Effects of immobilization on cartilage formation after periosteal grafting in the rabbit stifle

Autogenous periosteal grafts were harvested and placed in the trochlear grooves of the stifles of 32 rabbits. Postoperative immobilization periods of 0, 7, and 14 days were compared. Grafted areas were evaluated for gross appearance, histologic morphology, attachment of cartilage to subchondral bone, cartilage depth, chondrocyte density, proteoglycan presence, collagen fiber orientation, and mitotic activity. Nonimmobilized stifles had increased gross coverage of subchondral bone, better histologic quality, increased safranin O stain uptake, and more normal collagen fiber orientation at 60 days than stifles immobilized for 7 ir 14 days. Postoperative immobilization did not affect attachment of the graft to the subchondral bone.