Page 2 - Randlab TechTalk Newsletter Issue 2

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RANDLAB TechTalk
FIGUre 1: Cases with severe clinical and advanced radiographic signs are less likely to respond to treatment with HA, particularly in the short term.
In one such study (Grauw et al 2016) it was reported that horses treated with a combination of HA and triamcinolone performed worse at three weeks compared to triamcinolone alone, although results of
the two groups were again equivalent by 3 months. However, this study had severe limitations including being a multicentre trial with lameness evaluation undertaken by many different veterinarians, multiple joints affected, results were subjective using owner- reported telephone follow-up, an unusually high portion of adverse reactions following injection and in particular the average age of the horses was approximately 13 years and small case numbers which included one horse whose intended use was breeding.
There were also no radiographic or ultrasonographic studies undertaken. There is no obvious reason that adding HA to the medication would result in a decrease in success rate at three weeks. It would seem imperative that the authors of the paper look for problems in the design of the study and most importantly case selection which would be far more likely to contribute to any potential skewed results rather than the detrimental effect of HA.
Another recent study by Niemelä et al (2016) reported that while horses receiving HA intra-articularly had significantly less pain on flexion at 2 week follow up there was no difference in lameness scores between treated and control groups. However there were only 27 horses in the entire study and saline, which was injected as the control, can have an influence on results. The lameness score improvement with HA was almost statistically
significant and had more horses been included in the study it is likely different results would have been obtained.
Despite these recent studies there is a large volume of scientific data as well as clinical experience that supports the use of HA in the clinical management of joint disease in horses.
It is important when considering the use of HA to remember that there is a considerable difference in
the quality and type of HA available for use in equine practice. There are both animal derived and newer synthetic products which are commonly Streptococcus equi fermentation products. Other factors that veterinarians should consider when selecting a hyaluronic acid are the viscosity, protein content, molecular weight and origin of the HA. Unfortunately not all this data is readily available when selecting the HA of choice. High viscosity is paramount to efficacy, while high protein content may mean more foreign proteins which may contribute to the flair reactions
seen after injection of many intra-articular products. The significance of molecular weight in exogenous HA is still unclear but there is evidence that very low molecular weight products may be less effective while very high molecular weight products may also cause adverse problems within the joint. It seems likely that middle
to high molecular weight exogenous HA may be most suitable for equine use.
There are different levels of adverse reactions following use of any intra-articular medication and there is considerable difference in reaction rates between different HA’s. Using a high quality HA from an established manufacturer will result in less, or potentially no, flair reactions.
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FIGUre 2: Horses with primary synovitis or low grade inflammatory joint disease are the best candidates for HA therapy.