Cryopreservation does not alter the ultrastructure of the meniscus.

Fresh frozen menisci have recently been shown to have an altered meniscal ultrastructure. The cause might be a deterioration of its permeability due to collagen net disarray. The purpose of this study was to evaluate the cryopreserved meniscus in terms of ultrastructure and cellularity. Ten fresh human lateral menisci were harvested. Collagen architecture was evaluated with transmission electron microscopy. The Collagen Meniscal Architecture scoring system was used to assess the degree of meniscal disarray. Cell population, was also evaluated. The fibril collagen diameters of those menisci which had been previously cryopreserved showed an average size in the longitudinal section of 12.6 +/- 1.3 nm, whereas it was 13.4 +/- 2.2 nm in the menisci used as controls (n.s.). In the transverse section, the cryopreserved menisci averaged 15.5 +/- 2.4 and 16.7 +/- 3.5 nm in the controls (n.s.). The study group scored 4.8 points +/- 1.7, whereas the control group did so at 4.1 +/- 1.3 (n.s.). The percentage of cell survival after the cryopreservation ranged from 4 to 54. The fibril diameters and degree of disarray showed a similar distribution in both groups. The results suggest that meniscal cryopreservation does not alter the meniscal ultrastructure. Therefore, an allograft stored in that way would not alter its biomechanical properties, although its cellular viability is highly unpredictable.