Overview of safety issues concerning the preparation and processing of soft-tissue allografts.

With the increasing use of allograft tissue and the recent infections found in patients undergoing surgical procedures, the current practices that prepare grafts for implantation must be examined. Initially, most tissue banks harvest allografts aseptically. There are many steps in the different techniques of preparation and processing of allograft tissue. Before allograft tissue is ready for clinical use, it undergoes specific disinfection methods, according to the individual tissue bank's specific process. Tissue banks use in-process bactericidal and virucidal steps via physical cleaning, chemical treatments, or application of irradiation to the allografts (or some combination thereof). Gamma irradiation may also be used as a terminal processing method to reach an assurance of sterility after the allograft has been packaged. Because of the allograft toxicity potential, the use of ethylene oxide as a final tissue sterilization measure is really nonexistent. The role of the Food and Drug Administration and American Association of Tissue Banks in allograft tissue handling is presented, as well as the new rules that regulate tissue banks and affect their processing methods.

Viruses adsorbed on musculoskeletal allografts are inactivated by terminal ethylene oxide disinfection.

In 1987 it was anticipated that unsterilized tissues would transmit virus diseases such as hepatitis and HIV-1 from infected donors so a freeze-drying process for musculoskeletal tissue was developed to include terminal ethylene oxide (EO) exposure for 14 h. We found no studies of EO efficacy when viruses were associated with human allografts so we studied the antiviral effect of terminal EO disinfection using all but the final freeze-drying phase of this clinical processing protocol (CPP). Specifically we looked at EO inactivation of HIV-1, a human hepatitis B surrogate and test viruses known to be highly resistant to disinfecting agents, including irradiation. Freeze-drying, ordinarily required after EO disinfection and part of the CPP, was not done. Suspensions of HIV-1, Bovine viral diarrhea, Reovirus type 3, Duck hepatitis B, Poliomyelitis and Canine parvovirus were adsorbed on glass, demineralized bone powder, and preprocessed strips of femoral cortex, iliac wedges, cancellous blocks and patellar bone-tendon-bone preparations and subjected to EO disinfection. Test viruses were inactivated at the end of 7 h of EO disinfection, providing a safety factor in the CPP of at least 100%. Because allografts can transmit viruses, terminal EO disinfection should provide safer musculoskeletal allografts than non-disinfected tissues or those irradiated with a standard irradiation dose. New spontaneously appearing viruses would probably be inactivated with this terminal EO disinfection but they and viral bioweapons will require individual validation to assure viral inactivation.

Allograft transplantation in the knee: tissue regulation, procurement, processing, and sterilization.

Use of musculoskeletal allografts has become increasingly popular, with widespread use among knee surgeons. The advantages and disadvantages of their use have been documented. In the knee, allografts are used for ligament reconstruction, meniscal transplantation, and articular surface reconstruction. The purpose of this review is to present issues surrounding the allograft industry, including regulation of tissues and tissue banks and procurement, processing, sterilization, and storage of allograft tissue. Tissue bank regulation is ultimately under the jurisdiction and authority of the Food and Drug Administration; some individual states regulate tissue banks. The American Association of Tissue Banks is a scientific organization that encourages education, research, and voluntary accreditation of tissue banks. It promotes safety and standards for retrieval, processing, storage, and distribution of transplantable human tissue. Allograft tissues are generally harvested and processed aseptically, which may not prevent contamination. Tissue sterilization is difficult and controversial. Tissue banks historically have used one of two methods of sterilization, ethylene oxide or gamma radiation. Both methods have risks and benefits. Newer methods of sterilization are being developed. Allograft tissue that is not transplanted fresh can be freeze-dried or deep frozen for storage. Ultimately, allograft transplantation in the knee facilitates knee form and function and enhances the patient's quality of life. Orthopaedic surgeons who use allograft tissue must understand the tissue banking process to provide safe and effective tissues to their patients.