Allograft Preservation
Definitions
Preservation: Methods used to maintain the integrity of the tissue grafts for specified periods of time while maintaining their biological potential. There are five methods: fresh, frozen, freeze-dried, hydrated and cryopreserved.
Transit: Tissue storage temperatures must be maintained throughout the mode of transport ensuring the integrity and biological potential of the tissue. Major commercial carriers are used, and grafts are packaged and shipped in validated containers.
Storage: Varies based on the preservation method: Fresh – Refrigerated; Frozen – -40°C or colder; Freeze-dried (Lyophilized) – Room Temperature; Cryopreserved – -40°C or colder; Hydrated – Room Temperature
Reconstitution: The method of restoring a freeze-dried allograft to its original state according to the instructions for use provided within each container.
Fresh (Refrigerated Temperature – Above freezing 0°C to 10°C)
Preservation: Fresh allografts are immersed in nutrient culture medium with antibiotics. This method is used for short term storage only and is intended to preserve viable cells. Fresh grafts have a short-term shelf life.
Transit: Ice packs/blue ice/wet ice is packed around the fresh tissue in Styrofoam boxes to maintain validated, refrigerated temperature during transit.
Storage: Upon receipt, the allograft should have the appearance of floating in solution. (If the liquid appears frozen, the graft should be treated as unusable). Fresh grafts are packaged in plastic jars or pouches with a dual layer of sterility.
When the allograft arrives at the end-user facility, if the surgery is not immediate, remove allograft from the Styrofoam container and place in the refrigerator (NOT FREEZER) until surgery.
Preparation: Rinse the fresh graft to remove excess storage media. Submerge the allograft in sterile solution recommended in the Instructions for Use (IFU), and ensure the fresh graft remains moist prior to implantation.
Frozen
Preservation: Freezing the tissue at a temperature below -40°C is used for preservation of musculoskeletal tissue. These tissues are frozen at uncontrolled rates which does not allow for the viable cells to be maintained.
Transit: The allograft is shipped on dry ice in a validated shipping container to maintain the appropriate storage conditions.
Storage: Allografts are frozen at -40°C or colder up to allograft expiration.
Preparation: Submerge the frozen allograft in a room temperature, sterile, lactated ringer’s bath or similar solution with or without antibiotics.
Note: Solution from a warmer will denature tissues and render them unusable.
Cryopreserved
Preservation: Freezing of tissue at a controlled rate of 1 to 2°C per minute in the presence of a cryoprotectant solution (glycerol) and controlled by a computer with liquid nitrogen vapor as the coolant. This method is intended to preserve cell viability at a higher rate than frozen grafts.
Transit: The allograft is shipped on dry ice in a validated shipping container to maintain the appropriate storage conditions.
Storage: The allografts are cryopreserved with little or no solution and stored at -40°C, or colder.
Preparation: Submerge the cryopreserved allograft in a room temperature, sterile, lactated ringer’s bath or similar solution with or without antibiotics.
Note: Solution from a warmer will denature tissues and render them unusable.
Freeze-Dried (Lyophilized)
Preservation: Freeze-drying is the removal of water from a substance 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. Tissue that is freeze-dried can be stored at room temperature for extended periods as well as transported long distances without the need for dry ice. Rehydration is required before the use of freeze-dried tissue.
Transit: Freeze-dried tissue is packaged to avoid breakage and is shipped at ambient temperatures.
Storage: All lyophilized allografts are maintained at ambient or room temperature unless otherwise specified on the package label.
Preparation: Submerge freeze-dried allograft into a room temperature, sterile, lactated ringer’s bath or similar solution, with or without antibiotics. This should be done as the surgery is beginning so that by the time the surgical site is prepared to receive the allograft, the tissue will be rehydrated.
Hydrated
Preservation: Tissue is suspended in a preservation solution at ambient temperatures.
Transit: Pre-hydrated tissue is packaged in a sterile pouch and is shipped at ambient temperatures.
Storage: All pre-hydrated allografts are maintained at ambient room temperature unless otherwise specified on the package label.
Preparation: Follow instructions for use. Most pre-hydrated tissue is ready-to-use, only requiring a brief soak in sterile solution prior to implantation, or ready for immediate use after removal from sterile packaging.
Storage Conditions for Commonly Transplanted Human Tissue
(AATB standards for Tissue Banking, Current Edition)
Preservation |
Temperature |
Apparatus |
Fresh |
Above freezing (0°C) to 10°C |
Refrigerator |
Cryopreserved frozen (long-term) |
-40°C and colder |
Dry Ice or Allograft Freezer |
Cryopreserved frozen (less than 6 months) |
-20°C to -40°C |
Dry Ice or Allograft Freezer |
Frozen (long-term) |
-40°C and colder |
Dry Ice or Allograft Freezer |
Frozen (lesss than 6 months) |
-20°C to -40°C |
Dry Ice or Allograft Freezerr |
Freeze-Dried |
Ambient Temperature |
Room Temperature (secure location) |
Hydrated or Saline Suspended |
Ambient Temperature |
Room Temperature (secure location) |