Arthroscopic subchondral bone plate microfracture technique augments healing of large chondral defects in the radial carpal bone and medial femoral condyle of horses

Objective-To evaluate the effect of arthroscopic subchondral bone microfrac ture on healing of large chondral defects in horses. Study Design-Short- (4 months) and long-term (12 months) in vivo experiment al chondral defect model. Animals-10 horses, aged 2 to 5 years. Methods-Each horse had a 1 cm(2) full-thickness chondral defect created in both radial carpal bones and both medial femoral condyles. One carpus and o ne femoral condyle of each horse had the subchondral bone plate under the d efect perforated using an orthopedic awl. All horses were exercised, five h orses were evaluated after 4 months and five horses after 12 months. Gross, histologic, and histomorphometric examination of defect sites and repair t issues was performed, as was collagen typing of the repair tissue. Results-On gross observation a greater volume of repair tissue filled treat ed defects (74%) compared with control defects (45%). Histomorphometry conf irmed more repair tissue filling treated defects, but no difference in the relative amounts of different tissue types was observed. There was an incre ased percentage of type II collagen in treated defects compared with contro l defects and evidence of earlier bone remodeling as documented by changes in porosity. Conclusions-In full-thickness chondral defects in exercised horses, treatme nt with subchondral bone microfracture increased the tissue volume in the d efects and the percentage of type II collagen in the tissue filling the def ects when compared to nontreated defects. Clinical Relevance-No negative effects of the microfracture technique were observed and some of the beneficial effects are the basis for recommending its use in patients cases with exposed subchondral bone. (C)Copyright 1999 by The American College of Veterinary Surgeons.