Freeze-drying is the removal of water from a substance by using a vacuum process, which turns the water in its crystalline form to water vapor without it ever passing through the liquid phase. This is very useful for the long-term preservation and storage of tissue when other means are impractical. Tissue that is freeze-dried can be stored at room temperature for long periods of time as well as transported long distances without the need for dry ice. Rehydration is required before the use of freeze-dried tissue.
Freeze-Dried allograft packaging can be jars or plastic pouches. There are always two layers of packaging. The first is an outer packaging, handled by the OR circulator while the inside packaging is opened by a scrubbed personnel because it is sterile.
Freeze-dried allografts are shipped in packaging intended to avoid breakage, and is shipped at ambient temperatures. These grafts can be stored at room temperature.
Freeze-dried allografts are reconstituted by submerging the graft into room temperature sterile saline bath with or without antibiotics. This should be done at the beginning of surgery to ensure that the allograft is completely reconstituted by the time that the surgical site is prepared.