VETERINARY
JOINT INJECTIONS Which medications give the best results?
Joint injuries are common conditions in all types of horses, and this very definitely includes the racehorse. There are always two or more bones coming together at a joint but joints are composed of various additional tissues: cartilage covers the end of the opposing bones and forms a smooth gliding surface for movement, and the joint capsule and ligaments support the joint, holding everything in place. Joints are lined by a synovial membrane. Cells within this membrane are responsible for producing synovial fluid, the lubricating fluid that is essential for joint health and movement. Any or all of these tissues can be involved in injury. When inflammation is confined to the lining membrane, this is termed “synovitis” and generally involves excessive fluid within the joint, and the chemical make-up of that fluid can be disrupted. The term “arthritis” implies that additional tissues are inflamed and can involve cartilage or bone. WORDS: PROFESSOR CElia M MaRR, EquinE VEtERinaRy JOuRnal PHOtOS: PROFESSOR CElia M MaRR, SaRaH POWEll, PEtER RaMzan (ROSSDalES llP, nEWMaRkEt, SuFFOlk)
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OINT medications allow targeted treatment of one or more specific joints, particularly if initial rest and anti-inflammatory therapy do not resolve lameness. Drugs from the corticosteroid family are often used, in particular triamcinolone. Corticosteroids are very potent anti-inflammatories, reducing lameness and joint effusion in horses with synovitis arthritis and decreasing the production of destructive and proinflammatory factors in cartilage and synovial membrane. However, corticosteroids also have the potential to do harm and can have especially detrimental effects on cartilage. These negative effects are related to the type and dose of corticosteroid used, the frequency of repeated administration, and to joint loading after injection. Research studies indicate that triamcinolone (TA), a corticosteroid with medium duration of action, has the most favourable effect in terms of equine cartilage metabolism compared to other corticosteroid preparations like methylprednisolone acetate (MPA) and betamethasone, and therefore, most vets choose to use TA in preference to other preparations. Joint injection with hyaluronate (HA) is another popular treatment that can reduce lameness and provide clinical antiinflammatory and analgesic effects, without
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detriment to cartilage or the synovial membrane morphology. HA is not a corticosteroid. In fact, HA is made by the body naturally, and it acts as a “goo” within synovial fluid to maintain its lubricating function. When used as a medication, HA reduces joint friction and pain, and research suggests it blocks the release of inflammatory products from the synovial lining and might have a protective effect on cartilage. A common treatment strategy is to combine a corticosteroid with HA in a single joint injection. The theory is that addition of HA might minimise any potential negative effect of the corticosteroid on cartilage metabolism and/ or that the drug combination provides more effective alleviation of lameness than the corticosteroid alone. However, theories are not facts and, until recently, this assumption was never investigated in a large-scale randomised clinical trial in horses.
The Utrecht Joint Medication Study
A report recently published in Equine Veterinary Journal set out to find out whether the combination of TA and HA produced better long-term effects than TA alone. The
research study was led by Dr Janny De Grauw from Utrecht University in the Netherlands and involved a collaborative effort with colleagues from local veterinary practices. Dr De Grauw’s study was ambitious because it involved recruiting a large number of horses with naturally occurring joint inflammation whose owners were prepared to allow the vets not only to examine their horses on several occasions but also to randomly allocate the horses for treatment with either TA or TA plus HA. The study was actually performed in pleasure and sports horses but the results are also informative for racehorse trainers.
How was the clinical trial performed?
Horses and ponies aged two years and older were screened for eligibility for the clinical trial based on the following four criteria: 1. The horse had lameness of at least grade 2 on a 0-5 scale, lameness localised to one limb only; 2. Only one joint was involved of pastern, fetlock, middle carpal, or antebrachiocarpal joints, which make up the knee; 3. Joint blocks confirmed that the lameness was localised to this joint; 4. The owner was willing for the horse to receive intra-articular medication. Horses were excluded from their trial if they had a joint injection in the same joint