Shell osteochondral allografts of the knee: Comparison of MR imaging findings and immunologic responses

PURPOSE: To define the magnetic resonance (MR) imaging appearance of shell osteochondral allografts of the knee and compare the MR findings with antib ody responses. MATERIALS AND METHODS: Thirty-six grafts were evaluated with a 1.5-T unit W ith T1-, intermediate-, and T2-weighted, and three-dimensional spoiled grad ient-recalled MR imaging at 3, 6, 12, 24, and/or 36 months after surgery. N ineteen patients underwent imaging serially. Two osteoradiologists scored b y consensus host marrow edema, thickness of graft-host interface, signal in tensity of graft marrow, cyst formation, joint effusion, articular cartilag e defects, and surface collapse. Patients were divided into antibody-positi ve (AP) (n = 11) and antibody-negative (AN) (n = 25) groups evenly distribu ted across the different time points on the basis of results of anti-human leukocyte antigen antibody screening. MR findings for the two groups were c ompared. RESULTS: AP patients demonstrated greater mean edema (P < .002), thicker in terface (P < .03), and more abnormal graft marrow (P < .04) than AN patient s, and they had a higher proportion of surface collapse (P < .03). CONCLUSION: Humoral immune responses were associated with more inflammation and less complete incorporation after allograft placement. MR imaging-show s promise as a surrogate biomarker for success of shell osteochondral allog raft implantation.