Objective. The objective of this study was to better understand the MR
I appearance of massive bone allografts. Design. The MRI findings of t
hree massive bone allografts imaged in vivo were correlated with the h
istologic findings following removal of the allografts. A fourth allog
raft, never implanted, was imaged and evaluated histologically. Patien
ts. Allografts were placed for the treatment of primary or recurrent o
steosarcoma. Results and conclusions. The in-vivo allografts have a he
terogeneous appearance on MRI which we attribute to the revascularizat
ion process. Fibrovascular connective tissue grows into the graft in a
patchy, focal fashion, down the medullary canal from the graft-host j
unction and adjacent to the periosteum. The marrow spaces are initiall
y devoid of normal cellular elements and occupied by fat and gelatinou
s material. This normal postoperative appearance of massive bone allog
rafts must not be interpreted as recurrent neoplasm or infection in th
e allograft. Recognition of these complications rests on features outs
ide the marrow.