EFFECT OF CENTRAL OR MARGINAL LOCATION AND POSTOPERATIVE EXERCISE ON THE HEALING OF OSTEOCHONDRAL DEFECTS IN THE EQUINE CARPUS

The effects of osteochondral defect location and postoperative walking exercise on structural repair and recovery of joint function were exa mined in the midcarpal joints of ponies. Functional recovery was monit ored by measuring ground reaction forces using a force plate. Structur al repair was evaluated histologically and by measuring the total coll agen and uronic acid content and relative proportions of Type I and II collagen in the repair tissue. Central defects tended to cause a more marked functional disturbance but were repaired with fibrocartilage r ather than fibrous tissue in 3 out of 6 ponies while marginal defects were repaired almost exclusively with fibrous tissue. There was no sig nificant difference between defect locations with regard to the bioche mical measures evaluated. Exercise produced no beneficial effect on st ructural repair of the defects. Secondary 'kissing' lesions in the thi rd carpal bones opposite the defects appeared grossly more severe in t he exercised ponies which also show ed a trend to more marked function al disturbance.