Tibial Stress Fractures – More Common Than You Think | Trainer Magazine | European Trainer Article Index

Jul 1

Jul 1 Tibial Stress Fractures – More Common Than You Think

AFTER winning the Group Two Royal Lodge and coming second in the Group One Racing Post Trophy as a two-year-old, hopes were high that Jukebox Jury would top the charts as a three-year-old. However, he was found to be lame behind after a routine canter in the spring. An investigation revealed that the lameness was being caused by a ‘micro- fracture’ of his tibia. The problem soon settled and he resumed full-speed cantering just over a month after the injury before embarking on a very successful three-year-old season, winning three Group races including the Group One Preis Von Europa in Cologne before coming a creditable second in the Grade One Canadian International. Where is the tibia? The tibia is the large bone in the hind leg between the hock and the stifle, which is the equivalent of our shinbone. Most people probably have very little to do with this bone unless they have sent horses for ‘bone scanning’ (nuclear scintigraphy). This is because tibial stress fractures are usually only diagnosed via a bone scan although sequential x-raying of the tibia is in fact more helpful – something that will be discussed later in this article. What does a horse with a tibial stress fracture look like? A horse with a tibial stress fracture is often quite lame on the day of injury but usually comes sound in approximately a week, hence the under-diagnosis of this injury in most yards in the country. The lower limb is often cold and free from swelling whereas the upper limb musculature of the horse is usually quite sensitive, with many of the large muscles being in spasm. If the horse is only lame for a few days it is unlikely that it will be sent for a bone scan and hence a diagnosis of a ‘pulled muscle’ is likely to be made, particularly if the horse is seen or ‘treated’ by a physiotherapist or ‘back manipulator’ in the meantime. When do they occur? Tibial stress fractures are most commonly seen in young horses especially, if they are returning from a lengthy period of enforced rest. If horses are restricted to box rest due to injury then their skeleton can become ‘soft’ and so predisposed to minor bony injuries when they are returned into full cantering. These bony injuries include well- known problems such as ‘splints’ and sore shins but, perhaps even more commonly, tibial stress fractures. A typical scenario is a horse that has suffered an injury which may or may not have needed surgery but that required one-to-two months of complete box rest followed by a similar amount of horse- walker exercise. The horse then undergoes a period of light ridden exercise before resuming full speed cantering. However, after approximately two-to-four weeks of full- speed cantering it is found to be lame behind. If the cause of the lameness is not obvious and the horse’s lower limb is cold with no signs of swelling or pain, then the most likely cause of such an injury in a hind leg is a tibial stress fracture. How are tibial stress fractures diagnosed? Tibial stress fractures can only be diagnosed by either bone scanning or sequential x-rays. If a speedy diagnosis is required or if the lameness persists for a while then the horse might be sent for a precautionary bone scan. This will reveal increased bone turnover in one tibia compared to the other and hence the diagnosis of a tibial stress fracture will be made. On the other hand, if a horse is found to be lame behind and a tibial stress fracture is considered to be a possible diagnosis then the tibia can be x-rayed when the horse is first found to be lame. Whilst this x-ray is unlikely to reveal any significant abnormalities, the tibia can then be re-x-rayed every few days and if there is any evidence of active new bone or ‘callus’ formation appearing on the surface of the tibia within a week or two of the onset of lameness, this signifies that the cause of the horse’s lameness was a tibial stress fracture. Jukebox Jury had a problem in the winter with a wound on his fetlock that necessitated an enforced period of box rest. He recovered well from this but after a few weeks cantering he was found to be quite lame on his right hind. These are his sequential tibial x-rays. 1. The first x-ray was taken the day after he was lame following cantering and did not reveal any significant abnormalities. He remained on box rest. 2. The second x-ray taken seven days after the onset of lameness suggested that there may be a small amount of ‘new bone’ forming on his upper tibia. He was sound shortly after this x-ray was taken and so started walker exercise. 3. The third x-ray taken 17 days after the onset of lameness revealed a large lump or ‘callus’ of new bone on his upper tibia signifying a ‘micro-fracture’ within the bone. He resumed ridden walk/trotting exercise following this x-ray. 4. The fourth x-ray taken one month after the injury suggested that the new bone was settling and so he would soon be ready to resume full-speed cantering. 5. The fifth x-ray taken a few days later confirmed that the injury had settled and so he resumed full work. He did not have any further setbacks. 2 3 Why are tibial stress fractures so under-diagnosed? The main reason why tibial stress fractures are so under-diagnosed is that affected horses often come sound within a week and providing that the trainer is sufficiently patient then the tibia is likely to settle by the time the horse is returned into full work, and so an investigation is never carried out. In addition, if a physiotherapist or ‘back manipulator’ is called to see the horse, they will ‘treat’ the horse’s upper limb muscle spasm and probably advise that it undergoes a period of rest – something that will probably ensure that it has enough time off for the tibial stress fracture to settle. Why are we only learning about tibial stress fractures now? The advent of equine bone scanning in the early 1990s brought about the diagnosis of the tibial stress fracture. A bone scan measures bone turnover and it soon became apparent that the bone turnover and remodelling in a young horse’s tibia is massive and hence many horses that underwent a hind limb bone scan came back with a diagnosis of one or even two tibial stress fractures. However, these injuries started to be diagnosed with such regularity that many began to questio whether they really were fractures or simply ‘normal’ remodelling within the young horse’s tibia. After x-raying the tibias of a large number of young horses, it has now become apparent that tibial stress fractures are indeed very common but the diagnosis can only really be certain if it is possible to demonstrate an ‘active’ callus forming and then settling on x-ray in the period shortly after the horse was first found to be lame. Treatment Having made the diagnosis of a tibial stress fracture in a horse that is probably sound by the time of diagnosis, the question is then posed – how long should the horse be rested? A few years ago, most tibial stress fractures were treated with one month or more of box rest. However, as veterinary surgeons have become more familiar with these injuries, they have tried to reduce the amount of rest that a horse requires to recover. It is at this point I would like to suggest that most tibial stress fractures should actually be managed more like severe sore shins. Sore shins are caused by micro-fractures in the horse’s cannon bone and are readily diagnosed by feeling the hot, painful shin which forms new bone on the front of the cannon. This is commonly known as a ‘bucked’ shin but is actually more accurately described as an external callus. The soreness is easily monitored, and as soon as the heat and pain has gone, the horse is returned to cantering just days after being diagnosed with micro-fractures (sore shins). This has been an accepted protocol for many years for recovery from this type of injury. Tibial stress fractures and sore shins occur in exactly the same type of horse – either the immature horse or the horse returning from injury. I am suggesting that tibial stress fractures should be treated more like severe sore shins than serious fractures. However, there are some problems with this. Firstly, it is difficult to monitor the tibia because much of the bone is covered by muscle and only a small portion of it is palpable and so only x-rays show us how the bone is changing. Secondly, there is a fear of a more serious tibial fracture and this is something that deters the majority of people from treating a tibial micro-fracture as a less serious problem. Obviously, each injury should be treated on its merits but on average a young horse with a tibial stress fracture can be returned into full cantering approximately one month after injury. The horse should be box rested until it is sound, which usually takes about seven days, after which time it should commence horse-walker exercise for a further seven days. On completion of this period of box rest and walker exercise, the horse can then be returned into light ridden exercise for approximately two weeks and then it can resume full-speed cantering providing that an x-ray confirms that the injury has settled. Prognosis Whilst no-one wants a horse to be out of full-speed cantering for a month, a tibial stress fracture is not an undesirable injury. This is because it very rarely recurs providing that the tibial injury being dealt with is a tibial stress fracture and not a more serious fracture. As long as the horse is given enough time then the prognosis for a full and fairly rapid recovery is excellent. Conclusion In summary, tibial stress fractures occur much more frequently than many people think and are commonly misdiagnosed as pulled muscles. If a young horse that has just resumed cantering after an enforced rest suddenly becomes lame behind and the problem is not obvious, then a tibial stress fracture is the most likely cause. These injuries can be diagnosed by a ‘bone scan’ but sequential x-rays diagnose them more accurately and are also very helpful in determining when the horse can be returned into training. The average tibial stress fracture can resume full-speed cantering approximately one month after injury and the prognosis is usually excellent. The next time the reader has a horse that is lame behind in similar circumstances, I would urge them to consider this diagnosis. CLICK ON IMAGE TO READ ARTICLE

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