OR50 Donor specific HLA antibody formation following distal tibial allograft and subsequent graft resorption: A case report

Abstract

Background The association between donor specific Human Leukocyte Antigen (HLA) antibody formation and small bone allograft resorption has not been studied. We present the case of a patient treated for glenoid bone loss with a distal tibial allograft who formed donor specific HLA antibodies against the allograft and had subsequent graft resorption. Methods The patient received a right glenoid reconstruction using distal tibia allograft with Bankart repair in June 2015. X-ray and CT-Scans were performed pre-and post-surgery at standard checkpoints. Patient blood and serum samples were collected pre-and-post-surgery for HLA typing and HLA antibody testing. Results Pre-operative CT scans revealed large Hill-Sachs and bony Bankart lesions, and pre-operative HLA antibody testing revealed no HLA antibodies. The 2-week post-operative radiograph revealed proper graft fixation, and the patient had good range of motion 6-weeks post-surgery. However, 6-week post-operative HLA antibody testing revealed development of donor specific HLA antibodies directed at HLA-A2 antigen as well as several antigens belonging to the A2 crossreactive group (A24, A68, A69, B57 and B58), cPRA of 69%. Eplet analysis showed reactivity to 62GE and 151AHV eplets. At 3-months post-surgery, the patient was weak in internal rotation, and the HLA-A2 antibodies continued to be detected at 5-months post-surgery. Shortly after the antibody peak, the 6-month post-operative CT arthrogram revealed significant graft resorption. Interestingly, the donor specific HLA-A2 antibodies were undetectable 6 months after resorption was complete. Discussion This case report shows that small bone allografts can lead to HLA sensitization. The temporal correlation between donor specific HLA antibody formation and clinical findings strongly suggest an association between HLA antibody formation and graft resorption. It is unclear what impact HLA antibody formation may have on future regrafting in this patient. This case shows a clear association between the formation of donor specific HLA antibodies and graft resorption, which suggests a link between the two events. Our future studies will address the frequency of HLA antibody formation, and investigate whether tissue processing techniques could be improved to reduce bone allograft antigenicity.