What is the risk of disease transmission with bone allografts?

An allograft is a graft between genetically dissimilar members of the same species. An allograft may be obtained from living donors who are having bone removed during surgery or cadaveric donors. Allograft material has been used for more than 30 years in periodontal therapy. There are several types of allografts:

1. Fresh, fresh-frozen
    
2. Freeze-dried bone allograft (FDBA)
    
3. Demineralized freeze-dried bone allograft (DFDBA)

Both FDBA and DFDBA materials are widely used in periodontal therapy and there are no reports of disease transmission during the 30-year history of using freeze-dried bone allografts. However, there have been four cases of human immunodeficiency virus (HIV) infection following procedures using fresh-frozen bone allografts. These cases involved surgeries of the spine, hip, and knee. It is important to note, however, that fresh-frozen and fresh allografts are not typically used in periodontal therapy. Also, when using FDBA and DFDBA, the delay in processing ensures adequate time for testing for potential pathogens.

Most bone banks adhere to the guidelines of the American Association of Tissue Banks (AATB) with respect to procurement, processing, and sterilization of bone grafts. The AATB advocates excluding collection of bone under the following circumstances:

1. Donors from high-risk groups, as determined by medical testing and behavioral risk assessments.
    
2. Donors test positive for HIV antibody by ELISA.
    
3. Autopsy of donor reveals occult disease.
    
4. Donor bone tests positive for bacterial contamination.
    
5. Donor and bone test positive for hepatitis B surface antigen (HbsAG) or hepatitis C virus (HCV).
    
6. Donor tests positive for syphilis.

Using donor screening recommendations, it has been calculated that the chance of obtaining a bone graft from an HIV-infected donor (e.g., one who failed to be excluded by one of the exclusionary techniques) is one in 1.67 million [Buck 1989]. Furthermore, the probability that DFDBA might contain HIV has been calculated to be one in 2.8 billion [Russo 1995]. Therefore, the established exclusionary criteria combined with recommended processing procedures (harvesting in a sterile manner, repeated washings, immersion in ethanol, freezing in liquid nitrogen, freeze-drying, demineralization, and vacuum sealing) render DFDBA and FDBA grafts safe for human implantation.

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Selected References and Additional Resources

American Academy of Periodontology Position Paper: Tissue banking of bone allografts used in periodontal regeneration, J Periodontol 2001;72:834-838.

Buck BE, Malinin T, Brown MD. Bone transplantation and human immunodeficiency virus. Clin Orthop 1994;303:8-17.

CDC. Epidemiologic notes and reports transmission of HIV through bone transplantation: Case report and public health recommendations. MMWR 1988;37:597-599.

CDC. Guidelines for preventing transmission of human immunodeficiency virus through transplantion of human tissue and organs. MMWR 1994;43(RR-8):1-17.

Mellonig JT. Donor selection, testing, and inactivation of the HIV virus in freeze-dried bone allografts. Pract Periodontics Aesthet Dent 1995;7:13-22.

Mellonig JT, Prewett AB, Moyer MP. HIV inactivation in a bone allograft. J Periodontol 1992;12:979-983.

Simmonds RJ, Holmberg SD, Hurwitz RL, et al. Transmission of human immunodeficiency virus type 1 from a seronegative organ and tissue donor. N Engl J Med 1992;326:726-732.