Multiple freeze-thaw cycled meniscal allograft tissue: A biomechanical, biochemical, and histologic analysis

Meniscus allografting has provided relief of meniscal injuries that were previously thought irreparable. However, meniscus allograft tissue remains limited and a significant problem. To improve allograft tissue yield, decrease processing costs, and increase graft availability, this study investigated the biomechanical changes of meniscal allograft tissue frozen and thawed multiple times. Specifically, our study compared the intrinsic compressive resistances of meniscus undergoing four Freeze-Thaw cycles versus tissue undergoing a single Freeze-Thaw cycle. Seven menisci that were originally procured and processed for allografting were donated for the study. Each meniscus was segmented and samples independently underwent novel constant slow-rate compression testing, and histological and biochemical evaluation. The menisci that underwent a single Freeze-Thaw cycle demonstrated a significantly higher Young's Modulus (14 megapascals) as compared to menisci undergoing multiple Freeze-Thaw cycles (10 megapascals, p = 0.03). These results were maintained when medial and lateral menisci were compared independently. Histological and biochemical analyses supported, but did not provide an explanation for the change in intrinsic compressive resistance. From these results, transplantation of meniscal allograft tissue frozen and thawed four times may be compromised in its ability to resist compression; and thus may undermine its role in replacing native meniscal tissue.