IN-DEPTH: RACING-RELATED LAMENESS


including the corticosteroid recommendations, on a regional uniformed basis. Numerous regulators and horsemen expressed concerns regarding the dis- parity between the 7-day ban on intra-articular use of MPA and the 21-day recommendation for the ex- perimental dose to comply with the proposed regu- latory threshold. There was a feeling from veterinarians as well that compliance with the rec- ommendations would be difficult and could place horsemen and veterinarians attempting to comply with the recommendations in good faith in “harm’s way” and that the better approach may be to ban the drug and recommended use of alternative therapies. To continue the principal goal of the RMTC in hav- ing regulatory thresholds adopted and uniformity attained, a decision was made to remove methyl- prednisolone from the list of approved therapeutics.


3. Working Within the 7-Day Rule


As discussed in an earlier review,1 controlled studies have been performed in the horse to clarify thera- peutic response as well as deleterious effects for betamethasone esters,a MPA,b and triamcinolone acetonidec (TA). In a survey of AAEP members, a lower number of respondents were using MPA in high-motion joints (25.7%), with most (77.3%) opting for TA instead.2 A higher percentage (72.7%) were still using MPA in low-motion joints. In contrast to the published works documenting the negative ef- fects of MPA, most respondents indicated that sci- entific papers and data determined their choice of corticosteroid use. The use of Depo-Medrolb has decreased since demonstration of negative effects on the cartilage, but there is still considerable use. It is expected that the pragmatics of prolonged with- drawal time will further decrease the use of the drug. In addition to the options of betamethasone esters and TA as well as isoflupredone acetate,d there are other medication options that are also presented below. A window into the future can eas- ily be examined by looking at racetrack practitio- ners’ use in other countries. In the author’s native country of New Zealand, there is currently a 48-day withholding period for Depo-Medrol; personal com- munications indicate that there is no use of that drug in racehorses and that it is not missed.e Race- track practice has emerged with considerable TA use (withdrawal period is 4 to 5 days) and an in- creasing use of interleukin-1 receptor antagonist protein therapy in carpal, fetlock, and distal tarsal joints.


4. Hyaluronan


Combination therapy of corticosteroids and hyaluro- nan (HA) is quite common and can be defended scientifically. In an experimental study of equine osteoarthritis induced by osteochondral fragmenta- tion in the middle carpal joint, eight horses received 20 mg of HAf intra-articularly 14, 21, and 28 days after induction of OA.3 No adverse treatment-re- lated events were detected. No changes in clinical


438 2013  Vol. 59  AAEP PROCEEDINGS


signs were seen with HA compared with that in control horses, but, histologically at day 70, there was significantly less fibrillation with HA treatment compared with that in controls. The place for HA in combination therapy is therefore not as an acute anti-inflammatory but as a long-term disease-modi- fying osteoarthritis drug (DMOAD).


5. Polysulfated Glycosaminoglycan


Work examining the effect of intra-articular polysul- fated glycosaminoglycan (PSGAG)g suggests that this product has significant effects on acute synovi- tis and can be used in lieu of intra-articular cortico- steroids.4 In a controlled study with the use of the equine osteochondral fragment–OA model, eight horses received PSGAG (250 mg) and amikacin sul- fate (125 mg) intra-articularly at 14, 21, and 28 days after induction of OA, and eight control horses re- ceived 2 mL of saline (0.9% NaCl) solution and ami- kacin sulfate (125 mg) intra-articularly on study days 14, 21, and 28. The degree of synovial mem- brane vascularity and subintimal fibrosis was sig- nificantly reduced with PSGAG treatment, and there was a trend for reduced fibrillation at day 70. This indicated significant symptom-modifying OA effects as well as potential DMOAD effects. In other unpublished work, however, it was shown that the combination of triamcinolone acetonide and PS- GAG was inferior to either triamcinolone acetonide alone or PSGAG alone and so current indications are that PSGAG, if used intra-articularly, should be used alone and not in combination with corticosteroids.


6. Extracorporeal Shock Wave Therapy


Evaluation of extracorporeal shock wave therapy (ESWT) in the osteochondral fragment model of OA also showed symptom-modifying effects in the car- pal joint.5 Extracorporeal shock wave therapy has also been used to treat horses with OA.6,7 Horses were randomly allocated to receive local application of ESWT at days 14 and 28, a positive control ther- apy (intramuscular PSGAG), or sham ESWT (pla- cebo). The degree of lameness in horses treated with ESWT improved significantly compared with the degree of lameness in placebo-treated or PSGAG-treated horses. No disease-modifying ef- fects were evident in the results for synovial fluid, synovial membrane, or cartilage from the ESWT- treated or PSGAG-treated horses. There were no significant effects ofESWTon any bone variable, but serum osteocalcin concentration was significantly greater than in horses that received ESWT com- pared with placebo-treated control horses. The in- crease of serum biomarkers was indicative of bone remodeling, but there were no negative effects re- vealed. It could be concluded that ESWT is a viable non-pharmaceutical treatment for acute inflamma- tion in equine joints.


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