Effects of 6 alpha-methylprednisolone acetate on an equine osteochondral fragment exercise model

Objective-To determine effects of intra-articularly administered 6 alpha-me thylprednisoione acetate (MPA) in exercised horses with carpal osteochondra l fragmentation. Animais-18 horses: 3 groups of 6 each. Procedure-An osteochondral (chip) fragment was created in 1 randomly chosen middle carpal joint of each horse. Polyionic fluid (PF) was injected into both middle carpal joints of horses in the control group. In horses of the MPA-control group, MPA was injected into the middle carpal joint without an osteochondral fragment; a similar volume of PF was injected into the contr alateral middle carpal joint. In the MPA-treated group of horses, 100 mg of MPA was injected into the middle carpal joint containing the osteochondral fragment; a similar volume of PF was injected into the contralateral joint . Injections were administered on postsurgical days 14 and 28, and horses w ere exercised on a high-speed treadmill for 8 weeks, starting on postsurgic al day 15. Results-Clinical improvement in degree of lameness was not associated with MPA administration. Joints that contained an osteochondral fragment and wer e treated with MPA had lower prostaglandin E-2 concentration in synovial fl uid, and lower scores for intimal hyperplasia and vascularity in synovial m embrane, compared with PF-treated joints. However, articular cartilage eros ion and morphologic lesions suggested possible deleterious effect of intra- articular MPA administration. Conclusions-Some beneficial effects of MPA administration on synovial fluid and synovial membrane were identified; however, the deleterious findings c ontrast with those associated with triamcinolone acetonide used in a simila r model, but agree with other results of MPA administration in normal and a bnormal joints.