Fate of implanted autologus cartilage grafts in rabbits: an experimental histological study

ABSTRACT

Cartilage grafts are commonly used for a variety of purposes in plastic and reconstructive surgery. Despite their extensive use, the fate of cartilage as a graft is frequently disputed; many factors could affect such fate, among which the role of perichondrium and that of surgical trauma. The present study was conducted to evaluate the fate of implanted autologous cartilage grafts in rabbits and to study the effect of the perichondrium and that of the scoring on cartilage survival and resorption. 10 adult male New Zealand white rabbits were operated upon. Four equal sized auricular cartilage grafts were harvested from each rabbit, as well as a pre-implanted control cartilage graft. After accurate measuring and weighing of the grafts, they were implanted in a dorsal subcutaneous pocket in the same rabbit. The role of perichondrium was examined by implanting three types of cartilage grafts; the first with no perichondrium on either side, the second with perichondrium removed from one side, while in the third, the perichondrium was left intact on both sides. The effect of mechanical surgical trauma was examined by implanting a scored cartilage graft. Twelve weeks after their implantation. all cartilage grafts were retrieved, examined macroscopically. measured accurately, weighted and subjected to histological examination. Pre and post-implanted cartilage grafts were stained by Haematoxylin and Eosin, Orcein and Toluidine blue stains. They were also examined by the scanning electron microscope. The results were compared to the preoperative values. Gross examination revealed ho obvious deviation from the preimplanted auricular cartilage graft regarding color, texture and consistency, although cartilage grafts without perichondrium seemed to be thinner and more pliable. These findings correlate well with the histological [light microscopic and scanning electron microscopic findings in which unscored cartilage grafts retaining their perichondrium were the most viable with active chondrocytes, healthy looking matrix and increased proliferative activity of chondroblasts adjacent to the perichondrium. These grafts have shown a modest increase in their post-implantation weight which could be either due to the observed neochondrogenesis or to a change in the ability of the cartilage grafts to retain water. Cartilage grafts in which perichondrium was removed from both sides has shown an insignificant decrease in their post-implantation weight, yet histologicaly they were viable but no chondrocytic activity was observed They showed definite decrease in the metachromatic reaction which was more evident at the periphery of either side of the cartilage plates which could be due to a change in the chemical composition of the bare mucopolysaccharides. Peripheral decrease in metachromasia along with the lack of chondrocyte activity could represent an early but slow resorption process of the bare cartilage. In scored cartilage grafts, although the perichondrium was preserved on both sides of the grafts, no significant change in the weight was observed; also on histological examination, they did not show any evident chondrocytic proliferation. This could reflect also a slow resorption process in the scored cartilage grafts. Cartilage grafts implanted subcutaneously do survive regardless the presence of perichondrium. Perichondrium enhances cartilage graft survival and seems to act as a protecting shell preventing direct exposure of the graft to the notorious effects of local mediators of wound healing environment that might lead to cartilage resorption. Although scored cartilage grafts implanted subcutaneously do survive and maintain its curvature, yet scoring increases the surface area of the bare cartilage exposed to the local mediators and thus might put them at risk of slow long term resorption