Objective: To evaluate the effects of arthroscopic surgery, osteochondral fragmentation, and treatment with IV administered hyaluronate on histologic, histochemical, and biochemical measurements within the carpal 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 carpal joint to simulate osteochondral fragmentation. Horses were treated with 40 mg of hyaluronate or saline solution (placebo) intravenously once 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 obtained aseptically from both middle carpal joints on days 0, 13, 20, 27, 34, and 72 after surgery, and total protein, inflammatory cell, hyaluronate, glycosaminoglycan, and prostaglandin E2 concentrations were measured in each sample. All horses were euthanatized on day 72. Synovial membrane and articular cartilage were obtained for histologic evaluation. Articular cartilage samples were also obtained aseptically for determining glycosaminoglycan content and chondrocyte synthetic rate for glycosaminoglycans.
Results: Horses treated with hyaluronate intravenously had lower lameness scores (were less lame), significantly better synovial membrane histologic scores, and significantly lower concentrations of total protein and prostaglandin E2 within synovial fluid 72 days after surgery, compared with placebo-treated horses. Treatment with intravenously administered hyaluronate had no significant effects on glycosaminoglycan content, synthetic rate or morphologic scoring in articular cartilage, or other synovial fluid measurements.
Conclusion: Intravenously administered hyaluronate appears to alleviate signs of lameness by interacting with synoviocytes, and by decreasing production and release of inflammatory mediators.