARTICLES 2008

August 2008 - How pro-active shoeing enhances long-term soundness

 

Archive - Forge Magazine - August 2008
How pro-active shoeing enhances long-term soundness

by Mark Aikens DWCF

Mark Aikens DWCF has worked with horses for 25 years, commencing his apprenticeship in farriery nearly 20 years ago. He founded Anglia Equine in Norfolk in 1993, and believes in taking a proactive approach to shoeing. “A foot imbalance will result in impaired performance and lameness,” he says. Mark specialises in shoeing event, dressage and endurance horses, and also provides locomotive screening using Equinalysis technology.
Visit: www.angliaequine.co.uk

 

This article aims to showcase some of the farriery techniques employed to help horses in my care move at their optimum, encourage the correct forces to be applied, and the correct hoof and limb angles to be aligned. I have used a series of photographs to illustrate the techniques used:

Protecting the tendons and suspensory apparatus

I was able to give this horse an addition six degrees carpal flexion by using tailored shoeing techniques – pre-shoeing, the knee was under pressure to propel the horse forward over a long toe, so with the new shoeing programme, we are now protecting the horse’s flexor tendons and the suspensory apparatus.

Pre Shoeing – Pics 1 and 2

This horse was last shod approximately eight weeks previously with natural balance shoes, as is evident here. The toes were long, the heels under run, and a medial heel crack is apparent on the near fore. I trimmed the feet to restore the horse’s hoof pastern axis, and fitted the shoe to offer greater medial support. Forces at the toe, medial and lateral heels collectively are the lowest when the hoof and pastern angles are aligned.

Post shoeing – Pics 3 and 4

Prior to shoeing, this horse displayed a maximum carpal flexion of 115 degrees, and post shoeing 121 degrees. This horse had to use more effort and energy by having to bend its knee more to propel itself forward over a long toe. A six degree differential may not seem much, but a long toe will put a greater strain on flexor tendons and the suspensory apparatus. A horse’s tendon has a strain rate of about 21% before the tendon fails and is damaged. When you consider that in the galloping horse the superficial flexor tendon undergoes a strain rate of 17%, you can appreciate how little margin for error there is.

Using video based technology – Pics 5 and 6

In terms of protecting the flexor tendons and the suspensory apparatus, this evidence can be seen from a video clip of a horse moving freely on a flat level surface, above – note the increased angle in picture 6. Imagine the strain placed on its limbs if this horse was being ridden around a cross country course carrying 12 stone, or on slippery, uneven ground, being asked to jump 3ft 6in whilst fatigued. Something will break! Using Equinalysis video-based screening, we can see the results from carpal flexion are of great use to determine forelimb health, symmetry between both forelegs and to allow us to quantify and monitor the ergonomics of that individual horse.

The use of traction – Picture 7

In picture 7, a photograph of the same horse’s near hind, the red line is that of the toe at the first point of contact, and the blue line is the position of the toe at the moment of zero movement, prior to breakover. This distance measured 22 cms, and is easily quantified and measured using Equinalysis. Horses’ feet slip to dissipate energy and dampen impact, but with this in mind, farriers must be cautious as to the use and placement of studs, or any other traction methods. If a horse such as this were to have a single stud on the outside of its hind shoe, we could only imagine the strain placed on its joints, as the stud would act as a fulcrum for the foot and limb to pivot around as the stud grips the ground surface.
To increase traction, it is common for farriers to use nails with a tungsten pin in its centre; these are usually placed towards the back of the shoe, as can be seen here in picture 9. This will create ‘point loading’, which can overload the structural integrity of the hoof wall and will also create instability and imbalance to the foot when the horse is on a hard surface. This becomes more evident as the shoe wears down, but the tungsten pin does not. I often encounter horses that are stood in front of me prior to shoeing rocking back and forth on these nails.
(Picture 9 shows ‘point loading, with the tungsten pin, and pictures 10 and 11 show the same shoe without the nail).
That is not to say that I am opposed to traction; and people are often confused between slip and grip. Some road surfaces are lethal for horses to be ridden on, and one has to compromise on the lesser of two evils, that being the horse remaining upright for its own safety, and that of the rider. In these cases, I prefer to simply drill a hole in the heel of the shoe and insert a tungsten pin; at least this way, you eliminate the instability of the horse rocking to and fro. Research by Dr Tom Witte has found that tungsten carbide not only prevents slippage, but also increases stance duration-the amount of time the foot remains on the ground between the swing phase.

Using straight bar shoes to reduce fetlock hyperextension

I had shod the horse pictured in images 12-15 three times prior to screening using Equinalysis. He had slightly asymmetrical front feet, with his off fore being lower in both heels. On each occasion, the lateral heel of the off fore was under run and collapsed. Despite trimming this foot perpendicular to the long axis when he was due for re shoeing, the lateral heel would again have collapsed and the medial heel would be half an inch higher than the opposing heel. He has a toe in configuration in the forelimbs, and can be seen to be landing lateral heel first, the forelimbs load laterally, though this is more apparent on the off fore.
After screening, I re-shod him with a straight bar shoes in front initially to support the lateral heel by distributing the force evenly over both heels. Subsequent shoeings have indicated that this has been successful, as both heels have been stronger and the heels have remained perpendicular to the long axis during a five week shoeing interval. As well as supporting the heels of the hoof, a bar shoe will offer support to the fetlock and suspensory apparatus, therefore reducing fetlock hyperextension. Prior to application of bar shoes, hyperextension differential measured six degrees. As can be clearly seen here after shoeing, no differential exists.
(Pictures 12 and 13 are pre shoeing, pictures 14 and 15 are post shoeing)
Fetlock hyperextension is a critical measurement, as it largely relates to the vertical ground reaction forces that are exerted on either the left or right limb. At the trot, the fetlock joint shows increasing hyperextension until the moment of maximum loading, which occurs mid stance. During supporting limb lameness, the horse will attempt to reduce the load on the painful limb, and so therefore the angle between the carpus, fetlock and the coffin joint will be less acute at the point of maximum fetlock hyperextension on the affected limb due to a decrease in vertical ground force. The greater the horse’s velocity, the greater the amount of hyperextension, which is why it is important to know if a progressive increase in hyperextension is due to an increase in velocity, or the horses natural gait. In this case, locomotive screening was used to confirm that the shoeing process had eliminated the hyperextension shown pre shoeing.

Image Nos - From left to right, top to bottom - 1-15