HLA sensitization and allograft bone graft incorporation

Achieving union between host bone and massive structural allografts can be difficult. Donor and recipient human leukocyte antigen (HLA) mismatches and recipient antibody response to donor HLA antigens might affect union. In a prospective multiinstitutional study, we enrolled a consecutive series of patients receiving cortex-replacing, massive structural bone allografts to determine the rate of donor-specific HLA antibody sensitization and to investigate the potential effect of such HLA alloantibody sensitization on allograft incorporation. HLA typing of patients and donors was determined by molecular typing methods. Donor-specific HLA sensitization occurred in 57% of the patients but had no demonstrable effect on graft incorporation or union. The type of host-allograft junction did have a major effect on graft incorporation. Cortical-to-cortical allograft-to-host junctions healed more slowly (mean, 542 days) than corticocancellous to corticocancellous allograft-to-host junctions (mean, 243 days). Although HLA sensitization does not appear to delay structural allograft bone incorporation, further followup is required to determine if there is an association between HLA sensitization and long-term graft survival. Based on these preliminary data, measures to further minimize or modulate HLA sensitization or response are not indicated at present for the purposes of improving structural bone allograft union.