Pulsing direct current-induced repair of articular cartilage in rabbit osteochondral defects

Osteochondral defects in the distal femoral condyles of rabbits exposed to a pulsing direct current exhibits an enhanced quality of repair. The signal, with a peak value of 2 microA repeating at 100 Hz, imposed an electric field in the tissue of 20-60 mV/cm2. Maximum efficacy was seen with a shorter period of exposure (40 vs. 160 h) initiated 48 h after surgery for 4 h/day. Repair tissue originated primarily from metaplasia of subchondral elements although hyperplasia of pre-existing chondrocytes at the margins of the defect could be detected. Defects in treated joints contained Safranin O staining material that was histologically similar to a disorganized hyaline cartilage. Central areas of the defects in control animals contained Safranin O-negative material that generally extruded over the surface as a pannus. The edges of nontreated defects also had characteristics of cartilaginous healing, stressing the importance of using serial sectioning techniques in this model of cartilage repair.