Transplantation of osteochondral allografts after cold storage

Abstract

Background: Transplantation of fresh osteochondral allografts stored at hypothermia into knee cartilage defects is a common procedure; however, the length of time that allografts can be stored prior to transplantation is controversial and has been determined, in part, by the results of vital stain uptake by chondrocytes. This study was performed to further define the limits of allograft storage.

Methods: Articular cartilage from six cadavers was stored for up to fifty-one days in tissue-culture media, and histologic sections were evaluated histomorphometrically to quantify the loss of chondrocytes. Samples of the cartilage were also placed into tissue culture to assess cell growth. Animal studies were performed in parallel on sixteen adult baboons with osteochondral allografts transplanted into the medial femoral condyle. Prior to transplantation, all allografts were stored in RPMI-1640 with 10% fetal calf serum at 4 degrees to 6 degrees C for up to eighty-five days. The transplants were graded on their gross and histological appearance, as well as their histochemical properties.

Results: Many of the human samples stored at hypothermia in culture media for up to forty days retained some recognizable chondrocytes, but morphometry showed a gradual, significant decrease in the number of chondrocytes after nine days (p = 0.001). In addition, the cell outgrowth occurred from all specimens stored for up to fifteen days but not in samples stored for longer than thirty-four days. In animal studies, transplanted allograft cartilage that had been stored for less than eighteen days looked smooth and glistening, but grafts stored for over twenty-one days were pale, pitted, fragmented, or yellow, and chondrocytes were absent.

Conclusions: Time-dependent loss of chondrocytes in articular cartilage stored at hypothermia, especially in specimens stored for longer than fifteen to twenty days, was observed in this study. Cartilage allografts transplanted into nonhuman primates after twenty-one days of storage underwent more severe degenerative changes than allografts that had been stored for less than twenty-one days. These findings suggest caution when transplanting cartilage stored at hypothermia for over twenty days.