Hoof Cracks - a very common problem in racehorses
/A keen-eyed racegoer spotted a horse running in the USA last summer with six quarter cracks spread between three of its feet. While this number would be highly unusual in the UK, the problem of the hoof crack is not, and is one, which plagues the trainer, vet and farrier.
For the trainer, the words “The apple of your eye has popped a quarter crack, guv’nor,” are not welcome. Some great names have won Group One and other big races carrying hoof cracks, but the onset of a crack will result at minimum in serious problems in the horse’s preparation. Nevertheless, it is quite common for several horses to have cracks of one kind or another in a larger yard at the height of summer. “Some years you might have none, other years you might have two or three,” says Phil Brook, a leading Newmarket racing farrier who works with likes of David Loder, Chris Wall and Cheveley Park Stud.
The key to the treatment of hoof cracks lies in a determination of why they have occurred. This in turn relies on an understanding of the anatomy and dynamics of the hoof. TYPES OF HOOF CRACK Hoof cracks can occur at various locations on the hoof wall, and can be of varying degrees of severity. Cracks are normally defined by their location (toe, quarter or heel) and may also be defined by their type (e.g. sand, grass or horizontal) A grass crack originates at the ground surface and extends up the hoof wall; a sand crack originates at the coronary band, and runs downwards towards the base of the hoof. A horizontal crack runs more or less parallel with the coronary band. Cracks may be ‘superficial’ or ‘deep’. A deep crack can be defined as one, which has penetrated the sensitive laminae.
These are by far the more serious problem being the result of some trauma that has taken, or is taking place inside the hoof capsule. These can bleed during or after exercise and carry the additional risk of infection.
CAUSES OF CRACKS
Standard farriery textbooks will explain that the most likely cause of hoof cracks is either anterior-posterior (front to back) or medio-lateral (side to side) imbalance. Anterior-posterior imbalance may be caused by ‘long toe / low heel’ syndrome, which can result in breakover being forced too far forward through poor foot dressing. The pull of the deep digital flexor tendon conflicts with the point of breakover to cause a tearing of the laminae from the hoof wall and a consequent toe crack.
Likewise, medio-lateral imbalance may also be the result of the failure by the farrier to detect and correct, so far as is within his power, any imbalances. However, in most modern racing yards, good farriery can be taken as a given; and we have to look elsewhere for the causes of these cracks. Medio-lateral imbalance is more usually caused by conformation. Where it has not been possible to correct a limb imbalance when the animal was a foal, then the resultant incorrect loading will inevitably cause stress on other areas of the body, including the hoof. As the horse develops, this creates a potential for quarter-cracks.
A further cause may be injury – an overreach may cause injury to the coronary band, which results in poor hoof growth and a consequent crack in one area of the hoof. Alternatively, simply kicking the walls can open up a weak hoof or an old injury. “Thin-walled hooves with narrow heels can be particularly important causes of quarter-cracks,” says Phil Brook. “Likewise, flat and contracted feet can result in excessive tension at the coronary margin, also resulting in cracks.”
Another contributory factor is the breed itself. Bad feet are often inherited. If the hoof itself is of a weak structure, then it is even more susceptible to the development of cracks, whether through imbalances, conformation or injury. It is significant that cracks tend to appear in the spring and early summer as horses step up to faster work. All-weather surfaces have been cited as one of their root causes, the hard core exploiting any potential weaknesses in the hoof as both speed and concussion increase. Firm going may have the same effect.
TREATMENT OF CRACKS IN RACEHORSES
A hoof crack can never, of course, heal. The two sides of the hoof that have split will never grow together again. But, if the prime cause of the crack can be resolved, then there is usually no reason why good, solid hoof wall should not grow down from the coronary band to replace the area of the crack. The ultimate treatment for a serious hoof crack is of course rest. “Ideally,” says Phil Brook, “ you will want to get 1 – 1 ½ inches of growth from the coronary band before doing any work with the horse.” But for a horse in training, that is not often an option. Farriery techniques that might be used for the same problem on a horse that was not in training are not available to the racing farrier. For instance, lateral extension shoes to correct the weight-bearing through the hoof and limb, are not an optionwhilst the horse is in training, since these shoes will inevitably be lost in work and the problem perhaps exacerbated.
SUPERFICIAL CRACKS
Superficial cracks, which penetrate only the insensitive laminae, can normally be resolved by cleaning out and dressing by the farrier. It is important for the two sides of the crack to be separated so that the edges do not rub together as the hoof naturally expands and contracts with the horse’s action. If this is allowed to happen, then the crack will be perpetuated.
DEEP CRACKS
In the case of deep cracks, two different aspects of treatment are involved. On the one hand, action is required in order to address the original cause of the crack; and, on the other, the split hoof needs to be patched in order to immobilise the two sides, stabilise the hoof capsule and, when possible, allow the horse to continue to work. As Nick Curtis, farrier to Newmarket vets Greenwood Ellis, says, “You can put on any patch you want, but the underlying cause of the crack is what you need to find out. It is a 3-D thing – you have to take everything into consideration. The goal is to get the foot landing level and in line with the skeleton.” Without this double-handed attention, a horse can easily become lame. If, for instance, the two sides of a deep toe crack are pinching the sensitive laminae as the horse puts weight on the hoof, then lameness will follow. In addressing the cause of the hoof crack, the farrier has a number of options open to him. First and foremost, he will ensure that hoof balance is correct and will do whatever he can to correct any limb imbalances. Secondly he will probably use bar shoes to provide more support at the heel. On a racehorse, he is more likely to use ‘straight’ bar shoes than ‘egg’ bars, which can be pulled off in training and certainly in racing. Straight bar shoes are available either in steel or in aluminium versions. The aluminium version can be used for racing or simply as a lightweight therapeutic shoe. A secondary technique sometimes used is to relieve the bar shoe in the area directly beneath the crack in order to reduce the pressure being transmitted to that section of the hoof. This section of the hoof and shoe obviously has to be kept clean so that the effect of the relief is maintained. Thirdly, he may use a shock-absorbent sole packing material such as Vettec’s Equi-Pak. This is a liquid urethane dispensed onto the sole and frog which will ease concussion through the hoof. “Keep him off the all-weather surface for a while” could easily be additional advice from farrier to trainer. A nutritional supplement designed specifically for the hoof might also be recommended if the original problem has been a poor quality or thin-walled hoof.
PATCHING A CRACK
There are a number of ways that may be used to patch a crack, sometimes used on their own or in conjunction with each other. Shallow self-tapping screws may be inserted in the horn to either side of the crack. Wire or strong fibre filament is then wound between them to stabilise the crack. Similarly, a metal plate can be secured with screws on either side Wire can also be sutured directly into the good horn on either side of the crack without the use of screws. Another method, only open to the farrier over the last fifteen years, is the use of acrylic adhesives such as Equilox or Hoof Life and fibreglass cloth. Once the sensitive laminae exposed by the crack have healed sufficiently, a piece of fibreglass large enough to span the crack is impregnated with the adhesive, and is then applied over the surrounding area. Further adhesive is then applied on top To avoid infection, a straw or some form of removeable putty may be used underneath the adhesive, to create a cavity through which the area may be dressed and flushed out regularly. The acrylic or PMMA adhesives, whose main ingredient is Polymethyl Methacrylate, have proven the most effective in imitating hoof horn. Once cured, they can be rasped, and, when used for hoof repair, can be nailed into as if they were normal hoof wall. The Hoof Staple can also be used. This is a product resembling a double-ended fish-hook that spans the crack and is driven in on either side. In the USA, some senior veterinarians have started to use a product called Lacerum, manufactured by BeluMed X of Little Rock, Arkansas, in the treatment of hoof cracks. This is a platelet-rich plasma solution, obtained either from the horse being treated or a donor horse, that is used to promote healing, to accelerate the growth of healthy tissue and to fight off bacterial infection.
Thus, while cracks are, if anything, becoming more prevalent, new products and techniques are becoming available to the farrier as the result of developing technologies that permit him to address the issues in new ways and to find new solutions to the hoof crack problem. For further reading: ‘Farriery – Foal to Racehorse’ by Simon Curtis ‘No Foot, No Horse’ by Gail Williams and Martin Deacon ‘Hickman’s Farriery ‘(2nd Edition) by J. Hickman and Martin Humphrey ‘Principles of Horseshoeing II’ by D. Butler.