Effects of exercise and polysulfated glycosaminoglycan on repair of articular cartilage defects in the equine carpus.

Our aim was to determine if mild to moderate postoperative exercise and intra-articular polysulfated glycosaminoglycan result in improved repair of large, experimentally induced osteochondral defects in a weight-bearing surface of equine joints. Arthroscopic debridement was used to produce full-thickness defects in a weight-bearing area of the radial carpal bones in 18 ponies. The ponies were randomly assigned to two groups balanced for age: nine animals in the exercise and nine in the no exercise group. Six ponies in each group were medicated weekly for 5 weeks with an intra-articular injection of polysulfated glycosaminoglycan in one middle carpal joint beginning at the time of operation. Walking (twice daily) was begun 6 days postoperatively, and by the twelfth week postoperatively the ponies were trotting for 25 min and walking for 15 min twice daily. At the time of the ponies' death, 17 weeks postoperatively, each defect had an average of 50-75% coverage with repair tissue. Exercised, medicated joints had a significantly smaller area of coverage with repair tissue than exercised, nonmedicated joints. Cartilaginous repair tissue from exercised ponies contained significantly more glycosaminoglycan and type-II collagen (r = 0.53, p < 0.05). The ratio of hydroxylysine to hydroxyproline was significantly lower and the ratio of collagen content to total protein was significantly higher in the repair tissue of medicated joints than in the repair tissue of nonmedicated joints; this is consistent with the presence of less type-II collagen in the repair tissue in medicated joints. We concluded that postoperative exercise was beneficial and that the immediate postoperative use of intra-articular polysulfated glycosaminoglycan was detrimental to the development of cartilaginous repair tissue in large osteochondral defects of equine joints.