Effects of Immobilization on Cartilage Formation after Periosteal Grafting in the Rabbit Stifle

Abstract

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 0 stain uptake, and more normal collagen fiber orientation at 60 days than stifles immobilized for 7 or 14 days. Postoperative immobilization did not affect attachment of the graft to the subchondral bone.SummaryIn this investigation, postoperative immobilization for 7 and 14 days did not enhance attachment of periosteal grafts to subchondral bone. Postoperative joint immobilization for 7 and 14 days, in fact, decreased the production and maturation of neocartilage formed by day 60. Histologic quality of the neocartilage at day 60 was directly correlated with safranin O staining, collagen fiber orientation, and gross appearance of the neocartilage. Although the beneficial aspect of early joint mobility on neocartilage formation must have occurred before day 7, it was not evidenced by increased chondrocyte mitotic activity, increased degree of graft attachment, enhanced collagen fiber orientation, or differences in safranin O staining at days 7 or 14.