Fibrous tissue armoring increases the mechanical strength of an impacted bone graft

Impacted, morselized bone allografts are used with good clinical results in revision of hip prostheses with loosening and osteolysis. The impacted bon e graft appears radiographically to remodel, hut histological analyses have shown a heterogeneous picture with a mixture of living and dead bone. Thus , complete remodeling of the graft may be neither a prerequisite nor a caus e of the good clinical results. The present study concerns the mechanical e ffect of the mere armoring of the bone graft by ingrowing fibrous tissue. W e compared the compression strength of freshly-impacted grafts to grafts th at had been inserted into a bone chamber and thus were penetrated by fibrou s tissue growing in between the graft trabeculae. The compressive strength was doubled after 4 weeks of fibrous ingrowth, We conclude that the mechani cal properties of an impacted graft are enhanced by armoring with ingrowing fibrous tissue. Strengthening of the parts of the impacted grafts which ha ve not yet remodeled, would be clinically relevant for the outcome of the o peration, since these parts are at high stress during the whole remodeling period. Complete osseous remodeling may not be necessary to obtain a good c linical result with a morselized impacted graft.