Introduction and Objectives: Cryopreservation as a meniscus conservation method affects cellularity to a lesser degree than simple freezing. Recent studies have shown that freezing alters meniscus ultrastructure. The effects of cryopreservatioin on the meniscus collagen net has not been so extensively studied. The aim of this study was to determine if cryopreservation alters meniscus ultrastructure and cellularity.

Materials and Methods: We obtained 10 external menisci for the purpose of studying their cellularity and collagen structure before and after cryoprservation at −180°C. We analyzed the architecture of the meniscus collagen using transmission electronic microscopy and assessed the degree to which this was altered according to a previously determined scale. We measured collagen fibers in transverse and longitudinal sections, and also calculated the percentage of cells that survived cryopreservation.

Results: Cryopreserved menisci averaged 4.8 points and the control menisci 4.1 (p< 0.17). In the cryopreserved menisci the collagen fibers in longitudinal section had a mean length of 12.61 nm and in the control menisci 13.38 nm (p=0.34), whereas in transverse sections the average was 15.48 nm and 16.7 nm respectively (p=0.41). The percentage of cells that survived cryopreservation went from 3.99 to 53.57%.

Discussion and Conclusions: Cryopreservation does not alter meniscus ultrastructure. Cell survival is highly variable. Results suggest that cryopreservation would be a more appropriate method than freezing at −80°C for the preservation of meniscal allografts.