Discussion

Hopefully this presentation will appear as a logical progression from the previous talk on the science behind the treatment of lameness. There is a mystique surrounding the treatment of high- level sport horses but the majority of the time it is just the proactive application of standard orthopaedic principals. The rider will have far more influence than the vet over keeping the competition horse sound. Veterinary involvement in the selection and training process of sport horses is critical. Veterinary involvement in the routine monitoring of horses in training for the early identification of problems is critical but this presentation will concentrate on treatment. Debates rage about 'prophylactic' treatment and this can be a very lucrative field, more commonly employed in the USA than in Great Britain. More commonly we would be looking at the early treatment of any problems. This may be followed by maintenance therapy of previously diagnosed problems, often timed around competitions. Different veterinary surgeons employ different strategies with respect to medication. I prefer to work-up and block mild lamenesses to identify the pathology to be treated. Others would claim to have more developed clinical or psychic powers and to be able to tell the type of treatment required based on a brief clinical examination. Sometimes this is the only course of action available if there is only a very short time between presentation and competition.
The majority of sport horses receive some sort of nutraceutical. Unfortunately the scientific rationale behind these has often failed to keep up with the commercial marketing. There is some rationale for glucosamine, chondroitin sulphate, omega 3 fatty acids and antioxidants, although there are issues with bioavailability. For low-grade conditions and for joint maintenance there may be a role for these products.
Systemic treatment with intramuscular polysulphated glycosaminoglycans and intravenous hyaluronic acid is popular due to the simplicity of administration and lack of requirement of a specific diagnosis. The clinical benefits are often subtle although they can be useful in mild conditions. They may be used tactically in the run up to competition, and some promote their use for
'routine joint maintenance'.
Bisphosphonates such as tiludronate are being used increasingly in the treatment of joint pain. Some horses do appear to respond well, though the mechanism action is still uncertain and picking which cases are likely to respond can be challenging. In our practice tiludronate has been rather disappointing in its effectiveness for distal tarsal joint pain and for subchondral bone pain in racing Thoroughbreds, both areas that intuitively it would likely be beneficial. Conversely, we have not noted any increased incidence of fracture in racehorses treated with this product. They can be useful in some sport horses, and offer a different mechanism of action to other treatments.
Intra-articular treatment remains the most effective method of treatment of localised joint disease. Intra-articular corticosteroids are the most potent and effective drugs. Appropriate products used in low dosages can be beneficial to the joint rather than detrimental. Less experienced clients are often nervous about the use of steroids, whereas the majority of professionals will request their use. The majority of research work suggests that triamcinolone is more chondroprotective than betamethasone or methylprednisolone acetate (MPA), and is generally considered the drug of choice in our practice. With appropriate aseptic technique for injection the risk of infection is very low in practical terms, even without clipping. I would not normally administer intra-articular antibiotics as a routine, but would inject 100 mg of amikacin along with corticosteroids if the joint had been blocked within the previous week. Steroid medication is often combined with hyaluronic acid. There is no firm evidence that this is beneficial but it may possibly ameliorate some of the deleterious effects of corticosteroids as well as having a beneficial effect in its own right and many clinicians comment that they may get a longer duration of positive effects after medication with steroids if they are combined with hyaluronic acid. Because of the risk of laminitis I would normally use a maximum dose of 20 mg of triamcinolone in a sport horse. Racing Thoroughbreds seem more resistant to developing laminitis and a dose of up to 40 mg would commonly be used in our practice. A dose of 5 - 10 mg per joint would be used generally, depending on the number of joints to be treated. Methylprednisolone acetate still tends to be used more in low-motion joints, although the long withdrawal period for medication control tends to preclude its use during the competition season.
More recently there has been an increased interest in the use of biological products. Autologous conditioned serum (Irap) can be a helpful product in the treatment of arthritic conditions and damaged soft tissue structures associated with joints, such as collateral ligament injuries within the distal interphalangeal joint. I do not find it as potent as corticosteroids, but it has the advantage of no withdrawal period. Platelet-rich plasma (PRP) can also be used intra-articularly and I tend to use this in more severely affected joints where there is more need for an anabolic effect. The benefits of intra-articular stem cells are less well defined currently, although there is some rationale for their use and there may be room for a combined approach using a sequence of biological products. Over the next few years we need to work hard to develop an accurate evidence base to be able to more effectively choose appropriate medications for particular conditions.