EFFECTS OF INTRAVENOUS ADMINISTRATION OF SODIUM HYALURONATE ON CARPALJOINTS IN EXERCISING HORSES AFTER ARTHROSCOPIC SURGERY AND OSTEOCHONDRAL FRAGMENTATION

Objective-To evaluate the effects of arthroscopic surgery, osteochondr al fragmentation, and treatment with IV administered hyaluronate on hi stologic, histochemical, and biochemical measurements within the carpa l joints of horses. Animals-12 clinically normal horses, 2 to 7 years of age. Procedure-Horses had an osteochondral fragment created at the distal aspect of the radiocarpal bone of 1 randomly chosen middle carp al joint to simulate osteochondral fragmentation. Horses were treated with 40 mg of hyaluronate or saline solution (placebo) intravenously o nce a week for 3 consecutive weeks (days 13, 20, and 27 after surgery) . Treadmill exercise proceeded 5 days per week beginning 15 days, and ending 72 days, after surgery. Clinical evaluations were performed at the beginning and end of the study. Synovial fluid samples were obtain ed aseptically from both middle carpal joints on days 0, 13, 20, 27, 3 4, and 72 after surgery, and total protein, inflammatory cell, hyaluro nate, glycosaminoglycan, and prostaglandin E-2 concentrations were mea sured in each sample. All horses were euthanatized on day 72. Synovial membrane and articular cartilage were obtained for histologic evaluat ion. Articular cartilage samples were also obtained aseptically for de termining glycosaminoglycan content and chondrocyte synthetic rate for glycosaminoglycans. Results-Horses treated with hyaluronate intraveno usly had lower lameness scores (were less lame), significantly better synovial membrane histologic scores, and significantly lower concentra tions of total protein and prostaglandin E-2 within synovial fluid 72 days after surgery, compared with placebo-treated horses. Treatment wi th intravenously administered hyaluronate had no significant effects o n glycosaminoglycan content, synthetic rate or morphologic scoring in articular cartilage, or other synovial fluid measurements. Conclusion- Intravenously administered hyaluronate appears to alleviate signs of l ameness by interacting with synoviocytes, and by decreasing production and release of inflammatory mediators.