The repair of osteochondral defects using an exogenous fibrin clot. An experimental study in dogs.

To evaluate the ability of an exogenous fibrin clot to hasten or optimize the repair of full-thickness articular cartilage defects, 4-mm diameter, full-thickness articular cartilage defects in 20 adult mongrel dogs were packed with an exogenous fibrin clot that had been prepared from each animal. The defects were created in a loaded and unloaded portion of the femoral trochlea. The healing response was then examined using routine histology at various intervals from 2 weeks to 6 months. Both the experimental (clot-filled) and control (empty) defects healed through a proliferation of fibrous connective tissue that eventually modulated into fibrocartilage. However, in the 2-, 4-, and 8-week animals, the experimental defects (both loaded and unloaded) demonstrated a more organized and advanced healing response than did the control defects. This difference was less pronounced in the 12- and 24-week animals. In all specimens, the clot-filled defects healed more uniformly than controls with less surface depression. In general, the unloaded sites were more uniform in healing than the corresponding loaded sites.