Working to reduce risk of veterinary problems in National Hunt Racing

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THIS ARTICLE FIRST APPEARED IN - EUROPEAN TRAINER - ISSUE 40

Pilates For Horses - enhancing performance and reducing injuries

Pilates is increasingly used amongst professional athletes as a method to enhance athletic performance and to reduce injuries.

Nicole Rossa (European Trainer - issue 21 - Spring 2008)

Current research on Pelvic Asymmetry in Racehorses

Steeplechase racing in particular is a high risk sport for the horse. There is currently some fairly extensive research into racehorse injuries and fatalities on the racecourse, with previously published scientific reports on the subject being widely available. The racing industry is aware of the need for such reports, as the industry itself is very much in the public eye with regard to injury rates on the racecourse. Lameness is one of the main reasons for wastage in the racehorse industry, and was the reported cause of 68% of total horse days lost to training in a study of racehorses in England (Rossdale et al. 1985).

This study also suggested that 10% of all diagnosed lameness cases were caused by tendon injury. Overstrain injuries to the superficial digital flexor tendon (SDFT) are amongst the most common injuries observed in the athletic horse (Goodship, 1993). It is therefore important to determine all possible causative factors of SDFT injury so that methods for preventing injury can be implemented as part of a training programme.

HINDQUARTER ASYMMETRY

The hindquarters of the horse provide the propulsion, and the forelimbs support 60% of the horse’s weight. Problems affecting the pelvic structure in the horse can lead not only to poor performance, but also to an unlevel gait and to lameness of the hindlimb. There are to date very few scientific reports on the frequency of hindquarter asymmetries in the horse, although Bathe (2002) found that most hard working horses were likely to have some degree of pelvic asymmetry.

This factor may not always affect performance, as many successful horses have been found to have asymmetry of the pelvis. Dalin et al. (1985) investigated the hindquarter asymmetry in Standardbred Trotters for any correlation with poor performance. He measured differences in height between the left and right tuber sacrale when the horse was standing square. Of the 500 horses measured 39 of them showed marked hindquarter asymmetry. In 30 horses the tuber sacrale was lower on the left, and in 9 horses it was lower on the right. The asymmetric horses had significantly inferior performance (measured by total earnings) compared to the symmetrical horses.

All the horses were trained and raced in Sweden on a left handed track. The asymmetrical horses were also of significantly larger body size than the symmetrical horses. In a recent study undertaken by Stubbs et al. (2006) in conjunction with the Hong Kong Jockey Club, a number of racehorses were presented for euthanasia (for injury and/or lameness). Racing and training details were examined in detail, and a clinical examination was carried out before the horses were euthanased. Following post mortem the thoracolumbar spine and pelvis were dissected out and examined. Although not part of the study it was noted that asymmetry of the pelvis was prevalent in many of the horses that had been dissected, the reason probably being due to a natural torsion of the pelvis as a result of training and racing on right handed tracks only.

It is suggested that asymmetrical loads on the pelvic structure caused by external factors (such as racetrack), and by internal factors (such as locomotor apparatus pain) may lead to a higher stress being placed on one hindlimb, and as a result lead to the development of pelvic asymmetry which may be apparent as pelvic rotation. Improper movement patterns of the hindquarters, due to pain caused by overuse or from fatigue, may also result in abnormal alignment of the pelvic structure.

This in turn may then cause overloading on the forelimbs (by off loading the hindquarters) and therefore predisposing the forelimbs to injury. If this can be proved then surely this would emphasise the importance of correcting pelvic misalignments using manipulation techniques such as chiropractic, osteopathic and myofascial release approaches. There is some unpublished material available to support the use of McTimoney manipulation methods and other soft tissue manipulation in the correction of pelvic rotation. Hindquarter asymmetry is often associated with sacroiliac joint lesions or with chronic hindlimb lameness.

The tuber sacrale can appear asymmetrical in clinically normal horses as well as in horses with misalignment of the sacroiliac joint (Dyson, 2004). Horses with longstanding poor performance attributed to chronic sacroiliac damage were investigated by Jeffcott et al. (1985). The majority of these horses showed some asymmetry of the hindquarters with the tuber coxae and tuber sacrale lower on the same side that the animal was lame on. Hindquarter asymmetry may be due to some tilting or rotation of the pelvis in addition to muscle wastage of one quarter, usually the side the horse is lame on.

ABNORMAL ALIGNMENT OF THE PELVIS

Pelvic rotation or abnormal alignment of the pelvis to the thoracolumbar spine can be measured by the level of the tuber coxae to the ground. If the horse is unable to produce the propulsion from its hindquarters due to discomfort in the pelvic region, then the forelimbs may be required to provide more horizontal propulsion. The horse will in effect be pulling himself forward with his forelimbs, rather than pushing from his hindquarters. This may result in over development of the shoulder muscles, thereby reducing the efficiency of the forelimb movement by adding unnecessary weight. Unpublished data has suggested a positive relationship between injury to the forelimb stay apparatus and pelvic asymmetry, particularly where the presence of functional asymmetry in the hindquarters was found to be due to pelvic rotation, and not as a result of differences in individual bone lengths of the hindlimb.

LAMENESS AND COMPENSATORY MOVEMENT PATTERNS

The compensatory mechanisms of horses with lameness have been extensively researched and reported. The potential for secondary injuries resulting from a horse’s attempt to compensate for lameness by altering its gait pattern are still unclear. Clayton (2001) found that when a lame limb is supporting body weight, the horse minimises pain by decreasing the load on that limb, resulting in a compensatory increase in the vertical forces in other limbs. The compensating limbs are therefore subjected to abnormally high forces, and these may lead to lameness in the compensating limbs. Uhlir et al. (1997) found that in all cases of diagnosed hindlimb lameness that true lameness of the left hind caused a compensatory lameness of the left fore, and that true stance phase lameness of the left fore caused a compensatory lameness in the right hind. TENDON INJURY The SDFT is the most frequently injured tendon in horses. In a recent study of steeplechase horses diagnosed with tendon and ligament injuries sustained during training, 89% occurred in the SDFT (Ely et al. 2005). It has been suggested that an optimum level of exercise is required at an early age for tendon adaptation to training, but with increasing age accumulation of microdamage and localised fatigue, failure to the tendon will occur with increasing exercise (Smith et al. 1999). The induction of injury to the SDFT occurs when loading overcomes the resistive strength of the tendon. Factors which increase the peak loading of the SDFT, such as weight of rider, ground surface, shoeing, conformation, incoordination, jumping, and speed will act not only to increase the rate of degeneration, but will also increase the risk of the onset of SDFT strain (Smith, 2006). Therefore the prevention of tendon strain-induced injuries by reducing some of the risk factors that increase loading on the tendon may provide the most satisfactory answer.

ANIMAL MANIPULATION TECHNIQUES

McTimoney Animal Manipulation aims to improve asymmetries through manipulation. There has been much anecdotal evidence for the benefits of McTimoney Manipulation Techniques on animals (Andrews and Courtney, 1999). There is anecdotal evidence to suggest that McTimoney and other manipulative therapies can make a difference where veterinary medication has failed (Green, 2006), although the application of manipulation techniques in veterinary medicine may be dependent of further research into the clinical effects of manipulation. Manipulation techniques are thought to cause muscle relaxation and to correct abnormal motor patterns which may be the result of muscular imbalances and restricted joint motion or altered joint mobility (Haussler, 1999). There is some unpublished material to support that there are significant changes in the symmetry of the pelvis after the application of McTimoney manipulation techniques, and that there is continued improvement one month after initial treatment.

CURRENT RESEARCH INTO PELVIC ALIGNMENT

In a recent unpublished study a group of 40 steeplechase horses in training, all using the same gallop, were measured for pelvic asymmetry. The measurement technique used was a somewhat simple (but reliable) method. Each horse was measured on flat, level concrete while standing completely square and weight bearing on all four limbs. Measurements were taken vertically using a horse measuring stick with a spirit level, from the most dorsal aspect of the lateral wing on the ilium (the tuber coxae) to the ground, on the left and right sides. Various data was collected on each horse, regarding race history, how many races run, whether “bumper” (flat races for steeplechase bred horses), hurdle or steeplechase, prize money earnings, handicap rating, and also brief veterinary history. The aim of the study was to compare pelvic rotation in 20 sound horses to the incidence and degree of pelvic rotation in a group of 20 horses with SDFT strain in either one or both forelimbs. Both the sound horses and the injured horses were in training with the same trainer, and therefore had used the same gallops, and underwent the same training regime. Although no significant difference was found in the number of horses with pelvic rotation in sound horses compared with the number of horses with tendon strain, there was a high incidence of pelvic rotation in the group as a whole, with a predominance towards pelvic rotation on the right.

This could have been due to training methods or gallops used, and certainly warrants further research. There was no significant association between side of pelvic rotation and side of forelimb tendon strain, but again warrants further investigation using a larger number of horses. Due to the prevalence of right side pelvic rotation it would not have been possible to show any significant associations anyway between left and right forelimb injury. The study did present some trends for age of horse, sex, and race history; showing that the number of horses with pelvic rotation and tendon injury increased with age. Geldings tended towards a higher incidence of tendon injury, and mares tended towards a higher incidence of pelvic rotation. There were equal numbers of sound and injured horses for each race type, but the degree of pelvic rotation in horses that had fallen was notably larger than in the horses that had not fallen.

FUTURE STUDIES INTO PELVIC ASYMMETRY

The preliminary investigation as described above has formed the basis for further research into abnormal pelvic alignment in racehorses, and whether or not there is any association between side of misalignment and side of forelimb injury. Further research is due to be carried out with a larger sample of horses, and from different yards, to investigate whether there is any prevalence as to the side of misalignment, or if pelvic alignment is affected by training methods and the use of different gallops.

Back problems - how they can affect performance, and how to treat them

It is well documented that horses can suffer with back problems and they tell us by their actions. Sometimes the signs are blatant – for instance the horse stops jumping, or displays an obvious aversion to being saddled. Most of the time the signs are much more subtle. The animal may slightly change its way of moving in order to avoid pain and if untreated this becomes a chronic and long term problem, the slight change of gait becoming a progressive shortening of stride and a reduced level of performance.

The power source in the equine comes from the hind limbs propelling the body forward. If there is pain within that area the animal will use less power – and therefore go slower, or be unable to clear fences – than if it felt no pain. Traditionally we look at a horse being ‘trotted up’ in a straight line as a way of assessing soundness. This is an adequate measure in many cases where there is obvious lameness in one limb however a lame horse can ‘trot up’ sound and this shouldn’t be the only measure of soundness. Other tests such as trotting on a circle in both directions, on both hard and soft surfaces should be used. Assessing the animal at a walk on a level surface and observing from both the rear and from the side is also a very useful tool in diagnosing a slight lameness or restriction of gait. What manifests itself at a walk will still be there at a gallop. And knowing how the animal moves when sound and supple is key to knowing when something is starting to go wrong – perhaps catching a small problem before it becomes a serious lameness issue. Just saving itself from a fall or slip up when in the field can be enough to cause a problem.

A momentary error of judgment by horse or rider can force a horse to use its athletic ability to get out of trouble. A twist or over-big jumping effort can be enough. The horse can go on to complete the course or win the race that day but later, when the body has cooled down and the tired muscles are trying to recover pain can develop because of that over exertion. A subluxation may have occurred An almost imperceptible lameness or a restriction of free movement of the limbs can make all the difference between winning and losing. A slight ache or low grade back pain can make all the difference between staying the distance and tailing off last. Do horses have an ‘off day’? Or is there an underlying problem which is preventing full extension, making the animal hold itself back in order to avoid pain? The Spinal Cord is the keystone of the body. Maintaining its health and integrity is imperative in maintaining the health and wellbeing of the body as a whole, and doubly so in the case of a performance athlete.

The protection of the spinal cord is paramount in the actions of the horse or any vertebrate. The nervous system controls the whole body, with nerve control of practically every cell of the body. Subluxations or trapped nerves can interfere with the ability of the nervous system to function to the best of its ability both in control and in counteracting disease. Manipulation is therefore a means of reducing these subluxations to improve the functioning of the whole body. The skeleton is responsible for supporting the body and providing it with a strong framework consisting of rigid components which can move relative to each other at articulating joints. The spinal column provides protection to the spinal cord.

If a joint in the spinal column were to be dislocated that would result in damage to the spinal cord and paralysis or death. Between each pair of vertebrae a pair of spinal nerves leave the spinal cord through a small ‘gap’ in the muscles, ligaments and other soft tissues. A subluxation is where the joint between two bones is misaligned – muscles go into spasm and can pull one of the bones of the joint slightly out of alignment. If a joint is subluxated then the two surfaces are not quite in the correct position and nerves become impinged or ‘trapped’.

A nerve which has become trapped cannot send signals to muscles therefore function is affected. The equine athlete, and particularly the race horse, is highly susceptible to damage of the back, neck and poll. The body is put under a great deal of stress and pressure during breaking and fitness work whilst still immature. Added to this the horse must learn to carry the weight of a rider on its back and to balance itself with this shifting weight. Exertion such as galloping and jumping stresses the musculoskeletal structure and it is whilst under stress and when fatigued that injuries can occur more easily. The neck, chest withers and shoulders are of paramount importance to the action of the forelimbs.

The main nerves which feed the forelimbs leave the spinal cord between vertebrae in the lower neck and chest area (C6 –T2). If a horse struggles to flex and bend its neck to each side, up and down, shows stiffness or pain reactions it will cause restricted limb action, reduced ability to gallop, reduced speed, reduced stamina and reduced performance. As a highly strung and active animal the young horse is likely to be ‘sharp’ and difficult to handle during breaking. Whilst lunging they are prone to over-excitement resulting in leaping, bucking, rearing, spinning around etc - once backed they are still likely to display these behaviours. Rearing followed by unbalancing and going over backwards, or rearing whilst tied up with the entire weight of the body being taken over the poll region by the headcollar can lead to damage of the neck, withers and back. Rearing and hitting their head on a stable beam or flinging up the head and hitting it on the door frame or in a vehicle are all possible scenarios for damage to the poll and neck resulting in tension, pain and the development of other symptoms.

Sensitive withers can be just ticklishness but could also be soreness from the front limbs and neck. Concussion can travel right up the forelimbs resulting in sore withers. Of course a horse of any age can become sensitive in the neck and poll and often we do not know what they have done or when they have done it, unless it can be attributed to a particular incident such as a crashing fall or getting cast in the stable. Often the problem exists without explanation and could have been there for months or years – like living with a permanent head ache. Treatment with manipulation is straightforward and can give lasting relief. The main nerves which feed to the hind limbs leave the spine in the lumbar and sacral region (L4 - S2) and inflammation, soreness and pain in this area can and does cause the horse to take a shorter hind stride or unequal hind strides. The result of this will be a reduction in power leading to slower galloping speed and/or reduced stamina and failing to stay the distance.

The inexplicable poor performance of any horse could be attributed to any of the above. Fitness to do the job required is a vital part of injury prevention. Weeks of slowly building up the workload are necessary to attain the level of fitness needed for the job in mind. Additionally training involves keeping the body free from aches and pains which might lower the level of performance that the individual can attain. During training nerve damage can and does occur which will cause restrictive movement and a loss of straightness. This can be due to conformational defects, concussion, over-exertion, muscle strain, or injury.

There are no absolutes when it comes to conformation of the limb and the flight of the limb through the phases of a stride. Generally we look at conformation relating to the breed or type of the animal when standing. Some abnormalities or defects may only be evident during a phase of stride and may affect a pair of limbs or a single limb. Abnormal development within a joint can also cause a limb to exhibit a lateral gait defect. Normally the joints such as fetlock, carpus and tarsus work in a hinge-like fashion, backward and forward in a straight line parallel to the horse’s midline. An abnormality can produce a swivel-like motion and cause the limb to arc in flight. Even if a horse shows all the conformational traits that theoretically add up to straightness, if it experiences pain in any part of its body it may break all of the conformation rules in order to use its limbs in a manner which creates the least stress and pain.

An injury or soreness in a limb can cause a horse to protect one portion of the limb when landing, subsequently altering the arc of the foot’s flight. When a horse has pain in a part of the body other than the hooves or limbs, its balance during movement may be negatively altered as it compensates for the soreness. Back soreness can mimic lower limb lameness and alter foot flight. A variety of factors can cause a horse to carry its body in a stiff or crooked fashion. Sometimes the stiffness or pain is subtle but just enough to prevent the horse from tracking straight. As most people will know from personal experience – back pain reduces their ability to move freely, slows them down and if left untreated is debilitating and can lead to a long term loss of full musculoskeletal function together with general irritability.

This is no less the case in the horse and it does not necessarily mean that the horse is lame only that performance has been reduced. A horse suffering with back or neck pain will be unable to gallop as fast as it did prior to the injury, will be unable to ‘stay’ as far. The pain will restrict it and it will be unwilling to keep galloping thereby being seen to fade in the last furlongs or in severe cases never being able to lay up with the pace and being adrift from the offset. By being vigilant to the signs pain and of over-exertion and by allowing for recovery of the musculoskeletal system after work these problems can be minimised. The signs can be subtle but they are there – sometimes rest is needed, sometimes an injury has occurred which will require treatment.