Prolonged storage effects on the articular cartilage of fresh human osteochondral allografts

Background: Fresh osteochondral allograft transplantation is a well-established technique for the treatment of cartilage defects of the knee. It is believed that the basic paradigm of the technique is that the transplantation of viable chondrocytes maintains the articular cartilage matrix over time. Allograft tissue is typically transplanted up to forty-two days after the death of the donor, but it is unknown how the conditions and duration of storage affect the properties of fresh human osteochondral allografts. This study examined the quality of human allograft cartilage as a function of storage for a duration of one, seven, fourteen, and twenty-eight days. We hypothesized that chondrocyte viability, chondrocyte metabolic activity, and the biochemical and biomechanical properties of articular cartilage would remain unchanged after storage for twenty-eight days. Methods: Sixty osteochondral plugs were harvested from ten fresh human femoral condyles within forty-eight hours after the death of the donor and were stored in culture medium at 4degreesC. At one, seven, fourteen, and twenty-eight days after harvest, the osteochondral plugs were analyzed for (1) viability and viable cell density by confocal microscopy, (2) proteoglycan synthesis by quantification of (SO4)-S-35 incorporation, (3) glycosaminoglycan content, (4) indentation stiffness, (5) compressive modulus and hydraulic permeability by static and dynamic compression testing, and (6) tensile modulus by equilibrium tensile testing. Results: Chondrocyte viability and viable cell density remained unchanged after storage for seven and fourteen days (p > 0.7) and then declined at twenty-eight days (p < 0.001). Proteoglycan synthesis remained unchanged at seven days (p > 0.1) and then declined at fourteen days (p < 0.01) and twenty-eight days (p < 0.001). No significant differences were detected in glycosaminoglycan content (p > 0.8), indentation stiffness (p > 0.4), compressive modulus (p > 0.05), permeability (p > 0.3), or equilibrium tensile modulus after storage for twenty-eight days (p > 0.9). Conclusions: These data demonstrate that fresh human osteochondral allograft tissue stored for more than fourteen days undergoes significant decreases in chondrocyte viability, viable cell density, and metabolic activity, with preservation of glycosaminoglycan content and biomechanical properties. The cartilage matrix is preserved during storage for twenty-eight days, but the chondrocytes necessary to maintain the matrix after transplantation decreased over that time-period. Clinical Relevance: Fresh osteochondral allografting is well established and increasingly used, but little information is available about the changes in the tissue that occur during storage over a period of time. Surgeons who perform fresh osteochondral allograft transplantation should understand the consequences of prolonged storage on the quality of the graft.