EFFECT OF BETAMETHASONE AND EXERCISE ON EQUINE CARPAL JOINTS WITH OSTEOCHONDRAL FRAGMENTS

Osteochondral fragments were created arthroscopically on the distal as pect of both radial carpal bones in 12 horses. On day 14 after surgery , one middle carpal joint of each horse was injected with 2.5 mL Betav et Soluspan (3.9 mg betamethasone sodium phosphate and 12 mg beta-meth asone acetate per milliliter) and the contralateral joint was injected with 2.5 mL saline as a control. Intra-articular treatments were repe ated on day 35. On day 17, six horses began exercising 5 days per week on a high-speed treadmill. The other six horses were kept in box stal ls throughout the study as nonexercised controls. On day 56, all horse s were examined clinically and radiographically and then were euthanat ized. Samples were obtained for histological, histochemical, and bioch emical evaluation. Mild lameness was observed in five of the six exerc ised horses at day 56; four horses were lame in the control limb and o ne horse was lame in the treated limb. Of the five nonexercised horses evaluated for lameness, two were lame in the control limb, two were l ame in the treated limb, and one was lame in both the control and the treated limb. No differences were noted on radiographs or palpation of steroid treated limbs versus control limbs. Firm reattachment of the osteochondral fragment to the radial carpal bone occurred in all but t hree joints. Gross cartilage damage was not different between steroid- treated joints and joints injected with saline. Histologically, there were no significant detrimental effects of beta-methasone with or with out exercise, but there was a tendency for more pathological change in treated joints. There was a trend toward decreased glycosaminoglycan staining in steroid treated joints of rested horses, whereas exercised horses had similar glycosaminoglycan staining in treated and control joints. No significant difference in the water content or uronic acid concentration was detected between treated and control joints. Intra-a rticular betamethasone administration in this carpal chip model was no t associated with any significant detrimental effects in either rested or exercised horses. (C) Copyright 1994 by The American College of Ve terinary Surgeons