Chondrocyte survival and material properties of hypothermically stored cartilage - An evaluation of tissue used for osteochondral allograft transplantation

Background: There is little information available on the material properties of hypothermically stored allograft specimens used to repair osteochondral defects. Purpose: To analyze the effect of hypothermic storage on the material properties of fresh knee specimens over a 60-day interval. Study Design: Controlled laboratory study. Methods: Twelve sheep knee condyles were isolated. The femoral and tibial condyles and the patella were stored in a nutritive medium containing Dulbecco's Modified Eagle's Medium for 1, 8, 15, 29, 45, or 60 days. Total chondrocyte density, chondrocyte viability, matrix proteoglycan content, matrix water content, and matrix dynamic modulus of elasticity were determined. Results: Mean chondrocyte viability decreased significantly over the storage interval: 100% (day 1), 98.2% (day 8), *80.2% (day 15), *80.6% (day 29), *64.6% (day 45), and *51.6% (day 60) (*P < 0.05). Qualitative analysis demonstrated a preponderance of nonviable chondrocytes in the superficial cartilage layer. Significant decreases in matrix proteoglycan were observed in day 15 through day 60 specimens (P < 0.05). The matrix dynamic modulus significantly decreased from day 1 through day 60 (P < 0.05). Conclusion: The material properties of hypothermically stored knee condyles progressively decline over 60 days. Clinical Relevance: This observed decline may have significant ramifications on long-term graft survival following stored-allograft implantation.